A process for the production of a thermally and electrically conductive power module

Abstract

The application discloses a preparation process of a heat-conducting and electricity-conducting power module and relates to the technical field of semiconductors. The process comprises the following steps: 1, performing a first sand blasting treatment on a spraying area of an aluminum radiator; 2, spraying a first copper coating layer on the spraying area; 3, performing a second sand blasting treatment on the first copper coating layer; 4, spraying a second copper coating layer on the first copper coating layer; 5, emitting laser to irradiate the second copper coating layer, softening the surface of the second copper coating layer, spraying a third copper coating layer on the second copper coating layer, and obtaining a heat-conducting and electricity-conducting copper plating layer; 6, eliminating internal stress of the heat-conducting and electricity-conducting copper plating layer by using a directional high-frequency magnetic field; and 7, directly mounting a chip on the heat-conducting and electricity-conducting copper plating layer to obtain the heat-conducting and electricity-conducting power module. The process alternately performs sand blasting and cold spraying, and increases the processes of softening copper powder and eliminating stress, so that the internal stress of the copper plating layer and the porosity are eliminated, the bonding force between the copper plating layer and the aluminum radiator and between copper powder particles is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a preparation process of a heat-conducting and electricity-conducting power module. BACKGROUND

[0002] A semiconductor power module is a power device that is combined according to a certain function and then encapsulated into an integrated power device. The semiconductor power module can realize rectification and inversion functions according to different encapsulated components. The semiconductor power module is widely used in the fields of industrial frequency conversion, current converters, automobile motor controllers and other fields requiring power conversion, because it can work at a very high frequency and has intelligent functions of precisely adjusting output according to load requirements and self-protection according to overheat, overvoltage and overcurrent.

[0003] The semiconductor power module generates a large amount of heat during operation. In order to ensure that the semiconductor power module can operate stably and reliably, it is necessary to effectively dissipate heat. At present, there are many related technologies about 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 heat sink through a DBC ceramic copper-clad plate and a copper plating layer. Compared with the traditional heat dissipation structure, the foregoing new heat dissipation structure cancels the contact layer and the heat-conducting silicone grease, and the heat can be quickly transferred to the heat sink through the DBC ceramic copper-clad plate and the copper plating layer, thus having a good heat dissipation effect. However, the applicant found that in the foregoing new heat dissipation structure, the copper plating layer is simply set on the heat sink by cold spraying. Influenced by process control, there are pores and stress in the copper plating layer, and the bonding force between the copper plating layer and the aluminum heat sink and between the copper powder particles of the copper plating layer is insufficient, 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

[0005] In order to overcome the above technical problems existing in the prior art, the present application provides a preparation process of a heat-conducting and electricity-conducting power module. The process adopts sand blasting and cold spraying alternately, forms a copper plating layer in a multiple spraying manner, and increases the processes of softening the copper powder by laser irradiation and eliminating stress by high-frequency magnetic field. The internal stress of the copper plating layer can be eliminated, the pores can be reduced, the bonding force between the copper plating layer and the aluminum heat sink and between the copper powder particles can be increased, and the technical problems that the existing copper plating layer affects the heat transfer effect and product quality due to insufficient internal pores, stress and bonding force are solved.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation process of a heat-conducting and electricity-conducting power module, comprising the following steps:

[0008] Step S1: selecting a spraying area on the plane of the aluminum heat sink and performing a first sand blasting treatment on the spraying area by using a sand blasting device, so that the surface roughness of the spraying area reaches 80-100 μm;

[0009] Step S2: forming a first copper coating layer with a thickness of 10-800 μm on the spraying area by using a low-pressure cold spraying device with copper powder as raw material;

[0010] Step S3: performing a second sand blasting treatment on the first copper coating layer by using a sand blasting device, so that the surface roughness of the first copper coating layer reaches 60-80 μm;

[0011] Step S4: forming a second copper coating layer with a thickness of 10-600 μm on the first copper coating layer by using a low-pressure cold spraying device;

[0012] Step S5: controlling a semiconductor laser emitter to emit laser to irradiate the second copper coating layer at a constant moving speed, so that the surface of the second copper coating layer is softened, and the low-pressure cold spraying device follows the moving track of the semiconductor laser emitter to form a third copper coating layer with a thickness of 10-400 μm on the surface-softened second copper coating layer, and after the third copper coating layer is polished flat, a heat-conducting and electricity-conducting copper-plated layer composed of the first copper coating layer, the second copper coating layer and the third copper coating layer is obtained on the aluminum heat sink;

[0013] Step S6: preparing a high-frequency pulse generator, strong magnetic rods, an N-pole coil and an S-pole coil, fixing the N-pole coil and the S-pole coil on two strong magnetic rods which are spaced apart, connecting the high-frequency pulse generator with the N-pole coil and the S-pole coil, starting the high-frequency pulse generator to form a directional high-frequency magnetic field between the strong magnetic rods, and placing the heat-conducting and electricity-conducting copper-plated layer obtained in step S5 into the directional high-frequency magnetic field to eliminate the internal stress of the heat-conducting and electricity-conducting copper-plated layer by using the directional high-frequency magnetic field;

[0014] Step S7: directly installing a chip on the heat-conducting and electricity-conducting copper-plated layer, and fixing the chip on the aluminum heat sink by tin paste sintering, so that a heat-conducting and electricity-conducting power module in which the chip is electrically connected with the aluminum heat sink through the heat-conducting and electricity-conducting copper-plated layer is obtained.

[0015] The low-pressure cold spraying device has a spraying pressure of 5-6.5 Mpa, a gas preheating temperature of 400-500 ℃, a powder delivery amount of 1-150 g / min, and a spraying distance of 20-30 cm.

[0016] In step S5, the semiconductor laser emitter is fixed on a spray gun of the low-pressure cold spraying device and located at the front side of the moving track of the spray gun.

[0017] The interval between the laser spot emitted by the semiconductor laser emitter and the spraying point of the low-pressure cold spraying device in step S5 is 3-6mm.

[0018] The laser power of the semiconductor laser emitter in step S5 is 500-600W.

[0019] The thickness of the heat-conducting and electricity-conducting copper-plated layer in step S5 is 30-1800um, and the thickness of the third copper-plated layer is less than or equal to the thickness of the second copper-plated layer, and the thickness of the second copper-plated layer is less than or equal to the thickness of the first copper-plated layer.

[0020] The magnetic induction intensity of the directional high-frequency magnetic field in step S6 is 220-300μt.

[0021] The time for eliminating stress of the heat-conducting and electricity-conducting copper-plated layer in the directional high-frequency magnetic field in step S6 is 2-8 minutes.

[0022] The two sets of independent sand blasting devices are respectively used for sand blasting treatment in steps S1 and S3, and the three sets of independent low-pressure cold spraying devices are respectively used for spraying copper-plated layers in steps S2, S4 and S5, and each sand blasting device and each low-pressure cold spraying device form a continuous production line.

[0023] The copper powder used for spraying copper-plated layers in steps S2, S4 and S5 is spherical powder, the purity of the spherical powder is greater than 99.5%, and the particle size is 8-20um.

[0024] By using the above technical scheme, the application has the following beneficial technical effects:

[0025] 1、The present application can form a spraying area with a certain roughness on the plane of the aluminum heat sink through one-time sand blasting treatment, and after the first copper-plated layer is sprayed onto the surface rough spraying area, the copper powder and the protruding peaks and recessed valleys of the surface of the spraying area form a mutually embedded structure, thereby improving the bonding force between the first copper-plated layer and the aluminum heat sink.

[0026] Further, through two-time sand blasting treatment, a rough area can be formed on the surface of the first copper-plated layer, thereby forming a mutually embedded structure between the first copper-plated layer and the second copper-plated layer, which not only can improve the bonding force between the first copper-plated layer and the second copper-plated layer, but also can increase the density of copper powder particles, thereby being beneficial to reducing the internal porosity and stress of the copper-plated layer.

[0027] Furthermore, the laser irradiation can slightly soften the surface of the second copper-plated layer without melting, which can make the second copper-plated layer and the third copper-plated layer combine more closely, which is beneficial to improving the deposition efficiency and bonding strength of the copper powder, and is also beneficial to further reducing the porosity between the copper powders.

[0028] Further, the internal stress of the heat-conducting and electricity-conducting copper plating layer can be effectively eliminated by the directional high-frequency magnetic field.

[0029] In addition, the surface roughness after the secondary sand blasting treatment is set to be less than the surface roughness after the primary sand blasting treatment, and the spraying thicknesses of the first copper plating layer, the second copper plating layer and the third copper plating layer are gradually reduced, which is beneficial to further improve the bonding force between the first copper plating layer and the aluminum heat sink and further improve the bonding force between the copper plating layers, so that the firmness of the heat-conducting and electricity-conducting copper plating layer on the aluminum heat sink is better and the tensile strength is higher.

[0030] In summary, the present application adopts the sand blasting and cold spraying alternately, forms the copper plating layer in the manner of multiple spraying, and adds the processes of softening the copper powder by laser irradiation and eliminating the stress by high-frequency magnetic field, which not only can eliminate the internal stress of the copper plating layer and reduce the porosity, but also can increase the bonding force between the copper plating 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.

[0031] 2、The present application adopts the pressure of 5-6.5Mpa, the gas preheating temperature of 400-500℃, the powder delivery amount of 1-150g / min and the spraying distance of 20-30cm when spraying, which is beneficial to obtain the uniform and dense, stable and reliable copper plating layer, otherwise, if the spraying parameters exceed the above range, it will affect the spraying effect of the copper plating layer, and further affect the heat transfer effect and quality of the power module.

[0032] 3、The present application sets the distance between the laser spot emitted by the semiconductor laser emitter and the spraying point of the low-pressure cold spraying equipment to 3-6mm, which can make the second copper plating layer and the third copper plating layer on the surface soften to obtain the best bonding effect, and further improve the density and bonding force of the heat-conducting and electricity-conducting copper plating layer.

[0033] 4、The present application sets the laser power of the semiconductor laser emitter to 500-600W, which is beneficial to soften the surface of the second copper plating layer more quickly, and further can shorten the preparation time of the power module.

[0034] 5、The present application sets the magnetic induction intensity of the directional high-frequency magnetic field to 220-300μt, which is beneficial to better eliminate the stress of the heat-conducting and electricity-conducting copper plating layer.

[0035] 6、The present application only needs to place the heat-conducting and electricity-conducting copper plating layer in the directional high-frequency magnetic field for 2-8 minutes, which can effectively eliminate the internal stress, has the advantages of short time and good stress elimination effect.

[0036] 7、The present application adopts independent sand blasting equipment and low-pressure cold spraying equipment for each step, which can form a continuous production line and is beneficial to realize the batch production of the power module.

[0037] 8、The application adopts specific spherical powder as spraying raw material, and has the advantage of improving the heat conduction and electric conduction effect. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the application is shown in the figure;

[0039] Figure 2 The structural schematic diagram of the application is shown in the figure;

[0040] Figure 3 The copper-coated stress buffering test diagram of the application is shown in the figure;

[0041] Figure 4 The solderability and soldering cavity rate test diagram of the application is shown in the figure.

[0042] The figure is marked as: 1, aluminum heat sink, 2, chip, 3, heat conduction and electric conduction copper-coated layer, 3.1, first copper-coated layer, 3.2, second copper-coated layer, 3.3, third copper-coated layer. DETAILED DESCRIPTION

[0043] Example 1

[0044] The embodiment provides a preparation process of a heat conduction and electric conduction power module, as shown in the figure, which comprises the following steps: Figure 1

[0045] Step S1: obtain an aluminum heat sink 1, which is a finned heat sink with a plane on one side and fins on the other side. Select a spraying area on the plane of the aluminum heat sink 1, which can be the entire plane or part of the plane. Then use a sandblasting device to perform a first sandblasting treatment on the spraying area, so that the surface roughness of the spraying area reaches 80 μm.

[0046] Step S2: use copper powder as raw material, and use a low-pressure cold spraying device to form a first copper-coated layer 3.1 with a thickness of 10 μm on the spraying area. Since the surface of the spraying area has a certain roughness, after spraying the first copper-coated layer 3.1, the copper powder of the first copper-coated layer 3.1 and the protruding peaks and recessed valleys of the surface of the spraying area form a mutually embedded structure, which can improve the bonding force between the first copper-coated layer 3.1 and the aluminum heat sink 1.

[0047] Step S3: use a sandblasting device to perform a second sandblasting treatment on the surface of the first copper-coated layer 3.1, so that the surface roughness of the first copper-coated layer 3.1 reaches 60 μm.

[0048] ​Step S4: using copper powder as raw material, a second copper layer 3.2 with a thickness of 10 μm is formed on the first copper layer 3.1 by the low-pressure cold spraying equipment. Since the surface of the first copper layer 3.1 has a certain roughness, after the second copper layer 3.2 is sprayed, the copper powder of the second copper layer 3.2 and the protruding peaks and recessed valleys of the surface of the first copper layer 3.1 form a mutually embedded structure, which can increase the density of the copper layer and improve the bonding force between the first copper layer 3.1 and the second copper layer 3.2.

[0049] Step S5: a semiconductor laser emitter with a laser power of 500 is selected, and the semiconductor laser emitter is controlled to emit laser at a constant moving speed to irradiate the second copper layer 3.2, so that the surface of the second copper layer 3.2 is softened, and the low-pressure cold spraying equipment follows the moving track of the semiconductor laser emitter to form a third copper layer 3.3 with a thickness of 10 μm on the surface-softened second copper layer 3.2. After the third copper layer 3.3 is polished flat, a thermally and electrically conductive copper plating layer 3 composed of the first copper layer 3.1, the second copper layer 3.2 and the third copper layer 3.3 is obtained on the aluminum heat sink 1. The thickness of the thermally and electrically conductive copper plating layer 3 is 30 μm, the thickness of the third copper layer 3.3 is equal to the thickness of the second copper layer 3.2, and the thickness of the second copper layer 3.2 is equal to the thickness of the first copper layer 3.1.

[0050] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying equipment and located at the front side of the moving track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the spraying 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 beneficial to ensure better bonding effect between the second copper layer 3.2 and the third copper layer 3.3.

[0051] This step can slightly soften the copper powder on the surface of the second copper layer 3.2 by irradiating the second copper layer 3.2 with laser of a specific power without melting, which is beneficial to enable the third copper layer 3.3 to be more closely and stably fixed on the second copper layer 3.2, further increase the density of the copper layer, and improve the bonding force between the second copper layer 3.2 and the third copper layer 3.3.

[0052] Step S6: a high-frequency pulse generator, strong magnetic rods, an N-pole coil and an S-pole coil are prepared, the N-pole coil and the S-pole coil are fixed on two strong magnetic rods which are spaced apart, the high-frequency pulse generator is connected with the N-pole coil and the S-pole coil, the high-frequency pulse generator is started, a directional high-frequency magnetic field with a magnetic induction intensity of 220 μt is formed between the strong magnetic rods, the thermally and electrically conductive copper plating layer 3 obtained in step S5 is put into the directional high-frequency magnetic field and maintained for 2 minutes, and the internal stress of the thermally and electrically conductive copper plating layer 3 is eliminated by the directional high-frequency magnetic field.

[0053] Step S7: Directly mounting the chip 2 on the internal stress-eliminated thermally and electrically conductive copper-plated layer 3, and fixing the chip 2 on the aluminum heat sink 1 through tin paste sintering, and obtaining the thermally and electrically conductive power module as shown in Figure 2 FIG. 4 after completion.

[0054] According to a preferred embodiment of the present embodiment, the copper powder used in the spraying of the copper layer in steps S2, S4 and S5 is spherical powder with a purity greater than 99.5% and a particle size of 8-20 um. In addition, in steps S2, S4 and S5, the low-pressure cold spraying equipment has a spraying pressure of 5 Mpa, a gas preheating temperature of 400°C, a powder delivery rate of 1 g / min and a spraying distance of 20 cm.

[0055] According to another preferred embodiment of the present embodiment, two sets of independent sandblasting equipment are used for sandblasting in steps S1 and S3 respectively, and three sets of independent low-pressure cold spraying equipment are used for spraying the copper layer in steps S2, S4 and S5 respectively, and the sandblasting equipment and the low-pressure cold spraying equipment form a continuous production line.

[0056] Those skilled in the art can understand that, in the above steps, in order to obtain a copper layer with a suitable thickness, 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 heat sink 1 and the spraying speed of the spray gun, which can be set according to the needs.

[0057] It should be noted that, in the present application, the back surface (negative electrode) of the chip 2 is fixed on the thermally and electrically conductive copper-plated layer 3 through tin paste. Since the chip 2 prepared by the present scheme is electrically connected to the aluminum heat sink 1 through the thermally and electrically conductive copper-plated layer 3, the aluminum heat sink 1 is also in an electrically conductive state. Therefore, when the power module is applied to an actual welding machine or the like, the welding machine can be insulated, for example, the power module can be fixed inside the device through an insulating column, and the aluminum heat sink 1 and the output end of the welding machine are connected through 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.

[0058] Embodiment 2

[0059] The present embodiment provides a preparation process of a thermally and electrically conductive power module, as shown in Figure 1 FIG. 5, which includes the following steps:

[0060] Step S1: Obtain an aluminum heat sink 1, which is a finned heat sink with a flat surface on one side and fins on the other side. Select a spraying area on the flat surface of the aluminum heat sink 1, which can be the entire flat surface or a partial flat surface. Then use a sandblasting device to perform a first sandblasting treatment on the spraying area to make the surface roughness of the spraying area reach 90 μm.

[0061] Step S2: Use a low-pressure cold spraying device to form a first copper layer 3.1 with a thickness of 500 μm on the spraying area using copper powder as raw material. Since the surface of the spraying area has a certain roughness, after spraying the first copper layer 3.1, the copper powder of the first copper layer 3.1 and the protruding peaks and recessed valleys of the surface of the spraying area form a mutually embedded structure, which can improve the bonding force between the first copper layer 3.1 and the aluminum heat sink 1.

[0062] Step S3: Use a sandblasting device to perform a second sandblasting treatment on the surface of the first copper layer 3.1 to make the surface roughness of the first copper layer 3.1 reach 70 μm.

[0063] Step S4: Use a low-pressure cold spraying device to form a second copper layer 3.2 with a thickness of 400 μm on the first copper layer 3.1 using copper powder as raw material. Since the surface of the first copper layer 3.1 has a certain roughness, after spraying the second copper layer 3.2, the copper powder of the second copper layer 3.2 and the protruding peaks and recessed valleys of the surface of the first copper layer 3.1 form a mutually embedded structure, which can increase the density inside the copper layer and improve the bonding force between the first copper layer 3.1 and the second copper layer 3.2.

[0064] Step S5: Select a semiconductor laser emitter with a laser power of 550 W, and control the semiconductor laser emitter to emit laser to irradiate the second copper layer 3.2 at a constant moving speed, so that the surface of the second copper layer 3.2 is softened, and the low-pressure cold spraying device follows the moving track of the semiconductor laser emitter to form a third copper layer 3.3 with a thickness of 300 μm on the surface-softened second copper layer 3.2. After polishing the third copper layer 3.3, a copper plating layer 3 composed of the first copper layer 3.1, the second copper layer 3.2, and the third copper layer 3.3 is obtained on the aluminum heat sink 1. The thickness of the copper plating layer 3 is 1200 μm, and the thickness of the third copper layer 3.3 is less than the thickness of the second copper layer 3.2, and the thickness of the second copper layer 3.2 is less than the thickness of the first copper layer 3.1.

[0065] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying device and located at the front side of the moving track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the spraying point of the low-pressure cold spraying device 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 beneficial to ensure better bonding effect of the second copper-clad layer 3.2 and the third copper-clad layer 3.3.

[0066] This step can slightly soften the copper powder on the surface of the second copper-clad layer 3.2 by irradiating the second copper-clad layer 3.2 with laser of a certain power without melting the copper powder, which is beneficial to enable the third copper-clad layer 3.3 to be more closely and stably fixed on the second copper-clad layer 3.2, further increase the density inside the copper-clad layer, and improve the bonding force between the second copper-clad layer 3.2 and the third copper-clad layer 3.3.

[0067] Step S6: Prepare a high-frequency pulse generator, strong magnetic rods, an N-pole coil and an S-pole coil, fix the N-pole coil and the S-pole coil on two strong magnetic rods spaced apart, 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 with a magnetic induction intensity of 260 μt between the strong magnetic rods, put the heat-conducting and electricity-conducting copper-plated layer 3 obtained in step S5 into the directional high-frequency magnetic field and maintain for 5 minutes, and use the directional high-frequency magnetic field to eliminate the internal stress of the heat-conducting and electricity-conducting copper-plated layer 3.

[0068] Step S7: directly install the chip 2 on the heat-conducting and electricity-conducting copper-plated layer 3 with the internal stress eliminated, and fix the chip 2 on the aluminum heat sink 1 by tin paste sintering, to obtain a heat-conducting and electricity-conducting power module in which the chip 2 is electrically connected with the aluminum heat sink 1 through the heat-conducting and electricity-conducting copper-plated layer 3. Figure 2

[0069] According to the preferred embodiment of the first embodiment, the copper powder used in the spraying of the copper-clad layer in steps S2, S4 and S5 is spherical powder with a purity of greater than 99.5% and a particle size of 8-20 um. In addition, in steps S2, S4 and S5, the pressure of the low-pressure cold spraying device during spraying is 6 Mpa, the gas preheating temperature is 450°C, the powder delivery rate is 80 g / min, and the spraying distance is 25 cm.

[0070] Embodiment 3

[0071] The present embodiment provides a preparation process of a heat-conducting and electricity-conducting power module, as shown in Figure 1 which includes the following steps:

[0072] ​Step S1: Obtain an aluminum heat sink 1, which is a finned heat sink with a flat surface on one side and fins on the other side. Select a spraying area on the flat surface of the aluminum heat sink 1, which can be the entire flat surface or a partial flat surface. Then use a sandblasting device to perform a first sandblasting treatment on the spraying area to make the surface roughness of the spraying area reach 100 μm.

[0073] Step S2: Use a low-pressure cold spraying device to form a first copper layer 3.1 with a thickness of 800 μm on the spraying area using copper powder as raw material. Since the surface of the spraying area has a certain roughness, after spraying the first copper layer 3.1, the copper powder of the first copper layer 3.1 and the protruding peaks and recessed valleys of the surface of the spraying area form a mutually embedded structure, which can improve the bonding force between the first copper layer 3.1 and the aluminum heat sink 1.

[0074] Step S3: Use a sandblasting device to perform a second sandblasting treatment on the surface of the first copper layer 3.1 to make the surface roughness of the first copper layer 3.1 reach 80 μm.

[0075] Step S4: Use a low-pressure cold spraying device to form a second copper layer 3.2 with a thickness of 600 μm on the first copper layer 3.1 using copper powder as raw material. Since the surface of the first copper layer 3.1 has a certain roughness, after spraying the second copper layer 3.2, the copper powder of the second copper layer 3.2 and the protruding peaks and recessed valleys of the surface of the first copper layer 3.1 form a mutually embedded structure, which can increase the density inside the copper layer and improve the bonding force between the first copper layer 3.1 and the second copper layer 3.2.

[0076] Step S5: Select a semiconductor laser emitter with a laser power of 600 W, and control the semiconductor laser emitter to emit laser at a constant moving speed to irradiate the second copper layer 3.2, so that the surface of the second copper layer 3.2 is softened. At the same time, control the low-pressure cold spraying device to follow the moving track of the semiconductor laser emitter to form a third copper layer 3.3 with a thickness of 400 μm on the softened surface of the second copper layer 3.2. After polishing the third copper layer 3.3, a copper plating layer 3 composed of the first copper layer 3.1, the second copper layer 3.2 and the third copper layer 3.3 is obtained on the aluminum heat sink 1. The thickness of the copper plating layer 3 is 1800 μm, and the thickness of the third copper layer 3.3 is less than that of the second copper layer 3.2, and the thickness of the second copper layer 3.2 is less than that of the first copper layer 3.1.

[0077] Preferably, the semiconductor laser emitter is fixed on the spray gun of the low pressure cold spraying device and located at the front side of the moving track of the spray gun. Specifically, the distance between the laser spot emitted by the semiconductor laser emitter and the spraying point of the low pressure cold spraying device is 6mm. 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 beneficial to ensure the better bonding effect of the second copper clad layer 3.2 and the third copper clad layer 3.3.

[0078] This step can slightly soften the copper powder on the surface of the second copper clad layer 3.2 by irradiating the second copper clad layer 3.2 with a specific power laser, without melting it, which is beneficial to enable the third copper clad layer 3.3 to be more closely and stably 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.

[0079] Step S6: Prepare a high-frequency pulse generator, strong magnetic rods, N-pole coils and S-pole coils, fix the N-pole coils and S-pole coils on two strong magnetic rods respectively, connect the high-frequency pulse generator with the N-pole coils and S-pole coils, 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 heat-conducting and electrically-conducting copper clad layer 3 obtained in step S5 into the directional high-frequency magnetic field and maintain for 8 minutes, and use the directional high-frequency magnetic field to eliminate the internal stress of the heat-conducting and electrically-conducting copper clad layer 3.

[0080] Step S7: directly install the chip 2 on the heat-conducting and electrically-conducting copper clad layer 3 with the internal stress eliminated, and fix the chip 2 on the aluminum heat sink 1 by tin paste sintering, to obtain a heat-conducting and electrically-conducting power module as shown in Figure 2

[0081] According to the preferred embodiment of the first embodiment, the copper powder used in the spraying of the copper clad layer in steps S2, S4 and S5 is spherical powder with a purity of more than 99.5% and a particle size of 8-20um. In addition, in steps S2, S4 and S5, the pressure of the low pressure cold spraying device during spraying is 6.5Mpa, the gas preheating temperature is 500℃, the powder delivery rate is 150g / min, and the spraying distance is 30cm.

[0082] Embodiment 4

[0083] For embodiments 1-3, the frame structure of the heat-conducting and electrically-conducting copper clad layer fixed on the aluminum heat sink after step S6 and the final heat-conducting and electrically-conducting power module are tested as follows:

[0084] 1. Copper stress buffer test

[0085] ​The frame structure of each of Examples 1-3 was subjected to a large stress material accelerated temperature shock test, with a temperature transfer time of 30 s, as shown in Figure 3 The test results show that no delamination was found between the thermally and electrically conductive copper plating layer and the aluminum heat spreader, and the solder has a smaller creep energy and a lower stress strain.

[0086] 2. Thermal shock test

[0087] The frame structure of each of Examples 1-3 was subjected to a thermal shock test, with a temperature of 0-400° and a temperature shear time of 3 s. The test results show that no peeling occurred between the thermally and electrically conductive copper plating layer and the aluminum heat spreader after 500 thermal shock tests at 0-400°.

[0088] 3. Weldability and solder void rate test

[0089] After applying tin paste (6337) on the thermally and electrically conductive copper plating layer, the same area of pure copper test block was welded, as shown in Figure 4 The test results show that the frame structure of each of Examples 1-3 has excellent weldability, and the solder void rate is <5%.

[0090] 4. Bonding strength-tensile strength test

[0091] The frame structure of each of Examples 1-3 was subjected to a tensile strength test on a tensile testing machine, and the thermally and electrically conductive copper plating layer with different thicknesses was tested multiple times. The test results show that the bonding strength-tensile strength between the thermally and electrically conductive copper plating layer and the aluminum heat spreader in the frame structure of each of Examples 1-3 is between 25-100 MPa.

[0092] 5. Temperature cycle test

[0093] The power module prepared in each of Examples 1-3 was subjected to a temperature cycle test at -40°-125°, with a test number of 1000 times, and the test results all met the test requirements.

[0094] The above is only a specific embodiment of the present application, and any feature disclosed in this specification can be replaced by other equivalent or similar purpose replacement features, unless specifically described. All features disclosed, or steps in all methods or processes, except mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A process for the production of a thermally and electrically conductive power module, characterized in that The method comprises the following steps: Step S1: selecting a spraying area on the plane of the aluminum heat sink and performing a first sand blasting treatment on the spraying area by using a sand blasting device to make the surface roughness of the spraying area reach 80-100 μm; Step S2: taking copper powder as raw material and forming a first copper coating with a thickness of 10-800 μm on the spraying area by using a low-pressure cold spraying device; Step S3: performing a second sand blasting treatment on the first copper coating by using a sand blasting device to make the surface roughness of the first copper coating reach 60-80 μm; Step S4: forming a second copper coating with a thickness of 10-600 μm on the first copper coating by using a low-pressure cold spraying device; Step S5: controlling the semiconductor laser emitter to emit laser to irradiate the second copper coating at a constant moving speed, softening the surface of the second copper coating, and making the low-pressure cold spraying device follow the moving track of the semiconductor laser emitter to form a third copper coating with a thickness of 10-400 μm on the surface-softened second copper coating, and then polishing the third copper coating to obtain a heat-conducting and electricity-conducting copper plating layer composed of the first copper coating, the second copper coating and the third copper coating on the aluminum heat sink; Step S6: preparing a high-frequency pulse generator, strong magnetic rods, an N-pole coil and an S-pole coil, fixing the N-pole coil and the S-pole coil on the two strong magnetic rods which are spaced apart, connecting the high-frequency pulse generator with the N-pole coil and the S-pole coil, starting the high-frequency pulse generator to form a directional high-frequency magnetic field between the strong magnetic rods, and putting the heat-conducting and electricity-conducting copper plating layer obtained in Step S5 into the directional high-frequency magnetic field to eliminate the internal stress of the heat-conducting and electricity-conducting copper plating layer by using the directional high-frequency magnetic field; Step S7: directly installing a chip on the heat-conducting and electricity-conducting copper plating layer and fixing the chip on the aluminum heat sink by tin paste sintering to obtain a heat-conducting and electricity-conducting power module in which the chip is electrically connected with the aluminum heat sink through the heat-conducting and electricity-conducting copper plating layer.

2. The process of claim 1, wherein: The low-pressure cold spraying device has a pressure of 5-6.5 Mpa, a gas preheating temperature of 400-500 ℃, a powder delivery amount of 1-150 g / min and a spraying distance of 20-30 cm.

3. The process of claim 1, wherein: In Step S5, the semiconductor laser emitter is fixed on the spray gun of the low-pressure cold spraying device and located at the front side of the moving track of the spray gun.

4. The process of claim 3, wherein: In Step S5, the distance between the laser spot emitted by the semiconductor laser emitter and the spraying point of the low-pressure cold spraying device is 3-6 mm.

5. The process of claim 1, wherein: In Step S5, the laser power of the semiconductor laser emitter is 500-600 W.

6. The process for preparing a thermally and electrically conductive power module according to any one of claims 1 to 5, characterized in that In Step S5, the thickness of the heat-conducting and electricity-conducting copper plating layer is 30-1800 μm, and the thickness of the third copper coating is less than or equal to the thickness of the second copper coating, and the thickness of the second copper coating is less than or equal to the thickness of the first copper coating.

7. The process of claim 1, wherein: In Step S6, the magnetic induction intensity of the directional high-frequency magnetic field is 220-300 μt.

8. The process of claim 7, wherein: In Step S6, the heat-conducting and electricity-conducting copper plating layer is subjected to stress elimination in the directional high-frequency magnetic field for 2-8 minutes.

9. The process of making a thermally and electrically conductive power module according to claim 1, characterized in that: Steps S1 and S3 are performed by using two independent sets of sand blasting devices respectively, and Steps S2, S4 and S5 are performed by using three independent sets of low-pressure cold spraying devices respectively, and each sand blasting device and each low-pressure cold spraying device form a continuous production line.

10. The process of claim 1, wherein: 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 8-20um.

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