Welding structure, welding process and welding device of power module

Abstract

The present application relates to a kind of welding structure of power module, the welding structure includes power device and metal radiator, the metal bottom of the power device is directly welded together with the metal radiator by high-frequency welding process.The present application also relates to a welding process, including: the surface of the metal bottom of power device and the surface of the metal radiator are mutually fitted to form welding surface, then high-frequency coil is sleeved on the periphery of the welding surface, the high-frequency coil is energized, high-frequency welding is started, and the welding structure of power module is obtained after welding is completed.The present application also relates to the welding device for implementing the welding process.The welding structure of the present application directly welds the metal bottom of power device and metal radiator together, omits intermediate solder layer, reduces the thermal resistance of intermediate solder layer, and greatly improves the heat dissipation performance of entire power module.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and in particular to a welding structure, a welding process and a welding device for a power module. Background Art

[0002] With the development of third-generation semiconductor technology, the welding technology used for power devices has evolved from thermal paste bonding in the beginning, to lead-tin solder eutectic welding, and then to silver sintering technology, and further to nano-silver sintering technology, and even to nano-copper sintering technology that is currently being widely researched and discussed in the industry. The development of such technology is to reduce thermal resistance by optimizing the welding process, thereby improving the heat dissipation capacity of power devices.

[0003] See also Figure 1 The existing power module is made by welding the power device and the heat sink using a general solder welding process. The welding structure is formed by welding and bonding through the intermediate solder medium. From the perspective of thermal management, the thermal resistance of this type of welding structure is the sum of the thermal resistance of the multi-layer dielectric and the interface thermal resistance. Figure 1 The shown equivalent is:

[0004] R[thermal resistance] = R[heat sink] + R[interface 1] + R[solder layer] + R[interface 2] + R[heat sink].

[0005] From a material perspective, the introduction of a solder layer inevitably adds two interfacial thermal resistances to the heat conduction path. When interfacial thermal resistance exists, its value is closely related to the soldering process. If soldering quality is poor, even with silver, the most thermally conductive metal, as solder (silver sintering process), the resulting interfacial thermal resistance will far exceed the silver's contribution to thermal management. Summary of the Invention

[0006] Based on this, the present invention provides a welding structure of a power module, which directly welds the metal bottom of the power device to the metal heat sink, omitting the intermediate solder layer, reducing the thermal resistance of the intermediate solder layer, and greatly improving the heat dissipation performance of the entire power module.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A welding structure of a power module comprises a power device and a metal radiator, wherein the metal bottom of the power device and the metal radiator are directly welded together by a high-frequency welding process.

[0009] The soldering structure of this invention directly welds the metal base of the power device to the metal heat sink, eliminating the intermediate solder layer and reducing its thermal resistance, effectively improving the heat dissipation performance of the entire power module. High-frequency welding is commonly used in the field of metal welding. This invention, through cross-disciplinary technical optimization, is applied to the field of power device welding, achieving low internal resistance welding of power devices.

[0010] More preferably, the metal bottom of the power device is a metal heat sink or a metal substrate.

[0011] More preferably, the metal bottom of the power device and the metal heat sink are both made of copper.

[0012] The present invention also provides a welding process, comprising: laminating the surface of the metal bottom of the power device and the surface of the metal heat sink to form a welding surface, then sleeve a high-frequency coil on the periphery of the welding surface, and then energizing the high-frequency coil to start high-frequency welding, and after completing welding, obtaining a welding structure of the power module.

[0013] More preferably, before welding, the surface of the metal bottom of the power device and the surface of the metal heat sink are respectively subjected to oxide layer removal and surface nano-crystallization treatment.

[0014] More preferably, the surface nano-processing forms a nano-copper structure on the surface of the metal bottom of the power device and a nano-copper structure on the surface of the metal heat sink; after welding, a homogeneous interface layer is formed between the metal bottom of the power device and the metal heat sink.

[0015] More preferably, during the high-frequency welding process, the heating temperature of the welding surface is 600-800° C., and the heating time is 5-10 minutes.

[0016] More preferably, the surface nano-processing forms a nano-copper structure on the surface of either the metal bottom of the power device or the metal heat sink, and forms a nano-silver structure on the surface of the other; after welding is completed, a heterogeneous interface layer is formed between the metal bottom of the power device and the metal heat sink.

[0017] More preferably, during the high-frequency welding process, the heating temperature of the welding surface is 300-400° C., and the heating time is 5-10 minutes.

[0018] More preferably, the high-frequency welding is performed under a condition of continuously applying pressure to the power device and the metal heat sink.

[0019] The present invention also provides a welding device for implementing the aforementioned welding process, comprising:

[0020] The bottom platform is used to support the power device and the metal heat sink. The power device is placed on the metal heat sink. The surface of the metal bottom of the power device and the surface of the metal heat sink are bonded to each other to form a welding surface.

[0021] A high-frequency coil is used to be sleeved on the periphery of the welding surface formed by the power device and the metal heat sink, and to generate heat to perform high-frequency welding on the welding surface after a high-frequency current is passed through it;

[0022] The high-frequency electromagnetic generator is connected to the high-frequency coil and is used to transmit the generated high-frequency current to the high-frequency coil.

[0023] More preferably, the high-frequency coil includes a plurality of coil groups with different diameters, and the plurality of coil groups are arranged together on the same plane from the inside out in order of increasing diameter.

[0024] More preferably, the coil group includes an isolation pipe and a plurality of metal coils wound around each other in the isolation pipe. Several metal coils in the coil group are connected in series to form a multi-layer coil ring, which effectively gathers the electromagnetic field.

[0025] More preferably, the isolation pipe is provided with a cooling water inlet and a cooling water outlet communicating with the interior thereof.

[0026] When the coil is energized, the resistance of the metal coil will generate huge energy consumption, which is dissipated in the form of heat. The design of the isolation tube and cooling system can effectively reduce the instantaneous heating of the metal coil, so that the metal coil will not easily melt due to high temperature.

[0027] More preferably, an isolation layer is provided in the isolation pipe, and the isolation layer divides the interior of the isolation pipe into two unconnected chambers, one of which is provided with the metal coil, and the other chamber is connected to the cooling water inlet and the cooling water outlet.

[0028] More preferably, the metal coil is made of copper wire with a silver coating on the surface. High-frequency coils will produce a skin effect when working, and the use of silver coating can better reflect the coil's conductivity and reduce power loss.

[0029] More preferably, the width of the heating zone formed when the high-frequency coil is energized does not exceed 5 mm.

[0030] The high-frequency coils described in this invention utilize multiple nested ring structures to superimpose the electromagnetic field density, minimizing the thickness of the high-frequency magnetic field and thereby achieving the desired effect of heating the weld surface. Conversely, if the heating zone formed by the electromagnetic field is too wide, the energy will be dispersed, hindering concentrated, high-density electric field heating. The present invention utilizes ultra-thin ring coils to effectively superimpose the magnetic induction energy of multiple ring coils, forming an energy field with low total energy and ultra-high density within a minimally slender cross-section.

[0031] The welding of the power device and its metal heat sink is actually a process of welding two planes into one plane. Therefore, the high plane energy density is conducive to the realization of welding. At the same time, the total amount of plane energy is reduced, which helps when the material heats up during the welding process. The heat can be quickly dissipated through the device heat sink, thereby ensuring that the temperature of the power device chip, bonding wire, etc. is reduced in time and is not even affected by high temperature.

[0032] More preferably, the welding device also includes a top platform and a driving mechanism, wherein the top platform is fixed above the bottom platform and is used to fit the top of the power device during high-frequency welding and pressurize the power device and the metal heat sink together with the bottom platform; the driving mechanism is connected to the bottom platform and is used to drive the bottom platform to rise or fall.

[0033] More preferably, the driving mechanism is a lifting screw.

[0034] During the welding process of the welding device described in the present invention, the power device and the metal radiator are placed on the bottom platform, and the lifting screw is controlled so that the power device and its radiator can pass through the high-frequency coil and are placed under the top platform. After the positions are adjusted, the inlet / outlet water pipes and the high-frequency electromagnetic generator are opened to make the high-frequency coil generate high-density magnetic flux lines. At this time, the lifting screw remains in an ascending state, continuously increasing the pressure on the power device and the metal radiator, and finally the power device and the metal radiator are welded under the low energy continuously provided by the high-frequency coil.

[0035] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The figure shows the welding structure of the existing power module and its equivalent thermal resistance. The left side of the figure shows the welding structure and the right side shows the equivalent thermal resistance.

[0037] Figure 2 is a schematic diagram of the welding structure of the power module of the present invention;

[0038] Figure 3 This is a schematic diagram of the alignment of the power device and the metal heat sink before welding;

[0039] Figure 4 A schematic diagram of the welding of the power device and the metal heat sink of the present invention;

[0040] Figure 5 is a structural diagram of the welding device of the present invention;

[0041] Figure 6 is a cross-sectional view of the high-frequency coil of the present invention;

[0042] Figure 7 is a cross-sectional structural diagram of the high-frequency coil of the present invention;

[0043] Figure 8 A schematic diagram of the magnetic flux lines generated when the high-frequency coil of the present invention is energized;

[0044] Figure 9 A top view of the high-frequency coil of the present invention;

[0045] Figure 10 Schematic diagram of the mutual diffusion and penetration of metal atoms on both sides of the welding surface in the welding process of the present invention;

[0046] Figure 11A The figure shows the welding structure of nano-copper formed on the welding surface and its equivalent thermal resistance in some preferred embodiments of the present invention. Figure 11B The figure shows the welding structure and equivalent thermal resistance of the welding surface formed with nanosilver in some other preferred embodiments of the present invention. Figure 11A and Figure 11B The left side of the figure is the welding structure, and the right side is the equivalent thermal resistance.

[0047] Reference numerals:

[0048] Power device 1, metal bottom 10 of power device, metal radiator 2, welding surface 3, nanometal structure 30, bottom platform 4, high-frequency coil 5, coil group 50, isolation pipe 51, metal coil 52, jumper 53, isolation layer 54, heating zone A, high-frequency electromagnetic generator 6, driving mechanism (lifting screw) 7, top platform 8, box B, water inlet pipe 91, water outlet pipe 92. DETAILED DESCRIPTION

[0049] In the description of the present invention, it should be noted that directional words, such as the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and cannot be understood as limiting the specific scope of protection of the present invention. In addition, in the description of the present invention, "several" means one or more, and "multiple" means two or more, unless otherwise clearly and specifically defined.

[0050] like Figure 2 As shown, the welding structure of the power module of the present invention includes a power device 1 and a metal heat sink 2. The metal bottom 10 of the power device 1 and the metal heat sink 2 are directly welded together by a high-frequency welding process.

[0051] Specifically, the metal bottom 10 of the power device 1 is a metal heat sink or a metal substrate.

[0052] Specifically, the metal bottom 10 of the power device 1 and the metal heat sink 2 are both made of copper.

[0053] See also Figure 3 and Figure 4 The welding process provided by the present invention is used to manufacture the welding structure of the power module. The welding process includes: laminating the surface of the metal bottom 10 of the power device 1 and the surface of the metal heat sink 2 to each other to form a welding surface 3, then sleeved the high-frequency coil 5 on the periphery of the welding surface 3, and then energized the high-frequency coil 5 to start high-frequency welding. After the welding is completed, the welding structure of the power module is obtained.

[0054] As a further optimization, the welding process further includes: before welding, respectively performing oxide layer removal and surface nano-processing on the surface of the metal bottom 10 of the power device 1 and the surface of the metal heat sink 2 .

[0055] After the surface nano-processing, the surface of the metal bottom 10 of the power device 1 forms a nano-metal structure 30, and the surface of the metal heat sink 2 forms a nano-metal structure 30. Figure 3 shown.

[0056] Specifically, the high frequency welding is performed under the condition of continuously pressurizing the power device 1 and the metal heat sink 2. Figure 4 , Figure 4 The middle arrow indicates the direction of pressure application.

[0057] In some preferred embodiments, the surface nano-processing forms a nano-copper structure on the surface of the metal bottom 10 of the power device 1, and forms a nano-copper structure on the surface of the metal heat sink 2. Specifically, during the high-frequency welding process, the heating temperature of the welding surface 3 is 600-800°C, and the heating time is 5-10 minutes. After the welding is completed, a homogeneous interface layer is formed between the metal bottom 10 of the power device 1 and the metal heat sink 2.

[0058] In other preferred embodiments, the surface nanocrystallization treatment forms a nano-copper structure on the surface of either the metal base 10 of the power device 1 or the metal heat sink 2, and a nano-silver structure on the surface of the other. Specifically, during the high-frequency welding process, the welding surface 3 is heated to a temperature of 300-400°C for 5-10 minutes. After welding, a heterogeneous interface layer is formed between the metal base 10 of the power device 1 and the metal heat sink 2. Because the formed nano-silver structure is a very thin layer of silver atomic particles, after welding, no solder interface layer is formed between the metal base 10 and the metal heat sink 2, but rather a heterogeneous interface layer of a mixed alloy.

[0059] More specifically, the surface nano-processing adopts existing metal material surface nano-processing methods, such as sputtering, laser cladding, ultrasonic shot peening, etc.

[0060] See also Figure 5 The welding device provided by the present invention is used for the welding process, including a bottom platform 4, a high-frequency coil 5, a high-frequency electromagnetic generator 6, a driving mechanism 7, a top platform 8 and a cooling system.

[0061] The bottom platform 4 is used to support the power device 1 and the metal heat sink 2. The power device 1 is placed on the metal heat sink 2. The surface of the metal bottom 10 of the power device 1 and the surface of the metal heat sink 2 are bonded to each other to form a welding surface 3. The bottom platform 4 is provided with a preset groove, which is used to accommodate the metal heat sink 2.

[0062] The high-frequency coil 5 is used to be sleeved on the periphery of the welding surface 3 formed by the power device 1 and the metal heat sink 2, and generates heat to perform high-frequency welding on the welding surface 3 after a high-frequency current is passed through it.

[0063] See also Figures 6-9 The high-frequency coil 5 is a high-frequency inductor coil. Specifically, the high-frequency coil 5 includes a plurality of coil groups 50 of different diameters. The plurality of coil groups 50 are arranged together on the same plane in the order of diameter from small to large from the inside to the outside. Moreover, the centers of the plurality of coil groups 50 coincide. Figure 9 .

[0064] The coil group 50 includes a hollow isolation pipe 51 and a plurality of metal coils 52 wound around each other in the isolation pipe 51 . The metal coils 52 in several of the coil groups 50 are connected in series, specifically through a jumper 53 provided outside the front of the isolation pipe 51 .

[0065] The metal coil 52 is made of a copper wire with a silver coating on the surface. The isolation pipe 51 is made of a non-metallic material, such as plastic, and can play the role of insulating the metal coil 52.

[0066] Preferably, the width of the heating area A formed after the high-frequency coil 5 is energized does not exceed 5 mm, that is, Figure 6 The width of the heating zone A shown in the figure does not exceed 5 mm in the vertical direction.

[0067] The high-frequency electromagnetic generator 6 is connected to the high-frequency coil 5 and is used to transmit the generated high-frequency current to the high-frequency coil 5 .

[0068] The top platform 8 is fixed above the bottom platform 4 and is used to fit the top of the power device 1 during high-frequency welding, and to pressurize the power device 1 and the metal heat sink 2 together with the bottom platform 4 .

[0069] The driving mechanism 7 is connected to the bottom platform 4 and is used to drive the bottom platform 4 to rise or fall. The driving mechanism 7 is specifically a lifting screw 7.

[0070] The cooling system is used to continuously provide cooling water to the high-frequency coil 5 and is provided with a water inlet pipe 91 and a water outlet pipe 92. The cooling water inlet of the isolation pipe 51 is connected to the water inlet pipe 91 through a pipe, and the cooling water outlet thereof is connected to the water outlet pipe 92 through a pipe.

[0071] The cooling water provided by the cooling system enters the isolation pipe 51 of each coil assembly 50 through the water inlet pipe 91 and the cooling water inlet, cools the metal coil 52, and then returns to the cooling system through the cooling water outlet and the water outlet pipe 92.

[0072] Better, if Figure 6 and Figure 7 As shown, an isolation layer 54 is provided within the isolation pipe 51. This isolation layer 54 divides the interior of the isolation pipe 51 into two mutually disconnected chambers. The metal coil 52 is located in one chamber, while the other chamber is connected to the cooling water inlet and outlet. Cooling water flows through the other chamber to cool the metal coil 52. Thus, the isolation layer 54 prevents direct contact between the metal coil 52 and the cooling water, thereby extending the life of the metal coil 52.

[0073] The welding device may further include a sealed box B, the internal environment of which can achieve a vacuum. The bottom platform 4, high-frequency coil 5, high-frequency electromagnetic generator 6, drive mechanism 7, top platform 8, etc. are arranged in the box B.

[0074] More specifically, the process of welding the power device 1 and the metal heat sink 2 using the welding device comprises the following steps:

[0075] (1) In a vacuum or protective gas environment, remove the oxide layer on the surface of the metal heat sink 2 to be welded, and remove the oxide layer on the surface of the metal bottom 10 (metal heat sink or metal substrate) to be welded.

[0076] (2) After the oxide layer is removed, the surface of the metal heat sink 2 to be welded is nano-processed in a vacuum or protective gas environment, and the surface of the metal bottom 10 (metal heat sink or metal substrate) to be welded is nano-processed.

[0077] (3) The semiconductor chip is mounted on the metal bottom 10 (metal heat sink or metal substrate) after nano-processing to form a whole, thereby obtaining a power device 1.

[0078] (4) Align the metal heat sink 2 with the metal bottom 10 (metal heat sink or metal substrate) of the power device 1, as shown in the following example: Figure 3 As shown, and placed in the preset groove of the bottom platform 4.

[0079] (5) Turn on the switch of the lifting screw 7 to make the bottom platform 4 (lifting end) rise, and make the metal radiator 2 and the metal bottom 10 (metal heat sink or metal substrate) and the welding surface 3 formed between the two pass through the high-frequency coil 5, as shown in FIG. Figure 4 As shown, the power device 1 is finally tightly fitted with the top platform 8 (fixed end), and the closing and holding pressure parameters are set. Among them, the high-frequency welding area (heating area A) of the high-frequency coil 5 is set as close as possible to one end of the metal heat sink 2. Figure 4 , to avoid damage to the device caused by the heat generated during welding.

[0080] (6) Turn on the high-frequency electromagnetic generator 6, so that the high-frequency coil 5 is in operation and high-frequency welding begins. At this time, the bottom platform 4 (lifting end) continuously pressurizes the metal heat sink 2 and the metal heat sink (metal substrate) for about 5-10 minutes. During the welding process, the cooling system continuously provides cooling water to the high-frequency coil 5.

[0081] (7) After welding is completed, turn off the switch of the high-frequency electromagnetic generator 6, lower the bottom platform 4 (lifting end) to complete the welding.

[0082] The working principle of the welding process of the present invention is as follows:

[0083] 1. If Figure 8 As shown, when the high-frequency coil 5 is working, an ultra-high-density electromagnetic field is generated in the middle. After the metal radiator 2 and the metal heat sink or metal substrate are placed in the heating area A in the middle of the high-frequency coil 5, heat will be generated rapidly to achieve welding. The high-frequency welding process can make non-magnetic materials such as copper also generate huge heat.

[0084] 2. If Figure 10 As shown, due to the nano-surface treatment of the metal heat sink 2 and the metal base 10 of the power device 1, the metal atoms at the weld surface 3 formed by the two surfaces are relatively active. Under the energy provided by electromagnetic heating and the continuous pressure applied by the top platform 8 and the bottom platform 4, the active metal atoms quickly penetrate each other at the interface through atomic diffusion, thus forming a connection. This connection is formed by the diffusion of metal atoms, without a rigid interface, effectively reducing thermal resistance.

[0085] 3. If Figure 11A As shown, if nanocrystallization treatment forms nano-copper on the surfaces of both the metal heat sink 2 and the metal base 10 of the power device 1, active copper atom diffusion occurs at temperatures of 500-600°C. Maintaining the temperature at 600-800°C for 5-10 minutes can achieve good metal atom diffusion welding results. By the time the temperature reaches 800-1000°C, the copper surface has begun to melt. From the perspective of material thermal resistance, the interface layer formed by the welding surface 3 is a "homogeneous interface layer," with a thermal resistance equivalent to that of metal atom injection of homogeneous materials, and its thermal resistance is much lower than that of conventional welding processes using intermediate silver solder.

[0086] 4. In addition, Figure 11B As shown, in order to reduce the energy that causes atomic transition and make the low thermal resistance welding process easier to achieve, the surface nano-processed nanomaterial can also use silver as a single substance, and form a nano-silver structure on the surface of the metal heat sink 2 and the metal bottom 10 of the power device 1, and then perform electromagnetic welding. The atomic diffusion temperature of silver is much lower than that of copper. Generally, good diffusion welding can be achieved at 300-400°C. The interface layer formed by the welding surface 3 is a "heterogeneous interface layer", which is different from the "homogeneous interface layer" of nano-processed metal using copper. It requires lower energy to diffuse, but has a larger thermal resistance. The relationship between the thermal resistance is as follows: R[silver sintering]>R[silver heterogeneous interface]>R[copper homogeneous interface].

[0087] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A welding device, characterized in that: The welding device comprises: The bottom platform is used to support the power device and the metal heat sink. The power device is placed on the metal heat sink. The surface of the metal bottom of the power device and the surface of the metal heat sink are bonded to each other to form a welding surface. A high-frequency coil is used to be sleeved on the periphery of the welding surface formed by the power device and the metal heat sink, and to generate heat to perform high-frequency welding on the welding surface after a high-frequency current is passed through it; A high-frequency electromagnetic generator is connected to the high-frequency coil and is used to transmit the generated high-frequency current to the high-frequency coil; the high-frequency coil includes several coil groups of different diameters, and the several coil groups are arranged together from the inside to the outside on the same plane in order of diameter from small to large; the coil group includes an isolation pipe and multiple metal coils that are intertwined with each other and arranged in the isolation pipe, and the metal coils in several coil groups are connected in series with each other; the isolation pipe is provided with a cooling water inlet and a cooling water outlet connected to its interior; an isolation layer is provided in the isolation pipe, and the isolation layer divides the interior of the isolation pipe into two unconnected chambers, the metal coil is arranged in one chamber, and the other chamber is connected to the cooling water inlet and the cooling water outlet.

2. The welding device according to claim 1, characterized in that The metal coil is made of copper wire with silver plating on the surface.

3. The welding device according to claim 1, characterized in that The width of the heating zone formed after the high-frequency coil is energized does not exceed 5 mm.

4. The welding device according to claim 1, characterized in that It also includes a top platform and a driving mechanism. The top platform is fixed above the bottom platform and is used to fit the top of the power device during high-frequency welding, and to pressurize the power device and the metal heat sink together with the bottom platform; the driving mechanism is connected to the bottom platform and is used to drive the bottom platform to rise or fall.

5. The welding device according to claim 4, characterized in that The driving mechanism is a lifting screw.

6. A welding structure of a power module, characterized in that: It comprises a power device and a metal heat sink, wherein the metal bottom of the power device and the metal heat sink are directly welded together by a high-frequency welding process, and the high-frequency welding process is achieved by the welding device according to claim 1.

7. The welding structure according to claim 6, characterized in that: The metal bottom of the power device is a metal heat sink or a metal substrate.

8. The welded structure according to any one of claims 6 or 7, characterized in that: The metal bottom of the power device and the metal heat sink are both made of copper.

9. A welding process, characterized in that: Welding is achieved using the welding device as described in claim 1, including the steps of: laminating the surface of the metal bottom of the power device and the surface of the metal heat sink to form a welding surface, then sleeved a high-frequency coil on the periphery of the welding surface, and then energizing the high-frequency coil to start high-frequency welding, and after completing welding, obtaining a welding structure of the power module.

10. The welding process according to claim 9, characterized in that: Also includes: Before welding, the surface of the metal bottom of the power device and the surface of the metal heat sink are respectively subjected to oxide layer removal and surface nano-crystallization treatment.

11. The welding process according to claim 10, characterized in that: The surface nano-processing forms a nano-copper structure on the surface of the metal bottom of the power device and a nano-copper structure on the surface of the metal heat sink; after welding, a homogeneous interface layer is formed between the metal bottom of the power device and the metal heat sink.

12. The welding process according to claim 11, characterized in that During the high-frequency welding process, the heating temperature of the welding surface is 600-800° C., and the heating time is 5-10 minutes.

13. The welding process according to claim 10, characterized in that The surface nano-processing forms a nano-copper structure on the surface of either the metal bottom of the power device or the metal heat sink, and forms a nano-silver structure on the surface of the other; after welding is completed, a heterogeneous interface layer is formed between the metal bottom of the power device and the metal heat sink.

14. The welding process according to claim 13, characterized in that During the high-frequency welding process, the heating temperature of the welding surface is 300-400° C., and the heating time is 5-10 minutes.

15. The welding process according to any one of claims 9 to 14, characterized in that: The high-frequency welding is performed under the condition of continuously applying pressure to the power device and the metal heat sink.

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