A method for preparing a double-sided heat dissipation power module with aluminum nitride ceramic substrate

Abstract

The invention relates to the field of semiconductor technology, in particular to a preparation method of a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate; the method comprises the following steps: S01: taking an aluminum-coated aluminum nitride ceramic substrate, chemically copper-plating to obtain a copper-plated substrate; taking two copper-plated substrates as an upper substrate and a lower substrate respectively; S02: taking the upper substrate, cold-spraying copper in multiple chip welding areas to obtain a cold-sprayed copper layer; then grinding height compensation to obtain a pre-treated copper layer to obtain a pre-treated upper substrate; S03: taking the lower substrate, printing nano silver solder paste, attaching a SiC chip to the chip area, placing power terminals and signal terminals at corresponding positions, and welding to obtain a welded lower substrate; S04: bonding the leads to complete power interconnection between a gate area of ​​the SiC chip and a welded lower substrate; S05: printing nano silver solder paste for a second time and welding; S06: plastic sealing to obtain a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate. Background Art

[0002] As wide bandgap semiconductors are increasingly used, the heat dissipation, inductance, and reliability of power modules also need to be improved. The double-sided heat dissipation structure is currently the most efficient heat dissipation method for power modules. Compared with traditional packaged modules, the double-sided heat dissipation power module has significantly improved parasitic inductance, heat dissipation capacity, and reliability, and is a power module device with good performance.

[0003] Existing double-sided heat dissipation power modules still have problems, such as uneven welding height, gaps, mismatched thermal expansion coefficients, etc. The existing technology usually solves such problems by welding micro-metal columns as a pad layer to the substrate chip welding area. However, the pad layer and its welding layer have a large thermal resistance, which has become the main bottleneck restricting the reduction of thermal resistance of double-sided heat dissipation power modules, affecting the reliability of power devices.

[0004] As the packaging substrate of IGBT, the direct bonding aluminum substrate has excellent heat cycle resistance, excellent interface bonding reliability, high thermal conductivity, and high insulation strength, and is one of the ideal packaging substrates for high-voltage devices. However, after nickel plating on the surface of the direct bonding aluminum substrate, the nickel surface is easily rippled due to the mutual sliding and extrusion of aluminum grains, which affects the reliability of the chip and substrate welding interface. Therefore, it is of great significance to study a high-reliability double-sided heat dissipation power module with a direct bonding aluminum substrate and its preparation method. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate: comprising the following steps: S01: copper plating on the surface of the aluminum-coated aluminum nitride ceramic substrate: taking an aluminum-coated aluminum nitride ceramic substrate, chemically plating copper to obtain a copper-coated substrate, taking two copper-coated substrates, and using them as an upper substrate and a lower substrate respectively;

[0007] S02: Pretreatment: S12: Take the upper substrate and perform cold spraying of copper on multiple chip welding areas to obtain a cold sprayed copper layer; wherein the copper powder particle size is 1 to 3 μm and the porosity is ≤ 0.05%;

[0008] S22: taking the upper substrate processed in step S12, and performing height compensation on the chip welding area by grinding so that the chip welding area is at the same height, thereby obtaining a pre-treated copper layer and a pre-treated upper substrate;

[0009] S03: one-time printing of nano silver solder paste and welding: S13: removing the substrate, and using the designed printing steel mesh to print the nano silver solder paste on the corresponding position of the lower substrate;

[0010] S23: Using a high-precision chip mounter, the SiC chip is mounted on the chip area of ​​the lower substrate, and power terminals and signal terminals are placed at corresponding positions;

[0011] S33: taking the lower substrate processed in step S23 and placing it in a vacuum welding furnace for welding to obtain a welded lower substrate;

[0012] S04: Wire bonding: Use ultrasonic wire bonding equipment to bond the wires to complete the power interconnection between the SiC chip gate area and the lower substrate;

[0013] S05: Secondary printing of nano silver solder paste and welding: S15: Printing nano silver solder paste on the cold spray copper surface of the pre-treated upper substrate and the surface of the SiC chip of the welding lower substrate through the printing steel mesh;

[0014] S25: taking the upper substrate processed in step S15 and welding the lower substrate, and placing them in a vacuum welding furnace for welding;

[0015] S06: Plastic encapsulation to obtain a double-sided heat dissipation power module covered with aluminum nitride ceramic substrate.

[0016] Preferably, the process of chemical copper plating comprises the following steps: alkali washing for 3 to 4 minutes, acid washing for 80 to 100 seconds, zinc immersion for 30 to 50 seconds, acid washing for 80 to 100 seconds, zinc immersion for 20 to 30 seconds, and chemical copper plating using a chemical copper plating solution to obtain a copper-plated substrate; pure water washing is performed after each step is completed; the chemical copper plating temperature is 40 to 45° C., and the time is 15 to 20 minutes.

[0017] Preferably, the alkaline washing solution for alkali washing is a 40g / L sodium hydroxide aqueous solution; the pickling solution for pickling is a 30% concentration nitric acid aqueous solution; the zinc dipping solution for zinc dipping includes 100g / L sodium hydroxide, 25g / L zinc oxide, and the rest is pure water.

[0018] Preferably, the copper layer obtained by the chemical copper plating has a thickness of 1 to 3 μm.

[0019] Preferably, the chemical copper plating solution comprises the following raw materials: 10-40 g / L CuSO4·5H2O, 20-60 g / L Na2·EDTA, 4-8 g NaOH, 20-40 ml / L NH3·H2O, and the rest is pure water.

[0020] Preferably, the cold spray copper process parameters are: nozzle diameter of 0.5-1.5 mm, spray gun air pressure of 0.7-1 MPa, gas flow rate of 100-400 L / min, powder gas flow velocity of 300-600 m / s, powder feeding amount of 5-20 g / min, and cold spray thickness of 1-3 mm.

[0021] Preferably, the grinding method is a machining method; after the height compensation, the thickness of the pre-treated copper layer is 1 to 3 mm.

[0022] Preferably, in the aluminum-coated aluminum nitride ceramic substrate, the thickness of the aluminum nitride ceramic is 0.635-1.0 mm, the thickness of the aluminum layer is 0.2-0.4 mm, and the surface layer is a bare aluminum layer.

[0023] Preferably, the printing thickness of the nano silver solder paste is 100-110 μm.

[0024] Preferably, the welding process is as follows: temperature: 250° C., atmosphere: formic acid atmosphere, welding time: 30 min, pressure: 6-8 MPa, heating rate: 5° C. / min.

[0025] Preferably, the lead wire is an 8 mil aluminum wire.

[0026] Preferably, the plastic encapsulation process is an epoxy resin plastic encapsulation process; the epoxy resin plastic encapsulation process respectively encapsulates the upper and lower surfaces and the side surfaces of the double-sided heat dissipation power module of the aluminum nitride ceramic substrate covered with aluminum.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: firstly, a copper layer is prepared on an aluminum-coated aluminum nitride ceramic substrate through a chemical copper plating process, thereby avoiding the problem that the nickel surface is easily slipped and squeezed by aluminum grains and produces water ripples, resulting in reduced reliability of the chip and liner welding interface; secondly, copper is cold-sprayed on the upper substrate through a cold spraying process, thereby replacing the traditional gasket as a pad layer, solving the problems of uneven welding height, gap and mismatched thermal expansion coefficient, and also solving the problem of large thermal resistance of the pad layer, thereby further improving the reliability of the double-sided heat dissipation power device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 It is a flow chart of a method for preparing a double-sided heat dissipation power module with an aluminum nitride ceramic substrate;

[0030] Figure 2 It is a cross-sectional schematic diagram of a double-sided heat dissipation power module with an aluminum nitride ceramic substrate covered with aluminum;

[0031] Figure 3 This is a photo of the finished product of Example 2 after 1000 hot and cold cycles;

[0032] Figure 4 This is a photo of the finished product of Example 2 after 1000 hot and cold cycles. DETAILED DESCRIPTION

[0033] The following is a preferred implementation of the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. For ordinary technicians in this technical field, all other embodiments obtained by ordinary technicians in this field without creative work without departing from the principle of the embodiment of the present invention are within the scope of protection of the present invention.

[0034] The following parts are by mass unless otherwise specified;

[0035] Embodiment 1: S01: Copper plating on the surface of aluminum-coated aluminum nitride ceramic substrate: take an aluminum-coated aluminum nitride ceramic substrate of size 10*10mm, alkali wash for 3min, acid wash for 90s, zinc immersion for 40s, acid wash for 90s, zinc immersion for 30s, wash with pure water after each step, use chemical copper plating solution to chemically copper plate, the temperature is 42℃, and the time is 15min; the chemical copper plating solution includes the following raw materials: 30g / L CuSO4·5H2O, 50g / L Na2·EDTA, 7g NaOH, 30ml / L NH3·H2O, and the rest is pure water, the thickness of the copper plating layer is 2.5μm, and a copper-plated substrate is obtained, and two copper-plated substrates are taken as the upper and lower substrates respectively;

[0036] S02: Pretreatment: Take the upper substrate and cold spray copper on the chip welding area through the cold spray process. The nozzle diameter is 1mm, the spray gun air pressure is 1Mpa, the gas flow rate is 350L / min, the powder air flow rate is 500m / s, the powder feeding amount is 10g / min, the cold spray copper layer thickness is 2mm, the copper powder particle size is 2μm, and the porosity is ≤0.05%; the cold spray area is height compensated by grinding to obtain a pretreated copper layer with a thickness of 1.9μm, and the pretreated upper substrate is obtained;

[0037] S03: One-time printing of nano silver solder paste and welding: remove the substrate, use the designed printing steel mesh to print the nano silver paste on the corresponding position of the lower substrate, the printing thickness is 100μm, then use a high-precision placement machine to attach the SiC chip to the chip area of ​​the lower substrate, and place the power terminal and signal terminal at the corresponding position; place it in a vacuum pressure furnace for welding, the welding process is: temperature: 250℃, atmosphere: formic acid atmosphere, welding time: 30min, pressure: 8MPa, heating rate is 5℃ / min; get the welded lower substrate;

[0038] S04: Wire bonding: Use ultrasonic wire bonding equipment to bond 8mil aluminum wires to complete the power interconnection between the SiC chip gate area and the lower substrate;

[0039] S05: Secondary printing of nano silver solder paste and welding: Print nano silver solder paste on the cold spray copper surface of the pre-treated upper substrate and the surface of the SiC chip of the welding lower substrate through the printing steel mesh; the printing thickness is 100μm; put it into a vacuum welding furnace for welding, and the welding process is the same as the first welding process;

[0040] S06: Plastic packaging: Plastic packaging is performed through epoxy resin plastic packaging process to obtain a double-sided heat dissipation power module covered with aluminum nitride ceramic substrate, which is the finished product.

[0041] Embodiment 2: S01: Copper plating on the surface of aluminum-coated aluminum nitride ceramic substrate: take two pieces of aluminum-coated aluminum nitride ceramic substrates with a size of 10*10mm, alkali wash for 3min, acid wash for 90s, zinc immersion for 40s, acid wash for 90s, zinc immersion for 30s, wash with pure water after each step, use chemical copper plating solution to chemically copper plate, the temperature is 40℃, and the time is 15min; the chemical copper plating solution includes the following raw materials: 30g / L CuSO4·5H2O, 50g / L Na2·EDTA, 7g NaOH, 30ml / L NH3·H2O, and the rest is pure water, the thickness of the copper plating layer is 2.5μm, and a copper-plated substrate is obtained, and two copper-plated substrates are taken as the upper and lower substrates respectively;

[0042] S02: Pretreatment: Take the upper substrate, and cold spray copper on the chip welding area through the cold spray process, the nozzle diameter is 1mm, the spray gun air pressure is 1Mpa, the gas flow rate is 350L / min, the powder air flow rate is 500m / s, the powder feeding amount is 10g / min, the cold spray thickness is 2.1mm, the copper powder particle size is 2.2μm, and the porosity is ≤0.05%; the cold spray area is height compensated by machining, and the pretreated copper layer thickness is 2μm after height compensation, and the pretreated upper substrate is obtained;

[0043] S03: One-time printing of nano silver solder paste and welding: remove the substrate, use the designed printing steel mesh to print the nano silver paste on the corresponding position of the lower substrate, the printing thickness is 110μm, then use a high-precision placement machine to attach the SiC chip to the chip area of ​​the lower substrate, and place the power terminal and signal terminal at the corresponding position; place it in a vacuum pressure furnace for welding, the welding process is: temperature: 250℃, atmosphere: formic acid atmosphere, welding time: 30min, pressure: 7MPa, heating rate is 5℃ / min; get the welded lower substrate;

[0044] S04: Wire bonding: Use ultrasonic wire bonding equipment to bond 8mil aluminum wires to complete the power interconnection between the SiC chip gate area and the lower substrate;

[0045] S05: Secondary printing of nano silver solder paste and welding: Print nano silver solder paste on the cold spray copper surface of the pre-treated upper substrate and the surface of the SiC chip of the welded lower substrate through the printing steel mesh; the printing thickness is 110μm; put it into a vacuum welding furnace for welding, and the welding process is the same as the first welding process;

[0046] S06: Plastic packaging: Plastic packaging is performed through epoxy resin plastic packaging process to obtain a double-sided heat dissipation power module covered with aluminum nitride ceramic substrate, which is the finished product.

[0047] Comparative Example 1: The upper and lower substrates are copper-clad ceramic substrates, and the padding layer is a micro-metal column: S01: Remove the substrate, use the designed printing steel mesh to print nano silver paste at the corresponding position of the lower substrate, the printing thickness is 110μm, and then use a high-precision placement machine to attach the SiC chip to the chip area of ​​the lower substrate, and place the power terminal and the signal terminal at the corresponding position; place it in a vacuum pressure furnace for welding, the welding process is: temperature: 250℃, atmosphere: formic acid atmosphere, welding time: 30min, pressure: 7MPa, heating rate is 5℃ / min; the welded lower substrate is obtained;

[0048] S02: Wire bonding: Use ultrasonic wire bonding equipment to bond 8mil aluminum wires to complete the power interconnection between the SiC chip gate area and the lower substrate;

[0049] S03: Pad layer welding: Print nano silver solder paste on the pad layer area of ​​the lower substrate and the surface of the SiC chip welded to the lower substrate through a printed steel mesh; the printing thickness is 110μm; attach 2mm micro metal columns as pad layers to the pad layer area and the surface of the SiC chip for welding, wherein the height difference between the micro metal columns in the pad layer area and the metal columns in the chip welding area is consistent, and put them into a vacuum welding furnace for welding, and the welding process is the same as the first welding process;

[0050] S04: Welding of upper and lower substrates: Take the upper substrate and print nano silver solder paste in the chip welding area and the pad layer area; the printing thickness is 110μm, and the upper and lower substrates are bonded together and placed in a vacuum welding furnace for welding. The welding process is the same as the first welding process.

[0051] S04: Plastic sealing: Plastic sealing is performed through epoxy resin plastic sealing process to obtain the finished product.

[0052] Comparative Example 2: The upper and lower substrates are aluminum-coated aluminum nitride ceramic substrates with nickel plating: S01: Nickel plating on the surface of aluminum-coated aluminum nitride ceramic substrates: Take two aluminum-coated aluminum nitride ceramic substrates with a size of 10*10mm, and perform alkali washing for 3min, acid washing for 90s, zinc immersion for 40s, acid washing for 90s, and zinc immersion for 30s. After each step is completed, wash with pure water, and then perform chemical nickel plating. Use chemical plating technology to plate nickel on the surface of aluminum nitride aluminum-coated ceramic substrates. The chemical nickel plating solution consists of 25g / L NiSO4·7H2O, 36g / L NaH2PO2·H2O, 12g / L Na3C6H5O7·2H2O, and the rest is pure water; the pH value is controlled to be 5.6, the nickel plating reaction conditions are chemical plating at 85°C for 60min, and the thickness of the nickel plating layer is 7μm. After the nickel plating is completed, the surface is washed with pure water to obtain a substrate, and two substrates are taken as the upper and lower substrates respectively;

[0053] S02: Pretreatment: Take the upper substrate, and cold spray copper on the chip welding area through the cold spray process, the nozzle diameter is 1mm, the spray gun air pressure is 1Mpa, the gas flow rate is 350L / min, the powder air flow rate is 500m / s, the powder feeding amount is 10g / min, the cold spray thickness is 2.1mm, the copper powder particle size is 2.2μm, and the porosity is ≤0.05%; the cold spray area is height compensated by machining, and the pretreated copper layer thickness is 2μm after height compensation, and the pretreated upper substrate is obtained;

[0054] S03: One-time printing of nano silver solder paste and welding: remove the substrate, use the designed printing steel mesh to print the nano silver paste on the corresponding position of the lower substrate, the printing thickness is 110μm, then use a high-precision placement machine to attach the SiC chip to the chip area of ​​the lower substrate, and place the power terminal and signal terminal at the corresponding position; place it in a vacuum pressure furnace for welding, the welding process is: temperature: 250℃, atmosphere: formic acid atmosphere, welding time: 30min, pressure: 7MPa, heating rate is 5℃ / min; get the welded lower substrate;

[0055] S04: Wire bonding: Use ultrasonic wire bonding equipment to bond 8mil aluminum wires to complete the power interconnection between the SiC chip gate area and the lower substrate;

[0056] S05: Secondary printing of nano silver solder paste and welding: Print nano silver solder paste on the cold spray copper surface of the pre-treated upper substrate and the surface of the SiC chip of the welded lower substrate through the printing steel mesh; the printing thickness is 110μm; put it into a vacuum welding furnace for welding, and the welding process is the same as the first welding process;

[0057] S06: Plastic sealing: Plastic sealing is performed through epoxy resin plastic sealing process to obtain the finished product.

[0058] Experiment: The finished products obtained from Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2 were subjected to hot and cold cycle tests, respectively, wherein the hot and cold cycle temperature was 40-140°C, and each cycle lasted 30 seconds. The power module after the power cycle was subjected to a chip junction temperature test (tested after the high temperature stage of the hot and cold cycle) by a thermal transient tester. The test data are as follows:

[0059]

[0060] It can be seen from the above table that the junction temperature of the finished product of Comparative Example 1 is higher than that of Example 1. The reason is that the thermal resistance of the micro-metal pillar is higher than that of the pad layer of the cold-sprayed copper layer. Figure 3 and Figure 4 It can be seen that the finished product of Comparative Example 2 has water ripples after 1000 hot and cold cycles, resulting in reduced reliability of chip and substrate welding, affecting the reliability of double-sided heat dissipation power devices; therefore, the double-sided heat dissipation power module with aluminum nitride ceramic substrate coated with aluminum prepared by the present invention improves the reliability of chip and liner welding, solves the problem of large thermal resistance of the pad layer of the double-sided heat dissipation device, and further improves the reliability of the double-sided heat dissipation power module.

[0061] In the above embodiments, the test methods used are conventional methods unless otherwise specified; the raw materials used are commercially available unless otherwise specified, and the sources of the raw materials are as follows: nano silver paste (Shenzhen Advanced Connection Technology Co., Ltd., ADGE-01), aluminum wire (8mil, Heraeus), and epoxy resin for plastic encapsulation (Sumitomo Bakelite, EME-M100).

[0062] Finally, it should be noted that the above is only a preferred embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the spirit and principle of the present invention and within the technical scope disclosed in this application should be included in the protection scope of this application; in the absence of conflict, the embodiments of this application and the features in the embodiments can be combined with each other. Therefore, the protection scope of this application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a double-sided heat dissipation power module with an aluminum-coated aluminum nitride ceramic substrate, characterized in that: The following steps are involved: S01: Copper plating on the surface of aluminum-coated aluminum nitride ceramic substrate: take an aluminum-coated aluminum nitride ceramic substrate, chemically plate copper to obtain a copper-plated substrate; take two copper-plated substrates as an upper substrate and a lower substrate respectively; S02： Pretreatment: Take the upper substrate, cold-spray copper on multiple chip welding areas to obtain a cold-spray copper layer; then perform height compensation by grinding to obtain a pre-treated copper layer and a pre-treated upper substrate; S03: One-time printing of nano silver solder paste and welding: remove the substrate, print the nano silver solder paste, attach the SiC chip to the chip area, place the power terminal and the signal terminal at the corresponding position, and perform welding to obtain the welded substrate; the welding process is: temperature: 240-250°C, atmosphere: formic acid atmosphere, welding time: 30-40min, pressure: 6-8MPa, heating rate: 5-6°C / min; S04: Wire bonding: Wire bonding is performed to complete the power interconnection between the gate area of ​​the SiC chip and the substrate under welding; S05: Secondary printing of nano silver solder paste and welding: Printing nano silver solder paste on the cold spray copper surface of the pre-treated upper substrate and the surface of the SiC chip of the welding lower substrate, and placing them in a vacuum welding furnace for welding; the welding process is: temperature: 240-250°C, atmosphere: formic acid atmosphere, welding time: 30-40min, pressure: 6-8MPa, heating rate: 5-6°C / min; S06: Plastic encapsulation to obtain a double-sided heat dissipation power module covered with aluminum nitride ceramic substrate.

2. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The specific process of chemical copper plating The method comprises the following steps: sequentially performing alkali washing, acid washing, zinc immersion, acid washing, zinc immersion, and chemical copper plating using a chemical copper plating solution on an aluminum-coated aluminum nitride ceramic substrate to obtain a copper-plated substrate; performing pure water washing after each step is completed; and the chemical copper plating temperature is 40-45° C. and the time is 15-20 minutes.

3. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The thickness of the copper layer obtained by the chemical copper plating is 1 to 3 μm.

4. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 2, characterized in that: The chemical copper plating solution comprises the following raw materials: 10-40 g / L CuSO4·5H2O, 20-60 g / L Na2·EDTA, 4-8 g NaOH, 20-40 ml / L NH3·H2O, and the rest is pure water.

5. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The aluminum-clad aluminum nitride ceramic substrate comprises aluminum nitride ceramic and an aluminum layer. The thickness of the aluminum nitride ceramic is 0.635-1.0 mm, and the thickness of the aluminum layer is 0.2-0.4 mm.

6. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: In the cold copper spraying process, the copper powder particle size is 1-3 μm and the porosity is ≤0.05%.

7. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The cold copper spraying process parameters are: nozzle diameter of 0.5-1.5 mm, spray gun air pressure of 0.7-1 MPa, gas flow rate of 100-400 L / min, powder gas flow velocity of 300-600 m / s, and powder feeding amount of 5-20 g / min.

8. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The thickness of the cold sprayed copper layer is 1 to 3 mm, and the thickness of the pretreated copper layer is 1 to 3 mm.

9. The method for preparing a double-sided heat dissipation power module of an aluminum-coated aluminum nitride ceramic substrate according to claim 1, characterized in that: The printing thickness of the nano silver solder paste is 100-110 μm.

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