Ceramic copper-clad plate and preparation method thereof

Abstract

The present invention provides a ceramic copper-clad laminate and a preparation method thereof. Active elements are first deposited directly on a ceramic substrate through a coating process, and a brazing material layer is pre-compounded on a copper plate to obtain a "brazing material-Cu" composite plate. Under vacuum brazing process conditions, when the brazing material melts, it stimulates an active brazing reaction between the active metal elements plated on the ceramic plate and the ceramic, tightly welding the ceramic plate and the copper plate together to obtain a ceramic copper-clad laminate. The copper-clad laminate manufacturing process of the present invention does not involve organic matter, so common defects such as holes and cold solder joints caused by organic decomposition residues will not appear at the interface, thereby greatly improving the brazing adhesion of the ceramic copper-clad laminate and significantly improving the cold and hot cycle reliability.

Description

Technical Field

[0001] The present application belongs to the technical field of ceramic copper clad laminates, and in particular relates to a ceramic copper clad laminate and a preparation method thereof. Background Art

[0002] Ceramic copper-clad laminates (CCLs) are critical, basic components widely used in the industrial electronics field. Reliably bonding the copper layer to the ceramic layer is a key technical challenge in their manufacture. Common methods for copper coating ceramic surfaces include thin-film, thick-film, electroless plating, laser copper coating, direct copper deposition (DBC), and active metal brazing (AMB). Ceramic CCLs used for high-power, high-current-carrying IGBTs and SIC components typically utilize the AMB method to bond the conductive copper foil to the ceramic substrate. The current AMB process requires first screen-printing a layer of active metal solder paste onto the surface of the ceramic substrate, followed by a layer of oxygen-free copper tape. The three components are then tightly clamped together and placed in a vacuum brazing furnace for high-temperature brazing.

[0003] The reliability of the AMB process depends largely on a number of key factors, including the composition of the active solder powder, the brazing process, and the microstructure of the brazing layer. First, the active element (usually Ti) is prone to oxidation, segregation, or forming a brittle intermediate phase with the brazing alloy elements, affecting brazing reliability. Second, the thick-film printed solder paste process releases a large amount of organic matter during heating in a vacuum furnace. The residual organic matter can easily cause numerous holes at the brazing interface, making the substrate susceptible to high-voltage breakdown, induced cracks, and solder layer shedding during service. Summary of the Invention

[0004] In order to overcome the technical problems of poor stability of active elements and volatilization of a large amount of organic matter during heating in the existing copper clad laminate manufacturing process, the present application provides a preparation method for a ceramic copper clad laminate. During the preparation process of the copper clad laminate, active brazing elements are directly deposited on the ceramic substrate through a coating process, and a brazing layer is pre-compounded on the copper plate. Under vacuum brazing process conditions, when the brazing layer melts, the active brazing reaction at the interface is stimulated, so that the ceramic plate and the copper plate are tightly welded together to obtain a ceramic copper clad laminate.

[0005] A method for preparing a ceramic copper-clad laminate comprises the following steps:

[0006] S1, coating an active brazing element film on the surface of a ceramic substrate;

[0007] S2, clamping the brazing alloy-Cu composite strip on the ceramic substrate coated with the active brazing element film;

[0008] S3. Vacuum brazing the sandwiched composite material to obtain the ceramic copper clad laminate.

[0009] In response to the defects of the existing copper clad laminate production technology, the present invention creates a new production process, which deposits the active elements in a single substance form on the ceramic substrate in advance through a thin film process to ensure that they can play their maximum role in the subsequent active brazing process. In addition, an appropriate process is selected to compound the brazing material layer with oxygen-free copper to obtain a "brazing material-Cu" composite plate of a certain thickness; the side of the composite plate containing the brazing material is bonded and clamped to the ceramic plate coated with the active metal layer, and then placed in a vacuum furnace for brazing; during the brazing process, when the brazing material melts, it stimulates the active metal elements plated on the ceramic plate to produce an active brazing reaction with the ceramic, so that the Cu plate and the ceramic substrate are firmly welded together to form a ceramic copper clad laminate. The copper clad laminate manufacturing process of the present invention does not involve organic matter, so common defects such as holes and cold solder joints caused by organic decomposition residues will not appear at the interface, which greatly improves the brazing adhesion of the ceramic copper clad laminate and the reliability of hot and cold cycles.

[0010] Preferably, the solder alloy is AgCuX solder, the typical composition of which is Ag. 余 Cu (10-50wt％) X (0.01-30wt％) , wherein X is at least one of Sn, In, Ni, Li, Bi, Pb, Ge, Ga or P, and the solder is AgCu 28 The eutectic alloy is the basic formula, in which the X component is added to control the melting point of the solder and adjust the wettability of the solder to meet the needs of different brazing process conditions.

[0011] Another preferred embodiment is that the solder alloy is a CuSnX solder alloy, the typical composition of which is Cu 余 Sn (5-30wt％) X (0.01-20wt％) , wherein X is at least one of In, Ni, Li, Bi, Pb, Ge, Ga or P, and the solder is CuSn (10-30wt％) The addition of X component is to control the melting point of the solder and adjust the wettability of the solder to meet the needs of different brazing process conditions.

[0012] Preferably, in step S2, the preparation process of the solder alloy-Cu composite strip is as follows: the solder alloy foil strip and the copper plate are composited by rolling or diffusion welding, and the solder layer is composited with oxygen-free copper to obtain a "solder-Cu" composite plate of a certain thickness.

[0013] Another preferred embodiment is that in step S2, the preparation process of the solder alloy-Cu composite strip is as follows: the solder alloy powder is sprayed by supersonic flame spraying, supersonic cold air power spraying, plasma spraying or laser cladding spraying to composite the solder alloy with the copper plate, and an appropriate process is selected to composite the solder layer with oxygen-free copper to obtain a "brazing-Cu" composite plate of a certain thickness.

[0014] Preferably, in step S2, in the solder alloy-Cu composite strip, the copper layer has a thickness of 0.2-2.5 mm, and the solder layer has a thickness of 5-80 μm. This application strictly controls the thickness of each layer in the solder alloy-Cu composite strip, and the side of the composite plate containing the solder is bonded and clamped to the ceramic plate coated with the active metal layer, and then placed in a vacuum furnace for brazing; during the brazing process, when the solder melts, an active brazing reaction is stimulated between the active metal elements plated on the ceramic plate and the ceramic, so that the Cu plate and the ceramic substrate are firmly welded together to form a ceramic copper-clad plate.

[0015] Preferably, the active brazing element is one or more of Ti, Zr, and Hf. In the present application, the active elements Ti, Zr, or Hf are pre-deposited in a single-element form onto a ceramic substrate through a thin film process. The active elements will react with the ceramic substrate during the subsequent brazing process, so that the brazing layer and the ceramic are tightly combined.

[0016] Further preferably, the thickness of the active brazing element film is 0.2-10 μm. The present application strictly controls the coating process to ensure that a continuous, uniformly thick, and surface-oxidized active metal coating layer is formed on the ceramic substrate.

[0017] Preferably, in step S1, the active brazing element film on the surface of the ceramic substrate is obtained by a physical vapor deposition (PVD) method (including but not limited to electron beam vacuum evaporation coating, magnetron sputtering coating, ion plating and other process technologies), and the film layer can also be obtained by chemical plating; a high-purity active element metal is made into a target material, installed on a coating equipment, and a clean ceramic sheet is used as a substrate for vacuum coating. It is necessary to ensure that the active metal deposited on the ceramic substrate is in a single state and is not oxidized or reacted to form other compounds.

[0018] Furthermore, the material of the ceramic substrate is any one of Al2O3, AlN, Si3N4, and ZTA (zirconia toughened alumina), and the active element Ti (or Zr, Hf) is pre-deposited on the ceramic substrate in a single substance form through a thin film process to ensure that it is most effective in the subsequent active brazing process.

[0019] Furthermore, in step S3, the vacuum brazing is carried out in a vacuum furnace with a vacuum degree ≥5×10-3Pa, a brazing temperature of 800-1050°C, and a holding time of 10-120min. The above-mentioned clamped plates are vacuum brazed so that the ceramic and copper are welded together through the brazing material layer between the two to obtain a ceramic copper clad plate.

[0020] Another object of the present application is to provide a ceramic copper-clad laminate, which is prepared using the above-mentioned method for preparing the ceramic copper-clad laminate. During the preparation of the copper-clad laminate, the active brazing element is directly deposited on the ceramic substrate through a plating process, and the brazing material layer is pre-compounded on the copper plate. Under vacuum brazing process conditions, when the brazing layer melts, the active brazing reaction at the interface is stimulated, so that the ceramic plate and the copper plate are tightly welded together to obtain the ceramic copper-clad laminate.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention provides a ceramic copper-clad laminate and a preparation method thereof. Active elements are first directly deposited on a ceramic substrate through a coating process, and a brazing material layer is pre-compounded on a copper plate to obtain a "brazing material-Cu" composite plate. Under vacuum brazing process conditions, when the brazing material melts, an active brazing reaction is stimulated between the active metal elements plated on the ceramic plate and the ceramic, so that the ceramic plate and the copper plate are tightly welded together to obtain a ceramic copper-clad laminate. The copper-clad laminate manufacturing process of the present invention does not involve organic matter, so common defects such as holes and cold solder joints caused by organic decomposition residues will not appear at the interface, thereby greatly improving the brazing adhesion of the ceramic copper-clad laminate and greatly improving the cold and hot cycle reliability. DETAILED DESCRIPTION

[0023] The technology of the present invention is described in detail below:

[0024] The specific technical solutions of the present invention are described with reference to specific examples 1-15 and comparative examples 1-2:

[0025] Example 1:

[0026] A method for preparing a ceramic copper-clad laminate comprises the following steps:

[0027] S1, Titanium plating on ceramic substrate:

[0028] The film is coated by magnetron sputtering: a high-purity Ti target is fixed on the cathode, and a clean AlN substrate is placed on the anode facing the target surface, 150-180 mm away from the target; the system is evacuated to high vacuum and filled with 10 -1Pa of argon gas, a voltage of 3000-4000V is applied between the cathode and anode, causing a glow discharge between the two electrodes. The positive ions generated by the discharge fly toward the cathode under the action of the electric field and collide with the atoms on the surface of the Ti target. The Ti atoms escaped from the target surface due to the collision and deposited on the surface of the AlN substrate to form a film. The sputtering process time is controlled until a Ti film with a thickness of 1-3μm is obtained. After turning the substrate over, magnetron sputtering coating is continued until a Ti film with a thickness of 1-3μm is also obtained on the other side of the substrate.

[0029] S2. Preparation of solder-Cu composite plate:

[0030] The AgCu pre-prepared by rolling composite method 28 -Cu composite plate strip (AgCu 28 After cutting the solder layer (thickness of the brazing material is 25μm and the thickness of the Cu layer is 0.6mm) into the same size as the AlN substrate, two composite copper plates are used to sandwich the double-sided titanium-plated AlN substrate in the middle to make the AgCu 28 The brazing material layer is completely fitted to the titanium-plated surface, completing the clamping;

[0031] S3 vacuum brazing:

[0032] The clamped and bonded plates were placed in a vacuum furnace and the vacuum degree in the furnace was pumped to a value higher than 5×10 -3 Pa, the brazing temperature is 930℃, the holding time is 30min, and the furnace is cooled to below 200℃ and then taken out to complete the vacuum brazing; after brazing, the ceramic substrate and the copper plate are tightly welded together to obtain a ceramic copper clad laminate.

[0033] Example 2:

[0034] The difference from Example 1 is that the preparation method of the "solder-Cu" composite strip in step S2 is different. Specifically, step S2 is:

[0035] AgCu was deposited by high velocity oxygen fuel (HVOF) process. 28 The alloy powder was sprayed onto an oxygen-free copper plate with a thickness of 0.6 mm. The process parameters were as follows: kerosene 13 L / hr, oxygen 780 L / min, oxygen-oil ratio 1.73, combustion chamber pressure 1.53 MPa, spray gun movement speed 1000 mm / s, and spray distance 150 mm. After spraying, the composite blank was annealed at 650 ° C for 1 hour and then leveled. The sprayed surface was machined and thinned to make the AgCu 28 The thickness of the solder layer is 25 μm.

[0036] Example 3:

[0037] The difference from Example 1 is the titanium process in step S1, specifically step S1:

[0038] The multi-arc ion plating process is used for coating: the ALN ceramic substrate cleaned with acetone is placed in the sample holder of the multi-arc ion plating machine, the pressure in the vacuum chamber is evacuated to 1.6×10-4Pa, and the working gas argon is filled in. Ion bombardment is carried out for 10 minutes, the argon flow rate is 10-25sccm, the gas pressure is 1.0-2.0Pa, the anode filament input power is 200-300W, and after the auxiliary heating temperature reaches 250℃, the multi-arc ion plating Ti target power is turned on for coating, the sputtering power is 200W-250W, the single-element target current is 60-70A, the negative bias voltage is controlled at -120~-150V, and the coating time is controlled to obtain a film thickness of 2-3μm.

[0039] Example 4:

[0040] The difference from Example 1 lies in the titanium plating process in step S1 and the preparation method of the "solder-Cu" composite plate strip in step S2.

[0041] The specific step S1 is:

[0042] The multi-arc ion plating process is used for coating: the ALN ceramic substrate cleaned with acetone is placed in the sample holder of the multi-arc ion plating machine, the pressure in the vacuum chamber is evacuated to 1.6×10-4Pa, and the working gas argon is filled in. Ion bombardment is carried out for 10 minutes, the argon flow rate is 10-25sccm, the gas pressure is 1.0-2.0Pa, the anode filament input power is 200-300W, and after the auxiliary heating temperature reaches 250℃, the multi-arc ion plating Ti target power is turned on for coating, the sputtering power is 200W-250W, the single-element target current is 60-70A, the negative bias voltage is controlled at -120~-150V, and the coating time is controlled to obtain a film thickness of 2-3μm.

[0043] The specific step S2 is:

[0044] AgCu was deposited by high velocity oxygen fuel (HVOF) process. 28 The alloy powder was sprayed onto an oxygen-free copper plate with a thickness of 0.6 mm. The process parameters were as follows: kerosene 13 L / hr, oxygen 780 L / min, oxygen-oil ratio 1.73, combustion chamber pressure 1.53 MPa, spray gun movement speed 1000 mm / s, spray distance 150 mm. After spraying, the composite blank was annealed at 650°C for 1 hour and then leveled. The sprayed surface was machined and thinned to make the AgCu 28 The thickness of the solder layer is 25 μm.

[0045] Example 5:

[0046] The difference from Example 1 is that the solder formula in step S2 is different.

[0047] The specific step S2 is:

[0048] The AgCu pre-prepared by rolling composite method 26 In5-Cu composite strip (AgCu 26 After cutting the In5 solder layer (thickness of 25μm, thickness of Cu layer 0.6mm) into the same size as the AlN substrate, two composite copper plates were used to sandwich the double-sided titanium-plated AlN substrate in the middle. 26 The In5 brazing material layer is completely in contact with the titanium-plated surface, completing the clamping.

[0049] Example 6:

[0050] The difference from Example 1 is that the designed thickness of the solder in step S2 is different.

[0051] The specific step S2 is:

[0052] The AgCu obtained by rolling composite method 28 -Cu composite strip (AgCu 28 After cutting the solder layer (thickness of the brazing material is 12 μm and the thickness of the Cu layer is 0.6 mm) into the same size as the AlN substrate, two composite copper plates are used to sandwich the double-sided titanium-plated AlN substrate in the middle to make the AgCu 28 The brazing material layer is completely in contact with the titanium-plated surface, completing the clamping.

[0053] Example 7:

[0054] The difference from Example 1 is that the designed thickness of the solder in step S2 is different.

[0055] The specific step S2 is:

[0056] The AgCu obtained by rolling composite method 28 -Cu composite strip (AgCu 28 After cutting the brazing material layer (thickness of the brazing material is 35μm and the thickness of the Cu layer is 0.6mm) into the same size as the AlN substrate, two composite copper plates are used to sandwich the double-sided titanium-plated AlN substrate in the middle to make the AgCu 28 The brazing material layer is completely in contact with the titanium-plated surface, completing the clamping.

[0057] Example 8:

[0058] The difference from Example 1 lies in the difference in the titanium plating process in step S1 and the designed thickness of the titanium plating layer.

[0059] The specific step S1 is:

[0060] The multi-arc ion plating process is used for coating: the ALN ceramic substrate cleaned with acetone is placed in the sample holder of the multi-arc ion plating machine, the pressure in the vacuum chamber is evacuated to 1.6×10-4Pa, and the working gas argon is filled in. Ion bombardment is carried out for 10 minutes, the argon flow rate is 10-25sccm, the gas pressure is 1.0-2.0Pa, the anode filament input power is 200-300W, and after the auxiliary heating temperature reaches 250℃, the multi-arc ion plating Ti target power is turned on for coating, the sputtering power is 200W-250W, the single-element target current is 60-70A, the negative bias voltage is controlled at -120~-150V, and the coating time is controlled to obtain a film thickness of 2-3μm.

[0061] Example 9:

[0062] The difference from Example 1 lies in the difference in the titanium plating process in step S1 and the designed thickness of the titanium plating layer.

[0063] The specific step S1 is:

[0064] The multi-arc ion plating process is used for coating: the ALN ceramic substrate cleaned with acetone is placed in the sample holder of the multi-arc ion plating machine, the pressure in the vacuum chamber is evacuated to 1.6×10-4Pa, and the working gas argon is filled in. Ion bombardment is carried out for 10 minutes, the argon flow rate is 10-25sccm, the gas pressure is 1.0-2.0Pa, the anode filament input power is 200-300W, and after the auxiliary heating temperature reaches 250℃, the multi-arc ion plating Ti target power is turned on for coating, the sputtering power is 200W-250W, the single-element target current is 60-70A, the negative bias voltage is controlled at -120~-150V, and the coating time is controlled to obtain a film thickness of 5-6μm.

[0065] Example 10:

[0066] The difference from Example 1 is the selection of active elements in step S1.

[0067] The specific step S1 is:

[0068] The multi-arc ion plating process involves using Zr as the active metal and installing a 99.99% pure Zr target on the target position of the coating machine. An acetone-cleaned AlN ceramic substrate is placed in the sample holder of the multi-arc ion plating machine. The vacuum chamber is evacuated to a pressure of 1.6×10-4 Pa and filled with argon. Ion bombardment is performed for 10 minutes at an argon flow rate of 10-25 sccm and a pressure of 1.0-2.0 Pa. The anode filament input power is 200-300 W. After the auxiliary heating temperature reaches 250°C, the multi-arc ion plating Zr target power supply is turned on for coating. Sputtering power is 200-250 W, the target current is 60-70 A, and the negative bias voltage is controlled between -120 and -150 V. The coating time is controlled to achieve a film thickness of 3-4 μm.

[0069] Example 11

[0070] The difference from Example 1 is that the ceramic substrate used in step S1 is different.

[0071] The specific step S1 is:

[0072] Si3N4 is used as the ceramic substrate, and the magnetron sputtering method is used for coating. The coating time is controlled to make the titanium film thickness 1-3μm.

[0073] Example 12

[0074] The difference from Example 1 is that the ceramic substrate used in step S1 is different, and the coating process used is different.

[0075] The specific step S1 is:

[0076] Si3N4 was used as the ceramic substrate and the film was plated by multi-arc ion plating process. The specific process was the same as that in Example 3. The plating time was controlled to make the titanium film thickness 3-4 μm.

[0077] Example 13

[0078] The difference from Example 1 is that:

[0079] In the specific step S1, AlN is used as a ceramic substrate; a multi-arc ion plating process is used for coating, and the specific process is the same as that of Example 3. The coating time is controlled to make the titanium film thickness 3-4 μm;

[0080] The solder composition used in step S2 is CuSn 10 P 0.2 , the thickness of the solder layer in the composite plate is 35μm, and the thickness of the Cu layer is 0.6mm;

[0081] The brazing temperature in step S3 is also modified to be the same as that of CuSn 10 P 0.2 The physical properties of the brazing filler metals are matched, the brazing temperature is 1030°C, the holding time is 30 minutes, and the furnace is cooled to below 300°C and then taken out to complete the vacuum brazing; after brazing, the ceramic substrate and the copper plate are tightly welded together to obtain a ceramic copper clad laminate.

[0082] Example 14

[0083] The difference from Example 1 is that:

[0084] Specifically, step S1 uses Si3N4 as a ceramic substrate; a multi-arc ion plating process is used for coating, and the specific process is the same as that of Example 3. The coating time is controlled to make the titanium film thickness 3-4 μm;

[0085] The solder composition used in step S2 is CuSn10 P 0.2 , the thickness of the solder layer in the composite plate is 35μm, and the thickness of the Cu layer is 0.6mm;

[0086] The brazing temperature in step S3 is also modified to be the same as that of CuSn 10 P 0.2 The brazing filler metals are matched, the brazing temperature is 1030°C, the holding time is 30 minutes, and the furnace is cooled to below 300°C and then taken out to complete the vacuum brazing; after brazing, the ceramic substrate and the copper plate are tightly welded together to obtain a ceramic copper clad laminate.

[0087] Example 15

[0088] The difference from Example 1 is that:

[0089] Specifically, step S1 uses Al2O3 as a ceramic substrate; a multi-arc ion plating process is used for coating, and the specific process is the same as that of Example 3. The coating time is controlled to make the titanium film thickness 3-4 μm;

[0090] The solder composition used in step S2 is CuSn 10 P 0.2 , the thickness of the solder layer in the composite strip is 35μm, and the thickness of the Cu layer is 0.6mm;

[0091] The brazing temperature in step S3 is also modified to be the same as that of CuSn 10 P 0.2 The brazing temperature is 1030°C with a holding time of 30 minutes. The material is then cooled to below 300°C and removed from the furnace to complete the vacuum brazing. After brazing, the ceramic substrate and the copper plate are tightly welded together to form a ceramic copper-clad laminate.

[0092] Comparative Example 1:

[0093] Using commercially available paste-like active metal solder paste, according to the current AMB process, the active solder paste is printed on both sides of the AlN ceramic substrate using a screen printing process, and then covered with oxygen-free copper tape. The three are tightly clamped together and placed in a vacuum brazing furnace. Brazing is performed according to the process of step S3 in Example 1.

[0094] Comparative Example 2:

[0095] Using commercially available paste-like active metal solder paste, according to the current AMB process, the active solder paste was printed on both sides of the Si3N4 ceramic substrate using a screen printing process, covered with oxygen-free copper tape, and the three were tightly clamped together and placed in a vacuum brazing furnace. Brazing was performed according to the process flow of step S3 in Example 1.

[0096] The performance of the ceramic copper clad laminates prepared in Examples 1-4 and the products prepared in Comparative Examples 1-2 was tested. The test results are shown in Table 1:

[0097] Table 1: Comparison of test results of examples

[0098]

[0099] From the above comparative experiments, it can be seen that the ceramic copper-clad laminate prepared in the embodiment of the present application has excellent brazing adhesion, a good number of hot and cold cycles, a lower void rate, and better performance than the comparative example.

[0100] The above descriptions are provided in conjunction with specific content to provide one or more embodiments, and the specific implementation of the present invention is not limited to these descriptions. Any similarity or similarity with the methods, structures, etc. of the present invention, or any technical deduction or substitution based on the concept of the present invention, shall be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a ceramic copper-clad laminate, characterized in that: The following steps are involved: S1, coating an active brazing element thin film on the surface of a ceramic substrate, wherein the active brazing element is Ti, and the material of the ceramic substrate is Si3N4; S2, clamping the brazing alloy-Cu composite strip on the ceramic substrate coated with the active brazing element film, wherein the brazing alloy is AgCu 28 The preparation process of the brazing alloy-Cu composite strip is as follows: brazing alloy powder is composited with an oxygen-free copper plate by supersonic flame spraying, supersonic cold air power spraying, plasma spraying or laser cladding spraying; S3. Vacuum brazing the sandwiched composite material to obtain the ceramic copper clad laminate.

2. The method for preparing a ceramic copper-clad laminate according to claim 1, wherein: In step S2, in the solder alloy-Cu composite strip, the copper layer has a thickness of 0.2-2.5 mm, and the solder layer has a thickness of 5-80 μm.

3. The method for preparing a ceramic copper-clad laminate according to claim 1, wherein: In step S1, the thickness of the active brazing element film is 0.2-10 μm.

4. The method for preparing a ceramic copper clad laminate according to claim 1, wherein: In step S1 , a thin film of active brazing element is deposited on the surface of the ceramic substrate by using any one of vacuum evaporation process, magnetron sputtering process, multi-arc ion plating process or chemical plating process.

5. The method for preparing a ceramic copper clad laminate according to claim 1, wherein: In step S3, the vacuum brazing is carried out in a vacuum furnace with a vacuum degree of ≥5×10 -3 Pa, brazing temperature 800-1050℃, holding time 10-120min.

6. A ceramic copper-clad laminate, characterized in that: The ceramic copper-clad plate is prepared by the preparation method of any one of claims 1 to 5.

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