Preparation process of heat-conducting and electric-conducting power module

Abstract

The invention discloses a preparation process of a heat-conducting and electric-conducting power module, and relates to the technical field of semiconductors, and the preparation process comprises the following steps: 1, carrying out primary sand blasting treatment on a spraying area on an aluminum radiator; 2, spraying a first copper-clad layer on the spraying area; 3, carrying out secondary sand blasting treatment on the first copper-clad layer; 4, spraying a second copper-clad layer on the first copper-clad layer; 5, laser is emitted to irradiate the second copper-clad layer, so that the surface of the second copper-clad layer is softened, a third copper-clad layer is sprayed on the second copper-clad layer, and a heat-conducting and heat-conducting electroplated copper layer is obtained; 6, eliminating the internal stress of the heat-conducting and heat-conducting electroplated copper layer by using a directional high-frequency magnetic field; and 7, directly installing a chip on the heat-conducting and electricity-conducting electroplating copper layer to obtain the heat-conducting and electricity-conducting power module. According to the process, sand blasting and cold spraying are alternately carried out, and the procedures of softening copper powder and eliminating stress are added, so that the internal stress of a copper plating layer can be eliminated, pores can be reduced, and the binding force between the copper plating layer and an aluminum radiator and the binding force between copper powder particles can be increased.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a preparation process of a heat-conducting and electrically-conducting power module. Background Art

[0002] Semiconductor power modules are high-power electronic power devices that are first combined according to certain functions and then potted into one power device. Semiconductor power modules can realize rectification and inversion functions according to the different components packaged. Because semiconductor power modules can work at very high frequencies and have intelligent functions such as precise output adjustment according to load requirements and self-protection according to overheating, overvoltage, overcurrent, etc., they are widely used in fields that require power conversion, such as industrial frequency conversion, converters, and automotive motor controllers.

[0003] Semiconductor power modules emit a large amount of heat during operation. In order to ensure that the semiconductor power modules can operate stably and reliably, effective heat dissipation treatment is required. At present, there are many related technologies for heat dissipation of semiconductor power modules, such as the power modules disclosed in the patent documents with publication numbers CN108428682A and CN210668342U. These power modules adopt a new heat dissipation structure in which the chip is fixed to the radiator through the DBC ceramic copper-clad plate and the copper-plated layer. Compared with the traditional heat dissipation structure, the aforementioned new heat dissipation structure eliminates the contact layer and thermal conductive silicone grease, and the heat can be quickly transferred to the radiator through the DBC ceramic copper-clad plate and the copper-plated layer, so it has a better heat dissipation effect. However, the applicant analyzed and found that in the aforementioned new heat dissipation structure, the copper-plated layer is simply set on the radiator by cold spraying. Affected by process control, there are pores and stresses inside the copper-plated layer. There is a problem of insufficient bonding between the copper-plated layer and the aluminum radiator, and between the copper powder particles of the copper-plated layer, which not only affects the heat transfer effect, but also affects the product quality.

[0004] Therefore, it is necessary to develop new technologies to solve the above technical problems. Summary of the invention

[0005] In order to overcome the above-mentioned technical problems existing in the prior art, the present invention provides a preparation process for a thermally conductive and electrically conductive power module, which adopts sandblasting and cold spraying alternately to form a copper-plated layer by multiple spraying, and adds the steps of softening the copper powder by laser irradiation and eliminating stress by high-frequency magnetic field. It can not only eliminate the internal stress of the copper-plated layer and reduce the porosity, but also increase the bonding force between the copper-plated layer and the aluminum radiator, and between the copper powder particles, thereby solving the technical problem that the existing copper-plated layer affects the heat transfer effect and product quality due to internal porosity, stress and insufficient bonding force.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A process for preparing a thermally conductive and electrically conductive power module comprises the following steps: Step S1: Select a spraying area on the plane of the aluminum radiator, and use a sandblasting device to perform a sandblasting treatment on the spraying area so that the surface roughness of the spraying area reaches 80-100 μm; Step S2: using copper powder as raw material, using low-pressure cold spraying equipment to form a first copper coating layer with a thickness of 10-800 μm in the spraying area; Step S3: performing secondary sandblasting on the first copper clad layer using a sandblasting device to make the surface roughness of the first copper clad layer reach 60-80 μm; Step S4: forming a second copper clad layer with a thickness of 10-600 μm on the first copper clad layer using a low-pressure cold spraying device; Step S5: controlling the semiconductor laser emitter to emit laser to irradiate the second copper clad layer at a constant moving speed to soften the surface of the second copper clad layer, and making the low-pressure cold spraying equipment follow the moving track of the semiconductor laser emitter to form a third copper clad layer with a thickness of 10-400 μm on the second copper clad layer with softened surface, and after polishing the third copper clad layer to be smooth, a thermally conductive and electrically conductive copper-plated layer consisting of the first copper clad layer, the second copper clad layer and the third copper clad layer is obtained on the aluminum heat sink; Step S6: prepare a high-frequency pulse generator, a strong magnetic bar, an N-pole coil and an S-pole coil, respectively fix the N-pole coil and the S-pole coil on two spaced-apart strong magnetic bars, connect the high-frequency pulse generator with the N-pole coil and the S-pole coil, start the high-frequency pulse generator, form a directional high-frequency magnetic field between the strong magnetic bars, place the thermally conductive and electrically conductive copper-plated layer obtained in step S5 into the directional high-frequency magnetic field, and use the directional high-frequency magnetic field to eliminate the internal stress of the thermally conductive and electrically conductive copper-plated layer; Step S7: directly mounting the chip on the thermally conductive and electrically conductive copper-plated layer, and fixing the chip on the aluminum heat sink by sintering solder paste. After completion, a thermally conductive and electrically conductive power module is obtained in which the chip is electrically connected to the aluminum heat sink through the thermally conductive and electrically conductive copper-plated layer.

[0007] The low-pressure cold spraying equipment has a pressure of 5-6.5 MPa during spraying, a gas preheating temperature of 400° C.-500° C., a powder delivery rate of 1-150 g / min, and a spraying distance of 20-30 cm.

[0008] In step S5, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spray equipment and is located at the front side of the movement track of the spray gun.

[0009] In step S5, the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment is 3-6 mm.

[0010] In step S5, the laser power of the semiconductor laser transmitter is 500-600W.

[0011] In step S5, the thickness of the thermally conductive and electrically conductive copper-plated layer is 30-1800 um, and the thickness of the third copper-clad layer is less than or equal to the thickness of the second copper-clad layer, and the thickness of the second copper-clad layer is less than or equal to the thickness of the first copper-clad layer.

[0012] In step S6, the magnetic induction intensity of the directional high-frequency magnetic field is 220-300 μt.

[0013] In step S6, the thermally conductive and electrically conductive copper-plated layer is subjected to stress elimination in a directional high-frequency magnetic field for 2-8 minutes.

[0014] Step S1 and step S3 are sandblasted using two independent sandblasting equipments respectively, and step S2, step S4 and step S5 are copper-coated using three independent low-pressure cold spraying equipments respectively. Each sandblasting equipment cooperates with each low-pressure cold spraying equipment to form a continuous production line.

[0015] The copper powder used in the spraying of the copper layer in step S2, step S4 and step S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20 um.

[0016] By adopting the above technical solution, the beneficial technical effects of the present invention are: 1. The present invention can form a spraying area with a certain roughness on the plane of the aluminum radiator through a single sandblasting process. After the first copper cladding layer is sprayed onto the rough surface of the spraying area, the copper powder and the raised peaks and recessed troughs on the surface of the spraying area can form a mutually interlocking structure, thereby improving the bonding force between the first copper cladding layer and the aluminum radiator.

[0017] Furthermore, through secondary sandblasting, a rough area can be formed on the surface of the first copper cladding layer, so that a mutually interlocking structure is formed between the first copper cladding layer and the second copper cladding layer, which can not only improve the bonding force between the first copper cladding layer and the second copper cladding layer, but also increase the density between the copper powder particles, thereby helping to reduce the internal porosity and stress of the copper cladding layer.

[0018] Furthermore, laser irradiation can make the surface of the second copper cladding layer slightly softened without melting, which can make the second copper cladding layer and the third copper cladding layer more tightly bonded, which is not only beneficial to improve the deposition efficiency and bonding strength of the copper powder, but also beneficial to further reduce the porosity between the copper powders.

[0019] Furthermore, the internal stress of the thermally and electrically conductive copper plating layer can be effectively eliminated by directional high-frequency magnetic field.

[0020] In addition, the present invention also sets the surface roughness after the secondary sandblasting to be smaller than the surface roughness after the primary sandblasting, and gradually reduces the spraying thickness of the first copper cladding layer, the second copper cladding layer and the third copper cladding layer, which is beneficial to further improve the bonding force between the first copper cladding layer and the aluminum radiator, and further improve the bonding force between each copper cladding layer, so that the thermally conductive and electrically conductive copper-plated layer on the aluminum radiator has better firmness and higher tensile strength.

[0021] In summary, the present invention adopts sandblasting and cold spraying alternately to form a copper-plated layer by multiple spraying, and adds the steps of softening copper powder by laser irradiation and eliminating stress by high-frequency magnetic field. It can not only eliminate the internal stress of the copper-plated layer and reduce the porosity, but also increase the bonding force between the copper-plated layer and the aluminum heat sink, and between the copper powder particles, effectively improving the heat transfer effect and product quality of the power module.

[0022] 2. The present invention adopts a pressure of 5-6.5Mpa, a gas preheating temperature of 400℃-500℃, a powder delivery rate of 1-150g / min, and a spraying distance of 20-30cm during spraying. The use of such specific spraying parameters is conducive to obtaining a uniform, dense, stable and reliable copper coating. On the contrary, if the spraying parameters exceed the aforementioned range, the spraying effect of the copper coating will be affected, thereby affecting the heat transfer effect and quality of the power module.

[0023] 3. The present invention sets the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment to 3-6 mm, which can achieve the best bonding effect between the second copper clad layer with softened surface and the third copper clad layer, thereby improving the density and bonding strength of the thermal and electrical conductive copper plating layer.

[0024] 4. The present invention sets the laser power of the semiconductor laser emitter to 500-600W, which is conducive to softening the surface of the second copper cladding layer more quickly, thereby shortening the preparation time of the power module.

[0025] 5. The present invention sets the magnetic induction intensity of the directional high-frequency magnetic field to 220-300 μt, which is beneficial to achieve a better stress elimination effect on the thermally conductive and electrically conductive copper-plated layer.

[0026] 6. The present invention only needs to place the thermally conductive and electrically conductive copper-plated layer in a directional high-frequency magnetic field for 2-8 minutes to effectively eliminate internal stress, which has the advantages of short time and good stress elimination effect.

[0027] 7. Each step of the present invention uses independent sandblasting equipment and low-pressure cold spraying equipment, which can form a continuous production line and is conducive to the mass production of power modules.

[0028] 8. The present invention uses specific spherical powder as the spraying raw material, which has the advantage of improving the thermal and electrical conductivity effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flowchart of the present invention; Figure 2 It is a structural schematic diagram of the present invention; Figure 3 This is a copper clad stress buffer test diagram of the present invention; Figure 4 This is a test diagram of the solderability and solder void rate of the present invention.

[0030] The markings in the figure are: 1. aluminum heat sink, 2. chip, 3. thermal and electrical conductive copper plating layer, 3.1. first copper cladding layer, 3.2. second copper cladding layer, 3.3. third copper cladding layer. DETAILED DESCRIPTION

[0031] Example 1 This embodiment provides a preparation process of a thermally conductive and electrically conductive power module. Figure 1 As shown, it includes the following steps: Step S1: Obtain an aluminum radiator 1, which is a fin-type radiator with a flat surface on one side and fins on the other side. Select a spraying area on the plane of the aluminum radiator 1, which can be the entire plane or a part of the plane. Then use a sandblasting device to perform a sandblasting treatment on the spraying area so that the surface roughness of the spraying area reaches 80 μm.

[0032] Step S2: Using copper powder as raw material, a first copper clad layer 3.1 with a thickness of 10 μm is formed in the spraying area by using low-pressure cold spraying equipment. Since the surface of the spraying area has a certain degree of roughness, after spraying the first copper clad layer 3.1, the copper powder of the first copper clad layer 3.1 and the raised peaks and recessed valleys on the surface of the spraying area can form a mutually interlocking structure, thereby improving the bonding force between the first copper clad layer 3.1 and the aluminum heat sink 1.

[0033] Step S3: using a sandblasting device to perform secondary sandblasting on the surface of the first copper clad layer 3.1, so that the surface roughness of the first copper clad layer 3.1 reaches 60 μm.

[0034] Step S4: Using copper powder as raw material, a second copper clad layer 3.2 with a thickness of 10 μm is formed on the first copper clad layer 3.1 by using low-pressure cold spraying equipment. Since the surface of the first copper clad layer 3.1 has a certain degree of roughness, after spraying the second copper clad layer 3.2, the copper powder of the second copper clad layer 3.2 and the raised peaks and recessed valleys on the surface of the first copper clad layer 3.1 can form a mutually interlocking structure, thereby increasing the density inside the copper clad layer and improving the bonding force between the first copper clad layer 3.1 and the second copper clad layer 3.2.

[0035] Step S5: Select a semiconductor laser emitter with a laser power of 500, and control the semiconductor laser emitter to emit laser at a constant moving speed to irradiate the second copper clad layer 3.2, so that the surface of the second copper clad layer 3.2 is softened, and the low-pressure cold spraying equipment follows the moving track of the semiconductor laser emitter, and a third copper clad layer 3.3 with a thickness of 10 μm is formed on the second copper clad layer 3.2 with a softened surface. After the third copper clad layer 3.3 is polished and flat, a thermally conductive and electrically conductive copper-plated layer 3 consisting of the first copper clad layer 3.1, the second copper clad layer 3.2 and the third copper clad layer 3.3 is obtained on the aluminum heat sink 1. Among them, the thickness of the thermally conductive and electrically conductive copper-plated layer 3 is 30 μm, the thickness of the third copper clad layer 3.3 is equal to the thickness of the second copper clad layer 3.2, and the thickness of the second copper clad layer 3.2 is equal to the thickness of the first copper clad layer 3.1.

[0036] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying equipment and is located in front of the movement track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment is 3 mm. On the one hand, this can control the synchronous movement of the spray gun and the semiconductor laser, and on the other hand, it is conducive to ensuring a better bonding effect between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0037] In this step, the second copper clad layer 3.2 is irradiated with a laser of a specific power, which can slightly soften the copper powder on the surface of the second copper clad layer 3.2 irradiated by the laser without melting it, which is conducive to making the third copper clad layer 3.3 more tightly and firmly fixed on the second copper clad layer 3.2, further increasing the density inside the copper clad layer, and improving the bonding force between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0038] Step S6: prepare a high-frequency pulse generator, a strong magnetic rod, an N-pole coil and an S-pole coil, respectively fix the N-pole coil and the S-pole coil on two spaced-apart strong magnetic rods, connect the high-frequency pulse generator to the N-pole coil and the S-pole coil, start the high-frequency pulse generator, form a directional high-frequency magnetic field with a magnetic induction intensity of 220μt between the strong magnetic rods, put the thermally conductive and electrically conductive copper-plated layer 3 obtained in step S5 into the directional high-frequency magnetic field and maintain it for 2 minutes, and use the directional high-frequency magnetic field to eliminate the internal stress of the thermally conductive and electrically conductive copper-plated layer 3.

[0039] Step S7: directly mounting the chip 2 on the thermally conductive and electrically conductive copper-plated layer 3 from which the internal stress has been eliminated, and fixing the chip 2 on the aluminum heat sink 1 by sintering the solder paste. Figure 2 The chip 2 shown is a thermally conductive and electrically conductive power module electrically connected to an aluminum heat sink 1 via a thermally conductive and electrically conductive copper plating layer 3 .

[0040] According to a preferred implementation of this embodiment, the copper powder used in the copper coating spraying in step S2, step S4 and step S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20um. In addition, in step S2, step S4 and step S5, the pressure of the low-pressure cold spraying equipment during spraying is 5Mpa, the gas preheating temperature is 400°C, the powder delivery rate is 1g / min, and the spraying distance is 20cm.

[0041] According to another preferred implementation manner of the present embodiment, step S1 and step S3 are sandblasted using two independent sandblasting equipments respectively, and step S2, step S4 and step S5 are sprayed with copper coating using three independent low-pressure cold spraying equipments respectively, and each sandblasting equipment cooperates with each low-pressure cold spraying equipment to form a continuous production line.

[0042] Those skilled in the art will appreciate that, in order to obtain a copper coating of suitable thickness during spraying of copper powder in the above-mentioned steps, in addition to adjusting the pressure, powder delivery rate and spraying distance during spraying, the thickness can also be controlled by adjusting the moving speed of the spray gun / aluminum radiator 1 and the spraying speed of the spray gun, and the specific settings can be made according to needs.

[0043] It should be noted that the back side (negative electrode) of the preferred chip 2 of the present invention is fixed on the thermally conductive and electrically conductive copper-plated layer 3 by solder paste. Since the chip 2 prepared by this scheme is electrically connected to the aluminum heat sink 1 by the thermally conductive and electrically conductive copper-plated layer 3, the aluminum heat sink 1 is also in a conductive state. In this regard, when the power module is applied to an actual welding machine or other equipment, the welding machine can be insulated. For example, the power module can be fixed inside the equipment by an insulating column, and then the aluminum heat sink 1 is connected to the output end of the welding machine by a copper conductive sheet, so that the current reaches the output end through the chip 2, the aluminum heat sink 1 and the copper conductive sheet.

[0044] Example 2 This embodiment provides a preparation process of a thermally conductive and electrically conductive power module. Figure 1 As shown, it includes the following steps: Step S1: Obtain an aluminum radiator 1, which is a fin-type radiator with a plane on one side and fins on the other side. Select a spraying area on the plane of the aluminum radiator 1, which can be the entire plane or a part of the plane. Then use a sandblasting device to perform a sandblasting treatment on the spraying area so that the surface roughness of the spraying area reaches 90μm.

[0045] Step S2: Using copper powder as raw material, a first copper clad layer 3.1 with a thickness of 500 μm is formed in the spraying area by using low-pressure cold spraying equipment. Since the surface of the spraying area has a certain degree of roughness, after spraying the first copper clad layer 3.1, the copper powder of the first copper clad layer 3.1 and the raised peaks and recessed valleys on the surface of the spraying area can form a mutually interlocking structure, thereby improving the bonding force between the first copper clad layer 3.1 and the aluminum heat sink 1.

[0046] Step S3: using a sandblasting device to perform secondary sandblasting on the surface of the first copper clad layer 3.1, so that the surface roughness of the first copper clad layer 3.1 reaches 70 μm.

[0047] Step S4: Using copper powder as raw material, a second copper clad layer 3.2 with a thickness of 400 μm is formed on the first copper clad layer 3.1 by using low-pressure cold spraying equipment. Since the surface of the first copper clad layer 3.1 has a certain degree of roughness, after spraying the second copper clad layer 3.2, the copper powder of the second copper clad layer 3.2 and the raised peaks and recessed valleys on the surface of the first copper clad layer 3.1 can form a mutually interlocking structure, thereby increasing the density inside the copper clad layer and improving the bonding force between the first copper clad layer 3.1 and the second copper clad layer 3.2.

[0048] Step S5: Select a semiconductor laser emitter with a laser power of 550W, and control the semiconductor laser emitter to emit laser at a constant moving speed to irradiate the second copper clad layer 3.2, so that the surface of the second copper clad layer 3.2 is softened, and the low-pressure cold spraying equipment follows the moving track of the semiconductor laser emitter, and a third copper clad layer 3.3 with a thickness of 300μm is formed on the second copper clad layer 3.2 with a softened surface. After the third copper clad layer 3.3 is polished and flat, a thermally conductive and electrically conductive copper-plated layer 3 consisting of the first copper clad layer 3.1, the second copper clad layer 3.2 and the third copper clad layer 3.3 is obtained on the aluminum heat sink 1. Among them, the thickness of the thermally conductive and electrically conductive copper-plated layer 3 is 1200um, and the thickness of the third copper clad layer 3.3 is less than the thickness of the second copper clad layer 3.2, and the thickness of the second copper clad layer 3.2 is less than the thickness of the first copper clad layer 3.1.

[0049] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying equipment and is located in front of the movement track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment is 5 mm. On the one hand, this can control the synchronous movement of the spray gun and the semiconductor laser, and on the other hand, it is conducive to ensuring a better bonding effect between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0050] In this step, the second copper clad layer 3.2 is irradiated with a laser of a specific power, which can slightly soften the copper powder on the surface of the second copper clad layer 3.2 irradiated by the laser without melting it, which is conducive to making the third copper clad layer 3.3 more tightly and firmly fixed on the second copper clad layer 3.2, further increasing the density inside the copper clad layer, and improving the bonding force between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0051] Step S6: prepare a high-frequency pulse generator, a strong magnetic rod, an N-pole coil and an S-pole coil, respectively fix the N-pole coil and the S-pole coil on two spaced-apart strong magnetic rods, connect the high-frequency pulse generator to the N-pole coil and the S-pole coil, start the high-frequency pulse generator, form a directional high-frequency magnetic field with a magnetic induction intensity of 260μt between the strong magnetic rods, put the thermally conductive and electrically conductive copper-plated layer 3 obtained in step S5 into the directional high-frequency magnetic field and maintain it for 5 minutes, and use the directional high-frequency magnetic field to eliminate the internal stress of the thermally conductive and electrically conductive copper-plated layer 3.

[0052] Step S7: directly mounting the chip 2 on the thermally conductive and electrically conductive copper-plated layer 3 from which the internal stress has been eliminated, and fixing the chip 2 on the aluminum heat sink 1 by sintering the solder paste. Figure 2 The chip 2 shown is a thermally conductive and electrically conductive power module electrically connected to an aluminum heat sink 1 via a thermally conductive and electrically conductive copper plating layer 3 .

[0053] According to a preferred implementation of this embodiment, the copper powder used in the copper coating spraying in step S2, step S4 and step S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20um. In addition, in step S2, step S4 and step S5, the pressure of the low-pressure cold spraying equipment during spraying is 6Mpa, the gas preheating temperature is 450°C, the powder delivery rate is 80g / min, and the spraying distance is 25cm.

[0054] Example 3 This embodiment provides a preparation process of a thermally conductive and electrically conductive power module. Figure 1 As shown, it includes the following steps: Step S1: Obtain an aluminum radiator 1, which is a fin-type radiator with a flat surface on one side and fins on the other side. Select a spraying area on the plane of the aluminum radiator 1, which can be the entire plane or a part of the plane. Then use a sandblasting device to perform a sandblasting treatment on the spraying area so that the surface roughness of the spraying area reaches 100 μm.

[0055] Step S2: Using copper powder as raw material, a first copper clad layer 3.1 with a thickness of 800 μm is formed in the spraying area by using low-pressure cold spraying equipment. Since the surface of the spraying area has a certain degree of roughness, after spraying the first copper clad layer 3.1, the copper powder of the first copper clad layer 3.1 and the convex crests and concave troughs on the surface of the spraying area can form a mutually interlocking structure, thereby improving the bonding force between the first copper clad layer 3.1 and the aluminum heat sink 1.

[0056] Step S3: using a sandblasting device to perform secondary sandblasting on the surface of the first copper clad layer 3.1, so that the surface roughness of the first copper clad layer 3.1 reaches 80 μm.

[0057] Step S4: Using copper powder as raw material, a second copper clad layer 3.2 with a thickness of 600 μm is formed on the first copper clad layer 3.1 by using low-pressure cold spraying equipment. Since the surface of the first copper clad layer 3.1 has a certain degree of roughness, after spraying the second copper clad layer 3.2, the copper powder of the second copper clad layer 3.2 and the convex crests and concave troughs on the surface of the first copper clad layer 3.1 can form a mutually interlocking structure, thereby increasing the density inside the copper clad layer and improving the bonding force between the first copper clad layer 3.1 and the second copper clad layer 3.2.

[0058] Step S5: Select a semiconductor laser emitter with a laser power of 600W, and control the semiconductor laser emitter to emit laser at a constant moving speed to irradiate the second copper clad layer 3.2, so that the surface of the second copper clad layer 3.2 is softened, and the low-pressure cold spraying equipment follows the moving track of the semiconductor laser emitter, and a third copper clad layer 3.3 with a thickness of 400μm is formed on the second copper clad layer 3.2 with a softened surface. After the third copper clad layer 3.3 is polished and flat, a thermally conductive and electrically conductive copper-plated layer 3 consisting of the first copper clad layer 3.1, the second copper clad layer 3.2 and the third copper clad layer 3.3 is obtained on the aluminum heat sink 1. Among them, the thickness of the thermally conductive and electrically conductive copper-plated layer 3 is 1800um, and the thickness of the third copper clad layer 3.3 is less than the thickness of the second copper clad layer 3.2, and the thickness of the second copper clad layer 3.2 is less than the thickness of the first copper clad layer 3.1.

[0059] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying equipment and is located in front of the movement track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment is 6 mm. On the one hand, this can control the synchronous movement of the spray gun and the semiconductor laser, and on the other hand, it is conducive to ensuring a better bonding effect between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0060] In this step, the second copper clad layer 3.2 is irradiated with a laser of a specific power, which can slightly soften the copper powder on the surface of the second copper clad layer 3.2 irradiated by the laser without melting it, which is conducive to making the third copper clad layer 3.3 more tightly and firmly fixed on the second copper clad layer 3.2, further increasing the density inside the copper clad layer, and improving the bonding force between the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0061] Step S6: prepare a high-frequency pulse generator, a strong magnetic rod, an N-pole coil and an S-pole coil, respectively fix the N-pole coil and the S-pole coil on two spaced-apart strong magnetic rods, connect the high-frequency pulse generator to the N-pole coil and the S-pole coil, start the high-frequency pulse generator, form a directional high-frequency magnetic field with a magnetic induction intensity of 300μt between the strong magnetic rods, put the thermally conductive and electrically conductive copper-plated layer 3 obtained in step S5 into the directional high-frequency magnetic field and maintain it for 8 minutes, and use the directional high-frequency magnetic field to eliminate the internal stress of the thermally conductive and electrically conductive copper-plated layer 3.

[0062] Step S7: directly mounting the chip 2 on the thermally conductive and electrically conductive copper-plated layer 3 from which the internal stress has been eliminated, and fixing the chip 2 on the aluminum heat sink 1 by sintering the solder paste. Figure 2 The chip 2 shown is a thermally conductive and electrically conductive power module electrically connected to an aluminum heat sink 1 via a thermally conductive and electrically conductive copper plating layer 3 .

[0063] According to a preferred implementation of this embodiment, the copper powder used in the copper coating spraying in step S2, step S4 and step S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20um. In addition, in step S2, step S4 and step S5, the pressure of the low-pressure cold spraying equipment during spraying is 6.5Mpa, the gas preheating temperature is 500°C, the powder delivery rate is 150g / min, and the spraying distance is 30cm.

[0064] Example 4 For Examples 1-3, this example conducts the following tests on the frame structure in which the thermally conductive and electrically conductive copper-plated layer obtained after the step S6 is fixed on the aluminum heat sink and the thermally conductive and electrically conductive power module finally obtained: 1. Copper cladding stress buffer test The frame structures of Examples 1-3 were subjected to a large stress material accelerated temperature shock test, with a temperature transfer time of 30 seconds. Figure 3 As shown, the test results show that no delamination was found between the thermally conductive and electrically conductive copper plating layer and the aluminum heat sink, and the creep energy of the solder is smaller and has lower stress and strain.

[0065] 2. Thermal shock test The frame structures of Examples 1-3 were subjected to thermal shock tests at a temperature of 0-400° and a temperature shear time of 3 seconds. The test results showed that after 500 thermal shock tests at a temperature of 0-400°, no peeling occurred between the thermally conductive and electrically conductive copper plating layer and the aluminum heat sink.

[0066] 3. Solderability and welding void rate test Apply solder paste (6337) on the thermal and electrical conductive copper plating layer and then solder it to a pure copper test block of the same area. Figure 4 As shown, the test results show that the frame structures of Examples 1-3 all have excellent weldability, and the welding void rate is less than 5%.

[0067] 4. Bonding strength-tensile strength test On a tensile testing machine, the frame structures of Examples 1-3 were respectively subjected to tensile strength tests, and multiple tests were also carried out using thermally conductive and electrically conductive copper-plated layers of different thicknesses. The test results show that in the frame structures of Examples 1-3, the bonding strength (tensile strength) between the thermally conductive and electrically conductive copper-plated layers and the aluminum heat sink is between 25-100 MPa.

[0068] 5. Temperature cycle test The power modules prepared in Examples 1-3 were subjected to a temperature cycle test at -40°-125° for 1000 times, and the test results all met the test requirements.

[0069] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A process for preparing a thermally conductive and electrically conductive power module, characterized in that: The following steps are involved: Step S1: Select a spraying area on the plane of the aluminum radiator, and use a sandblasting device to perform a sandblasting treatment on the spraying area so that the surface roughness of the spraying area reaches 80-100 μm; Step S2: using copper powder as raw material, using low-pressure cold spraying equipment to form a first copper coating layer with a thickness of 10-800 μm in the spraying area; Step S3: performing secondary sandblasting on the first copper clad layer using a sandblasting device to make the surface roughness of the first copper clad layer reach 60-80 μm; Step S4: forming a second copper clad layer with a thickness of 10-600 μm on the first copper clad layer using a low-pressure cold spraying device; Step S5: controlling the semiconductor laser emitter to emit laser to irradiate the second copper clad layer at a constant moving speed to soften the surface of the second copper clad layer, and making the low-pressure cold spraying equipment follow the moving track of the semiconductor laser emitter to form a third copper clad layer with a thickness of 10-400 μm on the second copper clad layer with softened surface, and after polishing the third copper clad layer to be smooth, a thermally conductive and electrically conductive copper-plated layer consisting of the first copper clad layer, the second copper clad layer and the third copper clad layer is obtained on the aluminum heat sink; Step S6: prepare a high-frequency pulse generator, a strong magnetic bar, an N-pole coil and an S-pole coil, respectively fix the N-pole coil and the S-pole coil on two spaced-apart strong magnetic bars, connect the high-frequency pulse generator with the N-pole coil and the S-pole coil, start the high-frequency pulse generator, form a directional high-frequency magnetic field between the strong magnetic bars, place the thermally conductive and electrically conductive copper-plated layer obtained in step S5 into the directional high-frequency magnetic field, and use the directional high-frequency magnetic field to eliminate the internal stress of the thermally conductive and electrically conductive copper-plated layer; Step S7: directly mounting the chip on the thermally conductive and electrically conductive copper-plated layer, and fixing the chip on the aluminum heat sink by sintering solder paste. After completion, a thermally conductive and electrically conductive power module is obtained in which the chip is electrically connected to the aluminum heat sink through the thermally conductive and electrically conductive copper-plated layer.

2. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: The low-pressure cold spraying equipment has a pressure of 5-6.5 MPa during spraying, a gas preheating temperature of 400° C.-500° C., a powder delivery rate of 1-150 g / min, and a spraying distance of 20-30 cm.

3. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: In step S5, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spray equipment and is located at the front side of the movement track of the spray gun.

4. The process for preparing a thermally conductive and electrically conductive power module according to claim 3, characterized in that: In step S5, the distance between the laser spot emitted by the semiconductor laser emitter and the injection point of the low-pressure cold spraying equipment is 3-6 mm.

5. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: In step S5, the laser power of the semiconductor laser emitter is 500-600W.

6. A process for preparing a thermally conductive and electrically conductive power module according to any one of claims 1 to 5, characterized in that: In step S5, the thickness of the thermally conductive and electrically conductive copper-plated layer is 30-1800 um, and the thickness of the third copper-clad layer is less than or equal to the thickness of the second copper-clad layer, and the thickness of the second copper-clad layer is less than or equal to the thickness of the first copper-clad layer.

7. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: In step S6, the magnetic induction intensity of the directional high-frequency magnetic field is 220-300 μt.

8. The process for preparing a thermally conductive and electrically conductive power module according to claim 7, characterized in that: In step S6, the thermally conductive and electrically conductive copper-plated layer is subjected to stress elimination in a directional high-frequency magnetic field for 2-8 minutes.

9. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: Step S1 and step S3 are sandblasted using two independent sandblasting equipments respectively, and step S2, step S4 and step S5 are copper-coated using three independent low-pressure cold spraying equipments respectively. Each sandblasting equipment cooperates with each low-pressure cold spraying equipment to form a continuous production line.

10. The process for preparing a thermally conductive and electrically conductive power module according to claim 1, characterized in that: The copper powder used in the spraying of the copper layer in step S2, step S4 and step S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20 um.

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