Research Status And Development Trend of Surface Metallization of Ceramic Substrates

Abstract: The heat dissipation substrate is an important channel for the heat dissipation of high-power electronic components, and its thermal conductivity will directly affect the reliability and service life of power-type electronic components. This paper introduces in detail the technical scheme and development status of surface metallization of ceramic as a heat-dissipating substrate material with high thermal conductivity, points out the key technical difficulties of various metallization schemes, compares and analyzes the characteristics and performance differences of various ceramic packaging heat-dissipating substrates, and predicts the development trend of ceramic substrates on this basis. 

0. Introduction With the continuous progress of electronic technology, the problem of heat dissipation has gradually become a bottleneck restricting the development of power electronic products in the direction of high power and light. The continuous accumulation of heat in the power electronic components will gradually increase the chip junction temperature, and produce thermal stress, resulting in a series of reliability problems such as reduced life and color temperature changes. In the packaging application of power-type electronic components, the cooling substrate not only assumes the functions of electrical connection and mechanical support, but also an important channel for heat transmission. For power electronic devices, the packaging substrate should have high thermal conductivity, insulation and heat resistance, as well as high strength and thermal expansion coefficient matching the chip. 

At present, the common heat dissipation substrate on the market is mainly metal substrate (MCPCB) and ceramic substrate. Due to the extremely low thermal conductivity of the thermal insulation layer, MCPCB has become increasingly difficult to adapt to the development requirements of power-type electronic components. Ceramic substrate as an emerging heat dissipation material, its comprehensive performance such as thermal conductivity and insulation is unmatched by ordinary MCPCB, and the surface metalization of ceramic substrate is an important prerequisite for determining its practical application.

In this paper, the technology and research status of ceramic substrate surface metallization are introduced in detail, and the principle of various metallization schemes is described, and the key technical control points of each scheme are pointed out, in order to provide technical reference for the selection of power type LED ceramic packaging substrate.

1. Research status of metallization of ceramic surface

After sintering, the surface of the ceramic substrate needs to be metallized, and then the surface pattern is made by image transfer to achieve the electrical connection performance of the ceramic substrate. Surface metallization is a crucial part of the production of ceramic substrates, because the wetting ability of the metal at high temperatures on the ceramic surface determines the binding force between the metal and the ceramic, and a good binding force is an important guarantee for the stability of LED packaging performance.

Therefore, how to implement metallization on ceramic surfaces and improve the bonding force between them has become the focus of many scientific and technological researchers [4,5,6]. At present, the common metallization methods on ceramic surfaces can be roughly divided into several forms, such as co-firing method (HTCC and LTCC), thick film method (TFC), direct application of copper method (DBC), direct application of aluminum method (DBA) and thin film method (DPC) [7,8].

1.1 Co-firing Method (HTCC/LTCC)

Co-fired multilayer ceramic substrates have gained wide attention in recent years because they can meet many requirements of integrated circuits by embedding passive components such as signal lines and microwires into the substrates using thick film technology [9].

There are two kinds of co-firing method, one is high temperature co-firing (HTCC) and the other is low temperature co-firing (LTCC). The process flow of the two is basically the same. The main production process is slurry preparation, casting strip, drying green blank, drilling through hole, screen printing filling hole, screen printing line, laminated sintering and final slicing and other post-treatment processes. Alumina powder and organic adhesive are mixed to form a slurry, and then the slurry is processed into sheets with a scraper. After drying, ceramic green billet is formed [10]. Then, pilot holes are processed on the green billet according to the design requirements and metal powder is filled. Finally, each layer of green billet is laminated, sintered and formed in the co-firing furnace. Although the process of the two co-firing methods is roughly the same, the sintering temperature is very different. The co-firing temperature of HTCC is 1300~1600℃, while the sintering temperature of LTCC is 850~900℃. The main reason for this difference is that LTCC sintering slurry is added to reduce the sintering temperature of the glass material, which is not in HTCC co-fired slurry. Although the glass material can reduce the sintering temperature, the thermal conductivity of the substrate can be significantly decreased [11,12,13].

Co-fired ceramic substrate has significant advantages in increasing assembly density, shortening interconnect length, reducing signal delay, reducing volume and improving reliability. The more common application of co-fired substrate is to bury a variety of passive devices in ceramic paste sintering, to make three-dimensional integrated and non-interfering high-density circuit, mount IC and active devices on its surface, make a successful integrated module, further reduce the circuit structure, improve the integration density, especially suitable for high-frequency communication components [13]. However, since HTCC and LTCC both use screen printing to complete the graphics production, the dimensional accuracy and surface roughness of the graphics are greatly affected by the printing process. At the same time, the lamination process is also easy to cause the graphics alignment is not accurate, resulting in excessive tolerance accumulation. Moreover, the green billet is prone to inconsistent shrinkage during the sintering process, which to a large extent limits the application of the co-firing process [14,15].

1.2 Thick film ceramic (TFC) Method

Thick film method refers to the method of screen printing, the conductive paste is directly coated on the ceramic matrix, and then sintered at high temperature to make the metal layer firmly attached to the ceramic matrix. The selection of thick film conductor paste is a key factor in determining the thick film process, which consists of a functional phase (i.e. a metal powder with a particle size of less than 2μm), a bonding phase (binder) and an organic carrier. Common metal powders include Au, Pt, Au/Pt, Au/Pd, Ag, Ag/Pt, Ag/Pd, Cu, Ni, Al and W, among which Ag, Ag/Pd and Cu slurry are the majority [16]. The binder is generally a glass material or metal oxide or a mixture of the two, and its role is to connect the ceramic and metal and determine the adhesion of the thick film slurry to the matrix ceramic, which is the key to the production of thick film slurry. The function of the organic carrier is mainly to disperse the functional phase and bond the phase, and at the same time to maintain a certain viscosity of the thick film slurry to prepare for the subsequent screen printing, which will gradually evaporate during the sintering process [17].

At present, the research on aluminum oxide thick film electronic paste has become mature, while aluminum nitride thick film electronic paste still has a large room for development, which is caused by the unsatisfactory wettability of most metals to aluminum nitride ceramics [17]. In order to improve the bonding force between metal and aluminum nitride ceramics in the process of thick film production, there are two common methods. One is to use glass material as a bonding phase to make the metal layer and AlN layer reach mechanical bonding; The second is to add a substance that can react with AlN as a bonding phase, and achieve chemical bonding by reacting with AlN. At present, the main composition of most glass bonding systems of aluminum nitride slurry is SiO2-B2O3, which is because silicate glass and borate glass have good wetting effect on metal and aluminum nitride. In addition, the softening point of borate glass is low, which can improve the firing rate and enhance the density after sintering. However, the low softening point of borate will also make it soften before reaching the metallization sintering temperature, so that the metal layer can not form an effective network crosslinking structure with aluminum nitride ceramics. The addition of silicate can effectively solve this problem. At the same time, the performance of the glass phase can be further improved by adding an appropriate amount of alkali metal and alkaline earth metal to the glass phase, because alkali or alkaline earth metal can differentiate the glass and reduce the viscosity of the glass. Generally, with the increase of the amount of alkali or alkaline earth metal, the viscosity will be significantly reduced, which is conducive to improving the fluidity of the slurry and accelerating the metallization and sintering. Commonly used alkali or alkaline earth metals include Li2O, Na2O, K2O, BaO and PdO, etc. [18,19]. In addition, some substances that can react with aluminum nitride to form new phases can be added, such as Cr2O3, PdO, ZnO, etc., and the reaction bonding force formed by the new phase can be used to improve the adhesion strength of the slurry after metallization. It has been pointed out that some alkaline earth metal oxides of silicon and boron, as well as oxides of zirconium, iron, lead and phosphorus, can react with AlN to form new substances [20,21]. For example, the use of ZrB2 bonding phase, due to the formation of a new phase Al2O3·B2O3 (boral spinel) during the reaction process, the bonding force between the metallized layer and aluminum nitride ceramics can be as high as 24MPa, and the ZrO2 generated during the reaction process can also accelerate the oxidation of AlN, thus promoting the reaction.

The thickness of the metal layer after TFC sintering is generally 10~20μm, and the minimum line width is 0.1 mm. Due to the mature technology, simple process and low cost, TFC has been used in LED packaging with low graphic accuracy requirements. At the same time, TFC has some disadvantages such as low graphic accuracy (error is ±10%), coating stability is easily affected by slurry uniformity, poor line flatness (above 3μm) and adhesion is not easy to control, so its application range is limited.

1.3 Direct bonded copper (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 matrix and copper foil to form CuAlO2 or Cu(AlO2)2, and realize the bonding between copper foil and matrix under the action of intermediate phase. Because Al N is a non-oxide ceramic, the key to coating copper on its surface is to form an Al2O3 transition layer on its surface, and realize effective bonding between copper foil and matrix ceramics under the action of the transition layer [22].

The introduction of oxygen is a very critical step in DBC process. Oxidation time and oxidation temperature are the two most important parameters in this process, which have a very important influence on the binding force between the ceramic and the copper foil after bonding. When the oxidation time and oxidation temperature are fixed, the Al2O3 matrix without pre-oxidation treatment in the process of bonding with copper foil, because oxygen is difficult to penetrate into the interface of copper foil and ceramic substrate, the Cu/O liquid phase has poor wettability on the substrate, and finally a large number of holes and defects will remain on the interface. After the matrix is pre-oxidized, sufficient oxygen supply can be given at the same time as the coating, so the Cu/O liquid phase has good wettability on the ceramic matrix and copper foil, the interfacial cavities and defects are significantly reduced, and the binding force between copper foil and the matrix is also more firm. For AlN, because AlN is a strong covalent bond compound, the wettability of Cu/O liquid phase is poor. When DBC copper is applied on its surface, the wettability of Cu/O liquid phase on ceramic matrix must be enhanced by surface modification to ensure the binding force of copper foil and matrix. At present, the general practice is to use pre-oxidation to form a certain thickness, uniform dispersion and dense structure of Al2O3 film on the surface of AlN. Due to the mismatch between the thermal expansion coefficient of alumina film and aluminum nituse matrix, the bonding force of the two phase interface may deteriorate due to the existence of internal stress at room temperature, so the quality of the film is the key to the success of the subsequent coating. In general, in order to achieve an effective combination of the two, it is necessary to reduce the internal stress between the AlN and Al2O3 phases by reducing the thickness of the film as much as possible under the premise of ensuring the density of the oxide film. Jing Min et al. [23] carried out a systematic study on DBC process and obtained a DBC ceramic substrate with peel strength above 6.5N /mm and thermal conductivity of 11.86W/ (m·K) by roughening the ceramic surface with molten NaOH. Xie Jianjun et al. [24] prepared Cu/Al2O3 and Cu/AlN composite ceramic substrate materials with DBC technology. The bonding strength between copper foil and AlN ceramic substrate exceeded 8.00N /mm, and there was a transition layer with a thickness of about 2μm between copper foil and AlN ceramic. Its components are mainly Al2O3, CuAlO2 and Cu2O compounds, and the interfacial bonding strength of Cu/AlN increases gradually with the increase of bonding temperature. AKara-Slimane et al. [25] used DBC process to prepare aluminum nitride ceramic substrate under vacuum conditions, when the temperature was 1000℃ and the pressure was 4-12 MPa, and the peeling strength was as high as 32 MPa.

Copper foil has good electrical and thermal conductivity, and alumina not only has good thermal conductivity, strong insulation, high reliability, but also can effectively control the expansion of CuAl2O3-Cu complex, so that DBC ceramic substrate has a similar thermal expansion coefficient of alumina. It has been widely used in the package thermal management of IGBT, LD and CPV. Because DBC hot-pressed bonded copper foils are generally thicker, ranging from 100 to 600μm, they have a strong current-carrying capacity and have obvious advantages in the field of IGBT and LD packaging [26].

Although DBC has many advantages in practical engineering application, it also has the following shortcomings: (1) DBC process requires the introduction of oxygen elements under high temperature conditions to make Cu and Al2O3 eutectic reaction, which requires high equipment and process control, and the substrate production cost is high; (2) Micro-pores are easily generated between the Al2O3 and Cu layers, and the thermal shock resistance of the substrate will be affected; (3) The thickness of DBC surface bonded copper foil is generally more than 100μm, and the minimum line width of the surface pattern is generally greater than 100μm, which is not suitable for the production of fine lines.

1.4 Direct aluminum bonded (DAB)

Direct aluminum coating method is to use aluminum in the liquid state of ceramic has a good wettability to achieve the application of the two. When the temperature rises above 660℃, the solid aluminum liquefied, when the liquid aluminum wet the ceramic surface, with the decrease of temperature, aluminum directly on the ceramic surface provided by the crystal nucleus crystallization growth, cooling to room temperature to achieve the combination of the two. Because aluminum is more active, it is easy to oxidize Al2O3 film under high temperature conditions and exists on the surface of liquid aluminum, which greatly reduces the wettability of liquid aluminum on the ceramic surface, making it difficult to achieve the application, so it must be removed before the application or the application under oxygen-free conditions. Peng Rong et al. [23,27] adopted the graphite die casting method to lay pure liquid aluminum on the surface of Al2O3 substrate and AlN substrate by pressure, and the Al2O3 film remained in the mold cavity due to lack of fluidity. After cooling, the DAB substrate was prepared with sound coating.

Since the wettability of liquid aluminum on ceramic surface is the key to the success or failure of DAB, scholars at home and abroad have carried out a lot of research work on wettability. When KaraSlimane[25] used aluminum as an intermediate layer to bond Al N/Al/Fe, he pointed out that certain pressure must be applied during the coating process to break the Al2O3 layer appearing on the surface of liquid aluminum, so as to realize the effective coating of aluminum with aluminum nitride and iron. The above consideration is the physical coating, that is, there is no chemical reaction at the aluminum/ceramic interface, so the bond strength between aluminum and ceramics depends on the mechanical lock cooperation caused by the increase in roughness between the two, and the binding force is relatively small compared with DBC. However, the combination between the two has no second phase generation, and has the advantage of low interface stress and high interface thermal conductivity compared with DBC. Before coating aluminum, the surface treatment of ceramics to increase the strength of coating is a very key process link.

Imai[28] found that the surface roughness of ceramic substrate greatly affects the coating performance, and maintaining a certain roughness is a necessary condition for improving the coating strength. Therefore, how to treat ceramic substrate to change its roughness is the key to improve the bonding strength between aluminum and ceramic. Lin et Al. [29] studied the bonding temperature and properties of Al2O3/Al/Al2O3, and prepared DAB substrate with high bonding strength and thermal conductivity of 32 W/ (m·K) at 1100℃. Jing Min et al. [23] firstly formed a stable Cu Al2O4 phase by sintering Cu2O on the Al2O3 substrate, and a copper film was formed on the surface of the substrate by H2 reduction at 1 000℃. Finally, the contact between oxygen and metal aluminum was isolated by active metal magnesium and toner protection under vacuum environment. DAB ceramic substrate with Al/Al2O3 bonding strength up to 11.9 MPa was prepared by eutectic coating at 760℃.

DAB ceramic substrate has good thermal stability, the mass can be reduced by 44% compared with DBC of the same structure, the aluminum wire bonding ability is good, the thermal stress between aluminum/ceramic is relatively small, and it has developed rapidly in recent years. Al2O3-DAB substrate and AlN-DAB substrate have excellent thermal conductivity characteristics, good thermal shock fatigue resistance, excellent thermal stability, light structural weight and good aluminum wire bonding ability. The power device module based on DAB substrate has been successfully applied in the Japanese automobile industry. At present, a lot of research work has been done on DAB technology at home and abroad, but the research on the details of aluminum/ceramic interface is not deep enough [4]. Due to strict restrictions on oxygen content, DAB has higher requirements for equipment and process control, and the substrate production cost is higher. And the thickness of surface bonded aluminum is generally more than 100μm, which is not suitable for the production of fine lines, and its promotion and application are therefore limited.

1.5 Thin Film Method (Direct plated copper, DPC)

Thin film method is a process in which the metal layer is formed on the ceramic surface by physical vapor deposition (vacuum evaporation, magnetron sputtering, etc.), and then the metal circuit layer is formed by mask and etching. Among them, physical vapor deposition is the most common film manufacturing process [30].

Physical vapor deposition is to form a layer of 3~5μm metal film on the ceramic surface by evaporation or sputtering as the conductive layer of the ceramic substrate. The interface bonding strength is the technical bottleneck of DPC substrate because of the thermal cycling failure of copper layer and ceramic layer. The bonding force of ceramic and metal film, the welding performance of metal film and chip and the conductivity of metal film itself are three important indicators to measure the quality of the film. The bonding force between the metal film and aluminum nitride determines the practicability and reliability of the film process ceramic substrate, while the bonding force is affected by van der Waals force, chemical bonding force, diffusion adhesion, mechanical locking, electrostatic attraction and internal stress of the film itself, among which diffusion adhesion and chemical bonding force are the main factors. Therefore, it is necessary to select Al, Cr, Ti, Ni, Cu and other metals with high activity and good diffusion performance as the transition layer. The conductive layer undertakes the functions of electrical connection and welding, so it is necessary to select metal materials such as Au, Cu and Ag with low resistivity, high temperature resistance, stable chemical properties and small diffusion coefficient [31]. Zhang Xuebin [32] studied the preparation process of DPC ceramic substrate, and the results showed that the bonding strength could be improved by using W/Ti alloy as the transition layer. When the transition layer thickness was 200 nm, the bonding strength of the prepared thin film Al2O3 ceramic substrate was greater than 97.2N. In addition, in addition to the preparation of thin films by physical vapor deposition, some scholars have obtained copper thin films on the surface of ceramics by electroless plating. Xue Shengjie et al. [13] from Chongqing University used the electroless plating method to optimize various process parameters. Al N thin film ceramic substrate with binding force of 18.45 N, conductivity of 2.65×10^6 S/m, deposition rate of 0.026 g/ (s·cm2) and thermal conductivity of 147.29 W/ (m·K) was prepared.

Compared with other ceramic surface metallization methods, the DPC process has a low operating temperature, generally below 300 ° C, which reduces the manufacturing process cost and effectively avoids the adverse effects of high temperature on the material. The DPC substrate uses Huang Guangying technology to produce graphics circuit, the line width can be controlled in 20~30μm, the surface flatness can reach 3μm or less, and the graphics accuracy error can be controlled within ±1%, which is very suitable for electronic device packaging with high circuit accuracy requirements. In particular, the upper and lower surfaces of the ceramic substrate can be interconnected after cutting holes and filling copper through holes of the DPC substrate by laser, thus meeting the three-dimensional packaging requirements of electronic devices. DPC not only reduces the package volume, but also effectively improves the package integration. Although DPC ceramic substrate has the above advantages, it also has some shortcomings such as limited thickness of electroplating deposited copper layer, large pollution of electroplating waste liquid, low bonding strength between metal layer and ceramic, and low reliability in product application.

2 Performance comparison and development trend of ceramic substrate

2.1 Performance comparison of ceramic substrate

In addition to the electrical connection and heat dissipation function, the power type electronic packaging heat dissipation substrate also needs to have a certain insulation, heat resistance, pressure resistance and heat matching performance. Because ceramic substrate has excellent thermal conductivity and insulation properties, it has prominent advantages in the packaging application of power electronic components, and is one of the main development directions of power electronic packaging cooling substrate in the future [33]. The main characteristics of LTCC, HTCC, TFC, DBC, DBA, DPC process ceramic substrates are shown in Table 1.

Table 1 Main characteristics and performance comparison of various ceramic substrates

So far, Cree, Osram, Philips and Nichia and other international top manufacturers and domestic Jiangxi Jingrui, Yimei Xinguang, Hucheng Technology, Foshan Guoxing, Shenzhen Ruifeng, Guangzhou Hongli, Ningbo Shengpu and other enterprises have launched ceramic packaged power electronic products. At present, due to the technical capability, the manufacturing cost of ceramic substrate is still high. However, it can be predicted that with the continuous breakthrough of technical bottlenecks and the continuous improvement of package integration, the market acceptance of ceramic substrates will be increasingly improved, and the power electronic products using ceramics as packaging substrates will be increasingly rich.

2.2 Development trend of ceramic substrate

Ceramic substrate has low coefficient of thermal expansion, good thermal conductivity and insulation properties, and has become recognized as the most promising heat dissipation substrate material in the industry. In some cases, it is gradually replacing metal substrate and becoming the preferred thermal management solution for heat dissipation of high-power electronic components [34].

As mentioned above, the ceramic substrate manufacturing technology currently applied to high-power electronic component packaging has a total of HTCC, LTCC, TFC, DBC, DAB, DPC six kinds, of which the metal powder in the HTCC process is mainly tungsten, molybdenum, manganese and other metals with high melting point but poor electrical conductivity, and its production cost is high, so it is generally less used. LTCC process due to the addition of low thermal conductivity of glass materials in the slurry, its thermal conductivity is only 2~3 W/ (m·K), compared with ordinary MCPCB advantages are not obvious. At the same time, the line graphics of HTCC and LTCC are made by thick film (TFC) technology, which has the shortcomings of rough surface and inaccurate alignment. In addition, in the sintering process, there is also a problem of inconsistent shrinkage of ceramic green billet, which makes the process resolution of co-fired ceramics limited to a certain extent, and the popularization and application are also facing great challenges.

Due to the poor wettability of liquid phase copper on the ceramic surface in DBC process, oxygen elements need to be introduced under high temperature conditions to achieve the coating of copper foil and matrix ceramics, and micro-pores are easily generated on the interface surface, which has high equipment and technical requirements, and is still the focus of research by domestic and foreign researchers. The aluminum in DAB process is easy to oxidize at high temperature, which will affect the wettability of liquid aluminum on the ceramic surface, and the application needs to be carried out under oxygen-free conditions, so the requirements for equipment and technology are also relatively harsh, and large-scale industrialization has not been realized at present. At present, Western developed countries, Japan, South Korea has DBC and DAB technology and market advantages. Some scientific research institutions in China have also carried out some research work on DBC and DAB and made certain technical breakthroughs, but there is still a certain gap compared with the international advanced level, products are mainly used in IGBT (insulated gate bipolar diode) and LD (laser diode) and other power device packaging. Due to the thick conductive layer of DBC and DAB, the advantages of the two substrates applied to LED packaging are not obvious.

DPC process solves the problem of poor wettability of copper foil on ceramic surface by introducing transition layer metal on ceramic surface, and successfully realizes the metallization of ceramic surface on the premise of ensuring the binding force between conductive layer and ceramic substrate. DPC ceramic substrate not only has excellent electrical conductivity, but also has high line accuracy and surface smoothness, which is very suitable for LED cladding and eutectic process LED packaging, and has achieved industrialization in terms of production scale, and is currently the most able to meet the needs of LED to high power, high light density and small size direction of development of ceramic packaging cooling substrate. At present, China's Taiwan region holds a monopoly position on DPC core technology, accounting for 80% of the global product market share, and is the main supplier of ceramic cooling substrates for semiconductor lighting industry giants such as Cree, Lumileds and Osram in Germany. Nowadays, with the continuous increase of research and development efforts, DPC substrate technology in the mainland has also made breakthroughs, which can also meet the needs of high-power LED packaging for heat dissipation to a certain extent.

Under the background of continuous breakthrough of manufacturing process technology bottleneck, the brittleness of ceramic substrate is an indisputable fact, how to use its excellent thermal conductivity to provide heat dissipation management solutions for the rapidly developing LED industry, and to avoid cracking due to excessive brittleness in the production and use process is also a practical problem that cannot be ignored. Lejian Technology (Zhuhai) Co., Ltd. uses laser cutting or grinding wheel cutting to cut large pieces of ceramic into a number of small pieces, and selectively implanted into the FR4 structure, using the pressing process to combine the ceramic and FR4 together to form a composite heat dissipating structure. Among them, the ceramic acts as the heat dissipation channel of the chip, so that the heat generated by the electronic components during the working process can be rapidly diffused to the outside world along the ceramic, so as to avoid the reliability of the components caused by poor heat dissipation, resulting in the risk of premature failure, as shown in Figure 1 and Figure 2. This design not only retains the heat dissipation function of ceramics, but also solves the problem of fragile ceramics. At the same time, machining can be achieved on FR4, which greatly reduces the high cost of cutting pure ceramics. At present, this kind of composite substrate material has been applied to a certain scale in the fields of high-power LED and IGBT.

3 Closing remarks

Heat dissipation is a key technical problem in the development of power electronic components. In view of the high power, small size, lightweight has become the future development trend of power electronic component packaging, ceramic substrate in addition to excellent thermal conductivity characteristics, but also has good insulation, heat resistance, pressure resistance and good thermal matching performance with the chip, has become the first choice for medium and high-end power electronic component packaging heat dissipation. The metallization process of ceramic substrate surface is an important link to realize the use of ceramics in the packaging of power electronic components. The metallization method determines the performance, manufacturing cost, product yield and application range of ceramic substrate.