Aluminum-coated aluminum nitride ceramic substrate for packaging and preparation method thereof

Abstract

The present invention discloses an aluminum-clad aluminum nitride ceramic substrate for packaging and its preparation method, relating to the field of semiconductor technology. The present invention forms an alloy coating on the thin aluminum surface of a double-sided aluminum-clad aluminum nitride ceramic sheet through a cold spraying process, and then diffuses, sinters, and welds a copper layer for standby use. Diamond powder is sputtered with a niobium film and then chemically copper-plated through magnetron sputtering and chemical copper plating to obtain copper-plated diamond. This is then treated through a cold spraying process to cold-spray copper diamond onto the thick aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet to obtain a copper diamond layer. The double-sided aluminum-clad aluminum nitride ceramic sheet is then pre-treated, activated, and nickel-plated to obtain the final aluminum-clad aluminum nitride ceramic substrate. The finished product obtained by the present invention has good thermal conductivity, effectively reduces thermal resistance, and has good thermal cycle reliability.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to an aluminum-coated aluminum nitride ceramic substrate for packaging and a preparation method thereof. Background Art

[0002] With the rapid development of IGBT power electronic devices in China, power electronic device technology is rapidly developing towards high voltage, high current, high power density, and strong heat dissipation. As the packaging substrate for IGBTs, aluminum nitride-on-aluminum ceramic substrates offer excellent thermal conductivity, good thermal shock fatigue resistance, outstanding thermal stability, lightweight structure, and good aluminum wire bonding capabilities.

[0003] As power devices are exposed to increasingly wider voltage and current ranges, the probability of device failure is increasing. The primary reason for this is the increasing power dissipation per unit area, which in turn leads to increased heat generation. This heat cannot be dissipated in a timely manner, causing device failure. During this process, the aluminum-clad ceramic substrate warps due to temperature fluctuations, leading to internal stress accumulation. When this stress exceeds the fracture strength of the material, it fractures, causing device failure. Therefore, the research of an aluminum-clad aluminum nitride ceramic substrate for packaging and its preparation method is of great significance.

[0004] In order to overcome the defects of the prior art, the present invention provides an aluminum-coated aluminum nitride ceramic substrate for packaging and a preparation method thereof. Summary of the Invention

[0005] The object of the present invention is to provide an aluminum-coated aluminum nitride ceramic substrate for packaging and a preparation method thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A aluminum-clad aluminum nitride ceramic substrate for packaging, comprising a double-sided aluminum-clad aluminum nitride ceramic sheet, wherein the thin aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet is provided with a copper layer, and the surface of the copper layer is plated with a nickel layer; the thick aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet is provided with a copper-diamond layer, and the surface of the copper-diamond layer is plated with a nickel layer; wherein the thin aluminum layer of the double-sided aluminum-clad aluminum nitride ceramic sheet has a thickness of 0.1-0.4 mm, and the thick aluminum layer has a thickness of 0.4-0.8 mm; the copper layer has a thickness of 0.2-0.8 mm; and the copper-diamond layer has a thickness of 90-100 μm.

[0008] A method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging, comprising the following steps:

[0009] Step 1: Solder the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering and set aside;

[0010] Step 2: Pre-treating the diamond micropowder and then copper-plating it to obtain copper-plated diamond micropowder;

[0011] Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic sheet obtained in step 1 through a cold spray process. Then, the double-sided aluminum-coated aluminum nitride ceramic sheet is pretreated, activated, and nickel-plated on the surface to obtain the final aluminum-coated aluminum nitride ceramic substrate.

[0012] Preferably, the process parameters of the diffusion sintering in step 1 are: temperature of 500° C., pressure of 3 MPa, vacuum degree of 0.01-0.5 Pa, heat preservation time of 30 min, and heating rate of 10° C. / min.

[0013] Preferably, the particle size of the diamond powder in step 2 is 10-15 μm; the pretreatment process is boiling in a degreasing solution for 5 minutes, boiling in a roughening solution for 30 minutes, ultrasonically vibrating in a sensitizing solution for 30 minutes, heating to 70°C in an activation solution for 30 minutes, and soaking in a degumming solution for 15 minutes. After each step is completed, it is washed with pure water until neutral.

[0014] Preferably, the copper plating in step 2 is carried out by chemical plating, and the composition of the chemical copper plating solution is: 10-40g / L CuSO4·5H2O, 20-60g / L Na2·EDTA, 4-8g / L NaOH, 20-40mL / L NH3·H2O; during the chemical copper plating, the temperature is 50-55°C and the time is 15-20min; the thickness of the copper plating layer on the diamond surface is 1-3μm.

[0015] More preferably, the cold spraying process parameters in step 3 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 air flow velocity of 300-600 m / s, and powder feeding amount of 5-20 g / min.

[0016] Preferably, in step 3, the surface nickel plating adopts sodium hypophosphite system chemical nickel plating; the components of the sodium hypophosphite system are: 25-30g / L NiSO4·7H2O, 25-30g / L NaH2PO2·H2O, 15-20g / L CH3COONa, 10-20g / LNa3C6H5O·2H2O; when the surface nickel is plated, the temperature is 78-85°C, the time is 20-25min, and the stirring method is air stirring.

[0017] Preferably, in step 1, the double-sided aluminum nitride ceramic sheet is pretreated, and after ultrasonic cleaning of surface impurities with acetone and sandblasting roughening, a layer of alloy powder is cold sprayed on the thin aluminum surface of the double-sided aluminum nitride ceramic sheet, and then the copper sheet is welded; wherein the content of each element in the alloy powder is: by mass percentage, 2.00-4.00% Cu, 0.20-0.40% Mg, 18.00-24.00% Si, 0.20-0.40% Fe, 0.1-0.3% Sc and the balance is Al; the cold spraying process parameters are: nozzle diameter 0.5-1.5mm, spray gun air pressure 0.7-0.8MPa, spraying distance 10-20mm, gas temperature 500-600℃, and powder feeding rate 15-20g / min.

[0018] More preferably, after the diamond powder is pretreated in step 2, a W or Nb film is deposited by magnetron sputtering, and then copper is plated; the power of the magnetron sputtering is 100-200W, the applied bias voltage is -60V; and the coating thickness is 200-300nm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention is characterized in that an alloy coating is formed on the thin aluminum surface of a double-sided aluminum-coated aluminum nitride ceramic sheet through a cold spraying process, and then a copper layer is welded by diffusion sintering for standby use; a niobium film is sputtered on diamond powder and chemically copper is plated by magnetron sputtering and chemical copper plating to obtain copper-plated diamond, which is then treated by a cold spraying process to cold-spray copper diamond on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic sheet to obtain a copper diamond layer; the double-sided aluminum-coated aluminum nitride ceramic sheet is then pre-treated for activation and surface nickel plating to obtain an aluminum-coated aluminum nitride ceramic substrate having a structure of surface plating-copper-thin aluminum-aluminum nitride ceramic sheet-thick aluminum-copper diamond-surface plating; all steps in the preparation process have complete parameters, the layer thickness is strictly controlled, and the quality of the product is guaranteed.

[0021] A layer of alloy powder is cold-sprayed on the surface of the double-sided aluminum-coated aluminum nitride ceramic sheet, and then a copper layer is welded. On the one hand, the cold-sprayed alloy powder greatly improves the bonding strength between the copper layer and the aluminum layer, thereby increasing the product yield; on the other hand, the alloy has good thermal conductivity and low expansion properties, reducing the risk of damage to the aluminum-coated aluminum nitride ceramic substrate caused by temperature changes; after a niobium film is sputtered on the surface of the diamond micropowder, chemical copper plating is performed. The niobium film improves the interface bonding strength between copper and diamond, while also improving the thermal conductivity of copper diamond, further improving the thermal conductivity of the aluminum-coated ceramic substrate.

[0022] The finished product prepared by the present invention greatly improves the thermal conductivity of the aluminum-coated aluminum nitride ceramic substrate, reduces the thermal warping and stress accumulation problems caused by thermal cycling, and improves the thermal cycling reliability of the aluminum-coated aluminum nitride ceramic substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of the preparation method of Example 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the finished product structure of Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In the experiment, double-sided aluminum nitride ceramic wafers were sourced from Jiangsu Fulehua Semiconductor Technology Co., Ltd.;

[0027] The particle size of diamond micropowder is 10-15 μm and was purchased from Henan Huanghe Cyclone Co., Ltd.

[0028] The degreasing solution is a 10% sodium hydroxide solution; the roughening solution is a 15% nitric acid solution; the sensitizing solution is a mixed solution of 20g / L tin chloride and 30ml / L 36% hydrochloric acid; the activation solution is a 2g / L silver nitrate solution; and the degumming solution is a 40g / L sodium hypophosphite solution.

[0029] The micro-etching solution consists of 80 g / L sodium persulfate and 5% sulfuric acid; the pickling solution consists of 6% sulfuric acid; and the activation solution consists of 20 mL / L sulfuric acid and 15 mg / L palladium ions.

[0030] Example 1:

[0031] Step 1: Select a double-sided aluminum nitride ceramic sheet with a specification of 139×190mm, a thin aluminum surface thickness of 0.3mm, and a thick aluminum surface thickness of 0.6mm, and a copper sheet with a specification of 139×190×0.4mm. Weld the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500℃, pressure 3MPa, vacuum degree 0.4Pa, heat preservation 0.5h, heating rate 10℃ / min, and set aside.

[0032] Step 2: Pre-treating the diamond powder, boiling it in a degreasing solution for 5 minutes, boiling it in a coarsening solution for 30 minutes, ultrasonically vibrating it in a sensitizing solution for 30 minutes, heating it to 70°C in an activation solution for 30 minutes, and soaking it in a degumming solution for 15 minutes. After each step, it was washed with pure water until neutral. After the pretreatment, it was electrolessly copper-plated for 18 minutes. The composition of the electroless copper plating solution was: 20g / L CuSO4·5H2O, 40g / LNa2·EDTA, 6gNaOH, 30ml / LNH3·H2O, and the temperature of the electroless copper plating solution was 55°C. The thickness of the copper plating layer was 2.3μm, and copper-plated diamond powder was obtained.

[0033] Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer with a thickness of 90 μm on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic sheet in step 1 through a cold spray process, and then perform pretreatment activation, in which the micro-etching solution is micro-etched for 100 seconds, the pickling solution is pickled for 90 seconds, and the activation solution is activated for 150 seconds. After each step is completed, pure water washing is performed. After the pretreatment activation is completed, the surface is nickel-plated using a sodium hypophosphite system for chemical nickel plating. The sodium hypophosphite system composition is: 26 g / LNiSO4·7H2O, 27 g / LNaH2PO2·H2O, 17 g / L CH3COONa, and 15 g / LNa3C6H5O·2H2O; when the surface is nickel-plated, the temperature is 83°C, the time is 22 minutes, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0034] The cold spraying process parameters are: nozzle diameter of 1.2mm, spray gun air pressure of 0.8MPa, gas flow rate of 230L / min, powder air flow velocity of 450m / s, and powder feeding amount of 12g / min; after cold spraying, the roughness Ra of the ceramic piece is 1.0μm.

[0035] Example 2:

[0036] Step 1: Select a double-sided aluminum nitride ceramic sheet with a specification of 139×190mm, a thin aluminum surface thickness of 0.2mm, and a thick aluminum surface thickness of 0.7mm, and a copper sheet with a specification of 139×190×0.6mm, and weld the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500℃, pressure 3MPa, vacuum degree 0.5Pa, holding temperature 0.5h, heating rate 10℃ / min, and set aside;

[0037] Step 2: Pre-treating the diamond powder, boiling it in a degreasing solution for 5 minutes, boiling it in a coarsening solution for 30 minutes, ultrasonically vibrating it in a sensitizing solution for 30 minutes, heating it to 70°C in an activation solution for 30 minutes, and soaking it in a degumming solution for 15 minutes. After each step, it was washed with pure water until neutral. After the pretreatment, it was electrolessly copper-plated for 20 minutes. The composition of the electroless copper plating solution was: 22g / L CuSO4·5H2O, 50g / LNa2·EDTA, 6gNaOH, 40ml / LNH3·H2O, and the temperature of the electroless copper plating solution was 55°C. The thickness of the copper plating layer was 2.5μm, and copper-plated diamond powder was obtained.

[0038] Step 3: Take the copper-plated diamond micropowder obtained in step 2, and obtain a copper diamond layer with a thickness of 100 μm on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic piece in step 1 through a cold spray process. Then, after pretreatment and activation, the double-sided aluminum-coated aluminum nitride ceramic piece is micro-etched in a micro-etching solution for 100 seconds, pickled in a pickling solution for 90 seconds, and activated in an activation solution for 150 seconds. After each step is completed, it is washed with pure water. After the pretreatment and activation, the surface is nickel-plated using a sodium hypophosphite system chemical nickel plating, and the sodium hypophosphite system composition is: 25g / LNiSO4·7H2O, 25g / LNaH2PO2·H2O, 15g / L CH3COONa, 10g / LNa3C6H5O·2H2O; when the surface is nickel-plated, the temperature is 82°C, the time is 25min, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0039] The cold spraying process parameters are: nozzle diameter of 1.0 mm, spray gun air pressure of 0.9 MPa, gas flow rate of 200 L / min, powder air flow velocity of 400 m / s, and powder feeding amount of 14 g / min; after cold spraying, the roughness Ra of the ceramic piece is 1.2 μm.

[0040] Example 3: Referring to Example 1, pretreatment of the double-sided aluminum nitride ceramic sheet is added, and the specific steps are as follows:

[0041] Step 1: Select a double-sided aluminum nitride ceramic sheet with a specification of 139×190mm, a thin aluminum surface thickness of 0.3mm, and a thick aluminum surface thickness of 0.6mm, and a copper sheet with a specification of 139×190×0.4mm, pre-treat the double-sided aluminum nitride ceramic sheet, clean the surface impurities with acetone ultrasonically and roughen it with sandblasting, cold-spray a layer of alloy powder on the thin aluminum surface of the double-sided aluminum nitride ceramic sheet, and then weld the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500℃, pressure 3MPa, vacuum degree 0.4Pa, heat preservation 0.5h, heating rate 10℃ / min, and set aside;

[0042] Step 2: Pre-treating the diamond powder, boiling it in a degreasing solution for 5 minutes, boiling it in a coarsening solution for 30 minutes, ultrasonically vibrating it in a sensitizing solution for 30 minutes, heating it to 70°C in an activation solution for 30 minutes, and soaking it in a degumming solution for 15 minutes. After each step, it was washed with pure water until neutral. After the pretreatment, it was electrolessly copper-plated for 18 minutes. The composition of the electroless copper plating solution was: 20g / L CuSO4·5H2O, 40g / LNa2·EDTA, 6gNaOH, 30ml / LNH3·H2O, and the temperature of the electroless copper plating solution was 55°C. The thickness of the copper plating layer was 2.3μm, and copper-plated diamond powder was obtained.

[0043] Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer with a thickness of 90 μm on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic piece in step 1 through a cold spray process, and then pre-treat and activate the double-sided aluminum-coated aluminum nitride ceramic piece. The double-sided aluminum-coated aluminum nitride ceramic piece is sequentially micro-etched in a micro-etching solution for 100 seconds, pickled in a pickling solution for 90 seconds, and activated in an activation solution for 150 seconds. After each step is completed, it is washed with pure water. After the pre-treatment and activation, the surface is nickel-plated using a sodium hypophosphite system chemical nickel plating, and the sodium hypophosphite system composition is: 26 g / LNiSO4·7H2O, 27 g / LNaH2PO2·H2O, 17 g / L CH3COONa, 15 g / LNa3C6H5O·2H2O; when the surface is nickel-plated, the temperature is 83°C, the time is 22 minutes, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0044] The content of each element in the alloy powder in step 1 is: 4.00% Cu, 0.35% Mg, 20.05% Si, 0.30% Fe, 0.2% Sc, and the balance is Al, by mass percentage; the cold spraying process parameters are: nozzle diameter of 1.2 mm, spray gun air pressure of 0.8 MPa, spraying distance of 20 mm, gas temperature of 550°C, and powder feed rate of 15 g / min.

[0045] The cold spraying process parameters in step 3 are: nozzle diameter of 1.2 mm, spray gun air pressure of 0.8 MPa, gas flow rate of 230 L / min, powder air flow velocity of 450 m / s, and powder feeding amount of 12 g / min; after cold spraying, the roughness Ra of the ceramic piece is 1.0 μm.

[0046] Example 4: Referring to Example 1, magnetron sputtering of diamond powder was added to form a Nb film. The specific steps are as follows:

[0047] Step 1: Select a double-sided aluminum nitride ceramic sheet with a specification of 139×190mm, a thin aluminum surface thickness of 0.3mm, and a thick aluminum surface thickness of 0.6mm, and a copper sheet with a specification of 139×190×0.4mm. Weld the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500℃, pressure 3MPa, vacuum degree 0.4Pa, heat preservation 0.5h, heating rate 10℃ / min, and set aside.

[0048] Step 2: Pre-treating the diamond powder, boiling it in a degreasing solution for 5 minutes, boiling it in a coarsening solution for 30 minutes, ultrasonically oscillating it in a sensitizing solution for 30 minutes, heating it to 70°C in an activation solution for 30 minutes, and soaking it in a degumming solution for 15 minutes. After each step, it was washed with pure water until it was neutral. After the pre-treatment, magnetron coating was performed. The power of the magnetron sputtering was 125W, and a bias voltage of -60V was applied to obtain a Nb coating thickness of 300nm. Then, chemical copper plating was performed for 18 minutes. The composition of the chemical copper plating solution was: 20g / L CuSO4·5H2O, 40g / LNa2·EDTA, 6g NaOH, 30ml / LNH3·H2O, and the temperature of the chemical copper plating solution was 55°C. The thickness of the copper plating layer was 2.3μm, and copper-plated diamond powder was obtained.

[0049] Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer with a thickness of 90 μm on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic piece in step 1 through a cold spray process, and then pre-treat and activate the double-sided aluminum-coated aluminum nitride ceramic piece, in sequence, micro-etching in a micro-etching solution for 100 seconds, pickling in a pickling solution for 90 seconds, and activating in an activation solution for 150 seconds. After each step is completed, it is washed with pure water. After the pre-treatment and activation, the surface is nickel-plated using a sodium hypophosphite system chemical nickel plating, and the sodium hypophosphite system composition is: 26 g / LNiSO4·7H2O, 27 g / LNaH2PO2·H2O, 17 g / L CH3COONa, 15 g / LNa3C6H5O·2H2O; when the surface is nickel-plated, the temperature is 83°C, the time is 22 minutes, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0050] The cold spraying process parameters are: nozzle diameter of 1.2mm, spray gun air pressure of 0.8MPa, gas flow rate of 230L / min, powder air flow velocity of 450m / s, and powder feeding amount of 12g / min; after cold spraying, the roughness Ra of the ceramic piece is 1.0μm.

[0051] Example 5: Referring to Example 4, pretreatment of the aluminum nitride-coated ceramic sheet is added, and the specific steps are as follows:

[0052] Step 1: Select a double-sided aluminum-clad aluminum nitride ceramic sheet with a specification of 139×190 mm, a thin aluminum surface thickness of 0.3 mm, and a thick aluminum surface thickness of 0.6 mm, and a copper sheet with a specification of 139×190×0.4 mm, pre-treat the double-sided aluminum-clad aluminum nitride ceramic sheet, clean the surface impurities with acetone ultrasonically and roughen it with sandblasting, cold-spray a layer of alloy powder on the thin aluminum surface, and then weld the copper sheet to the thin aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500°C, pressure 3 MPa, vacuum degree 0.4 Pa, heat preservation 0.5 h, heating rate 10°C / min, and set aside;

[0053] Step 2: Pre-treating the diamond powder, boiling it in a degreasing solution for 5 minutes, boiling it in a coarsening solution for 30 minutes, ultrasonically oscillating it in a sensitizing solution for 30 minutes, heating it to 70°C in an activation solution for 30 minutes, and soaking it in a degumming solution for 15 minutes. After each step, it was washed with pure water until it was neutral. After the pre-treatment, magnetron coating was performed. The power of the magnetron sputtering was 125W, and a bias voltage of -60V was applied to obtain a Nb coating thickness of 300nm. Then, chemical copper plating was performed for 18 minutes. The composition of the chemical copper plating solution was: 20g / L CuSO4·5H2O, 40g / LNa2·EDTA, 6g NaOH, 30ml / LNH3·H2O, and the temperature of the chemical copper plating solution was 55°C. The thickness of the copper plating layer was 2.3μm, and copper-plated diamond powder was obtained.

[0054] Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer with a thickness of 90 μm on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic piece in step 1 through a cold spray process, and then pre-treat and activate the double-sided aluminum-coated aluminum nitride ceramic piece, in sequence, micro-etching in a micro-etching solution for 100 seconds, pickling in a pickling solution for 90 seconds, and activating in an activation solution for 150 seconds. After each step is completed, it is washed with pure water. After the pre-treatment and activation, the surface is nickel-plated using a sodium hypophosphite system chemical nickel plating, and the sodium hypophosphite system composition is: 26 g / LNiSO4·7H2O, 27 g / LNaH2PO2·H2O, 17 g / L CH3COONa, 15 g / LNa3C6H5O·2H2O; when the surface is nickel-plated, the temperature is 83°C, the time is 22 minutes, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0055] The content of each element in the alloy powder in step 1 is: 4.00% Cu, 0.35% Mg, 20.05% Si, 0.30% Fe, 0.2% Sc, and the balance is Al, by mass percentage; the cold spraying process parameters are: nozzle diameter of 1.2 mm, spray gun air pressure of 0.8 MPa, spraying distance of 20 mm, gas temperature of 550°C, and powder feed rate of 15 g / min.

[0056] The cold spraying process parameters in step 3 are: nozzle diameter of 1.2 mm, spray gun air pressure of 0.8 MPa, gas flow rate of 230 L / min, powder air flow velocity of 450 m / s, and powder feeding amount of 12 g / min; after cold spraying, the roughness Ra of the ceramic piece is 1.0 μm.

[0057] Comparative Example 1: Referring to Example 1, the difference is that the copper diamond layer is removed. The specific steps are as follows:

[0058] Step 1: Select a double-sided aluminum-clad aluminum nitride ceramic sheet with a specification of 139×190mm, a thin aluminum surface thickness of 0.3mm, and a thick aluminum surface thickness of 0.6mm, and a copper sheet with a specification of 139×190×0.4mm. Weld the copper sheet to the thin aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500℃, pressure 3MPa, vacuum degree 0.4Pa, holding temperature 0.5h, and heating rate 10℃ / min; forming a copper-aluminum-aluminum nitride ceramic sheet-aluminum structure;

[0059] Step 2: Take the double-sided aluminum-coated aluminum nitride ceramic wafer in step 1 and perform pretreatment activation, and sequentially perform micro-etching in a micro-etching solution for 100 seconds, pickling in a pickling solution for 90 seconds, and activation in an activation solution for 150 seconds. After each step is completed, wash with pure water. After the pretreatment activation is completed, perform surface nickel plating, and adopt a sodium hypophosphite system for chemical nickel plating. The composition of the sodium hypophosphite system is: 26g / LNiSO4·7H2O, 27g / LNaH2PO2·H2O, 17g / L CH3COONa, 15g / LNa3C6H5O·2H2O; when the surface nickel is plated, the temperature is 83°C, the time is 22min, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0060] Comparative Example 2: Referring to Example 5, the difference is that the copper diamond layer is removed. The specific steps are as follows:

[0061] Step 1: Select a double-sided aluminum-clad aluminum nitride ceramic sheet with a specification of 139×190 mm, a thin aluminum surface thickness of 0.3 mm, and a thick aluminum surface thickness of 0.6 mm, and a copper sheet with a specification of 139×190×0.4 mm, pre-treat the double-sided aluminum-clad aluminum nitride ceramic sheet, clean the surface impurities with acetone ultrasonically and roughen it with sandblasting, cold-spray a layer of alloy powder on the thin aluminum surface, and then weld the copper sheet to the thin aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet by diffusion sintering. The diffusion sintering process parameters are: temperature 500°C, pressure 3 MPa, vacuum degree 0.4 Pa, heat preservation 0.5 h, heating rate 10°C / min, and set aside;

[0062] Step 2: Take the double-sided aluminum-coated aluminum nitride ceramic wafer in step 1 for pretreatment activation, micro-etching for 100 seconds, pickling for 90 seconds, and activation for 150 seconds in sequence. After each step is completed, wash with pure water. After the pretreatment activation is completed, nickel plating is performed on the surface. Sodium hypophosphite system chemical nickel plating is adopted. The composition of the sodium hypophosphite system is: 26g / LNiSO4·7H2O, 27g / LNaH2PO2·H2O, 17g / LCH3COONa, 15g / LNa3C6H5O·2H2O; when nickel plating the surface, the temperature is 83°C, the time is 22 minutes, and air stirring is performed to obtain an aluminum-coated aluminum nitride ceramic substrate.

[0063] The content of each element in the alloy powder in step 1 is: 4.00% Cu, 0.35% Mg, 20.05% Si, 0.30% Fe, 0.2% Sc, and the balance is Al, by mass percentage; the cold spraying process parameters are: nozzle diameter of 1.2 mm, spray gun air pressure of 0.8 MPa, spraying distance of 20 mm, gas temperature of 550°C, and powder feed rate of 15 g / min.

[0064] Detection test:

[0065] Thermal Cycling Performance Test: The aluminum-clad aluminum nitride ceramic substrates prepared in Examples 1-5 and Comparative Examples 1-2 were used as samples and subjected to zinc immersion thermal cycling tests in a TSE-12-A high-low temperature cycling test chamber. Parameter settings: Cycling temperature: -40°C to 125°C. The test standard was GB / T 2423.22-2012 Environmental Testing Part 2: Test Methods Test N: Temperature Variation. Each sample was cycled 500 times. The warpage of the copper-clad surface of the sample was measured before and after the cycles. The test temperature was room temperature.

[0066] Before hot and cold cycle After hot and cold cycles Example 1 -142μm -60μm Example 2 -152μm -86μm Example 3 -132μm -85μm Example 4 -139μm -88μm Example 5 -129μm -90μm Comparative Example 1 -122μm 53μm Comparative Example 2 -134μm 36μm

[0067] Conclusion: According to the warpage value data before and after the hot and cold cycle test of the examples and comparative examples, it is concluded that by adding a copper diamond layer, the thermal conductivity of the aluminum-clad ceramic substrate can be significantly improved and the warpage can be improved; by comparing Example 1 with Examples 3-4, cold spraying alloy powder and sputtering a Nb layer on the diamond surface are beneficial to improving the thermal conductivity of the aluminum-clad aluminum nitride ceramic. By comparing Example 1 with Example 5, the aluminum-clad aluminum nitride substrate prepared by cold spraying alloy powder and sputtering a Nb layer on the diamond surface has obvious improvement in warpage.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging, characterized in that: The following steps are involved: Step 1: Solder the copper sheet to the thin aluminum surface of the double-sided aluminum nitride ceramic sheet by diffusion sintering and set aside; Step 2: Pre-treating the diamond micropowder and then copper-plating it to obtain copper-plated diamond micropowder; Step 3: Take the copper-plated diamond powder obtained in step 2, and obtain a copper diamond layer on the thick aluminum surface of the double-sided aluminum-coated aluminum nitride ceramic sheet obtained in step 1 through a cold spray process, and then pre-treat and activate the double-sided aluminum-coated aluminum nitride ceramic sheet and perform surface nickel plating in sequence to obtain the final aluminum-coated aluminum nitride ceramic substrate; The thin aluminum surface of the double-sided aluminum nitride ceramic sheet covered with aluminum in step 1 is pretreated by ultrasonically cleaning the surface impurities with acetone and roughening it with sandblasting. A layer of alloy powder is cold sprayed on the thin aluminum surface of the double-sided aluminum nitride ceramic sheet covered with aluminum, and then the copper sheet is welded. The content of each element in the alloy powder is as follows: 2.00-4.00% Cu, 0.20-0.40% Mg, 18.00-24.00% Si, 0.20-0.40% Fe, 0.1-0.3% Sc, and the balance is Al, by mass percentage; In step 2, after the diamond powder is pretreated, a W or Nb film is deposited by magnetron sputtering, and then copper is plated; the power of the magnetron sputtering is 100-200W, the applied bias voltage is -60V; and the coating thickness is 200-300nm.

2. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 1, characterized in that: The process parameters of the diffusion sintering in step 1 are: temperature of 500° C., pressure of 3 MPa, vacuum degree of 0.01-0.5 Pa, heat preservation time of 30 min, and heating rate of 10° C. / min.

3. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 2, characterized in that: The particle size of the diamond powder in step 2 is 10-15 μm; the pretreatment process is boiling in a degreasing solution for 5 minutes, boiling in a roughening solution for 30 minutes, ultrasonic vibration in a sensitizing solution for 30 minutes, heating to 70°C in an activation solution for 30 minutes, and soaking in a degumming solution for 15 minutes. After each step, it is washed with pure water until neutral.

4. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 2, characterized in that: In step 2, the copper plating is performed by chemical plating, and the composition of the chemical copper plating solution is: 10-40g / L CuSO4·5H2O, 20-60g / L Na2·EDTA, 4-8g / L NaOH, 20-40mL / L NH3·H2O; the chemical copper plating temperature is 50-55°C, and the time is 15-20min; the thickness of the copper plating layer on the diamond surface is 1-3μm.

5. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 2, characterized in that: The cold spraying process parameters in step 3 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 air flow velocity of 300-600 m / s, and powder feeding amount of 5-20 g / min.

6. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 2, characterized in that: In step 3, the surface nickel plating adopts sodium hypophosphite system chemical nickel plating; the components of the sodium hypophosphite system are: 25-30g / L NiSO4·7H2O, 25-30g / L NaH2PO2·H2O, 15-20g / L CH3COONa, and 10-20g / L Na3C6H5O·2H2O; when the surface nickel is plated, the temperature is 78-85°C, the time is 20-25min, and the stirring method is air stirring.

7. The method for preparing an aluminum-coated aluminum nitride ceramic substrate for packaging according to claim 1, characterized in that: The cold spraying process parameters are: nozzle diameter of 0.5-1.5mm, spray gun air pressure of 0.7-0.8MPa, spraying distance of 10-20mm, gas temperature of 500-600℃, and powder feeding rate of 15-20g / min.

8. An aluminum-clad aluminum nitride ceramic substrate for packaging obtained by the preparation method according to any one of claims 1 to 7, characterized in that: It comprises a double-sided aluminum-clad aluminum nitride ceramic sheet, wherein the thin aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet is provided with a copper layer, and the surface of the copper layer is plated with a nickel layer; the thick aluminum surface of the double-sided aluminum-clad aluminum nitride ceramic sheet is provided with a copper diamond layer, and the surface of the copper diamond layer is plated with a nickel layer; wherein the thickness of the thin aluminum layer of the double-sided aluminum-clad aluminum nitride ceramic sheet is 0.1-0.4mm, the thickness of the thick aluminum layer is 0.4-0.8mm; the thickness of the copper layer is 0.2-0.8mm; and the thickness of the copper diamond layer is 90-100μm.

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