Method for surface metallization of zirconia toughened alumina ceramic substrates

Abstract

The application discloses a method for surface metallization of a zirconia toughened alumina ceramic substrate, comprising the following steps: S1, providing a zirconia toughened alumina ceramic substrate, denoted as a ZTA ceramic substrate; S2, preparing a gamma-Al2O3 film on the surface of the ZTA ceramic substrate in step S1 by using a cold spraying process; S3, coating a metal foil on the surface of the ZTA ceramic substrate treated in step S2, and making the metal foil adhere to the surface of the ceramic substrate; and then sintering the ZTA ceramic substrate coated with the metal foil to obtain a surface metallized zirconia toughened alumina ceramic substrate. The method improves the bonding strength and bonding stability between the copper foil and the zirconia toughened alumina ceramic substrate, and further improves the cold-heat shock resistance of the zirconia toughened alumina ceramic substrate after surface metallization treatment.

Description

Technical Field

[0001] This invention relates to the field of ceramic substrate technology, and in particular to a method for metallizing the surface of a zirconia-toughened alumina ceramic substrate. Background Technology

[0002] Ceramic substrate surface metallization is used in electronic devices such as electric vehicle power modules, high-power LED lights, and industrial heat treatment equipment operating in high-temperature environments, as well as in the aerospace field. Surface metallization methods for ceramic substrates include DBC, DPC, TCP, and AMB. DBC involves pre-treating both the ceramic substrate and copper foil, then laying the copper foil flat on the ceramic substrate surface and using a fixture to bond the copper foil to the substrate surface. The copper-plated ceramic substrate is then placed in a high-temperature furnace for sintering, bonding the copper foil to the ceramic substrate. This is the main method for surface metallization of alumina ceramic substrates and ZTA substrates. Problems encountered during the use of metallized ceramic substrates include: the bonding strength between the metallized metal layer and the ceramic substrate being too high or too low, and insufficient strength of the ceramic substrate leading to breakage. The bonding strength between the metal layer and the ceramic substrate is mainly achieved by adding a transition layer. For example, DBC copper foil on an alumina substrate requires pre-oxidation of the copper foil surface to form a certain thickness of copper oxide / cuprous oxide due to the good wettability between copper oxide or cuprous oxide and alumina. The pre-oxidized layer is then bonded to the alumina substrate and sintered. To improve the strength of the ceramic substrate, in addition to optimizing the manufacturing process, the substrate composition can also be adjusted. For example, adding a certain amount of zirconium or zirconium oxide to alumina can prepare a zirconium oxide-toughened alumina substrate, i.e., a ZTA ceramic substrate, which is then surface-metallized. However, in practical applications, metallized ceramic substrates obtained by bonding ZTA ceramic substrates with pre-oxidized copper foil are more prone to ceramic substrate breakage and / or delamination between the ceramic substrate and the metal layer. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a method for surface metallization of a zirconia-toughened alumina ceramic substrate; the method improves the bonding strength and bonding stability between copper foil and the zirconia-toughened alumina ceramic substrate, thereby improving the thermal shock resistance of the zirconia-toughened alumina ceramic substrate after surface metallization treatment.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for metallizing the surface of a zirconia-toughened alumina ceramic substrate includes the following steps:

[0006] S1 provides a zirconia-toughened alumina ceramic substrate, denoted as ZTA ceramic substrate;

[0007] S2, a γ-Al2O3 thin film is prepared on the surface of the ZTA ceramic substrate described in step S1 using a cold spraying process;

[0008] S3, apply a metal foil to the surface of the ZTA ceramic substrate after step S2, and make the metal foil adhere to the surface of the ceramic substrate; then sinter the ZTA ceramic substrate with the metal foil to obtain a surface-metallized zirconia toughened alumina ceramic substrate.

[0009] Preferably, step S2 specifically includes the steps of: providing γ-Al2O3 powder, and spraying the γ-Al2O3 powder onto the surface of the ZTA ceramic substrate using a cold spraying process to form the γ-Al2O3 thin film.

[0010] Preferably, the average particle size of the γ-Al2O3 powder is 10-45 μm; the purity of the γ-Al2O3 powder is greater than or equal to 90%.

[0011] Preferably, the preparation method of the γ-Al2O3 powder includes the sol-gel method, the hydrothermal method, or the precipitation method.

[0012] Preferably, step S2 specifically includes the following steps: providing aluminum metal powder, using the cold spraying process to spray the aluminum metal powder onto the surface of the ZTA ceramic substrate to form an aluminum thin film layer, and heat-treating the ZTA ceramic substrate with the aluminum thin film layer in an oxygen atmosphere to oxidize the aluminum thin film layer to form a γ-Al2O3 thin film layer.

[0013] Preferably, the oxygen-containing atmosphere includes a high-temperature air atmosphere or an oxygen atmosphere; the temperature of the heat treatment is 600-800℃.

[0014] Preferably, the thickness of the γ-Al₂O₃ film is 10-100 μm; the porosity of the γ-Al₂O₃ film is less than 3%.

[0015] Preferably, the gas pressure of the cold spraying process is 0.3-0.8 MPa, the gas temperature is 300-600℃, the distance between the nozzle of the spraying device and the surface of the ZTA ceramic substrate is 10-30 mm, and the scanning speed of the nozzle is 8-12 L / min.

[0016] Preferably, step S1 includes a pretreatment step for the ZTA ceramic substrate, the pretreatment step including cleaning, grinding, and sandblasting. The beneficial effects of this invention include at least:

[0017] This invention employs a cold spraying process to coat a γ-Al₂O₃ film onto the surface of a zirconia-toughened alumina ceramic substrate. On one hand, this reduces the surface energy of the ceramic substrate, improves the wettability of the ceramic substrate to the copper foil, and enhances the bonding force between the copper foil and the ceramic substrate. On the other hand, the γ-Al₂O₃ film prevents the zirconia phase in the ceramic substrate from dissolving into the bonding interface during sintering, thus reducing the toughening effect of zirconia on the alumina ceramic substrate. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] This invention provides a method for metallizing the surface of a zirconia-toughened alumina ceramic substrate, comprising the following steps:

[0021] S1 provides a zirconia-toughened alumina ceramic substrate, denoted as ZTA ceramic substrate;

[0022] S2, a γ-Al2O3 thin film is prepared on the surface of the ZTA ceramic substrate described in step S1 using a cold spraying process;

[0023] S3, a metal foil is deposited onto the surface of the ZTA ceramic substrate after step S2, and the metal foil is made to adhere to the surface of the ceramic substrate; then the ZTA ceramic substrate with the metal foil is sintered to obtain a surface-metallized zirconia-toughened alumina ceramic substrate. Specifically, the metal foil includes copper foil or aluminum foil, preferably copper foil.

[0024] Furthermore, the surface metallization of the zirconia-toughened alumina ceramic substrate in this invention includes single-sided or double-sided surface metallization of the ceramic substrate.

[0025] The method for metallizing the surface of a zirconia-toughened alumina ceramic substrate described in this invention employs a cold spraying process to coat a γ-Al₂O₃ thin film onto the surface of the zirconia-toughened alumina ceramic substrate. This cold spraying process is a solid-state coating deposition technology that uses high-speed gas to accelerate powder to high speeds, causing it to deposit upon impact with the substrate. During particle impact, the sprayed powder particles undergo plastic deformation and adhere to the substrate due to kinetic energy. This utilizes the kinetic energy of the particles, rather than thermal energy, to achieve deposition, helping to avoid defects such as phase transitions, precipitation, and thermal stress within the substrate during traditional high-temperature deposition processes. Simultaneously, the high-speed impact of the particles during spraying releases residual stress in the substrate, thereby improving the substrate's performance. The cold spraying process reduces the surface energy of the ceramic substrate, which is beneficial for improving the wettability of the ceramic substrate to copper foil. The γ-Al₂O₃ thin film prepared using the cold spraying process avoids the impact of the zirconia phase dissolving to the bonding interface during sintering on the toughening effect of zirconia.

[0026] Preferably, step S2 specifically includes the steps of: providing γ-Al2O3 powder, and spraying the γ-Al2O3 powder onto the surface of the ZTA ceramic substrate using a cold spraying process to form the γ-Al2O3 thin film.

[0027] Preferably, the average particle size of the γ-Al2O3 powder is 10-45 μm; in some embodiments, it is preferably 10-30 μm, specifically 20 μm; the purity of the γ-Al2O3 powder is ≥90%.

[0028] The purity of the γ-Al₂O₃ powder described in this invention is ≥90%. Firstly, fewer impurity particles prevent stress concentration points from forming at the interface, thus reducing the interface's susceptibility to damage under load or thermal shock. Secondly, it avoids oxidation reactions of impurity elements, preventing the formation of low-melting-point oxides that would degrade the interface's performance at high temperatures. High-purity γ-Al₂O₃ powder helps maintain the stability of the interface layer in high-temperature environments, improving the oxidation resistance of the γ-Al₂O₃ film. Thirdly, high-purity γ-Al₂O₃ powder exhibits good flowability and dispersibility, a smaller particle size distribution, and higher purity, ensuring accelerated powder adhesion during spraying and resulting in a uniform and dense γ-Al₂O₃ film. This prevents pores or structural defects in the interface layer, which could negatively impact the performance of the zirconia-toughened alumina ceramic substrate.

[0029] More preferably, the purity of the γ-Al₂O₃ powder is not less than 95%. During the preparation of γ-Al₂O₃ powder, doping with α-Al₂O₃ or other phases of alumina is unavoidable. In practical applications, the inventors have found that when the γ-Al₂O₃ powder is doped with less than 5% of other phases of alumina, the resulting γ-Al₂O₃ film is more effective in preventing the dissolution and precipitation of zirconium oxide in the ZTA ceramic substrate at the interface. The strength of the ZTA ceramic substrate after metallization is not worse than before metallization, and may even be improved to some extent. This improved strength may be due to the impact force used in the cold spraying process releasing residual stress inside the substrate and eliminating internal defects such as vacancies and voids, thus further improving the substrate's microstructure. Preferably, the preparation method of the γ-Al₂O₃ powder includes the sol-gel method, hydrothermal method, or precipitation method.

[0030] The preparation method of the γ-Al2O3 powder can be selected according to the actual production needs, as long as it meets the requirements of this scheme for particle size distribution, purity, powder shape and loose packing density of γ-Al2O3 powder.

[0031] The powder shape should be spherical or nearly spherical to reduce powder agglomeration during spraying and improve the uniformity and density of the film. Loose packing density: Loose packing density is an important parameter for measuring powder flowability. A higher loose packing density helps improve powder delivery efficiency and film density during spraying. Typically, the loose packing density should be between 0.4 and 0.8 g / cm³. 3 Within the range.

[0032] Specifically, the sol-gel method includes the following steps:

[0033] a. Preparation of the precursor solution: Dissolve an aluminum salt in deionized water to form an aluminum salt solution, wherein the aluminum salt includes aluminum nitrate or aluminum chloride. Simultaneously, dissolve an organic compound in deionized water to form an organic compound solution, wherein the organic compound includes acetic acid or citric acid.

[0034] b. Mixed Solution: An aluminum salt solution is mixed with an organic compound solution to form a sol. During stirring, aluminum ions and the organic compound form a gel network structure.

[0035] c. Aging: Let the sol stand at 40-60℃ for a period of time to make the gel structure more stable.

[0036] d. Drying: The aged gel is placed in an oven for drying to remove residual moisture; the drying temperature is 80-120℃ and the drying time is 4-8h.

[0037] e. Calcination: The dried sample is calcined at a high temperature, preferably 600-800℃, to decompose the organic compound and generate γ-Al2O3 powder.

[0038] The hydrothermal method includes the following steps:

[0039] a. Prepare the precursor solution: Dissolve the aluminum salt in deionized water to form an aluminum salt solution.

[0040] b. Hydrothermal reaction: The aluminum salt solution is mixed with an appropriate amount of mineralizing agent, including sodium hydroxide, and placed in an autoclave for hydrothermal reaction at 100-220°C and pressure.

[0041] c. Separation and washing: The precipitate after the hydrothermal reaction is separated by centrifugation and washed with deionized water to remove impurities.

[0042] d. Drying and calcination: The washed sample is dried and then calcined at high temperature to generate γ-Al2O3.

[0043] The precipitation method includes the following steps:

[0044] a. Prepare the precursor solution: Dissolve the aluminum salt in deionized water to form an aluminum salt solution.

[0045] b. Precipitation reaction: An alkaline solution is slowly added to an aluminum salt solution to form a precipitate, wherein the alkaline solution includes one or both of sodium hydroxide or sodium carbonate solutions.

[0046] c. Aging: The precipitate is left to stand at a certain temperature for a period of time, said temperature being 60-80℃, to allow the precipitate to crystallize and grow.

[0047] d. Separation and washing: The precipitate is separated by centrifugation and washed with deionized water to remove impurities.

[0048] e. Drying and calcination: The washed sample is dried to further remove moisture. The drying temperature is 80-120℃ and the drying time is 4-8 hours. Then, it is calcined at a high temperature to generate γ-Al2O3 powder. The calcination temperature is 600-800℃, and the sample is held at the highest temperature for 1-2 hours.

[0049] Preferably, step S2 specifically includes the following steps: providing aluminum metal powder, using the cold spraying process to spray the aluminum metal powder onto the surface of the ZTA ceramic substrate to form an aluminum thin film layer, and heat-treating the ZTA ceramic substrate with the aluminum thin film layer in an oxygen atmosphere to oxidize the aluminum thin film layer to form a γ-Al2O3 thin film layer.

[0050] Preferably, the oxygen-containing atmosphere includes a high-temperature air atmosphere or an oxygen atmosphere; the heat treatment temperature is 600-800℃. Preferably, the heat treatment temperature is 650-750℃, and the oxidation time is 15±1 min.

[0051] The heat treatment is an oxidation process. During the oxidation process, the heat treatment conditions and processes are crucial to avoid the formation of porous structures in the γ-Al2O3 film and thus obtain a dense film structure.

[0052] Specifically, the heat treatment includes the following steps:

[0053] a. Place the substrate in an oxidation furnace, set the heating rate to 5℃ / min, and raise the temperature to 450℃;

[0054] b. Oxidize in air at 450℃ for 0.5-2 hours; during this process, the aluminum surface will react with oxygen to form an aluminum oxide layer;

[0055] c. Raise the temperature to 600℃ and keep it in the air for oxidation for 0.5-2 hours; during this process, the oxide layer will become denser.

[0056] d. Raise the temperature to 650-750℃ and maintain oxidation in air. The oxidation time at the highest temperature is 30 minutes. During this process, the oxide layer will continue to thicken, forming a relatively dense γ-Al2O3 film.

[0057] Preferably, the thickness of the γ-Al2O3 film is 10-100 μm. The thickness of the γ-Al2O3 film can be specifically set according to the actual application scenario, substrate properties, circuit design, and manufacturing process of the zirconia-toughened alumina ceramic substrate. For example, for IGBT modules, the thickness of the γ-Al2O3 film is preferably around 10 μm. The adhesion between the film and the substrate affects the stability and reliability of the film. A thinner film is easier to form a good bond with the substrate, thereby improving adhesion. However, an excessively thin film may not provide sufficient protection and performance; for the module, the thickness of the γ-Al2O3 film, as an insulating layer, affects the circuit performance. A thicker film can provide higher insulation performance, reducing leakage current and breakdown risk. However, an excessively thick film may lead to signal transmission delay and increased loss; the thickness of the film affects its thermal conductivity and coefficient of thermal expansion. A thinner film has higher thermal conductivity, which helps with heat dissipation. Simultaneously, the coefficient of thermal expansion of the film should be matched with the substrate and copper foil to avoid delamination and cracking caused by thermal stress. A thinner film's coefficient of thermal expansion is easier to match with the substrate and metal foils, including copper foil. The porosity of the γ-Al2O3 film is less than 3%. A preferred porosity of the γ-Al2O3 film is beneficial for obtaining a dense structure and helps improve the wettability between the metal foil and alumina.

[0058] In other embodiments, a layer of nano-copper can be deposited on γ-Al2O3 powder, and then a metal foil can be deposited on the nano-copper layer; the thickness of the nano-copper layer is 30-50 nm.

[0059] Preferably, the gas pressure in the cold spraying process is 0.3-0.8 MPa, ensuring the acceleration effect of the powder in the nozzle. Preferably, the gas pressure helps increase particle velocity, thereby improving the density and adhesion of the coating. The gas temperature is 300-600℃, which helps form better coating performance during spraying and improves the plasticity of the sprayed powder. The distance between the nozzle of the spraying device and the surface of the ZTA ceramic substrate is 10-30 mm. A suitable distance helps improve the density and adhesion of the coating, thus ensuring that the particles have sufficient kinetic energy when impacting the substrate. The nozzle scanning speed is 8-12 L / min. The nozzle scanning speed ensures the performance of the sprayed thin film layer, while the faster scanning speed improves the spraying efficiency. It is understood that the nozzle scanning speed can be adaptively adjusted according to the actual production requirements of the spraying area and the final coating thickness.

[0060] Controlling porosity is crucial in the preparation of alumina films. Besides adjusting parameters during the spraying process (such as gas pressure, nozzle-substrate distance, spraying temperature, and nozzle scanning speed, which affect the particle deposition rate; excessively fast deposition rates may lead to insufficient particle accumulation and increased porosity), this method also employs multi-layer spraying, compressing the film layers to precisely control porosity. Through the optimized combination of these methods, effective control of the porosity of cold-sprayed alumina films can be achieved.

[0061] At the same film thickness, the film formation process has a significant impact on film performance. Compared to single-layer spraying, multi-layer spraying can create different microstructures between different layers and improve the interfacial bonding between different layers. For example, the particle packing density and bonding strength can be controlled by adjusting the spraying parameters of each layer. Spraying the next layer of film is equivalent to heat-treating the previous layer. Therefore, multi-layer spraying can help alleviate internal stress caused by mismatch in thermal expansion coefficients or repair defects in the upper layer, improving film performance layer by layer, such as reducing the surface stress of the outermost layer in contact with copper foil and improving the wettability between the film and the metal.

[0062] Preferably, step S1 includes a pretreatment step for the ZTA ceramic substrate to remove surface impurities and improve the surface roughness of the ZTA ceramic substrate, thereby improving the adhesion between the ZTA ceramic substrate and the γ-Al2O3 film; the pretreatment step includes cleaning, grinding and sandblasting.

[0063] Example 1

[0064] S1 provides a zirconia-toughened alumina ceramic substrate, denoted as ZTA ceramic substrate;

[0065] S2, provide γ-Al2O3 powder, and spray the γ-Al2O3 powder onto the surface of the ZTA ceramic substrate using a cold spraying process to form the γ-Al2O3 thin film;

[0066] The process parameters in the cold spraying process are as follows: gas pressure is 0.5 MPa, gas temperature is 600℃, distance between nozzle and ceramic substrate surface is 10, nozzle scanning speed is 10 L / min, and a γ-Al2O3 film with a thickness of about 20 micrometers is prepared on ZTA ceramic substrate by cold spraying process, and the porosity of γ-Al2O3 film is 0.5%.

[0067] The γ-Al₂O₃ powder was prepared using a gel-sol method, specifically comprising the following steps: using aluminum chloride and citric acid as raw materials, stirring to form a gel, aging at 60°C for 4 hours, then drying in an oven at 100°C for 8 hours, and finally calcining in a muffle furnace at 800°C for 1 hour. The resulting γ-Al₂O₃ powder had an average particle size D50 of 10 micrometers, and by mass percentage, the γ-Al₂O₃ content was 95%, α-Al₂O₃ was 3%, and other impurities were 2%.

[0068] S3, using DBC, copper foil is deposited onto the γ-Al₂O₃ obtained in step S2, so that the metal foil is bonded to the surface of the ceramic substrate; then, the ZTA ceramic substrate with the metal foil is sintered to obtain a surface-metallized zirconia-toughened alumina ceramic substrate. Specifically, the metal foil includes copper foil or aluminum foil, preferably copper foil.

[0069] Example 2

[0070] Compared with Example 1, the difference in Example 2 is that the porosity of the γ-Al2O3 film obtained in step S2 is 1.8%.

[0071] Example 3

[0072] Compared with Example 1, the difference in Example 3 is that the porosity of the γ-Al2O3 film obtained in step S2 is 3%.

[0073] Example 4

[0074] Compared with Example 2, Example 4 differs in that:

[0075] In step S2, the γ-Al₂O₃ powder was prepared by precipitation method, and the average particle size D50 of the obtained γ-Al₂O₃ powder was 15 micrometers; the γ-Al₂O₃ content was 96% by mass percentage, α-Al₂O₃ was 2%, and other impurities were 2%.

[0076] Example 5

[0077] Compared with Example 2, Example 5 differs in that:

[0078] In step S2, the γ-Al₂O₃ powder was prepared by precipitation method, and the average particle size D50 of the obtained γ-Al₂O₃ powder was 15 micrometers; the γ-Al₂O₃ content was 98% by mass percentage, α-Al₂O₃ was 1%, and other impurities were 1%.

[0079] Example 6

[0080] Compared with Example 2, Example 6 differs in that:

[0081] In step S2, the γ-Al2O3 powder is obtained by precipitation method. The obtained γ-Al2O3 powder is then subjected to a high temperature treatment of about 750℃ for further phase transformation treatment to increase the content of γ-Al2O3. The average particle size D50 of the γ-Al2O3 powder is 13 micrometers. The γ-Al2O3 content is 99.2% by mass, and the rest is impurities.

[0082] Example 7

[0083] Compared with Example 1, Example 7 differs in that:

[0084] In step S2, the γ-Al2O3 content is 96% by mass percentage, the α-Al2O3 content is 2%, the porosity of the γ-Al2O3 film is 1.8%, and the film thickness is 40 micrometers. The film is coated with three layers with thicknesses of 20, 10, and 10 micrometers, and the coating temperatures are 600, 540, and 500 °C, respectively.

[0085] Example 8

[0086] Compared with Example 1, Example 8 differs in that:

[0087] In step S2, the γ-Al2O3 content is 96% by mass percentage, the α-Al2O3 content is 2%, the porosity of the γ-Al2O3 film is 1.8%, and the film thickness is 60 micrometers. The film is coated with three layers with thicknesses of 20, 20, and 10 micrometers, and the coating temperatures are 600, 555, and 450°C, respectively.

[0088] Example 9

[0089] Compared with Example 1, Example 9 differs in that:

[0090] In step S2, the γ-Al₂O₃ content is 96% by mass, the α-Al₂O₃ content is 2%, the porosity of the γ-Al₂O₃ film is 1.8%, and the film thickness is 80 micrometers. The film is coated with four layers with thicknesses of 20, 20, 30, and 10 micrometers, respectively, and the coating temperatures are 600, 500, 540, and 400°C, respectively.

[0091] Example 10

[0092] Compared with Example 1, Example 9 differs in that:

[0093] In step S2, the γ-Al₂O₃ content is 96% by mass, the α-Al₂O₃ content is 2%, the porosity of the γ-Al₂O₃ film is 1.8%, and the film thickness is 100 micrometers. The film is coated with five layers with thicknesses of 20, 30, 30, 10, and 10 micrometers, and the coating temperatures are 600, 545, 480, 400, and 300 °C, respectively.

[0094] Comparative Example 1

[0095] Compared with Example 1, the difference in Comparative Example 1 is as follows:

[0096] In the process of preparing powder by sol-gel method, the calcination temperature is 1020℃ and the temperature is held at 1020℃ for 1 hour to obtain alumina powder with 92% α-Al2O3 content, 6% γ-Al2O3 content, and 2% other impurities.

[0097] Comparative Example 2

[0098] Compared with Example 1, Comparative Example 2 differs in that:

[0099] In the process of preparing powder by sol-gel method, the calcination temperature is 950℃, and the temperature is kept at 950℃ for 1 hour to obtain alumina powder with 78% α-Al2O3 content, 11% γ-Al2O3 content, and the rest being impurities.

[0100] Comparative Example 3

[0101] Compared with Example 1, Comparative Example 3 differs in that:

[0102] The γ-Al2O3 film was subsequently processed to form a completely dense film with a porosity of less than 1%.

[0103] Comparative Example 4

[0104] Compared with Example 1, the difference in Comparative Example 4 is that the thickness of the γ-Al2O3 film is 10 micrometers.

[0105] Comparative Example 5

[0106] Compared with Example 7, the difference in Comparative Example 5 is that the 40-micrometer-thick γ-Al2O3 film was formed by a single spraying at a spraying temperature of 600°C.

[0107] Comparative Example 6

[0108] Compared with Example 10, the difference in Comparative Example 6 is that the 100-micrometer-thick γ-Al2O3 film was formed by a single spraying at a spraying temperature of 480°C.

[0109] Test case

[0110] The performance of the surface-metallized zirconia-toughened alumina ceramic substrates prepared in Examples 1-10 and Comparative Examples 1-6 was tested, and the test results are shown in the table below. The tests included:

[0111] I. High-temperature-cold water cycle test: The surface metallized zirconia toughened alumina ceramic substrate obtained in this invention is placed at 300℃ for 5 minutes. After multiple cycles, observe whether the copper foil lifts or falls off, and whether the ceramic substrate breaks. Record the maximum number of cycles.

[0112] II. Thermal shock resistance test: The temperature range is from -40℃ to 125℃, with a high and low temperature duration of 30 minutes and a transition time of less than 30 seconds. After multiple cycles, observe whether the copper foil curls up or the ceramic substrate breaks; record the number of cycles.

[0113] III. Peel Strength Test: The selected copper foil has a length ≥ 100 mm and a width of 5 ± 0.1 mm. The peel strength is tested under the conditions of a peeling speed of 50 mm / min and a peeling angle of 90° ± 5°.

[0114]

[0115]

[0116] As shown in the table above, in Examples 1-3, high porosity is beneficial for enhancing the bonding strength between the metal and the ceramic substrate, but excessively high bonding strength can lead to increased material brittleness. Test results from Examples 2, 4, 5, and 6 indicate that doping the γ-Al₂O₃ powder with an appropriate amount of α-Al₂O₃ is beneficial for improving the thermal shock resistance of the metallized ZTA substrate. Test results from Examples 1, 7, 8, 9, and 10 show that film thickness has little effect on high-temperature-cold water cycling and peel strength, but a significant effect on thermal shock resistance; when the film thickness is 40 micrometers, the thermal shock resistance reaches as high as 153 cycles. The test results from Comparative Examples 1-3 demonstrate that the optimal range of γ-Al₂O₃ content in the γ-Al₂O₃ powder, as well as the thickness and porosity of the γ-Al₂O₃ film, is crucial to the performance of the obtained surface-metallized zirconia-toughened alumina ceramic substrate.

[0117] Examples 1, 7, 8, 9, and 10, with film thicknesses of 20, 40, 60, 80, and 100 micrometers respectively, all exhibited a porosity of 1.8%. They demonstrated excellent performance in high-temperature-cold water cycling and thermal shock resistance. Example 7 achieved the highest values ​​in both aspects, with 23 cycles and 153 thermal shocks respectively. Using a multi-layer spraying method, the performance of Comparative Example 5 decreased to 9 cycles and 23 thermal shocks compared to Example 7; and compared to Example 10, Comparative Example 6 decreased from 19 and 117 in high-temperature-cold water cycling and thermal shock resistance to 5 and 17 respectively. At the same film thickness, the film formation process significantly affects the film performance.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A method of surface metallization of a zirconia toughened alumina ceramic substrate, characterized in that, The method comprises the steps of: S1, providing a zirconia toughened alumina ceramic substrate, denoted as a ZTA ceramic substrate; S2, preparing a γ-Al2O3 film on the surface of the ZTA ceramic substrate by a cold spraying process; specifically comprising the steps of: providing γ-Al2O3 powder, and spraying the γ-Al2O3 powder on the surface of the ZTA ceramic substrate by the cold spraying process to form the γ-Al2O3 film; The thickness of the γ-Al2O3 film is 20-100 μm; the porosity of the γ-Al2O3 film is 1.8%-3%; S3, bonding a metal foil to the surface of the ZTA ceramic substrate after the treatment in step S2, and then sintering the ZTA ceramic substrate with the metal foil to obtain a zirconia toughened alumina ceramic substrate with a metalized surface.

2. The method of claim 1, wherein: The average particle size of the γ-Al2O3 powder is 10-45 μm; the purity of the γ-Al2O3 powder is greater than or equal to 90%.

3. The method of claim 1, wherein, The preparation method of the γ-Al2O3 powder comprises a sol-gel method, a hydrothermal method or a precipitation method.

4. The method of claim 1, wherein: In step S2, specifically comprising the steps of: providing aluminum metal powder, spraying the aluminum metal powder on the surface of the ZTA ceramic substrate by the cold spraying process to form an aluminum film layer, and heat treating the ZTA ceramic substrate with the aluminum film layer in an oxygen-containing atmosphere to oxidize the aluminum film layer to form a γ-Al2O3 film layer.

5. The method of claim 4, wherein: The oxygen-containing atmosphere comprises a high-temperature air atmosphere or an oxygen atmosphere; the temperature of the heat treatment is 600-800 ℃.

6. The method of claim 1, wherein: The gas pressure of the cold spraying process is 0.3-0.8 MPa, the gas temperature is 300-600 ℃, the distance between the nozzle of the spraying device and the surface of the ZTA ceramic substrate is 10-30 mm, and the scanning speed of the nozzle is 8-12 L / min.

7. The method of claim 1, wherein, In step S1, the ZTA ceramic substrate is subjected to a pretreatment step, and the pretreatment step comprises cleaning, grinding and sandblasting.

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