Active metal brazing ceramic copper clad plate and preparation method thereof

Abstract

The application discloses an active metal brazing ceramic copper-clad plate and a preparation method thereof. The active metal brazing ceramic copper-clad plate has a structure from top to bottom as follows: an oxygen-free copper foil (201) with a thickness of 0.2mm-2mm; an active metal brazing paste (301) with a thickness of 10um-40um; a ceramic substrate (10) with a thickness of 0.25mm-1mm; an active metal brazing paste (302) with a thickness of 10um-40um; and an oxygen-free copper foil (202) with a thickness of 0.2mm-2mm. The active metal brazing paste comprises active metal brazing filler powder and active metal brazing filler organic carrier, and the mass percentage of the active metal brazing filler organic carrier is 10wt%-20wt%. Compared with the prior art, the application has the following beneficial effects: the active metal brazing ceramic copper-clad plate realizes low-stress and high-strength brazing combination of the ceramic substrate and the oxygen-free copper foil, and has the advantages of high peeling strength, low cavity rate, low surface warping degree, high heat cycle reliability and the like.

Description

Technical Field

[0001] This invention relates to the field of ceramic copper-clad laminate technology, specifically to an active metal brazing ceramic copper-clad laminate that can reduce residual stress and warpage of ceramic copper-clad laminate and its preparation method. Background Technology

[0002] Traditional manufacturing processes for ceramic copper-clad laminates mainly include two methods: direct bonding (DBC) and active metal brazing (AMB).

[0003] Direct bonding (DBC) refers to the process of directly welding copper foil to the surface of an alumina or aluminum nitride ceramic substrate through a Cu / O eutectic phase in an oxygen-containing nitrogen environment at a high temperature of 1063℃. The oxygen-free copper foil and the ceramic substrate are bonded through the Cu / O eutectic phase.

[0004] Active metal brazing (AMB) refers to the use of active metal brazing filler containing small amounts of active elements such as Ti, Zr, and Hf to achieve high-strength brazing between oxygen-free copper foil and ceramic substrate. The oxygen-free copper foil and ceramic substrate are bonded together through a brazing layer of a certain thickness.

[0005] The bonding strength between the oxygen-free copper foil and the ceramic substrate in DBC ceramic copper-clad laminates is not high. The significant difference in thermal expansion coefficients between copper and ceramic leads to high residual stress after cooling, which may cause detachment after high and low temperature shocks. Furthermore, the limited number of heat cycle withstand cycles severely impacts the reliability of the ceramic copper-clad laminate during long-term service. Additionally, the relatively large thickness of the oxygen-free copper foil results in low flatness of the DBC ceramic copper-clad laminate, directly affecting subsequent chip bonding. In summary, the DBC ceramic copper-clad laminate process is complex, costly, and its quality needs improvement.

[0006] Active metal brazing ceramic copper-clad laminate combines the high thermal conductivity, high insulation, high strength, and corrosion resistance of ceramics with the high electrical conductivity, high heat dissipation, and excellent welding performance of oxygen-free copper foil. The brazing layer at the weld joint can alleviate the thermal stress caused by the mismatch in thermal expansion coefficients between ceramic and metal, resulting in higher thermal cycling reliability. It can also be used to create various circuit patterns using a process similar to PCB etching, making it a core material for high-power module packaging in the power electronics field, especially in the third-generation semiconductor field.

[0007] As third-generation semiconductors, especially silicon carbide power modules, develop towards higher voltage, higher power density, and miniaturization, the requirements for the reliability and heat dissipation of ceramic copper-clad laminates used in high-power module packaging are becoming increasingly stringent. Currently, active metal brazing ceramic copper-clad laminates still have the following problems:

[0008] 1. Active solder is AgCuTi-based solder paste based on Ag72Cu28 eutectic alloy. The soldering temperature is generally higher than 850℃. The active element Ti is very prone to oxidation, segregation, or forming a brittle intermediate phase with Cu, Ag, C and other elements to form a near-eutectic structure. This near-eutectic structure is hard and brittle, and therefore has poor plasticity. The presence of this brittle intermediate phase not only affects the reliability of soldering, but also brings additional technical difficulties to the subsequent etching process.

[0009] 2. The AMB process is generally carried out under high vacuum conditions of 850℃~950℃ for high-temperature brazing. Under these conditions, oxygen-free copper foil often undergoes secondary crystallization, which leads to rapid growth of its grains. Excessively large copper grains will affect the identification of circuit patterns on the subsequent ceramic copper-clad substrate, and thus affect the automated packaging processes such as chip bonding and wire bonding on the circuit patterns.

[0010] 3. Active solder paste uses a large amount of organic solvents. Most of these organic substances evaporate during vacuum heating, but some remain at the solder interface, forming numerous voids and defects. This introduces the risk of partial discharge, significantly affecting the electrical performance of the active metal-brazed ceramic copper-clad laminate and reducing its reliability. Simultaneously, the presence of voids severely impacts the module's heat conduction and dissipation, making the active metal-brazed ceramic copper-clad laminate prone to high-voltage breakdown, induced cracking, and solder layer detachment during service.

[0011] 4. Because the coefficient of thermal expansion of oxygen-free copper is 16.5 × 10⁻⁶. -6 / K and ceramic substrate (2.6-7.1×10 -6 Due to significant differences in the / K) values, active metal brazing ceramic copper-clad laminates are prone to additional thermal stress at the brazing interface, which can easily lead to warping. This affects the flatness of the active metal brazing ceramic copper-clad laminate and impacts subsequent chip bonding.

[0012] In summary, there is a need for an active metal brazed ceramic clad laminate and its preparation method that can reduce the residual stress and warpage of the active metal brazed ceramic clad laminate. This method can solve the problems of low bonding strength, severe surface warpage, and poor thermal cycling reliability caused by the high residual stress in current active metal brazed ceramic clad laminates. Summary of the Invention

[0013] To address the problems existing in the background art, the present invention provides an active metal brazed ceramic copper-clad laminate that can reduce the residual stress and warpage of the active metal brazed ceramic copper-clad laminate, and a method for preparing the same.

[0014] To achieve the above objectives, the present invention provides the following technical solution:

[0015] A method for preparing an active metal brazed ceramic copper-clad laminate includes the following steps: providing a ceramic substrate; providing active metal brazing paste on opposite sides of the ceramic substrate; and providing oxygen-free copper foil on the active metal brazing paste on opposite sides of the ceramic substrate, thereby forming an active metal brazed ceramic copper-clad laminate comprising, from bottom to top, oxygen-free copper foil, active metal brazing paste, ceramic substrate, active metal brazing paste, and oxygen-free copper foil.

[0016] The active metal brazing paste includes active metal brazing powder and an active metal brazing organic carrier, wherein the active metal brazing organic carrier has a mass percentage content of 10wt% to 20wt%.

[0017] The active metal brazing powder comprises the following elements by mass percentage: Ag 10wt%–30wt%, Ti 3wt%–10wt%, Sn 3wt%–10wt%, In 2wt%–8wt%, Mo (or W) 5wt%–10wt%, with the balance being Cu.

[0018] The components and their mass percentages of the organic carrier of the active metal brazing filler are as follows: 5wt% to 10wt% binder, 1wt% to 3wt% dispersant, and the balance being organic solvent.

[0019] The thickness of the ceramic substrate can be, for example, 0.25 mm to 1 mm; the thickness of the active metal solder paste can be, for example, 10 μm to 40 μm; and the thickness of the oxygen-free copper foil can be, for example, 0.2 mm to 2 mm. However, the present invention is not limited to these, but can be specifically set as needed.

[0020] As a further improvement to this solution, the preparation method of the active metal brazing ceramic copper-clad laminate includes the following preparation steps:

[0021] Step P1 – Raw material cleaning

[0022] The ceramic substrate and oxygen-free copper foil are cleaned by degreasing, acid washing, water washing, and drying.

[0023] Step P2 – Printing and Coating of Active Metal Soldering Paste

[0024] The prepared active metal solder paste is printed and coated onto both sides of the ceramic substrate using a screen printing machine.

[0025] Step P3 – Printing, coating, and drying of active metal solder paste

[0026] The ceramic substrate coated with active metal solder paste obtained in step P2 is placed in a drying oven to dry the active metal solder paste and remove some of the organic solvent.

[0027] Step P4 – Sintering Unit Mounting

[0028] The oxygen-free copper foil and the dried ceramic substrate obtained in step P3 are fixed together on both sides to form a sintered unit structure of oxygen-free copper foil-ceramic substrate-oxygen-free copper foil from top to bottom.

[0029] Step P5 – Vacuum Brazing Sintering

[0030] The oxygen-free copper foil-ceramic substrate-oxygen-free copper foil sintering unit obtained in step P4 is placed in a vacuum brazing furnace for brazing sintering to obtain a ceramic copper-clad laminate.

[0031] As a further improvement to this solution, the preparation method of the active metal brazing ceramic copper-clad laminate, wherein the preparation method of the active metal brazing paste in step P2 is as follows: weigh the active metal brazing powder and the active metal brazing organic carrier according to the mass percentage, and add the active metal brazing organic carrier to the active metal brazing powder while stirring in a water bath at a temperature of 60℃~90℃ until the mixture is fully stirred and uniform. Then, stir the mixture with a solder paste mixer to prepare the required active metal brazing paste, the viscosity of which is (50~100) Pa·s@25℃.

[0032] As a further improvement to this solution, in the method for preparing the active metal brazing ceramic copper-clad laminate, the drying process conditions in step P3 are as follows: drying temperature is 150℃ and drying time is 60min.

[0033] As a further improvement to this solution, in the method for preparing the active metal brazed ceramic copper-clad laminate, the process conditions for vacuum brazing sintering in step P5 are as follows: brazing temperature 650℃~800℃, holding time 10min~30min, and vacuum degree of the vacuum furnace better than 1×10⁻⁶. -3 Pa.

[0034] As a further improvement to this solution, the method for preparing the active metal brazing ceramic copper-clad laminate includes the following:

[0035] Silver-containing alloys, including silver-copper alloys;

[0036] Titanium-containing alloys, including one or more of silver-copper-titanium alloys, copper-titanium alloys, silver-titanium alloys, titanium hydride, and titanium oxide compounds;

[0037] Tin-containing alloys, including one or more of copper-tin alloys and indium-tin alloys;

[0038] Indium-containing alloys, including indium-tin alloys;

[0039] Molybdenum / tungsten alloys, including molybdenum / tungsten copper alloys.

[0040] As a further improvement to this solution, the method for preparing the active metal brazing ceramic copper-clad laminate includes, wherein the active metal brazing material organic carrier comprises:

[0041] Adhesives, including one or more of the group consisting of methylcellulose, ethylcellulose, polyisobutyl methacrylate and mixtures thereof;

[0042] Dispersants include one or more of stearic acid, oleic acid, linoleic acid, linolenic acid, polyethylene glycol, and trioleic acid glycerides.

[0043] Organic solvents, including one or more of the group consisting of methyl cellosolve, ethyl cellosolve, toluene, ethyl acetate, terpineol, diethylene glycol monoethyl ether, and mixtures thereof.

[0044] This application also relates to an active metal brazing ceramic copper-clad laminate prepared according to the preparation method of the active metal brazing ceramic copper-clad laminate, wherein the active metal brazing ceramic copper-clad laminate includes a ceramic substrate and oxygen-free copper disposed on two opposite sides of the ceramic substrate, and the oxygen-free copper and the ceramic substrate are bonded together by the active metal brazing paste.

[0045] Optionally, the ceramic substrate includes any one of silicon nitride (Si3N4) ceramic substrate, aluminum nitride (AlN) ceramic substrate, alumina (Al2O3) ceramic substrate, and toughened alumina (ZTA) ceramic substrate.

[0046] The active metal brazed ceramic copper-clad laminate prepared by this invention has the following advantages compared with the prior art: it achieves low-stress, high-strength brazing bonding between the ceramic substrate and the oxygen-free copper foil, and has the advantages of high peel strength, low void ratio, low surface warpage, and high reliability in thermal cycling. Attached Figure Description

[0047] To provide a further understanding of the present invention, accompanying drawings are provided. These drawings are used for further explanation of the invention and do not constitute an undue limitation of the invention. In the drawings:

[0048] Figure 1 A schematic diagram of an active metal brazing ceramic copper-clad laminate structure is shown.

[0049] Figure 2 The peel strength test of active metal brazed ceramic copper-clad laminate and sample photos are shown;

[0050] Figure 3 The image shows an ultrasonic scanning test image of the void ratio of an active metal brazed ceramic copper-clad laminate.

[0051] Figure 4The process curve and sample photos of the heat resistance cycle test of ceramic circuit boards made of active metal brazed ceramic copper-clad laminates are shown.

[0052] Explanation of reference numerals in the attached figures:

[0053] 10-Ceramic substrate;

[0054] 20 - Oxygen-free copper foil: 201 - First oxygen-free copper foil, 202 - Second oxygen-free copper foil;

[0055] 30 - Active metal brazing paste: 301 - First active metal brazing paste, 302 - Second active metal brazing paste. Detailed Implementation

[0056] The present invention will now be discussed with reference to several exemplary embodiments, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present invention, and not to imply any limitation on the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Every feature disclosed in this specification, or every step in any disclosed method or process, except for mutually exclusive features and / or steps, may be replaced by other equivalent or similar alternative features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features. The following embodiments will enable those skilled in the art to gain a more comprehensive understanding of the invention, but do not limit the invention in any way.

[0058] Figure 1 A schematic diagram of the structure of the active metal brazing ceramic copper-clad laminate of the present invention is shown. The active metal brazing ceramic copper-clad laminate includes a ceramic substrate 10, oxygen-free copper foils located on opposite sides of the ceramic substrate 10, namely, oxygen-free copper 201 located on the upper side of the ceramic substrate 10 and oxygen-free copper 202 located on the lower side of the ceramic substrate. The active metal brazing ceramic copper-clad laminate also includes active metal brazing paste disposed between each oxygen-free copper layer and the ceramic substrate, namely, active metal brazing paste 301 located on the upper side of the ceramic substrate 10 between the ceramic substrate 10 and the oxygen-free copper layer and active metal brazing paste 302 located on the lower side of the ceramic substrate 10 between the ceramic substrate 10 and the oxygen-free copper layer.

[0059] The thickness of the ceramic substrate can be, for example, 0.25 mm to 1 mm;

[0060] The thickness of the active metal solder pastes 301 and 302 can be, for example, 10 μm to 40 μm;

[0061] The thickness of the oxygen-free copper foils 201 and 202 can be, for example, 0.2 mm to 2 mm.

[0062] The thickness mentioned above is merely an example, and the invention is not limited thereto; it can be set according to specific needs.

[0063] Before preparing the active metal brazing ceramic copper-clad laminate according to this application, the active metal brazing paste must first be prepared, and the preparation process is as follows:

[0064] First, a certain amount of raw material powders of various metal alloys are provided, such as one or more of silver-containing alloys, titanium-containing alloys, tin-containing alloys, indium-containing alloys, molybdenum or tungsten-containing alloys, and copper. Then, under inert gas protection, the measured raw material powders of the selected metal alloys are ball-milled and mixed to prepare active metal brazing powder. In the obtained active metal brazing powder, the content of each element is as follows: Ag 10wt%~30wt%, Ti 3wt%~10wt%, Sn 3wt%~10wt%, In 2wt%~8wt%, Mo (or W) 5wt%~10wt%, and the balance is Cu.

[0065] Then, a certain amount of various organic substances, such as binders, dispersants, and organic solvents, are provided, and the measured amounts of organic substances are then thoroughly stirred and mixed to prepare an organic carrier for active metal solder.

[0066] The components and their mass percentages of the organic carrier of the active metal brazing filler are as follows: 5wt% to 10wt% binder, 1wt% to 3wt% dispersant, and the balance being organic solvent.

[0067] Silver-containing alloys can include silver-copper alloys;

[0068] Titanium-containing alloys may include one or more of the following: silver-copper-titanium alloys, copper-titanium alloys, silver-titanium alloys, titanium hydride, and titanium oxide compounds;

[0069] Tin-containing alloys may include one or more of copper-tin alloys and indium-tin alloys;

[0070] Indium-containing alloys may include indium-tin alloys;

[0071] Molybdenum / tungsten alloys can include molybdenum / tungsten copper alloys.

[0072] In organic carriers of metal brazing fillers

[0073] The adhesive comprises one or more of the group consisting of methylcellulose, ethylcellulose, polyisobutyl methacrylate, and mixtures thereof;

[0074] The dispersant includes one or more of the following: stearic acid, oleic acid, linoleic acid, linolenic acid, polyethylene glycol, and trioleic acid glyceride.

[0075] The organic solvent includes one or more of the following: methyl cellosolve, ethyl cellosolve, toluene, ethyl acetate, terpineol, diethylene glycol monoethyl ether, and mixtures thereof.

[0076] Finally, the active metal brazing powder and the active metal brazing organic carrier are weighed out according to a certain mass percentage. The active metal brazing organic carrier is added to the active metal brazing powder at a set temperature and stirred, preferably while adding and stirring, to finally form an active metal brazing paste.

[0077] The active metal brazing paste contains an organic carrier with a mass percentage of 10wt% to 20wt%.

[0078] Subsequently, a ceramic substrate 10 is provided, and active metal solder paste prepared as described above is applied to opposite sides of the ceramic substrate 10. Then, oxygen-free copper foil is placed on the active solder paste on both sides respectively, and sintering is performed in a vacuum brazing furnace to form an active metal brazed ceramic copper-clad laminate comprising, from bottom to top, oxygen-free copper foil 201, active metal solder paste 301, ceramic substrate 10, active metal solder paste 302, and oxygen-free copper foil 202.

[0079] The ceramic copper-clad laminate prepared using the unique brazing material in this application exhibits significantly better performance compared to ceramic steel sheets prepared using brazing materials in the prior art.

[0080] The present invention will be further described below with reference to Examples 1 and 2 and Comparative Example 1. Examples 1 and 2 are active metal brazed ceramic copper-clad laminates prepared by the method of the present application, while Comparative Example 1 is an active metal brazed ceramic copper-clad laminate prepared by the method of the prior art.

[0081] Example 1

[0082] First, an active metal solder paste is prepared. The specific preparation steps are as follows:

[0083] Step S1:

[0084] Weigh out the following respectively:

[0085] (1) 100g of AgCuTi (68.8wt% Ag-26.7wt% Cu-4.5wt% Ti) alloy powder;

[0086] (2) 100g of CuSn20 (80wt% Cu-20wt% Sn) alloy powder;

[0087] (3) TiH2 (98wt% Ti-2wt%H) powder 15g;

[0088] (4) 50g of MoCu40 (60wt% Mo-40wt% Cu) alloy powder

[0089] (5) 160g of pure copper powder with a purity of 99.99%;

[0090] Step S2:

[0091] Under inert gas protection, the raw material powder weighed in step S2 is ball-milled and mixed to prepare active metal brazing powder, wherein the active metal brazing powder is characterized by...

[0092] The composition consists of 16.20 wt% Ag, 4.52 wt% Ti, 4.71 wt% Sn, and 7.06 wt% Mo, with the balance being Cu, which accounts for 67.51%.

[0093] Step S3:

[0094] Weigh and / or measure separately:

[0095] 8g of polyisobutyl methacrylate;

[0096] 2g of polyethylene glycol;

[0097] 100g of terpineol.

[0098] Step S4:

[0099] The organic matter weighed or measured in step S3 is thoroughly stirred and mixed to prepare an active metal brazing filler organic carrier, wherein the active metal brazing filler organic carrier is characterized by...

[0100] The binder contains 7.27 wt% polyisobutyl methacrylate, the dispersant contains 1.82 wt% polyethylene glycol, and the balance is the organic solvent terpineol, with a content of 90.91%.

[0101] Step S5:

[0102] 100g of the active metal brazing powder prepared in step S2 and 18g of the active metal brazing organic carrier prepared in step P4 were weighed separately. In an 80°C water bath, the above-mentioned active metal brazing organic carrier was added to the above-mentioned active metal brazing powder while stirring to prepare an active metal brazing paste precursor. The active metal brazing paste precursor is characterized in that the content of the active metal brazing organic carrier is 15.25% and the content of the active metal brazing powder is 84.75%.

[0103] Step S6:

[0104] The active metal soldering paste precursor obtained in step S5 is then placed into a solder paste mixer and stirred evenly to prepare the active metal soldering paste, characterized in that the viscosity is (50~100) mPa·s@25℃.

[0105] According to the technical solution of the present invention, the specific steps of a method for preparing an active metal brazed ceramic clad laminate that can reduce residual stress and warpage are as follows:

[0106] Step P1 – Raw material cleaning

[0107] The ceramic substrate and oxygen-free copper foil are cleaned by degreasing, acid washing, water washing, and drying.

[0108] Step P2 – Printing and Coating of Active Metal Soldering Paste

[0109] The active metal solder paste prepared in step S6 is printed and coated onto both sides of the ceramic substrate using a screen printing machine.

[0110] Step P3 – Printing, coating, and drying of active metal solder paste

[0111] The ceramic substrate coated with active metal solder paste obtained in step P2 is placed in a drying oven for drying. The drying conditions are: drying temperature of 150°C and drying time of 60 min, in order to dry the active metal solder paste and remove some organic solvents.

[0112] Step P4 – Sintering Unit Mounting

[0113] The oxygen-free copper foil and the dried ceramic substrate obtained in step P3 are fixed together on both sides to form a sintered unit structure of oxygen-free copper foil-ceramic substrate-oxygen-free copper foil from top to bottom.

[0114] Step P5 – Vacuum Brazing Sintering

[0115] The oxygen-free copper foil-ceramic substrate-oxygen-free copper foil sintering unit obtained in step P4 is placed in a vacuum brazing furnace for brazing sintering. The vacuum brazing process conditions are: brazing temperature 650℃~800℃, holding time 10min~30min, and vacuum degree better than 1×10⁻⁶. -3 Pa yields active metal brazed ceramic copper-clad laminates.

[0116] Example 2

[0117] In Example 1, step S1, the Sn component is replaced with In and Sn (50wt% In-50wt% Sn) components. Specifically, 30g of InSn50 (50wt% In-50wt% Sn) alloy powder is used to replace 100g of CuSn20 (80wt% Cu-20wt% Sn) alloy powder. Following step S2 of Example 1, an active metal brazing powder is prepared. The active metal brazing powder is characterized by...

[0118] The composition consists of 19.40 wt% Ag, 5.41 wt% Ti, 4.23 wt% Sn, 4.23 wt% In, and 8.46 wt% Mo, with the balance being Cu, which accounts for 58.27%.

[0119] The other contents in Example 2 are the same as the remaining steps in Example 1.

[0120] Comparison Example 1

[0121] The specific preparation steps for active metal soldering paste are as follows:

[0122] S1:

[0123] Weigh 100g of AgCuTi (68.8wt%Ag-26.7wt%Cu-4.5wt%Ti) alloy powder to be used as active metal brazing powder. Subsequent steps are the same as the remaining steps in Example 1.

[0124] The active metal brazed ceramic copper-clad laminates prepared in the above embodiments were tested for appearance, peel strength, void ratio, and thermal cycling resistance. The test data are shown in Table 1.

[0125] (1) Appearance: Visual inspection to check whether the surface is uniform and flat, and whether there are defects such as oxidation, peeling, bulging, bubbles and warping that are visible to the naked eye;

[0126] (2) 90° peel strength: JF-BL90 peel strength tester, the test sample is a 5mm wide copper-clad strip @ 50mm / min; Figure 2 The peel strength test of active metal brazed ceramic copper-clad laminate and sample photos are shown.

[0127] (3) Void ratio: GRD-GS3 ultrasonic scanning microscope, scanning mode is C-scan, scanning frequency is 30MHz, and scanning speed is 500m / s; Figure 3 The image shows an ultrasonic scanning test of the void ratio in an active metal brazed ceramic copper-clad laminate.

[0128] (4) Thermal cycling resistance: WDCJ-27C / 3 three-chamber thermal shock test chamber, test conditions are -50℃ / 30min~150℃ / 30min (high and low temperature conversion time 15s)@0.3mm Cu / 0.32mm Si3N4 / 0.3mm. Figure 4 The process curve and sample photos of the heat resistance cycle test of ceramic circuit boards made of active metal brazed ceramic copper-clad laminate are shown.

[0129] Table 1 - Summary Table of Sample Test Data for Examples

[0130] Performance indicators Example 1 Example 2 Comparison Example 1 Appearance Even and flat Even and flat There are bulges at the edges void ratio % 0.38 0.17 1.07 90° peel strength N / mm 14 16 13 Heat resistance cycle count 5000 5000 3000 Flatness um 207 163 352

[0131] From the above comparative experiments and Figure 2 , 3 As shown in Figures 4, the active metal brazed ceramic copper-clad laminate prepared by this invention has the following beneficial effects compared with the prior art: it achieves low-stress, high-strength brazing bonding between the ceramic substrate and the oxygen-free copper foil, and has advantages such as high peel strength, low void ratio, low surface warping, and high reliability in thermal cycling.

[0132] Furthermore, several embodiments of the present invention have been described; however, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can also be implemented in various other ways, with various omissions, substitutions, modifications, and improvements made without departing from the overall spirit of the invention. All such embodiments and variations should be included within the scope and spirit of the present invention, and are contained within the scope of the invention as described in the claims and its equivalents.

Claims

1. A method for preparing an active metal brazing ceramic copper-clad laminate, comprising the following steps: Provide a ceramic substrate (10); Active metal solder paste (301, 302) is provided on opposite sides of the ceramic substrate (10); oxygen-free copper foil (201, 202) is provided on the active metal solder paste (301, 302) on opposite sides of the ceramic substrate, thereby forming an active metal brazed ceramic copper-clad laminate comprising, from top to bottom, oxygen-free copper foil (201), active metal solder paste (301), ceramic substrate (10), active metal solder paste (302), and oxygen-free copper foil (202). The active metal brazing paste includes active metal brazing powder and an active metal brazing organic carrier, wherein the active metal brazing organic carrier has a mass percentage content of 10wt% to 20wt%. The active metal brazing powder comprises the following elements by mass percentage: Ag 10wt%–30wt%, Ti 3wt%–10wt%, Sn 3wt%–10wt%, In 2wt%–8wt%, Mo (or W) 5wt%–10wt%, with the balance being Cu. The components and their mass percentages of the organic carrier of the active metal brazing filler are as follows: 5wt% to 10wt% binder, 1wt% to 3wt% dispersant, and the balance being organic solvent.

2. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 1, wherein, It also includes the following preparation steps: Step P1 – Raw material cleaning The ceramic substrate and oxygen-free copper foil are then subjected to degreasing, acid washing, water washing, and drying to complete the cleaning process. Step P2 – Printing and Coating of Active Metal Soldering Paste The prepared active metal solder paste is printed and coated onto both sides of the ceramic substrate using a screen printing machine. Step P3 – Printing, coating, and drying of active metal solder paste The ceramic substrate coated with active metal solder paste obtained in step P2 is placed in a drying oven to dry the active metal solder paste and remove some organic matter. Step P4 – Sintering Unit Mounting The oxygen-free copper foil and the dried ceramic substrate obtained in step P3 are double-sided clamped and fixed, forming a sintered unit structure from top to bottom: oxygen-free copper foil - active metal solder paste - ceramic substrate - active metal solder paste - oxygen-free copper foil. Step P5 – Vacuum Brazing Sintering The sintering unit of oxygen-free copper foil-active metal brazing paste-ceramic substrate-active metal brazing paste-oxygen-free copper foil obtained in step P4 is placed in a vacuum brazing furnace for brazing sintering to obtain active metal brazed ceramic copper-clad laminate.

3. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 1, wherein, The ceramic substrate has a thickness of 0.25 mm to 1 mm; the active metal solder paste (301, 302) has a thickness of 10 μm to 40 μm; and the oxygen-free copper foil (201, 202) has a thickness of 0.2 mm to 2 mm.

4. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 2, wherein, The preparation method of the active metal solder paste in step P2 is as follows: Weigh the active metal solder powder and the active metal solder organic carrier according to the mass percentage. In a water bath at a temperature of 60℃~90℃, add the active metal solder powder while stirring until the mixture is fully stirred and uniform. Then, stir the mixture with a solder paste mixer to obtain the required active metal solder paste with a viscosity of (50~100) Pa·s@25℃.

5. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 2, wherein, The drying process conditions described in step P3 are: drying temperature of 150℃ and drying time of 60min.

6. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 2, wherein, The vacuum brazing sintering process conditions described in step P5 are: brazing temperature 650℃~800℃, holding time 10min~30min, and vacuum degree of the vacuum furnace better than 1×10⁻⁶. -3 Pa.

7. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 1, wherein, The active metal brazing powder includes: Silver-containing alloys, including silver-copper alloys; Titanium-containing alloys, including one or more of silver-copper-titanium alloys, copper-titanium alloys, silver-titanium alloys, titanium hydride, and titanium oxide compounds; Tin-containing alloys, including one or more of copper-tin alloys and indium-tin alloys; Indium-containing alloys, including indium-tin alloys; Molybdenum / tungsten alloys, including molybdenum / tungsten copper alloys.

8. The method for preparing the active metal brazing ceramic copper-clad laminate according to claim 1, wherein, The active metal brazing filler organic carrier includes: Adhesives, including one or more of the group consisting of methylcellulose, ethylcellulose, polyisobutyl methacrylate and mixtures thereof; Dispersants, including one or more of stearic acid, oleic acid, linoleic acid, linolenic acid, polyethylene glycol and trioleic acid glyceride; Organic solvents, including one or more of the group consisting of methyl cellosolve, ethyl cellosolve, toluene, ethyl acetate, terpineol, diethylene glycol monoethyl ether, and mixtures thereof.

9. The active metal brazed ceramic copper-clad laminate prepared by the method for preparing the active metal brazed ceramic copper-clad laminate according to any one of claims 1-8, wherein, The active metal brazing ceramic copper-clad laminate includes a ceramic substrate and oxygen-free copper foil disposed on two opposite sides of the ceramic substrate. The oxygen-free copper foil and the ceramic substrate are bonded together by the active metal brazing paste.

10. The active metal brazing ceramic copper-clad laminate according to claim 9, wherein the ceramic substrate comprises: Any one of silicon nitride (Si3N4) ceramic substrate, aluminum nitride (AlN) ceramic substrate, alumina (Al2O3) ceramic substrate, and toughened alumina (ZTA) ceramic substrate.

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