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Introduction This article includes the definition of metallized ceramics, manufacturing process of metallized ceramics, the types of ceramic metallization methods, the factors affecting metallized ceramics,quality assurance and its applications, you will discover insight from following: Chapter 1 : What are Metallized Ceramics Metallized ceramics refers to a layer of metal film is deposited onto the specific surface of engineered ceramics, and then curing in high-temperature reduction atmosphere (hydrogen or nitrogen) furnace, so that the metal film will tightly attach to the surface of the ceramic components, refer to figure 1 . Figure 1: Metallized ceramics After metallizing process, the ceramic surface offers the characteristics of metal, can be achieved effective connection between ceramic and metal by means of brazing. Chapter 2: Why are Ceramics Metallized? As a typical inorganic non-metallic material, advanced ceramics have been widely used in various high voltage, high current and high-pressure electrical & electronic vacuum devices, new energy vehicles, semiconductor packages and IGBT modules because of their excellent electrical, physical & chemical properties, mechanical properties, thermal properties and optical properties. In these practical applications, it often involves the joint of ceramics and metal parts in different materials, such as stainless steel, oxygen-free copper, Kovar and so on. Since the thermal expansion coefficient of ceramic and metal material has huge difference;In the meantime, the two materials naturally have poor wetting effect; And in these fields, the sealing surface of ceramic and metal parts has strict sealing strength (tensile strength) and air tightness requirements after brazing, thus they can not be directly and simply connected. So ceramic metallization technology was born. Chapter 3: Properties of Metallized Ceramic 1. High thermal conductivity: The heat generated by the chip can directly transfer to the ceramic parts without an insulating layer, bringing out more ideal heat dissipation. 2. Ideal thermal expansion coefficient: The thermal expansion coefficient of both advanced ceramics and chips is similar, and it will not cause too much deformation when the temperature difference changes, resulting in problems such as circuit desoldering and internal stress at connection section. 3. Low dielectric constant : The dielectric constant of the ceramic material itself makes the signal loss smaller, so the technical ceramic materials are widely used in communication equipment and signal transmission. 4. High bonding force : High bonding strength of metal layer and ceramic substrate of ceramic circuit board products, up to 45MPa (greater than the strength of 1mm thick ceramic parts themselves) 5. High operating temperature: Ceramics can withstand high and low temperature cycles with large fluctuations, and can even operate at a high operating temperature of 800 degrees for a long time. 6. High electrical insulation: Industrial ceramics themselves are insulating materials that can withstand high breakdown voltages, especially ceramic insulators after glazing, and can even be applied in fields with voltages above 100KV. 7. Chemical stability: The ceramic body has better chemical stability, and will not react with most of the strong acids and bases, and will not be oxidized in the high temperature environment. Chapter 4: Mechanism of Ceramic Metallization What is the mechanism of ceramic metallization? The mechanism of ceramic metallization takes advantage of the different chemical reactions and diffusion migration of various substances in advanced ceramics and metallized layers at different sintering stages, such as oxides and nonmetallic oxides. As the temperature rises, the liquid phase is formed when all substances react to form intermediate compounds and reach the common melting point. The liquid glass phase has a certain viscosity and produces a plastic flow at the same time. Afterwards, the glass particles are rearranged under the action of capillaries, and the atoms or molecules are diffused and migrated under the drive of surface energy. The pores gradually shrink and disappear with the increase of grain size, thus realizing the densification of the metallized layer. Refer to figure 2 below: Figure 2: Schematic of Ceramic Metallization Structure Chapter 5: Ceramic Metallization Methods 1. Mo-Mn method: The MO-Mn method is based on refractory metal powder Mo, and then dope a small amount of low-melting point Mn metallization formula, add a binder coating to the Al2O3 ceramic surface, and then sintering to form a metallized layer. The disadvantages of the traditional Mo-Mn method are high firing temperature, high energy consumption, and low sealing strength due to the absence of activator in the formula. 2. Activation Mo-Mn method: The activated Mo-Mn method is an improvement based on the traditional one. The main directions of improvement are: adding activators and replacing metal powder with molybdenum and manganese oxides or salts. Both of these improvements are designed to reduce the metallizing temperature. The disadvantage of activated Mo-Mn method is that the process is complex and the cost is high, but it can greatly improve the wettability, and significantly improve the bond strength between ceramics and metals, so the activated Mo-Mn method is still the most widely used process. 3. Silver paste sintering method: The silver method is to apply a layer of Ag paste on the ceramic surface, composed of Ag salt flux and adhesive, and then sintering at high temperature to reduce Ag ions to elemental Ag, Ag layer can be reduced by triethanolamine silver carbonate or by adding silver nitrate to ammonia and then reduced by formaldehyde or formic acid. 6Ag2CO3+N(CH2CH2OH)3=N(CH2CHOOH)3+12Ag↓+6CO2+3H2O AgNO3+N H4OH=AgOH+NH4NO3 , 2AgOH=Ag2O+H2O Ag2O+H2C=O=2Ag+HCOOH Or Ag2O+HCOOH=2Ag+CO2↑+H2O Due to the strong diffusion of silver ions, it is not appropriate to use the silver paste sintering method for electrical appliances used in strong electric fields, because the electrical properties will deteriorate rapidly under high temperature, high humidity and direct current electric fields. At present, the main problems of Ag layer sintered by sintering method are thin, discontinuous, non-uniform and poor corrosion resistance. 4. Active Metal Brazing (AMB method): Active metal brazing is also a more widely used ceramic-to- metal sealing process, it is 10 years later than the development of Mo-Mn method, characterized by fewer processes, shorter cycle, good welding reliability, and suitable for a variety of different ceramic materials. The ceramic-metal sealing can be completed with only one heating process. Brazing alloys contain added Ti, Zr, Hf and Ta active elements, the added active elements react with Al2O3 to form a reaction layer with metal characteristics at the interface, this method can be easily adapted to large-scale production, compared with molybdenum - manganese process, this method is relatively simple and economical. The disadvantage of the active metal brazing method is that the active filler metal is single, which causes its application to be limited to a certain extent, and it is not suitable for continuous production, but only suitable for large, single piece production or small batch production. 5.Direct Bond Cooper (DBC method): DBC is a metallization method of bonding copper foil on a ceramic surface (mainly Al2O3 and AlN), which is a new process developed with the rise of chip on board (COB) packaging technology. The basic principle is to introduce oxygen between Cu and ceramic, and then form Cu/O eutectic liquid phase at 1065 ~ 1083℃, and then react with ceramic base and copper foil to form CuAlO2 or Cu(AlO2)2, and realize the bonding between copper foil and ceramic matrix under the action of intermediate phase. 6. Magnetron sputtering: It is a kind of physical vapor deposition, which is to deposit multilayer film on the substrate by magnetic control technology, refer to the figure 3 Figure 3: The diagram of Magnetron vacuum sputtering which has the advantages that other deposition technologies do not have, with better adhesion, less pollution and improve the crystallinity of the deposited sample, to obtain high-quality film. The metallization layer obtained by this method is very thin, which can ensure the accuracy of the dimension of the part. The DPC process supports PTH (electroplated through hole) /Vias (through hole). High-density assembly is possible - line/pitch (L/S) resolution can reach 20μm, thus achieving lightweight, miniaturization, and integration of devices. Chapter 6: Metallization process 1. Pretreatment of ceramic base: The sintered ceramics were ground to optical smoothness with diamond abrasive paste to ensure that the surface roughness was ≤1.6µm. The ceramic bases were placed in acetone and alcohol, and ultrasonically cleaned at room temperature for 20 minutes. 2. Metallization paste preparation: The raw materials are weighed according to the metallization formula, and the metallization slurry with a certain viscosity is made after ball milling for a certain period of time. 3. Coating, drying: Apply the paste on the ceramic insulator or ceramic substrate by screen printing, pad printing or brush coating technology. The paste thickness should be appropriate. If the paste is too thin, the solder will easily flow into the metallization layer. If it is too thick, it is not conducive to the migration of components. 4. Heat treatment: The dried substrate is sintered in a reducing atmosphere to form a metallized layer. 5. Enamelling: The glaze spray process is used to evenly spray a layer of glaze on the non-metallized outer surface, and then glaze through medium temperature. 6. Secondary metallization: The most typical secondary metallization is nickel plating on the underlying Mo/Mn or W metallization, the purpose of following plating is to improve the fluidity and wettability of the solder in the subsequent brazing process, and to prevent the underlying metallization from being oxidized, so that the welding strength can`t be decreased. Chapter 7: Metallization Materials 1. The Mo-Mn method mainly includes molybdenum, manganese, tungsten, nickel, silver and gold. 2. DBC method mainly includes oxygen-free copper. 3. Materials of other metallization methods include Palladium (Pa), Platinum (Pt), Titanium (Ti), Aluminum (AL) Selected metal alloys may also be used. Chapter 8: Factors Affecting Quality of Ceramic Matallization 1. Ceramic itself reliability: The influence of ceramic on the quality of metallization is mainly its internal quality and surface characteristics. First, from the microscopic aspect of the analysis, in other word, the size of the ceramic grain, if the ceramic grain is getting properly large, the brazing force will increase with the size of the grain; However, if the grain is too large, the bonding strength will be reduced accordingly, and the optimal grain size of high purity alumina is about 30um. Second, from the macro analysis, and the finish and appearance quality of the ceramic surface, in order to ensure the adhesion and sealing strength of the metallized layer, the metallized surface of the ceramic needs to be precision grinding, and the ceramic components` roughness needs to be ensured at Ra0.8. 2. Formulation of metallization paste: Three activators, MnO, Al2O3 and SiO2, must be added to the metallization paste. MnO mainly reduces the viscosity of the glass phase, Al2O3 can improve the brazing strength of metallization, and SiO2 can improve the wettability of brazing. After the addition of these activators, the paste will obviously exhibits the following three characteristics: a. The thermal expansion coefficient of the glass phase is reduced; b. The sintering temperature of metallization will be reduced; c. The infiltrating characteristics of Mo will be improved. If nano powders are introduced into the preparation of the metallized paste, the density of the metallized layer, the metallizing temperature, and the brazing strength will be further optimized. 3. Metallizing temperature and holding time: Another factor affecting the quality of metallization is the metallizing temperature with the holding time. The metallizing temperature is divided into four grades: ultra-high temperature, high temperature, medium and low temperature. The temperature of ultra-high temperature is above 1600 ° C, the high temperature is 1450~1600 ° C, the medium temperature is 1300~1450 ° C, and the low temperature is below 1300 ° C.Different products in different materials need to use the appropriate metallization temperature. Too high temperature will weaken the adhesion of the metallization layer, and even the metallization layer will fall off from the ceramic surface, resulting in weakened brazing strength and even sealing failure; On the contrary, the temperature is too low, the diffusion of the glass phase will weaken the migration, and the adhesion of the metallized layer will also be weakened. 4. Microstructure of the metallized layer: The metallizing process determines the microstructure of the metallization, and its microstructure has a direct influence on the reliability of its brazed parts. The key is to ensure that the metallized layer can be continuously and densely covered on the ceramic body with ideal adhesion. If the microstructure of each level of the metallized layer is distinct, and no uniform brittle metal compounds are observed at any interface, such a metallized layer will reduce the record of brittleness and crack growth; With fewer tight cracks at each level, solder penetration can be reduced. 5. Influence of metallized powder particle size and reasonable grading: The particle size of metallization metal powder is closely related to the coating quality and sintering effect. The metal powder is too fine, the surface energy is large, the activity is stronger, and the agglomeration is easy to form, which will affect the flatness of the coating; If the powder is too coarse, the surface energy will be reduced, resulting in the need to increase the sintering temperature, which will affect the sintering quality. In addition, if the particle size distribution of various powders is relatively concentrated, there will be an "arch bridge effect" between the powders during the metallization process, resulting in an increase in the porosity of the metal layer, which will adversely affect the air tightness of the vacuum arc extinguishing chamber. 6. The effect of coating mode: The uniform distribution of each component of the metallized paste and the good coating performance directly affect the quality of the metallized layer. Coating can be manual pen coating, mechanical coating, spray gun spraying and screen printing and other methods, for a small number of products with inconsistent sizes should be used pen coating, for the large-scale production of the same product, it is appropriate to use screen printing. Screen printing allows precise and uniform thickness control. The thickness of the paste is usually 50~80 micros. 7. The effect of coating thickness: Different metallization formulations and preparation methods, the thickness of the metallization layer is different. Chapter 9: Types of Metallized Ceramics The types of metallized ceramics mainly include metallized ceramic structural parts and metallized ceramic substrates: 1. Metallized ceramic structural parts They mainly play a role of protection, hermetic, support, insulation, connection, heat dissipation and other functions. The main materials used include aluminum oxide (Al2O3), zirconia toughened aluminum oxide (ZTA), zirconia (ZrO2), aluminum nitride (AlN), beryllium oxide(BeO), boron nitride (BN) and silicon carbide (SiC). 2. Metallized ceramic substrate In the application, it is mainly used as a circuit carrier to assist chip heat dissipation and insulation. The main materials include alumina, aluminum nitride, silicon nitride and beryllium oxide. Chapter 10: How to Ensure the Quality The typical quality assessment and corresponding measurement methods for ceramic metallized products are described as follows: 1. Visual Inspection: It mainly includes crack, chips, metallization appearance, impurities inspection on surface of ceramic base. Ensure that the ceramic surface is smooth and free from abnormalities. The XRF, microscope and naked eyes are often used as inspection tools. 2. Metallization thickness measurement: Ensure that the metallization thickness within specification with non-destructive coating thickness gauge as inspection tool. 3. Resistance measurement: Using Ohmmeter to check the electrical resistance to ensure conducting electricity within specification 4. Metallization layer quality inspection: Using scanning electron microscopy (SEM) to observe the surface morphology and cross-sectional microstructure of metallization layer, and whether the interface is permeated to ensure the metallization layer. 5. Bond strength test: Using electronic universal testing machine to check the adhesion strength of brazed sub-assembly. 6. Hermeticity test: Using Helium mass spectrometer to check air tightness of sub-assembly to ensure the gas tightness /leak rate of metallized ceramics. 7. Reliability and lifetime test: It mainly includes thermal cycling test, Temperature coefficient of resistance, High-temperature aging test, Humidity and moisture resistance test, Thermal shock test, Mechanical stress test, Accelerated aging test, Electrical performance test and Failure analysis Chapter 11 : Challenges and Limitations 1. Thermal expansion mismatch: It`s critical challenge for metallized ceramics. 2.Metallization adhesion issues 3. Cost considerations 4. Metallization failure mechanisms Chapter 12: Typical Applications Metallized ceramics are widely used in many modern industries: High power and high frequency applications 1. Power electronics 2. Microwave devices 3. RF amplifers Electronic components and devices 1. Intergrated circuits 2. Resistors and capacitors 3. Sensors and transducers Hemetical packaging and sealing 1.Vacuum tubes and electron tubes 2. Optoelectronic devices 3. Medical implants and devices Chapter 13: Future trends and Advancements At present, the research of metallized ceramic technology includes the quality control of ceramic matrix, physical properties, microstructure, metallization mechanism, the development and popularization of new technology. Among them, there are more researches on the quality control, physical properties, structure and new process of ceramic matrix, but less on the metallization mechanism and applications. Considering that there is still no consensus in many aspects of the mechanism of metallization in the academic community, but the mechanism of metallization is the basis for improving the level of metallization and improving the sealing of ceramics and metals, the future will inevitably focus on the research of metallization mechanism. Chapter 14: Conclusion With the dynamically improvement of the power and integration of electronic components, more stringent requirements are also put forward for packaging and cooling materials. Therefore, the traditional metal cooling materials and hermetical components gradually cannot meet the requirements of electronic devices. As an emerging thermal conductivity and sealing material, advanced ceramics not only have a thermal expansion coefficient close to the chip, but also have excellent mechanical strength, insulation strength, high temperature resistance, corrosion resistance and other characteristics, which is the most ideal material choice for power electronic device packaging and heat dissipation. The deeper research on the metallization mechanism of ceramics, as well as the exploration and development of new processes, is the basis for improving the metal and ceramic sealing surface, which will further expand the application field,

From the technical level of the global electronic ceramics industry, Japan and the United States are in a leading position in the world. Among them, Japan, with its super-scale production and advanced preparation technology, has a dominant position in the world electronic ceramics market, accounting for more than 50% of the world electronic ceramics market. The United States has a strong force in basic research and new material development, and it pays attention to the cutting-edge technology of products and applications in the military field, such as underwater acoustic, electro-optic, optoelectronics, infrared technology and semiconductor packaging. In addition, the rapid development of South Korea in the field of electronic ceramics has attracted attention. 1. Multilayer Ceramic Capacitor (MLCC) Industry The main application area of electronic ceramics is passive electronic components. MLCC is one of the most used passive components, mainly used in all kinds of electronic machine oscillation, coupling, filter bypass circuit, its application fields involve automatic instrumentation, digital home appliances, automotive appliances, communication, computer and other industries. MLCC occupies an increasingly important position in the international electronics manufacturing industry, especially with the increasing demand from consumer electronics, communications, computers, networks, automotive, industrial and defense end customers, the global market reaches billions of dollars, and is growing at a rate of 10% to 15% per year. Since 2017, there have been several price increases for MLCC products due to supply and demand. Japan is a major producer of MLCC around the world, and Japan's nuRata, KYOCERA, TAIYO YUDEN, TDK-EPC, South Korea's Samsung Electric Co., LTD. (SEMCO) and China's Taiwan Huaxin Technology Co., LTD., Guoju Co., Ltd. are the world's famous MLCC manufacturers. The mainstream development trend of MLCC is miniaturization, large capacity, thin layer, base metallization and high reliability, among which the technology related to base metallization of internal electrodes has developed most rapidly in recent years. The use of base metal internal electrodes is the most effective way to reduce the cost of MLCC, and the key technology to realize base metallization is the development of high-performance anti-reduction barium titanate porcelain. Japan has completed the development of this technology in the early 21st century, and has remained the world's leader, and its large-capacity MLCC has all achieved base metallization. The miniaturization of size has always been the main trend in the development of MLCC. With the increasing development of electronic equipment in the direction of miniaturization and portable, product upgrading is rapid, and the demand for miniaturized products is strong, as shown in Figure 1. The basic material technology for miniaturizing components is the thinning technology of ceramic dielectric layer. At present, Japanese companies are in the leading position in the world, and the thickness of MLCC monolayers produced by them has reached 1µm, among which the research and development level of Murata and Sunlure Co., Ltd. in the top position has reached 0.3µm. The basis of dielectric thin-layering is the thinning of dielectric materials. While the single layer thickness of high-capacity thin-layered MLCC components is gradually reduced, in order to ensure the reliability of components, barium titanate, as the main crystal phase of MLCC ceramic media, needs to be further refined from 200 ~ 300 nm to 80 ~ 150nm. The future development trend is to prepare barium titanate material with particle size ≤ 150nm as the main crystal phase material of MLCC dielectric layer. 2. Chip Inductor Industry Chip inductors are another type of passive electronic components with a large amount demand, and are the most technologically complex of the three categories of passive chip components, and the core material is magnetic ceramics (ferrite). At present, the total demand for chip inductors in the world is about 1 trillion, and the annual growth rate is more than 10%. In the development and production of chip inductors, Japan's production output accounts for about 70% of the world's total. Among them, TDK-EPC, Murata and Suntrap Co., Ltd. have always mastered cutting-edge technologies in this field. According to the Industry Intelligence Network (IEK) statistics, in the global inductance market, TDK-EPC, Suntrap Co., LTD., and Murata three companies together account for about 60% of the global market. The main trends in the development of chip inductors include small size, high inductance, high power, high frequency, high stability and high precision. The core of the technology is soft magnetic ferrite and medium material with low temperature sintering characteristics. 3.High Performance Piezoelectric Ceramics Industry Piezoelectric ceramics are an important energy exchange material with excellent electromechanical coupling properties. They are widely used in electronic information, electromechanical energy exchange, automatic control, MEMS and biomedical instruments. In order to meet the new application requirements, piezoelectric devices are developing in the direction of multilayer, chip and miniaturization. In recent years, some new piezoelectric devices such as multi-layer piezoelectric transformer, multi-layer piezoelectric driver and chip piezoelectric frequency device have been developed and widely used in electrical, electromechanical and electronic fields. At the same time, in terms of new materials, the development of lead-free piezoelectric ceramics has made great breakthroughs, which may make lead-free piezoelectric ceramics replace lead zirconate titanate (PZT) based piezoelectric ceramics in many fields, and promote the upgrading of green electronic products. In addition, the application of piezoelectric materials in next-generation energy technologies is beginning to emerge. In the past decade, with the development of wireless and low-power electronic devices, the research and development of micro-energy harvesting technology using piezoelectric ceramics has received great attention from governments, institutions and enterprises. 4.Microwave Dielectric Ceramics Industry Microwave dielectric ceramics are the cornerstone of wireless communication devices. Widely used in mobile communications, navigation, global satellite positioning system, satellite communications, radar, telemetry, Bluetooth technology and wireless local area network (WLAN) and other fields. Components such as filters, resonators and oscillators composed of microwave dielectric ceramics are widely used in 5G networks, and their quality largely determines the final performance, size limits and cost of microwave communication products. Microwave electromagnetic dielectric materials with low loss, high stability and modulability are currently the core technology in the world. Microwave dielectric ceramic materials in the early stage of development had formed a fierce competition in the United States, Japan, Europe and other countries and regions, but then Japan gradually in a clear dominant position. With the rapid development of the third generation mobile communication and data microwave communication, the United States, Japan and Europe have made strategic adjustments for the development of this high-tech field. From the recent development trend, the United States takes nonlinear microwave dielectric ceramics and high dielectric constant microwave dielectric ceramic material technology as a strategic focus, Europe focuses on fixed frequency resonator materials, and Japan relies on its industrial advantages to vigorously promote the standardization and high quality of microwave dielectric ceramics. At present, the production level of microwave dielectric materials and devices is the highest in Japan's Murata, Kyocera Co., LTD., TDK-EPC Company, and Trans-Tech Company in the United States. 5.Semiconductor Ceramics Industry Semiconductor ceramics is a kind of information function ceramic materials that can convert physical quantities such as humidity, gas, force, heat, sound, light, and electricity into electrical signals, which is widely used and is the main basic material of Internet of Things technology, such as positive temperature coefficient thermistor (PTC), negative temperature coefficient thermistor (NTC) and varistor, as well as gas and humidity sensitive sensors. The output and output value of thermal and pressure sensitive ceramics are the highest in semiconductor ceramic materials. Internationally, thermistor ceramic materials and devices to Japan Murata, Shiura Electronics Co., LTD., Mitsubishi Group (Mitsubishi), TDK-EPC, Ishizuka Electronics Co., LTD. (Ishizuka), VISHAY (VISHAY), Germany EPCOS (EPCOS) and other companies are the most advanced ceramic technology, the largest output, Their total annual output accounts for about 60% to 80% of the world's total, and their products are of good quality and high prices. In recent years, foreign ceramic semiconductor devices are developing in the direction of high performance, high reliability, high precision, multilayer chip and scale. At present, some giants of technical ceramics have launched some chip semiconductor ceramic devices based on multi-layer ceramic technology, which have become high-end products in the field of sensitive devices.

In the process of electronic packaging, ceramic substrates are the key components, decreasing the defect rate of ceramic substrates is of self-evident importance for improving the quality of electronic devices. Due to without national or industry standards for ceramic substrate performance testing, which brings certain challenges to manufacturing. At present, the main inspection of finished ceramic substrate cover the visual inspection, mechanical properties inspection, thermal properties inspection, electrical properties inspection, packaging properties (working performance) checking and reliability inspection. Appearance Inspection The appearance inspection of ceramic substrates is regularly conducted by visual or optical microscopy, mainly including cracks, holes, scratches on surface of the metal layer, peeling, stains and other quality defects. In addition, the outline size of the substrates, the thickness of the metal layer, the warpage (camber) of the substrates, and the graphic accuracy of the substrate surface are needed to be tested. Especially for the use of flip-chip bonding, high-density packaging, the surface warpage is generally required to be less than 0.3% of dimensions. In recent years, with the continuous development of computer technology and image processing technology, manufacturing labor costs continue to rise, almost all manufacturers pay more and more attention to the application of artificial intelligence and machine vision technology in the transformation and upgrading of the manufacturing industry, and the detection methods and equipment based on machine vision have gradually become an important means to improve product quality and improve the yield. Therefore, the application of machine vision inspection equipment to the detection of ceramic substrate can improve the detection efficiency and reduce the labor cost accordingly. Mechanical Properties Inspection The mechanical properties of the ceramic substrate mainly refer to the bonding force of metal wire layer, indicating the bonding strength between the metal layer and the ceramic substrate, which directly determines the quality of the subsequent device package (solid strength and reliability, etc.). The bonding strength of ceramic substrates prepared by different methods is quite different, and the planar ceramic substrates prepared by high temperature process (such as TPC, DBC, etc.) are usually connected by chemical bonds between the metal layer and the ceramic substrate, and the bonding strength is high. In the ceramic substrate prepared by low temperature process (such as DPC substrate), the van der Waals force and mechanical bite force between the metal layer and the ceramic substrate are mainly, and the binding strength is low. Test methods for ceramic metallization strength onto substrate include: 1) Tape method: the tape is close to the surface of the metal layer, and the rubber roller is rolled on it to remove the bubbles in the bonding surface. After 10 seconds, pull the tape off with a tension perpendicular to the metal layer, and test whether the metal layer is removed from the substrate. Tape method is a qualitative test method. 2)Welding wire method: Select a metal wire with a diameter of 0.5mm or 1.0mm, weld directly on the metal layer of the substrate through solder melting, and then measure the pulling force of the metal wire along the vertical direction with a tension meter. 3)Peel strength method: The metal layer on the surface of the ceramic substrate is etched (cut) into 5mm~10mm strips, and then torn off in the vertical direction on the peel strength testing machine to test its peel strength. The stripping speed is required to be 50mm/min and the measurement frequency is 10 times /s. Thermal Properties Inspection The thermal properties of ceramic substrate mainly include thermal conductivity, heat resistance, thermal expansion coefficient and thermal resistance. Ceramic substrate mainly plays a heat dissipation role in device packaging, so its thermal conductivity is an important technical index. The heat resistance mainly tests whether the ceramic substrate is warped and deformed at high temperatures, whether the surface metal line layer is oxidized and discolored, foaming or delaminating, and whether the internal through hole fails. The thermal conductivity of the ceramic substrate is not only related to the material thermal conductivity of the ceramic substrate (body thermal resistance), but also closely related to the interface bonding of the material (interface contact thermal resistance). Therefore, the thermal resistance tester (which can measure the body thermal resistance and interface thermal resistance of multi-layer structure) can effectively evaluate the thermal conductivity of ceramic substrate. Electrical Properties Inspection The electrical performance of the ceramic substrate mainly refers to whether the metal layer on the front and back of the substrate is conductive (whether the quality of the internal through hole is good). Due to the small diameter of the through hole of the DPC ceramic substrate, there will be defects such as unfilled, porosity and so on when filling holes in electroplating, X-ray tester (qualitative, rapid) and flying needle tester (quantitative, cheap) can generally be used to evaluate the through hole quality of the ceramic substrate. Packaging Properties Inspection The packaging performance of ceramic substrate mainly refers to weldability and air tightness (limited to three-dimensional ceramic substrate). In order to improve the bonding strength of the lead wire, a layer of metal with good welding performance such as Au or Ag is generally electroplated or electroplated on the surface of the metal layer of the ceramic substrate (especially the welding pad) to prevent oxidation and improve the bonding quality of the lead wire. Weldability is generally measured by aluminum wire welding machines and tension meters. The chip is mounted on the 3D ceramic substrate cavity, and the cavity is sealed with a cover plate (metal or glass) to realize the airtight package of the device. The air tightness of the dam material and the welding material directly determines the air tightness of the device package, and the air tightness of the three-dimensional ceramic substrate prepared by different methods is different. The three dimensional ceramic substrate is mainly used to test the air tightness of the dam material and structure, and the main methods are fluorine gas bubble and helium mass spectrometer. Reliability Test and Analysis Reliability mainly tests the performance changes of ceramic substrate in a specific environment (high temperature, low temperature, high humidity, radiation, corrosion, high frequency vibration, etc.), including heat resistance, high temperature storage, high temperature cycle, thermal shock, corrosion resistance, corrosion resistance, high frequency vibration, etc. The failure samples can be analyzed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Scanning sound microscope (SAM) and X-Ray detector (X-ray) were used to analyze welding interfaces and defects.

With the progress and development of technology, the operating current, working temperature and frequency in devices have been gradually getting higher. In order to meet the dependability of devices and circuits, higher requirements have been put forward for chip carriers. Ceramic substrates are widely used in these fields because of their excellent thermal properties, microwave properties, mechanical properties and high reliability. At present, the main ceramic materials used in ceramic substrates are: alumina (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), silicon carbide (SiC) and beryllium oxide (BeO). Material Purity Thermal conductivity (W/k.m) Relative electrical constant Disruptive field intensity (KV/mm^(-1)) Brief Comments Al2O3 99% 29 9.7 10 Best cost performance, Much wider applications AlN 99% 150 8.9 15 Higher performance, with higher cost BeO 99% 310 6.4 10 Powder with highly toxic, Therefore,limit to use Si3N4 99% 106 9.4 100 Optimal overall performance SiC 99% 270 40 0.7 Only fit for low-frequency applications Let's see the brief characteristics of these 5 advanced ceramics for substrates as follows: 1. Alumina (Al2O3) Al2O3 homogenous polycrystals can reach more than 10 kinds, and the main crystal types are as follows :α-Al2O3, β-Al2O3, γ-Al2O3 and zta-al2o3. Among them, α-Al2O3 has the lowest activity and is the most stable among the four main crystal forms, and its unit cell is a pointed rhombohedron, belonging to the hexagonal crystal system. α-Al2O3 structure is tight, corundum structure, can exist stably at all temperatures; When the temperature reaches 1000 ~ 1600 ° C, other variants will irreversibly transform into α-Al2O3. Figure 1: Crystal microstruture of Al2O3 under SEM With the increase of Al2O3 mass fraction and the decrease of the corresponding glass phase mass fraction, the thermal conductivity of Al2O3 ceramics rises rapidly, and when the Al2O3 mass fraction reaches 99%, its thermal conductivity is doubled compared with that when the mass fraction is 90%. Although increasing the mass fraction of Al2O3 can improve the overall performance of ceramics, it also increases the sintering temperature of ceramics, which indirectly leads to an increase in production costs. 2. Aluminum Nitride(AlN) AlN is a kind of group ⅲ-V compound with wurtzite structure. Its unit cell is AlN4 tetrahedron, which belongs to hexagonal crystal system and has strong covalent bond, so it has excellent mechanical properties and high bending strength. Theoretically, its crystal density is 3.2611g/cm3, so it has high thermal conductivity, and the pure AlN crystal has a thermal conductivity of 320W/(m·k) at room temperature, and the thermal conductivity of the hot-pressed fired AlN substrate can reach 150W/(m·K), which is more than 5 times that of Al2O3. The thermal expansion coefficient is 3.8×10-6 ~ 4.4×10-6/℃, which is well matched with the thermal expansion coefficient of semiconductor chip materials such as Si, SiC and GaAs. Figure 2: Powder of aluminum nitride AlN ceramics have higher thermal conductivity than Al2O3 ceramics, which gradually replaces Al2O3 ceramics in high-power power electronics and other devices requiring high heat conduction, and has broad application prospects. AlN ceramics are also considered as the preferred material for the energy delivery window of power vacuum electronic devices due to their low secondary electron emission coefficient. 3. Silicon Nitride (Si3N4) Si3N4 is a covalently bonded compound with three crystal structures :α-Si3N4, β-Si3N4, and γ-Si3N4. Among them, α-Si3N4 and β-Si3N4 are the most common crystal forms, with hexagonal structure. The thermal conductivity of single crystal Si3N4 can reach 400W/(m·K). However, due to its phonon heat transfer, there are lattice defects such as vacancy and dislocation in the actual lattice, and impurities cause phonon scattering to increase, so the thermal conductivity of the actual fired ceramics is only about 20W/(m·K). By optimizing the proportion and sintering process, the thermal conductivity has reached 106W/(m·K). The thermal expansion coefficient of Si3N4 is about 3.0×10-6/ C, which is well matched with Si, SiC and GaAs materials, making Si3N4 ceramics an attractive ceramic substrate material for high thermal conductivity electronic devices. Figure 3: Powder of silicon nitride Among the existing ceramic substrates, Si3N4 ceramic substrates are considered to be the best ceramic materials with excellent properties such as high hardness, high mechanical strength, high temperature resistance and thermal stability, low dielectric constant and dielectric loss, wear resistance and corrosion resistance. At present, it is favored in IGBT module packaging and gradually replaces Al2O3 and AlN ceramic substrates. 4.Silicon Carbide(SiC) Single crystal SiC is known as the third generation semiconductor material, which has the advantages of large band gap, high breakdown voltage, high thermal conductivity and high electron saturation speed. Figure 4: Powder of silicon carbide By adding a small amount of BeO and B2O3 to SiC to increase its resistivity, and then adding the corresponding sintering additives in the temperature above 1900℃ using hot pressing sintering, you can prepare the density of more than 98% of SiC ceramics. The thermal conductivity of SiC ceramics with different purity prepared by different sintering methods and additives is 100 ~ 490W/(m·K) at room temperature. Because the dielectric constant of SiC ceramics is very large, it is only suitable for low-frequency applications, and is not suitable for high-frequency applications. 5. Beryllia (BeO) The BeO is wurtzite structure and the cell is cubic crystal system. Its thermal conductivity is very high, BeO mass fraction of 99% BeO ceramics, at room temperature, its thermal conductivity (thermal conductivity) can reach 310W/(m·K), about 10 times the thermal conductivity of the same purity Al2O3 ceramics. Not only has a very high heat transfer capacity, but also has low dielectric constant and dielectric loss and high insulation and mechanical properties, BeO ceramics are the preferred material in the application of high-power devices and circuits requiring high thermal conductivity. Figure 5: Crystal structure of beryllia The high thermal conductivity and low loss characteristics of BeO are so far unmatched by other ceramic materials, but BeO has very obvious shortcomings, and its powder is highly toxic. At present, the commonly used ceramic substrate materials in China are mainly Al2O3, AlN and Si3N4. The ceramic substrate made by LTCC technology can integrate passive components such as resistors, capacitors and inductors in the three-dimensional structure. In contrast to the integration of semiconductors, which are primarily active devices, LTCC has high-density 3D interconnect wiring capabilities.

Alumina (Al2O3) substrate is currently the most widely used, the most economical and effective ceramic substrate material. It offers excellent electrical insulation, chemical stability, high thermal conductivity, high frequency and other ideal comprehensive performance. In the field of automative industry, the demand for alumina ceramic substrates have been increasing year by year due to the rapid development of the industry. 1. The application of alumina ceramic substrate in the automotive industry 1.1 IGBT Packaging IGBT is one of dominant device in modern power electronic devices, and is internationally recognized as a most representative product of the third revolution of power electronic technology. IGBT is the core device of energy conversion and transmission, which can adjust the voltage, current, frequency, phase, etc. in the circuit according to the signal instructions, and is mainly used in the automobile manufacturing for motor controllers, vehicle air conditioners. In traditional IGBT modules, precision alumina ceramic substrate is the most universally used substrate. However, due to the relatively low thermal conductivity of al2o3 ceramic substrate and the poor match with the thermal expansion coefficient of silicon, it is not suitable for high power module packaging materials. 1.2 Sensor chip package Automotive sensors require the parts are that they can be applied to the harsh environment ((high temperature, low temperature, vibration, acceleration, humidity, noise, exhaust gas) unique to automobiles for a long time , as well as should have light weight, good reusability strength, and wide output range. Aluminum oxide ceramic substrate could perfectly withstand high-temperature, corrosion, abrasive and its potential excellent electromagnetic and optical functions, in recent years with the progress of manufacturing technology has been fully utilized, the sensors in alumina ceramic materials can fully meet the above requirements, representing the application of lidar, camera, millimeter wave radar and so on. 1.3 LED Packaging In recent years, LED lighting technology has been far and wide used in automobile manufacturing, such as headlights, taillights, indicators, atmosphere lights, display backlights and so on. The higher power of the LED, the more attention needs to be paid to its heat dissipation problem - if the heat generated by the LED operation can not be effectively dispersed, it will result in the LED junction temperature too high, not only leading to the rapid decay of the LED luminous efficiency, but also the life of the LED device. At present, the use of alumina ceramic substrate is not only low cost, but also can efficiently and environmentally friendly production of high power, high precision, low cost, high adhesion, high surface flatness of LED ceramic cooling substrate, so it has been exstensively used in the LED field. 2. Quality Points of Alumina Ceramic Substrate Although alumina ceramics can meet the rigid supporting requirements and the function of environmental erosion resistance,its theoretical and actual thermal conductivity are low, improving the quality of the substrate product is necessary in order to better meet the requirements of the development of the electronics industry, optimizing the quality of raw material Al2O3 powder, enhancing the value of properties, and choosing first-rank manufacturing process are adopted. 2.1 Raw Material Preparation Through long-term research and production applications, Al2O3 purity, α-phase content, crystal morphology, particle size distribution and other indicators have a great impact on the quality of substrate products. Therefore, the general requirements are: ●Na2O content is less than 0.1%, minimize Fe, Fe2O, H2O content; ●The optimal crystal morphology to be spherical; ●The α-phase conversion of raw alumina should be controlled appropriately and maintained stable; ●Alumina should be fully ground to reduce agglomerated particles. 2.2 Manufacturing Process In addition to the selection of raw materials, the forming and sintering process is also a key factor in determining success or failure. In terms of molding technology, injection molding, dry press molding and casting molding are commonly used, but the efficiency of injection molding is high, but it is difficult to make large-size sheet; The product density of dry pressing is high, the flatness of the substrate is easy to guarantee, but the production efficiency is low, the cost is high, and the preparation of ultra-thin substrate is difficult. Casting is a double advantage of high production efficiency and ultra-thin, but it is easy to deform during sintering because of the low density of the billet. Therefore, in order to improve the rate of excellent products of large-size substrates, the industry is focusing on the optimization of sintering methods and the selection of sintering additives. 3.Conclusion In short, at the present stage of automotive research and development and production stage has been more and more alumina ceramic substrate materials, but if in the future automotive manufacturing industry will be more alumina ceramic substrate, intelligent ceramic products are introduced and used in the automobile, in many aspects of alumina ceramic raw materials, material evaluation and utilization technology need to continue to be studied.

1. Why is Ultrafine Ceramic Fiber Material a Strategic Raw Material? Thermal protection materials are protective materials for daliy life, industrial production and military fields, which need to protect service components working under high temperature or ultra-high temperature conditions to avoid damage or destruction. The thermal resistance principle of the ultra-fine ceramic fiber felt is the no convection effect, infinite shielding plate effect and infinite path effect brought by its distinctive structure. The heat insulation principle is as follows: 1) No convection effect, the porosity of the ultra-fine ceramic fiber heat insulation felt is nano, and the internal air can`t flow freely; 2) Infinite shielding plate effect, nano-scale porosity, infinite porosity wall, minimizing radiation heat transfer to the lowest; 3) Infinite-length path effect, heat conduction occurs along the stomatal wall with the infinite nanoscale stomatal wall. Due to its unique structure, the ultra-fine ceramic fiber thermal insulation felt has shown excellent performance in many fields such as thermal, acoustics, optics, electricity, mechanics, etc., and has good application prospects in new energy vehicles, aerospace, military, energy and other fields. In the field of new energy vehicles, ultra-fine ceramic fiber thermal insulation felt as a key material for passive protection systems. It is mainly used for physical isolation between battery cells, battery modules and battery packs. In the field of aerospace and military industries, ultrafine ceramic fiber is the vital basic raw material of advanced ceramic composite materials,that's why it is a strategic raw material in the aerospace field and other extreme harsh service environments. 2.Superfine Ceramic Spinning Material Industry Manufacturing Technology Based on the completely independently developed microfiber spinning industrialization manfacuturing technology, matching equipment and process, the technology of macropreparation of microfiber materials with length to diameter ratio ≥1000 based on gas spinning has been developed. The gas spinning technology uses high-speed air flow to shear and deform the solution (molten liquid), the droplet surface forms a jet, and wind shear and stretch to prepare microfibers. The prepared fiber diameter can be adjusted in the range of 100nm-1000nm. High-speed air spinning technology is suitable for the efficient, controllable and large-scale preparation and production of microfibers in a variety of material systems. It is not only suitable for the manufacture of various polymer microfibers, but also for the manufacture of multi-system microfibers such as metal base and ceramic base. It can quickly improve the production efficiency of microfiber and reduce the unit cost of product. Ceramic fiber cotton with a diameter as low as 100 nanometers, pure inorganic material, maintains good flexibility and elasticity under ultra-high and ultra-low temperature conditions, has no pulverization and slag removal, and has excellent compression fatigue resistance, excellent adiabatic performance and high temperature stability. At present, the technology is applied to polymer microfibers and filter materials in high-end air filtration, water filtration and other fields; Ceramic microfibers and products for high temperature ultra-light heat insulation in the field of new energy batteries and aerospace; Carbon microfiber fluid collector and electrode materials for electrochemical energy storage fields such as lithium power; Silver microfibers and transparent electrodes for flexible electronics; Technical breakthroughs have been achieved in the fields of functional microfibers for uranium extraction from seawater. 3. Prime Application Fields of Superfine Ceramic Fiber Material In the civil aspect, ultrafine ceramic fiber materials can be widely used in new energy vehicle protection, power battery safety protection, energy storage battery safety protection, industrial pipeline energy conservation and insulation, building energy conservation, biomedical fields and other industries and fields. In the field of defense and aerospace, reliable thermal protection system is one of the key systems for safe flight of high-performance spacecraft, and the design of thermal protection structure and the selection of thermal protection materials are the key to the design and development of thermal protection system. Ultrafine ceramic fiber material is one of the main materials for thermal protection of aerospace aircraft because of its excellent properties of high temperature resistance, corrosion resistance and heat insulation. As a high-temperature insulation material, it has a huge market prospect in aerospace, aviation and military industries.

According to the Maxmize Market Research's data, the global ceramic substrate market size in 2021 reached 6.59 billion US dollars, will grow at an average annual rate of about 6.57%, and is expected to reach 10.96 billion US dollars in 2029. As an ideal material for ceramic substrate, aluminum nitride ceramic has a broad range of market, and different product types meet the needs of different applications, among which DBC, DPC,AMB,HTCC and structural ceramic parts are the main product types. Due to the rapid development of new energy and electric vehicles, AMB and DBC metallized substrates have risen strongly in the application of IGBT; DPC is favored by high-power LED market; HTCC because of radio frequency, military industry to drive demand growth; The electrostatic sucker used in semiconductor silicon wafers is an important application of lN structural parts. AlN demand will continue to benefit from the fast-growing semiconductor and new energy markets. With the rapid development of the electronics industry in recent years, the market demand for aluminum nitride powder in China is growing rapidly, and the demand for aluminum nitride powder in China will maintain a growth rate of about 15%, and the domestic market demand will be about 5,600 tons by 2025. The domestic production of aluminum nitride can not meet the market demand, and the powder relies heavily on imports. However, with the deepening of domestic research, aluminum nitride preparation technology continues to improve, the gap at home and abroad is gradually narrowing, and with the strong support of China's policy and the continuous expansion of market demand, the domestic powder industry is advancing to high quality. The following article will explain why aluminum nitride materials can stand out in the advanced ceramics' family. 1. The Outstanding Advantages of Aluminum Nitride : Because of its excellent thermal conductivity and thermal expansion coefficient matching silicon, aluminum nitride has become a concerned material in the field of electronics. Aluminum nitride is a hexagonal crystalline zincite covalent bonding compound with excellent thermal conductivity, reliable electrical insulation, low dielectric constant and dielectric loss, resistance to plasma erosion, non-toxic and matching thermal expansion coefficient with silicon. It is not only an ideal material for the packaging of a new generation of heat dissipating substrates and electronic devices, but also for heat exchangers, piezoelectric ceramics and thin films, thermal conductive fillers, aluminum nitride etching shields, aluminum nitride evaporation boats for OLED, etc., with broad application prospects. The microstructural of aluminum nitride determines its excellent thermal conductivity and insulation, refer to figure 1. According to the study "Casting Forming and Sintering Properties of Aluminum nitride Ceramics", due to the small atomic weight of the two elements composed of aluminum nitride molecules, relatively simple crystal structure, good harmonic property, the formed Al-N bond length, bond energy, and covalent bond resonance is favorable to phonon heat transfer mechanism. So that A lN material has excellent thermal conductivity than the general non-metallic materials, in addition, A lN has high melting point, high hardness and high thermal conductivity, and better dielectric properties. 2. The Conducive Strength of Aluminum Nitride According to the research of "New Progress in the study of the influencing Factors of the thermal conductivity and bending strength of A-LN Ceramics", A-LN has been widely concerned because of its high matching coefficient of thermal expansion with Si, while traditional substrate materials such as Al2O3 are widely concerned because of their low thermal conductivity. Its value is about 1/5 of A lN ceramics and the linear expansion coefficient does not match Si, which can not meet the actual demand, refer to the figure 2. The thermal conductivity of BeO and SiC ceramic substrate is also relatively high, but the toxicity of BeO is high and the insulation of SiC is poor. As A new type of high thermal conductivity ceramic material, A lN has the characteristics of thermal expansion coefficient close to Si, excellent dissipative heat performance, non-toxic, etc., and is expected to become an excellent material to replace the ceramic substrate Al2O3, SiC and BeO for electronic industry, refer to the following table for technical data. sheet of several technical ceramics Property AlN Al2O3 SiC BeO Density (g/cc) 3.26 3.9 3.12 2.9 Thermal conductivity (W/m.k at 25℃) 170~320 20~31 50~270 150~270 Average Coefficient of thermal expansion (1×10-6/℃) 4.4 8.8 5.2 9.0 Specific heat 1 x 10^3 J/(kg·K) 0.75 0.75 - 1.046 Mohs Hardness ( GPa) 9 9 9.2~9.5 9 Flexural strength (MPa) 300~500 300~400 350~450 20~40 Dielectric constant (1Mhz) 8.8 9.3 40 6.7 Volume resistivity (ohm.cm at 25℃) ＞1 x 10^14 ＞1 x 10^14 ＞1 x 10^15 ＞1 x 10^14 Toxic or not No No Yes No Jinghui Industry is a professional manufacturer of technical ceramics', we are dedicated to producing various of precision ceramic components more than 15 years. We believe you'll find an ideal solutions hereby for your project.

Showing Strength with Data & Winning Praise with Results IACE CHINA is a flagship exposition in the global powder metallurgy industry.It has grown from several hundred square meter since its establishment in 2008 to 40,000㎡ by 2023, expanding at an average annual growth rate of 30%, and has wide international reputation and global influence. The previous exhibition (2023) gathered 761 exhibitors from China, Untied Stated, Germany, France, Japan, The united Kingdom, Russia, Italy, Sweden, Switzerland, the Netherlands, etc. During the 3-days exhibition, a total of 54,506 professional visitors were received, coming from 42 countries and regions including Japan, South Korea, India, North Korea, Singapore, Russia, Germany, the United Stated, Canada, Australia, Argentina, Taiwan, HongKong and so on. It`s expected that the exhibition area of IACE CHINA 2024 will exceed 45,000 square meters, with about 900 global exhibitors and over than 1,500 exhibiting brands.The number of visitors is expected to reach over 65,000 from worldwide. Convergence of Famous Enterprises, Lead The Trend of The Industry As the world`s leading industry exhibition, IACE China builds a high-quality platform of technical exchanges and business cooperation, bringing together excellent enterprises and industry elites at home and abroad to share leading cutting-edge technologies as well as innovative applications and solutions, and injecting tremendous momentum into the high-quality development of the industry. Gathering of Industry Leaders, Empowering Multi-dimensional Upgrading During the exhibition, a number of high-quality forums will be held concurrently, inviting more than 100 speakers including academicians, professors, and business executives to deliver keynote speeches, sharing frontier views from the perspectives of the latest technological processes, industry solutions, innovative applications, industrial policy guidance, future trends and development, etc., and deconstructing advanced technologies in multiple dimensions as well as analyzing the market prospects in multiple aspects. Abundant exhibits, a full range of upstream and downstream products Where you can not only find partners and solutions, but also learn the trends of industry and cutting-edge technologies.

Aluminum nitride (ALN)ceramic, which is a advanced ceramic, has a series of brilliant characteristics, the core advantages are superb thermal conductivity, reliable electrical insulation, and that is similar to thermal expansion coefficient of silicon (Si), what fields it can be applied in? 1. Heat Dissipation Substrate and Electronic Device Packaging Heat dissipating substrates and electronic device packaging are the main applications of aluminum nitride ceramics. Thanks to excellent thermal conductivity, thermal expansion coefficient close to silicon, high mechanical strength, good chemical stability and environmental protection and non-toxic of AIN ceramics, It is considered to be an ideal heat transfer and spreader material of new generation of thermal substrate and electronic device packaging, very suitable for mixed power switch packaging and microwave vacuum tube package, but also the ideal material for large-scale integrated circuit substrate. 2. Structural Ceramics Electrostatic vacuum chuck for wafer processing are a common application of a structural ceramic. Aluminum nitride structure ceramics have good mechanical properties, high hardness, toughness better than Al2O3 ceramics, and high temperature and corrosion resistance. Using AIN ceramic heat resistance and corrosion resistance, it can be used to make crucible, evaporation pan and other high temperature corrosion resistance parts. 3. Functional Materials Aluminum nitride can be used to manufacture high-frequency and high-power devices with at high temperatures or in the presence of certain radiation conditions, such as high-power electronics and high-density solid-state memory. As one of the third generation semiconductor materials, aluminum nitride has not only broad-band gap, high thermal conductivity, high resistivity, but also good ultraviolet transmittance, high breakdown field strength and so on. AlN has a band-gap of 6.2eV and strong polarization effect. It is widely used in mechanical, microelectronics, optics and SAW manufacturing, high frequency broadband communication fields, such as aluminum nitride piezoelectric ceramic parts and ceramic films. In addition, high-purity AlN ceramics are transparent and such material has excellent optical properties with combination of their electrical properties, They are extensively used as functional components such as infrared deflectors and sensors. 4. Inert Heat-resistant Material As a heat-resistant material, AlN can be used to make crucible, protective tube, casting mold, etc. Aluminum nitride can be in 2000℃ non-oxidizing atmosphere, still has stable performance, is an excellent high temperature refractory material, resistant to molten metal erosion ability. 5. Heat Exchange Device Aluminum nitride ceramics have high thermal conductivity, low thermal expansion coefficient, excellent thermal conductivity efficiency and thermal shock resistance, and can be used as thermal shock and heat exchange materials, such as aluminum nitride ceramics can be used as heat exchange equipment materials for Marine gas turbines and heat resistant components of internal combustion engines. Due to the excellent thermal conductivity of aluminum nitride material, the heat transfer capacity of heat exchanger is effectively improved. 6. Filling Material Aluminum nitride has excellent electrical insulation, high thermal conductivity, good dielectric properties, good compatibility with polymer materials, is an excellent additive of polymer materials for electronic products, can be used in TIM filler, FCCL thermal dielectric layer filler, widely used in electronic devices heat transfer medium, thereby improving work efficiency. For example, the heat transfer medium at the gap between the CPU and the radiator, the high-power transistor and the thyristor element in contact with the substrate. JingHui Industry is a professional manufacturing for making aluminum nitride ceramics, the AlN products we supplied mainly cover ceramic substrates, ceramic heat sinks and AlN structural ceramic parts with high accuracy dimensional.

Ceramic disc taps are often used in bathroom sealing switches. Ceramic seal rings are composed of a moving sheet and a static sheet and become the core functional component of the sealing component. Compared with traditional rubber seals, ceramic seals are more durable and have better sealing performance. However, ceramic seals can still wear out over time. The two contact surfaces of the moving sheet and the static sheet are originally very smooth surfaces, which can evacuate the gas in the middle and form a vacuum to form a close fit. In theory, there is no wear. In reality, the ceramic sealing plate wears out. The main reason is the water inevitably contains impurities and particulate matter of various sizes. When the ceramic valves is turned on and off, these particulate matter will accumulate to varying degrees on the high polishing ceramic seal faces under the action of water pressure. At the same time, these particles will also enter the surface between the moving plate and the static plate, and is squeezed and rubbed by the two sheets, thereby causing friction with the surface of the sealing plate, causing the surface of the sealing plate to gradually wear. Wear will cause the sealing performance of the ceramic sealing disc to decrease, which may cause the faucet to leak. When a faucet leaks, it usually needs to be repaired by replacing the ceramic seal. However, ceramic seals wear more slowly than rubber seals. they are usually 95% Alumina ceramic disc, which has higher hardness and wear resistance and can better resist friction and wear. Therefore, ceramic seals usually have a longer service life than rubber seals. In order to extend the service life of the ceramic sealing disc, the following measures can be taken: 1. Clean the faucet regularly to prevent impurities and particulate matter from adhering to the surface of the ceramic seal and reduce wear. 2. Avoid turning the faucet on and off with excessive force to reduce the stamping friction on the surface of the ceramic sealing disc. 3. Regularly check whether the faucet is leaking. If there is water leakage, replace the ceramic seal in time. In short, although the ceramic sealing disc is relatively wear-resistant, it will still wear out during long-term use. What we need to pay attention to is that through the above measures, we can extend its service life and maintain good sealing performance.

Why Can Aluminum Nitride Ceramic Substrate Stand Out? 1. With the increasing requirements of performance for power modules, alumina (Al2O3) or aluminum nitride (AlN) ceramic substrates are no longer the best choice for the function of heat transfer and dissipation, and more and more designers have begun to consider using more advanced ceramic materials instead. For example, in the application of new energy vehicles (xEV), when the chip temperature rises from 150°C to 200°C, its switching loss will be reduced by 10% accordingly. In addition, new packaging technologies such as brazing and leadless modules also put forward more rigorous requirements on internal material parts. 2. Prolonging service life in harsh environments is another driving factor for the iteration of materials. Like wind turbines, the expected service life of the wind turbine is 15 years without any failures in all environmental conditions. As a result, wind turbine designers have been also trying to improve substrate technology. The third actuator for improving ceramic substrate is the use of silicon carbide components (SiC). The first modules using silicon carbide with optimized packaging technology reduce losses by 40% to 70% compared to conventional ones, but the latter needs to be combined with new packaging material such as silicon nitride (Si3N4) substrates. These trends reveals the limit the use of traditional alumina and aluminum nitride substrates in the future, and silicon nitride based substrates will become the preferred choice for high-reliability power module designers in the future. Outstanding Strength of Silicon Nitride Substrates Due to its outstanding thermal conductivity and thermal expansion coefficient close to the chip, as well as excellent bending strength and high fracture toughness, silicon nitride is very suitable for producing substrate products in the field of power electronics. The characteristics of silicon nitride ceramics and the detailed comparison of key values such as partial discharge or crack growth say that they have significant effect on the performance of the thermal conductivity and thermal cycle of the substrate. 1. Comparison between silicon nitride and other advanced ceramics When selecting insulation materials for power modules, the material characteristics that need to be considered mainly include thermal conductivity, bending strength and fracture toughness. High thermal conductivity is essential for fast heat dissipation of power modules. At the same time, the bending strength is very important for the processing and use of ceramic substrates in the packaging process, and that the fracture toughness is the key to predicting reliability. 96% alumina (Al2O3) Aluminum nitride (AlN) 9% Zirconia toughen alumina (9% ZTA) Silicon nitride (Si3N4) Thermal conductivity (W/m.K) 24 180 280 90 Bending strength (MPa) 450 450 700 650 Fracture toughness (MPa/√m) 3.8~4.2 3.0~3.4 4.5~5 6.5~7 Figure 1: Technical datasheet of advanced ceramics A.Alumina (96%) has low thermal conductivity and low mechanical value. However, the thermal conductivity of 24 W/mK is sufficient for most previous standard industrial applications. B. The biggest advantage of aluminum nitride is that it has a very high thermal conductivity (180 W/mK), but its reliability is only moderate. This is because the fracture toughness of aluminum nitride is low, and the bending strength is similar to that of alumina. C. In view of the increasing demand for higher reliability, zirconia toughened alumina (ZTA) ceramic materials came into being. These ceramic materials have higher flexural strength and fracture toughness, but their thermal conductivity is comparable to standard alumina. As a result, the former has limited use in high-power applications with the highest power density. D. Looking at the table, silicon nitride perfectly combines high thermal conductivity and high mechanical properties. It has a thermal conductivity of 90 W/mK and the highest high fracture toughness (6,5-7 [MPa / √m]). Silicon nitride These characteristics will make it the most reliable metallization substrate option. 2. Reliability The reliability of various metallized substrates was tested by passive thermal cycling. All substrate combinations are listed in Table 2. All combinations use the same design, including the same copper thickness (d(Cu)= 0.3mm). Other design features such as pitting or gradient etching are not used to improve reliability. The detection conditions are as follows: · Double cavity detection system · Thermal conductivity =205 K (-55°C to +150°C) · Exposure time: 15 min · Tilt heating time < 10 s In addition, different samples were examined by ultrasonic microscopy to detect stratification and conchoidal rupture: Alumina, 9% zirconia toughened alumina and aluminum nitride directly bonded to copper substrate: after 5 cycles per cycle Silicon nitride active metal brazing (AMB) : after 50 cycles Front surface copper (mm) Ceramic (mm) Back side copper (mm) Thermal cycle (1 cycle) Al2O3 DCB Substrate 0.30 0.38 0.30 55 9% ZTA DCB Substrate 0.30 0.32 0.30 110 AlN DCB Substrate 0.30 0.635 0.30 35 Si3N4 DCB Substrate 0.30 0.32 0.30 5000 Figure 2: Thermal cycle parameters of advanced ceramics A. Conch rupture is A typical failure mode in temperature cycling and has been detected in aluminum oxide, 9% zirconia toughened aluminum oxide and aluminum nitride directly bonded copper substrates. In general, the reason for the occurrence of conch rupture is that the coefficient of thermal expansion of copper and ceramics is different when the temperature changes. B. In 35 thermal cycles, the reliability of aluminum nitride directly bonded copper substrate is the worst. Among all ceramic materials, aluminum nitride directly bonded copper substrates have the lowest measured fracture toughness (K1C=3-3,4 [MPa /√m]), which may explain the above findings. The results of aluminum oxide directly bonded to copper substrate after 55 cycles are very close to these results. Among conventional materials, 9% zirconia doped directly bonded copper substrates have the best performance, and their reliability is twice that of standard alumina materials (110 cycles). C. No failure was detected in the silicon nitride active metal brazing sample after 5000 cycles. Compared with 9% zirconia toughened alumina directly bonded copper substrate, the reliability is 45 times higher. The excellent result of 5000 thermal cycles is due to the high fracture toughness of silicon nitride (K1C=6,5-7 [MPa / √m]), although its bending strength is slightly lower than 9% doped zirconia (650 MPa and 700 MPa). These results show that the flexural strength of the ceramic material used to fabricate the metallized substrate is not a key factor in determining the service life of the substrate. For reliability prediction, fracture toughness is the most important physical property of ceramic materials. Figure 3: Failure Ultrasonoscopy of 9% ZTA DBC substrate Figure 3: The main difference of failure mechanism between 9% zirconia toughened alumina directly bonded copper substrate and silicon nitride active metal brazing after multiple thermal cycles. Figure 4: Failure Mode Ultrasonoscopy of Si3N4 DBC Substrate After more than 5,000 cycles, the silicon nitride ceramic material remained intact.It can be seen in Figures 3 and 4 that after more than 5000 cycles, a conch-like rupture has occurred in 9% zirconia toughened alumina ceramic material,while the silicon nitride ceramic material is still intact. 3. Thermal characteristics The thermal resistance coefficients (Rth) of five sets of metallized substrate samples were measured below. The measurement setup is shown in Figure 5. Figure 5:Thermal resistance test result Figure 5 shows the results of the thermal resistance test. All samples involved in thermal resistance analysis were flanked by a 0.3mm thick copper layer. As expected, the substrate using 0.63 mm thick alumina has the highest thermal resistance coefficient. This is due to the low thermal conductivity of alumina (24W/mK). A. The thermal resistance coefficients of 0.32mm thick 9% zirconia toughened alumina directly bonded copper substrate and 0.32mm alumina directly bonded copper substrate belong to the same range. B. Even if the thickness of the ceramic layer used is 0.63 mm, the thermal resistance coefficient of the aluminum nitride directly bonded copper substrate with the highest thermal conductivity (180 W/mK) is the lowest. C. The thermal conductivity of silicon nitride is half that of aluminum nitride (90W/mK), which also explains why the silicon nitride active metal brazing with half the ceramic thickness has the same thermal resistance coefficient as the silicon nitride directly bonded copper substrate (silicon nitride is 0.32mm and aluminum nitride is 0.63mm). Conclusion High-strength silicon nitride insulation meets the growing demand for longer service life and higher thermal performance of power modules. A comparative investigation of the silicon nitride active metal brazing technology and the traditional 9% zirconia toughened alumina directly bonded copper substrate ceramic material shows that the reliability of silicon nitride is 50 times that of the latter. The superior mechanical properties of silicon nitride ceramic materials, especially the extremely high fracture toughness (K1), effectively improve their reliability. In addition, the higher flexural strength of silicon nitride allows it to be used in thinner cross sections, and its thermal properties are comparable to those of aluminum nitride.

The importance of polishing is totally self-evident in the manufacturing of advanced ceramics, where it plays a critical role in the performance,quality and appearance of the finished products. Polishing purpose is to minimize & remove visual defects, burrs, particles and other non-uniformity on the surface of ceramic parts, so that the ceramic surface would be more flat and smooth to further improve the appearance quality of fine ceramic products in the practical applications. Polishing can have positive effects on the following aspects of advanced ceramics: ① Surface Roughness: It can remove the roughness and unevenness of the surface of the ceramic material to achieve a higher surface finish. This is critical for applications such as optical components, laser components, semiconductor ceramics, etc., because the surface roughness will directly affects the optical performance and accuracy of beam path. For example, the importance of polishing for optical ceramics is appearance. As an advanced material used in the optical field, the surface quality and properties of optical ceramics definitely impact their functions and applications of final devices. The importance of polishing is that it can improve optical quality, reduce light scattering and reflection, enhance light transmittance and transmission performance, as well as maintain long-term optical stability. Further polishing can also elevate the wear resistance and corrosion resistance of optical ceramics, and enhance its stability and durability in harsh environments. These outstanding characteristics enable optical ceramics to perform well in the fields of optical devices, laser technology, optical communication and optical sensing, meeting the needs of high precision, high definition and demanding optical applications. ② Size and Shape Accuracy: To help ceramic products achieve rigorous size and shape accuracy. By controlling the processing parameters and technology in the polishing process, the precise machining and fine tuning of ceramic products can be realized to ensure that they meet the design requirements. ③ Surface Flatness: eliminate the bumps and depressions on the surface of ceramic products to improve the surface flatness. The improvement of the surface flatness can reduce the contact pressure and friction between the grinding media and the product surface, and reduce the wear and abrasive cutting effect on the ceramic. Therefore, polished ceramic products with a more flat surface usually have better wear resistance. This is critical for applications that require highly flat surfaces such as precision ceramic structural parts, ceramic seal components, etc., to ensure their performance and reliability. ④ Other Surface Quality and Wear Resistance: polishing can improve the surface quality of ceramic products, making them smoother and more delicate. Smooth surfaces reduce frictional resistance and adhesion with collaborative parts , reducing wear and abrasive damage. Polishing can also eliminate the microscopic sharp edges and roughness of the surface, reduce the embedding and scraping of particles, and improve wear resistance. This is particularly important for some applications that require wear resistance and fatigue resistance, such as ceramic bearings and ceramic cutting tools. Our facility offer a selection of polishing approach for technical ceramics, the best level after polishing treatment can be Ra0.05.

2. The Defects of Nickle (Ni) Coating: (1) Sintering and blistering of nickel plating layer; The prime reasons are: a. After sintering, due to long time exposure to the air of the metallized layer and the surface layer is easy to be slightly oxidized, resulting in bubbles after sintering of the coating; b. Metallized layer pollution, plating solution is polluted; c. When electroplating, the initial current density is too large; Improvement methods mainly include as follows: a. After metallization, the porcelain should be kept clean and arrange nickel plating process as soon as possible; b. Regularly check and adjust the plating solution; c. When electroplating, the initial current is appropriately reduced (for example, it is 2/3 to 3/4 of the normal electroplating current density). (2) The root cause for rough surface after the nickel plating as the following a. Excessive ampere density and too fast deposition rate of nickel ion; b. Too high sintering temperature of the metallized layer may form Mo-Ni alloy already; c. The composition of the electroplate liquid changes; The improvement methods are to reduce electroplating current density, to reduce sintering temperature and test & re- treat electroplating solution. 3. Defects of Finished Metallized Ceramics: 1). Black spots and yellow spots appear on surface of metallized ceramic parts for the following reasons: a. Crystals (impurities of ceramic compound) such as calcium-aluminum feldspar are transformed into gray spots under the condition of long-term heat treatment at high temperature due to phase change. b. There are more variable valence ions in advanced ceramics, such as Ti, Fe, Mn, etc., which are easy to produce black & yellow spots under high temperature and strong reduction conditions; The main improvement method as below: a. Shorten the high temperature heating time as much as possible, b. Meticulously select the raw materials for technical ceramics in the production c. And adjust the ceramic composition properly. 2). The below factors are for what the surface of the metallized porcelain is getting gray and black: a. The metallized layer and molybdenum wire heater are oxidized seriously, which resulting in blacken ceramic surface; b. The serious pollution of furnace chamfer & furnace tube, and the material volatilization, especially carbon deposition, make the black ceramic surface; d. Ceramic setter plate, corundum sintering media and too many multiply use of these auxiliary material are resulting in volatilization of adsorption. Improvement measures are not only to control the production of molybdenum oxide, but also to avoid the deposition of carbon, furnace tubes, furnaces chamfer, ceramic setter plate etc., should be cleaned and replaced periodically. 3). After metallization, there are the following reasons which result in deformation and cracking of ceramic parts: a. The thin wall thickness, the uneven wall thickness, and significant change of regional wall thickness are mostly easy to cause deformation or cracking; b. The product is easy to deform when placed uneven in the ceramic sagger tray ; c. Both oversintering and too long holding time in the furnace are easy to cause deformation. d. Changes in the composition of ceramic materials; e. The furnace heating rate and cooling speed are too fast, which will also cause ceramic parts to crack; In order to prevent such defects as cracking and deformation, the first is to select quality fired ceramic parts, rationally design the structural shape, reduce stress concentration, and try to be uniform in thickness. In the process, the heating and cooling rate should be proper, and the atmosphere of metallizing should be adjusted. When placing ceramic components on ceramic setter plate and sagger tray, it should be properly fixed and as flat as possible according to the shape and complexity of the structure. JingHui Industry Ltd is a professional manufacturer of metallized ceramics, the comprehensive production capabilities and skillful, veteran & well-trained manufacturing team is our core competition, every pieces flow to our customer must be inspected rigorously to reach fix theirs challenge.

The sintered metal powder method is the earliest, most mature and widely used process among ceramic-to-metal sealing processes. So far, the most of R&D institutes and manufacturing facilities of vacuum electronic devices use this process at home and abroad. The vast majority of these companies utilize the Mo-Mn formulation, so it is usually also called the Mo-Mn method, the ceramic parts after metallizing process with high-temperature cure are called as metallized ceramics. In order to make the solder wettability on the metallized layer as well as form a barrier layer, an additional coating of nickel is electroplated on the metallized surface. Metallized ceramics play a very critical roles in vacuum electronics technology, the typical usage as followings: Laser applications: RF feedthroughs, Electrical feedthroughs, Pinch off tubes. Medical applications: Scanners, imaging system, electrode and sensors. Aerospace applications: Satellite propulsion and engine management as high-temp structural parts. Energy storage applications: Optoelectronics and power tubes, Gas lasers, Deep Sea repeaters, Rechargeable batteries; X-ray applications: Electrosurgical instrumentation, Implantable packages and feedthroughs, Mass spectrometry, Gas detectors, Microscopes (TEM, SEM), High voltage feedthrough; The Mo-Mn method of ceramic metallization is related to many procedures; thus, the manufacturing process is much complicated. There are also many factors that affect the quality of metallized ceramic parts. In this article, some common defects in metallized products are summarized and analyzed, and corresponding improvement measures are put forward. 1. Defects of the metallized layer 1.1 Blistering of the metallized layer, this is attributed to the following factors: a. Imperfect quality of hydrogen resulting in incomplete decomposition and residual OH- ions; b. Too fast heating rate preventing gas exclusion, or excessively high sintering temperature leading to excessive liquid phase; c. Excessive solvent and binder content in the metallization paste causing thick coating and incomplete decomposition; d. Presence of internal impurities or coarse grinding traces in ceramic body resulting in micro cracks. In light of the aforementioned situation, improvement measures include enhancing hydrogen quality, implementing raw material particle size control, controlling paste thickness, adhering to standard sintering temperature specifications while ensuring the roughness of ceramic brazing surface to be Ra0.8. 1.2 The metallized layer cracks The metallized layer of ceramic surface often cracks during the drying process after coating. Its characteristics are turtle-shaped cracks, the main reason for the formation of this crack is due to too much binder in the powder paste, also the nonuniform thickness of the coating layer, which will inevitably cause in the drying process of the binder decomposition, volatilization and shrinkage resulting in uneven sizes and cracks. Three solutions have been proved in the production practice: a. Add appropriate amount of binder, but also grinding & stirring to make it uniform; b. The thickness of the coating at applying process should be uniform; c. Sintering heating rate should be properly slow. 1.3 The oxidized metallized layer:The main reasons are as follows: a. The surface temperature of oven-fresh metallized ceramics is too high; b. The dew point of hydrogen is too high; c. The cooling zone temperature is low, condensate water appears in the furnace pipe; d. Air enters when the outlet furnace is opened so that resulting in oxidation; In these cases, the improvement methods are: a.Reduce the temperature of metalized ceramics; b.When cooling, dry hydrogen is used; c.The exit door should be opened and closed quickly. 1.4 Scrapes away issue of metallization layer: The metallized surface looks dark, the surface layer of plating is easy to remove when scraped with ceramic, and the metallized layer can be completely scraped away when it is serious. The reason for scraping away is mostly that the metallization temperature is too low, or the oxidation capacity of the atmosphere is too low so that resulting in weaken adhesion strength. The improvement measures as followings: a. Increase the metallization temperature; b. Adjust the atmosphere humidity; c. Check whether the proportion is wrong when the metallization formula is prepared and whether the material properties of the components are changed. 1.5 Peeling off of metallized layer: The so-called metallized layer peeling refers to the serious shrinkage deformation of the metallized coating during the heating process, which causes the metallized layer to locally bulge out of the ceramic surface, and even most of the metallized layer to fall off. If the coating itself is sintered well, the root cause of this phenomenon is that the coating contains too much binder or the coating is too thick at the heating rate When it is relatively fast, the coating shrinks quickly and breaks off the porcelain surface. In addition, the paste is too sticky, applied too fast, the paste does not wet the porcelain surface well, and the coating is easy to leave the porcelain surface when heating up. Therefore, the paste viscosity should be appropriate, if the coating speed is accelerated, the paste viscosity should be reduced accordingly, and the rising and falling temperature should be properly controlled. [Continue...]

The preparation process of advanced ceramics mainly includes the synthesis of original powder, product molding, sintering, processing and inspection. In addition, according to the appearance characteristics of ceramic products, advanced ceramics can also be divided into advanced ceramic solid materials, advanced ceramic composite materials, advanced ceramic porous materials, etc. For the preparation of these advanced ceramic materials, the following figure shows the preparation process of advanced ceramic materials. 1. Raw materials Generally, they are chemical reagents or industrial chemical raw materials with high purity that have been purified and processed. Sometimes relatively primary raw materials can also be used, and the purification of raw materials is carried out together with the synthesis process of the powder. 2. Powder synthesis Powder that meets the requirements (chemical composition, phase composition, purity, particle size, fluidity, etc.) is synthesized from the starting raw materials through chemical reactions. The powder synthesis method can be mechanical crushing with particle refinement. It can also be prepared by the main method of nucleation and growth of particles in the medium, the latter is generally a chemical method. According to the different phases of chemical reactions, chemical methods can be divided into liquid phase methods, gas phase methods and solid phase methods 3. Powder adjustment If the synthesized powder does not meet the design or subsequent process requirements, the powder needs to be adjusted. If the powder is not fine enough or contains large agglomerates, the powder needs to be ground. If it contains undesirable ionic impurities, it can be washed. Powder adjustment also includes the addition of organic additives, humidity adjustment, granulation, mud (ductile material) and slurry preparation, and kneading to make it suitable for molding. 4. Forming Transform the dispersion system (powder, ductile material and slurry material) into a block with a certain geometric shape, volume and strength, also called a blank. Granular powders are molded by dry pressing or isostatic pressing; ductile materials are suitable for extrusion molding or injection molding; slurry materials are molded by casting. 5. Pretreatment before sintering Since the molded body contains a certain amount of organic additives and solvents, it generally needs to be processed before sintering, that is, drying and burning off of the organic additives. 6. Sintering Refers to the process of causing the microstructural changes of the molded body to cause its volume to shrink and its density to increase under a certain temperature and pressure. Sintering is a key step in the manufacture of ceramic materials. Through sintering, the material not only becomes dense, but also acquires considerable mechanical properties such as strength and various other functional properties. 7. Machining Engineering ceramics must be processed according to customer requirements before use. Due to the large shrinkage that occurs during the sintering process than green ceramic parts, the dimensional deviation of the sintered body is on the order of millimeters or even larger, which cannot meet the fitting requirements at all, so further finishing is required.

Due to the difference in thermal expansion coefficient between ceramic and metal materials, the two materials cannot achieve high-quality direct connection. Therefore, it is first necessary to sinter or deposit a layer of metal film on the ceramic. This process is called ceramic metallization, and the quality of metallization directly affects the airtightness and strength of the final seal are the most important part of the ceramic-metal sealing process. At present, this process is widely used in many fields such as vacuum electronic technology, microelectronic packaging technology, energy chemical industry, and aerospace. 1. Metallized Ceramic Insulator Metallized ceramic insulators are commonly made of aluminum oxide, zirconium oxide, aluminum nitride and beryllium oxide. A metallic layer will be deposited on specific surface of ceramic body to achieve ceramic to metal, ceramic to ceramic joining, to meet brazing and hermetically purpose. Metallized ceramic insulator is widely used in vacuum interrupters, vacuum capacitors/Thyristors, gas discharge tube, electron tubes, current feedthroughs, X-ray tubes, power switches and so on. 2. Vacuum Ceramic Component As shown in the picture, this vacuum ceramic component is an alumina ceramic vacuum switch housing, which is used in the field of power electronics. Its main function is that through the excellent insulation of the vacuum in the tube, the medium and high voltage circuits can quickly extinguish the arc and suppress the current after the power is cut off, so as to achieve the function of safely breaking the circuit and controlling the power grid to avoid accidents and accidents. The vacuum switching tube has the characteristics of energy saving, explosion-proof, small size, low maintenance cost, reliable operation and no pollution, etc. It is mainly used in the transmission and distribution control system of electric power. Relays are one of the most widely used automotive electronic components next to electronic sensors. They are widely used to control car starting, air conditioning, lights, oil pumps, communications, electric doors and windows, airbags, and automotive electronic instruments and fault diagnosis, etc. system. Metallized Ceramic Insulators used in the relay and some of its products are shown in right photo. The ceramic shell is insulated and sealed. The spark generated by the high-voltage and high-current circuit is connected to the power supply. When the high-voltage DC relay is switched off with load, an arc is generated. The arc is quickly extinguished by the cooling and surface adsorption of ceramics. Put an end to the short-circuit fire caused by the electric arc in the automobile circuit, and ensure the safety performance and service life of the whole vehicle. 3. Metallized Ceramic Ring Metallized ceramic ring is commonly made from high purity alumina, mainly including 95%, 99% aluminum oxide. As alumina ceramic offer excellent electrical insulation strength, great mechanism strength and good thermal properties, so metallized ceramic rings are always used as a ceramic insulator, ceramic washer at ceramic to metal jointing application in high-voltage, high-current fields. The most extensive type of metallization is ceramic body with molybdenum/manganese (Mo/Mn) metallization, then a following Nickle plating will be covered on it. Other different metallic coating is available to supply to meet different requirements, like direct silver (Ag) plating on ceramic body, tungsten (W) metallization with gold(Au) plating and so on. With our art-of-the-state manufacturing equipment, we are able to produce some different shapes from small-size to large-size, also we have very high precision flatting grinding, cylindrical grinding, glazing capability at house, the reach client`s tight dimensional requirement. As shown in the figure, the metallized ceramic ring is used as a ceramic sealed connector, which plays an important role in the high-voltage and high-current circuit on the car. When the high-voltage DC relay is switched off with load, an arc is generated, and the ceramic sealed connection will cool and surface in time. Absorb the arc and make it extinguish quickly. 4. Metallized Ceramic Tube The main difference of metallized ceramic tube than regular ones are the applied metal layer on the appointed area of ceramic body. With the applied metal layer on the surface, it can realize the bonding aim between the ceramic tube to metal, ceramic tube to ceramic tube. The metal film will be attached on ceramic parts tightly under high temperature cure. Then the ceramic tubes could be brazed with Kovar, stainless steel parts together directly. In order to increase the wettability at brazing process, in common case, an additional metal plating will be covered on metallization layer further, mainly including Nickle plating, gold plating and so on. In the recent market, alumina metallized ceramic tube is one of most extensive technical parts. They are features of high bonding strength, excellent electrical insulation and mechanical strength. Sometimes, high precision dimensions are needed to cater to the fitting purpose. With our in-house machining workshop, we are able to make the dimensional tolerance as expected according to customers` specification.

The new rapid sintering technology of advanced ceramics is a new type of ceramic material preparation technology, which has the advantages of fast sintering speed, high sintering density and excellent mechanical properties. These new processes can significantly improve the sintering conditions of ceramic parts, such as Self-propagation High temperature Synthesis(SHS), spark plasma sintering(SPS), flash sintering(FS), cold sintering(CS) and oscillatory pressure sintering(OPS), etc. First, the new rapid sintering technology for advanced ceramics is characterized by fast sintering speeds. Traditional ceramic material preparation methods usually require a long sintering process, but the new rapid sintering technology can complete the sintering process in a shorter time. This fast sintering speed can greatly improve production efficiency, shorten production cycle and reduce production cost. Secondly, the new rapid sintering technology of technical ceramics can prepare ceramic materials with high sintering density. Traditional sintering methods are prone to produce pores and defects, resulting in decreased strength and wear resistance of ceramic materials. The new rapid sintering technology, by controlling the sintering temperature and time, can make the ceramic components achieve higher density and improve its mechanical properties and wear resistance. In addition, the new rapid sintering technology of advanced ceramics also has excellent mechanical properties. Conventional ceramic materials are usually characterized by brittleness and low strength, which limit their widespread use in engineering applications. The new rapid sintering technology can prepare ceramic materials with higher strength and toughness, making it have wider application prospects in structural materials, wear-resistant materials and other fields. In conclusion, the new rapid sintering technology for advanced ceramics provides an efficient, economical and feasible method for the preparation of ceramic materials through the characteristics of fast sintering speed, high sintering density and excellent mechanical properties. The application of this technology will promote the development of ceramic materials, broaden its application range in various fields, and provide new possibilities for the development of engineering fields.

The etching factor, also known as the ceramic substrate etch factor, is an important factor in the production process of ceramic PCB substrate. It is a measure of the relative etch rate of a material in a certain etchant. It is expressed as the ratio of the etch rate of the material to the etch rate of the reference material. The etch factor is used to measure the etching rate of the blank ceramic substrate. It is an important parameter in the design of the etching process. The etch factor can be used to compare different materials and determine the etch rate of the substrate. The etch factor of a ceramic substrate is determined by measuring the etch rate of the substrate in a certain etchant. The etch rate is the rate at which the material is etched away in a certain etchant. The etch rate of a material is usually expressed in terms of the depth of etching per unit of time. The etch factor is an important parameter in the design of the etching process. It is used to compare different materials and determine the etch rate of the substrate. The etch factor of a ceramic substrate is determined by measuring the etch rate of the substrate in a certain etchant. By understanding the etch factor of a ceramic substrate, manufacturers can design the etching process to achieve the desired etch rate. This helps to ensure that the substrate is etched at the right rate and with the desired results. In conclusion, the etch factor is an important parameter in the design of the etching process of ceramic substrates. It is used to compare different materials and determine the etch rate of the substrate.

The preparation process of DPC ceramic substrate is shown in the figure. First, a laser is used to prepare through holes on the blank ceramic substrate (the aperture is generally 60 μm ~ 120 μm), and then the ceramic substrate is cleaned by ultrasonic waves; the magnetron sputtering technology is used to deposit metal on the surface of the ceramic substrate. Seed layer (Ti/Cu), and then complete the circuit layer production through photolithography and development; use electroplating to fill holes and thicken the metal circuit layer, and improve the solderability and oxidation resistance of the substrate through surface treatment, and finally remove the dry film, engraving Etch the seed layer to complete the substrate preparation. The front end of DPC ceramic substrate preparation adopts semiconductor micromachining technology (sputter coating, lithography, development, etc.), and the back end adopts printed circuit board (PCB) preparation technology (pattern plating, hole filling, surface grinding, etching, surface processing, etc.), the technical advantages are obvious. Specific features include: (1) Using semiconductor micromachining technology, the metal lines on the ceramic substrate are finer (the line width/line spacing can be as low as 30 μm ~ 50 μm, which is related to the thickness of the circuit layer), so the DPC substrate is very suitable for alignment accuracy Microelectronic device packaging with higher requirements; (2) Using laser drilling and electroplating hole filling technology to achieve vertical interconnection between the upper and lower surfaces of the ceramic substrate, enabling three-dimensional packaging and integration of electronic devices and reducing device volume, as shown in Figure 2( b); (3) The thickness of the circuit layer is controlled by electroplating growth (generally 10 μm ~ 100 μm), and the surface roughness of the circuit layer is reduced by grinding to meet the packaging requirements of high temperature and high current devices; (4) Low temperature preparation process (below 300°C) avoids the adverse effects of high temperature on substrate materials and metal wiring layers, and also reduces production costs. To sum up, the DPC substrate has the characteristics of high graphic accuracy and vertical interconnection, and is a real ceramic PCB substrate. However, DPC substrates also have some shortcomings: (1) The metal circuit layer is prepared by electroplating process, which causes serious environmental pollution; (2) The electroplating growth rate is low, and the thickness of the circuit layer is limited (generally controlled at 10 μm ~ 100 μm), which is difficult to meet the needs of large Current power device packaging requirements. At present, DPC ceramic substrates are mainly used in high-power LED packaging.

Thick-film printing ceramic substrate (TPC) is to coat the metal paste on the ceramic substrate by screen printing, and then sinter at high temperature (generally 850°C ~ 900°C) to prepare the TPC substrate after drying. The TFC substrate has a simple preparation process, low requirements for processing equipment and environment, and has the advantages of high production efficiency and low manufacturing cost. The disadvantage is that due to the limitation of the screen printing process, the TFC substrate cannot obtain high-precision lines (Min. line width/line spacing > 100 μm). Depending on the viscosity of the metal paste and the mesh size of the mesh, the thickness of the prepared metal circuit layer is generally 10 μm ~ 20 μm. If you want to increase the thickness of the metal layer, it can be achieved by multiple screen printing. In order to reduce the sintering temperature and improve the bonding strength between the metal layer and the blank ceramic substrate, a small amount of glass phase is usually added to the metal paste, which will reduce the electrical conductivity and thermal conductivity of the metal layer. Therefore, TPC substrates are only used in the packaging of electronic devices (such as automotive electronics) that do not require high circuit accuracy. The key technology of TPC substrate lies in the preparation of high-performance metal paste. The metal paste is mainly composed of metal powder, organic carrier and glass powder. The available conductor metals in the paste are Au, Ag, Ni, Cu, and Al. Silver-based conductive pastes are widely used (accounting for more than 80% of the metal paste market) due to their high electrical and thermal conductivity and relatively low price. The research shows that the particle size and morphology of the silver particles have a great influence on the performance of the conductive layer, and the resistivity of the metal layer decreases as the size of the spherical silver particles decreases. The organic carrier in the metal paste determines the fluidity, wettability and bonding strength of the paste, which directly affects the quality of screen printing and the compactness and conductivity of the later sintered film. Adding glass frit can reduce the sintering temperature of metal paste, reduce production cost and ceramic PCB substrate stress.