An assembled power assembly radiator mounting method

Abstract

The application discloses a kind of installation methods of assembled power component radiator, belong to the technical field of power component, comprising: copper layer is sprayed on the inside welding surface of each sub-radiator;Composite solder preform is prepared by solder alloy powder and pore-forming agent particles;After the superposition of radiator, composite solder preform and power module are sent into vacuum soldering furnace and are vacuum soldered;After vacuum soldering is completed, multiple independent power component radiator assemblies are obtained;Multiple independent power component radiator assemblies are spliced to obtain assembled power component radiator.The application forms exhaust passage by pore-forming agent before solder melting, and removes welding interface gas;Directional flow of molten solder is driven by electromigration effect, and bubbles are pushed to interface edge and discharged;Densification is realized by static pressure, and three-level strategy synergies, reduces the porosity, and improves heat dissipation performance and connection reliability.

Description

Technical Field

[0001] This invention belongs to the technical field of power components, and specifically relates to a method for installing a modular power component heat sink. Background Technology

[0002] Power modules (including but not limited to IGBT modules, MOSFET modules, and SiC power modules) are the core power conversion devices in power electronic systems. During operation, power modules generate a significant amount of heat, which must be efficiently dissipated through the solder layer between the power module and the heat sink to ensure the device junction temperature remains within acceptable limits. Therefore, the soldering quality between the power module and the heat sink, especially the void ratio and interface integrity of the solder layer, directly determines the heat dissipation performance and long-term reliability of the power module.

[0003] Currently, the mainstream soldering methods for power modules and heat sinks include vacuum reflow soldering and vacuum brazing. Vacuum reflow soldering melts a pre-placed solder layer (such as Sn-Ag-Cu solder) in a vacuum environment, using the vacuum negative pressure to expel gas from the solder interface, thus achieving a connection. Vacuum brazing, on the other hand, uses a filler metal with a higher melting point to complete the metallurgical bond under vacuum conditions.

[0004] However, existing vacuum welding methods still have the following technical drawbacks: (i) It is difficult to completely remove the gas inside the solder, resulting in a high void ratio. Current processes primarily rely on the negative pressure of a vacuum environment to allow gases released during solder melting to escape naturally. However, due to the viscosity and surface tension of molten solder, tiny air bubbles face significant resistance to migration within the solder, making it difficult to completely expel them within a limited time. Some existing technologies employ segmented vacuuming or extended vacuum holding time, yet they still cannot reduce the void ratio to below 1%. This is especially true for power modules with large welding areas (e.g., 100mm × 100mm or larger), where air bubbles in the central interface region are easily encapsulated by molten solder, forming persistent voids. These voids cause localized thermal resistance concentration, severely restricting heat dissipation efficiency and becoming a source of thermal fatigue crack initiation.

[0005] (ii) The gas escape channel at the welding interface is not unobstructed, resulting in low exhaust efficiency. In traditional vacuum welding, the solder preform has a dense structure and lacks preferential venting channels. After the solder melts, gases originally present in the gaps between the solder powder and gases released by the solder alloy itself must pass through the molten solder layer to reach the interface edge or free surface. The venting path is long and tortuous, and gases tend to get stuck in the middle of the solder layer. Some solutions improve venting by reducing the solder thickness or using preformed solder sheets, but it is difficult to balance the density and thickness uniformity of the weld layer. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing a method for installing a modular power component heat sink, thereby solving or improving the problems existing in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for installing a modular power component heat sink includes the following steps: S1. A copper layer is sprayed onto the inner welding surface of each sub-heater; S2. Perform plasma cleaning on the welding surfaces of each power module and each sub-heat sink. S3. The solder alloy powder and the hole-forming agent particles are mixed in proportion, and the composite solder preform is prepared by cold pressing and low-temperature pre-sintering. S4. Place the composite solder preform on the soldering surface of the heat sink, and cover the preform with the soldering surface of the power module facing down. S5. The stacked heat sink, composite solder preform and power module are clamped in the fixture and sent into the vacuum welding furnace for vacuum welding. S6. After vacuum welding is completed, multiple independent power component heat sink assemblies are obtained. S7. Assemble multiple independent power component heat sink components to obtain a modular power component heat sink.

[0008] Furthermore, S3 specifically includes: Solder alloy powder and pore-forming agent particles were mixed at a mass ratio of 92:8 to 98:2. The solder alloy powder used was Sn... Ag Cu-based alloys; the pore-forming agent particles are ammonium bicarbonate powder with a particle size of 10μm to 50μm; the mixed materials are cold-pressed and pre-sintered at low temperature to produce thin-sheet composite solder preforms with a thickness of 80μm to 200μm.

[0009] Furthermore, step S5 includes the following sub-steps: S51. Heat the vacuum welding furnace to the first preset temperature to decompose the pore-forming agent particles and pre-expel the gas. S52. Continue heating to the second preset temperature. While the solder alloy powder melts, a pulse current is applied to the power module and heat sink to perform electromigration-assisted debubbling. S53. Stop applying pulse current and apply static pressure to the power module; S54. Stop heating and static pressure, and perform gradient cooling.

[0010] Furthermore, S51 specifically includes: Vacuum the furnace until the pressure inside is below 5×10.- ³Pa, heated to the first preset temperature T1 at a heating rate of 5℃ / min~10℃ / min, T1 is set to 80℃~100℃, the temperature T1 is higher than the upper limit of the decomposition temperature of ammonium bicarbonate and lower than the liquidus temperature of the solder alloy powder. Hold for 10 to 20 minutes. During this holding period, ammonium bicarbonate decomposes completely, generating NH3, CO2 and water vapor. The solder alloy powder remains in solid particle form, and the decomposition gas diffuses along the initial interparticle pores inside the composite solder preform and is discharged from the welding interface under vacuum.

[0011] Furthermore, S52 specifically includes: Continue heating to the second preset temperature T2, which is 240℃~260℃, higher than the liquidus temperature of the solder alloy powder of 217℃, and hold for 60s~120s, so that the solder alloy powder is completely melted into molten solder. While the solder remains in a molten state, a pulsed current is applied to the power terminal of the power module through the feed electrode of the vacuum welding furnace. The current direction is configured such that the power module is connected to the positive terminal and the sub-heat sink is connected to the negative terminal, so that the electron flow is directed from the heat sink to the power module. Under the action of the pulsed current, electrons move in a directional manner in the molten solder to form an electron wind, which drives metal atoms to undergo electromigration along the direction of electron flow. This causes the molten solder to produce a uniform overall directional flow, and pushes the bubbles in the welding interface to the edge of the welding interface along the direction of solder flow. The edge of the welding interface is in a vacuum low-pressure environment. After the bubbles arrive, they burst or are extracted by the vacuum system. At the same time, the molten solder is driven to spread evenly to the edge of the welding interface.

[0012] Furthermore, in S52, the pulse current parameters are: current density 8A / mm²~15A / mm², pulse width 1s~2s, duty cycle 20%~40%, and total application duration 60s~90s.

[0013] Furthermore, S53 specifically includes: After the pulsed current stops, the solder remains molten. Static pressure is applied to the power module through the vacuum welding fixture. The pressure value is 1MPa to 2.5MPa, and the holding time is 60s to 90s.

[0014] Furthermore, S54 specifically includes: Stop heating and remove static pressure, then cool to 202°C under vacuum conditions at a cooling rate of 2°C / min to 4°C / min; subsequently, fill the vacuum welding furnace with high-purity argon gas to atmospheric pressure, and cool to room temperature at a cooling rate of 6°C / min to 8°C / min.

[0015] Furthermore, S7 specifically includes: Two adjacent power component heat sink assemblies are fixedly connected by a tenon-and-mortise interlocking structure, and multiple power component heat sink assemblies are spliced ​​together to form a closed modular power component heat sink.

[0016] The modular power component heat sink installation method provided by this invention has the following beneficial effects: 1. This invention breaks down the heat sink into identical small modular components, that is, each sub-heat sink independently corresponds to a power module. The individual sub-heat sink is small in size and has a moderate heat capacity, which can realize independent vacuum reflow welding of a single module. The temperature consistency during the welding process is good, and the welding void rate can be controlled below 3%. At the same time, it avoids the problems of high tooling requirements and complex operation in welding large-size heat sinks, which greatly improves the yield and production efficiency and lowers the welding process threshold.

[0017] 2. This invention introduces a pore-forming agent into the composite solder preform. During the solid stage before the solder alloy powder melts, the pore-forming agent is decomposed by heating. The gas generated by the decomposition of the pore-forming agent is discharged along the initial interparticle pores inside the preform, forming a three-dimensional interconnected open channel network in its original position. This channel network provides a preferential escape path for the gas before the solder melts, allowing the decomposed gas from the pore-forming agent and the gas adsorbed at the welding interface to escape in advance, preventing these gases from being trapped and forming bubbles after the solder melts.

[0018] 3. This invention applies a pulsed current to the power module during the solder melting stage. Utilizing the electromigration effect driven by electron wind, metal atoms in the molten solder migrate directionally along the electron flow direction, generating a controllable overall flow. This flow actively pushes residual bubbles in the welding interface to the edge of the interface and removes them under vacuum conditions, overcoming the limitations of passive bubble removal relying on buoyancy and capillary action in traditional processes. By adjusting the density, pulse width, duty cycle, and direction of the pulsed current, the speed and direction of the solder flow can be precisely controlled, adapting to welding interfaces of different sizes and shapes. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the installation method of the assembled power component heat sink in the embodiment.

[0020] Figure 2 This is a structural diagram of the sub-heater in the embodiment.

[0021] Figure 3 This is a schematic diagram of the assembled power component heat sink in the embodiment.

[0022] The components are: 1. Sub-heater; 2. Mounting part; 3. First connecting part; 4. Second connecting part; 5. Welding surface; 6. Welding protrusion; 7. Stress relief hole; 8. Protruding structure; 9. Slot structure; 10. Shovel teeth; 11. Stress relief groove. Detailed Implementation

[0023] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0024] This embodiment provides a method for installing a modular power component heatsink, referencing... Figure 1 Specifically, it includes the following: S1. A copper layer is sprayed onto the inner welding surface of each sub-heater.

[0025] S2. Perform plasma cleaning on the welding surfaces of each power module and each sub-heat sink to remove surface oxide layer and contaminants. After cleaning, dry in a vacuum oven.

[0026] S3. A composite solder preform is prepared by mixing solder alloy powder and pore-forming agent particles in a specific ratio, followed by cold pressing and low-temperature pre-sintering. Specifically, this includes: Solder alloy powder and pore-forming agent particles were mixed at a mass ratio of 92:8 to 98:2. The solder alloy powder used was Sn... Ag Cu-based alloys, such as SAC305, have a liquidus temperature of 217℃. The pore-forming agent particles are made of ammonium bicarbonate powder with a particle size of 10μm to 50μm and a decomposition temperature range of 36℃ to 70℃. The mixed material is cold-pressed and pre-sintered at a low temperature (sintering temperature below 36℃ to avoid premature decomposition of the pore-forming agent) to produce a thin-sheet composite solder preform with a thickness of 80μm to 200μm. The solder alloy powder particles are separated by pore-forming agent particles, and the initial interparticle porosity is retained.

[0027] S4. Place the composite solder preform on the soldering surface of the heat sink, and cover the preform with the soldering surface of the power module facing down.

[0028] S5. The stacked heat sink, composite solder preform, and power module are clamped in a fixture and sent into a vacuum welding furnace for vacuum welding. This process includes the following sub-steps: S51. Heat the vacuum welding furnace to the first preset temperature to decompose the pore-forming agent particles and pre-expel the gas. Vacuum the furnace until the pressure inside is below 5×10. -³Pa, heated to the first preset temperature T1 at a heating rate of 5℃ / min~10℃ / min, T1 is set to 80℃~100℃, the temperature T1 is higher than the upper limit of the decomposition temperature of ammonium bicarbonate and lower than the liquidus temperature of the solder alloy powder. Hold for 10 to 20 minutes. During this holding period, ammonium bicarbonate decomposes completely, generating NH3, CO2 and water vapor. The solder alloy powder remains in solid particle form, and the decomposition gas diffuses along the initial interparticle pores inside the composite solder preform and is discharged from the welding interface under vacuum.

[0029] S52. Continue heating to the second preset temperature. While the solder alloy powder melts, a pulse current is applied to the power module and heat sink to perform electromigration-assisted debubbling. Continue heating to the second preset temperature T2, which is 240℃~260℃, higher than the liquidus temperature of the solder alloy powder of 217℃, and hold for 60s~120s, so that the solder alloy powder is completely melted into molten solder. While the solder remains in a molten state, a pulsed current is applied to the power terminal of the power module through the feed electrode of the vacuum welding furnace. The current direction is configured such that the power module is connected to the positive terminal and the sub-heat sink is connected to the negative terminal, so that the electron flow is directed from the heat sink to the power module. Under the action of the pulsed current, electrons move in a directional manner in the molten solder to form an electron wind, which drives metal atoms to undergo electromigration along the direction of electron flow. This causes the molten solder to produce a uniform overall directional flow, and pushes the bubbles in the welding interface to the edge of the welding interface along the direction of solder flow. The edge of the welding interface is in a vacuum low-pressure environment. After the bubbles arrive, they burst or are extracted by the vacuum system. At the same time, the molten solder is driven to spread evenly to the edge of the welding interface.

[0030] The pulse current parameters are as follows: current density 8A / mm²~15A / mm², pulse width 1s~2s, duty cycle 20%~40%, and total application time 60s~90s.

[0031] S53. Stop applying pulse current and apply static pressure to the power module; Specifically, after the pulse current stops, the solder remains in a molten state, and static pressure is applied to the power module through the vacuum welding fixture. The pressure value is 1MPa to 2.5MPa, and the holding time is 60s to 90s.

[0032] S54. Stop heating and static pressure, and perform gradient cooling.

[0033] Specifically, heating is stopped and static pressure is removed, and the furnace is cooled to 202°C under vacuum conditions at a cooling rate of 2°C / min to 4°C / min; then, high-purity argon gas is introduced into the vacuum welding furnace to atmospheric pressure, and the furnace is cooled to room temperature at a cooling rate of 6°C / min to 8°C / min.

[0034] S6. After vacuum welding is completed, multiple independent power component heat sink assemblies are obtained. S7. Assemble multiple independent power component heat sink components to obtain a modular power component heat sink. In some embodiments, two adjacent power component heat sink assemblies are fixedly connected by a tenon-and-mortise interlocking structure, and multiple power component heat sink assemblies are spliced ​​together to form a closed modular power component heat sink.

[0035] In one specific embodiment, the specific structure of the modular power component heat sink is as follows: refer to Figure 2 and Figure 3 It includes several sub-heaters 1 with the same structure and size; each sub-heater 1 has an independent power module on its inner surface; two adjacent sub-heaters 1 are fixedly connected by a tenon-and-mortise interlocking structure, and multiple sub-heaters 1 are spliced ​​and snapped together to form a closed heatsink.

[0036] The sub-heater 1 is an integrally molded component, which includes a mounting part 2, and a first connecting part 3 and a second connecting part 4 disposed on both sides of the mounting part 2; the edge of the first connecting part 3 is provided with a slot structure 9, and the edge of the second connecting part 4 is provided with a protrusion structure 8; the protrusion structure 8 on the second connecting part 4 of a sub-heater 1 is inserted into the slot structure 9 of the first connecting part 3 of the adjacent heat sink.

[0037] The connection between the protruding structure 8 and the slot structure 9 is similar to that of a mortise and tenon joint. The connection is made through the material itself, without the use of any other adhesives or additional connection structures. The connection is stable and the installation is simple.

[0038] The heat sink is made of pure aluminum. Since brazing is not possible on pure aluminum, a copper spray layer is added so that it can be soldered. Based on this, the inner side of the mounting part 2 is provided as a flat welding surface 5. A copper layer is sprayed on the welding surface 5, and the power module is soldered onto the copper layer.

[0039] The copper layer thickness is 100-200µm. This embodiment is not limited to a specific power module, and may include, but is not limited to, IGBT power modules, MOSFET power modules, SiC silicon carbide power modules, etc.

[0040] Welding protrusions 6 are provided at the four corners of the welding surface 5 to ensure that the solder has a certain thickness after welding and to ensure the consistency of the solder thickness.

[0041] The back of the sub-heater 1 has an arc-shaped structure, on which multiple serrations 10 are evenly distributed. The serrations 10 are located on the side of the sub-heater 1 facing away from the power module. Between two adjacent serrations 10 is a stress relief groove 11, which is arranged vertically through the sub-heater 1. The purpose of the serrations 10 is to increase the contact area between the heatsink and the air, thereby improving heat dissipation efficiency; and the stress relief grooves 11 formed between the serrations 10 can prevent stress concentration, thus protecting the sub-heater 1.

[0042] Stress relief holes 7 are provided on the bottom of the sub-radiator 1 and on the mounting part 2 to release the stress of the radiator and avoid stress concentration.

[0043] There are 6 sub-radiators 1, which are arranged in a ring to form a circular radiator.

[0044] In this embodiment, the original monolithic heat sink is decomposed into multiple equal parts of the same structure. Vacuum reflow soldering of individual power modules is performed on each individual part (sub-heat sink 1) to reduce the welding difficulty. The welded individual parts are then connected by mechanical interlocking to form an integral power component heat sink. This integral power component heat sink is not limited to a circular shape and can be other assembly structures.

[0045] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A method for installing a modular power component heat sink, characterized in that, Includes the following steps: S1. A copper layer is sprayed onto the inner welding surface of each sub-heater; S2. Perform plasma cleaning on the welding surfaces of each power module and each sub-heat sink. S3. The solder alloy powder and the hole-forming agent particles are mixed in proportion, and the composite solder preform is prepared by cold pressing and low-temperature pre-sintering. S4. Place the composite solder preform on the soldering surface of the heat sink, and cover the preform with the soldering surface of the power module facing down. S5. The stacked heat sink, composite solder preform and power module are clamped in the fixture and sent into the vacuum welding furnace for vacuum welding. S6. After vacuum welding is completed, multiple independent power component heat sink assemblies are obtained. S7. Assemble multiple independent power component heat sink components to obtain a modular power component heat sink.

2. The method for installing a modular power component heat sink according to claim 1, characterized in that, S3 specifically includes: Solder alloy powder and pore-forming agent particles were mixed at a mass ratio of 92:8 to 98:

2. The solder alloy powder used was Sn... Ag Cu-based alloys; the pore-forming agent particles are ammonium bicarbonate powder with a particle size of 10μm to 50μm; the mixed materials are cold-pressed and pre-sintered at low temperature to produce thin-sheet composite solder preforms with a thickness of 80μm to 200μm.

3. The method for installing a modular power component heat sink according to claim 1, characterized in that, S5 includes the following sub-steps: S51. Heat the vacuum welding furnace to the first preset temperature to decompose the pore-forming agent particles and pre-expel the gas. S52. Continue heating to the second preset temperature. While the solder alloy powder melts, a pulse current is applied to the power module and heat sink to perform electromigration-assisted debubbling. S53. Stop applying pulse current and apply static pressure to the power module; S54. Stop heating and static pressure, and perform gradient cooling.

4. The method for installing a modular power component heat sink according to claim 3, characterized in that, S51 specifically includes: Vacuum the furnace until the pressure inside is below 5×10. - ³Pa, heated to the first preset temperature T1 at a heating rate of 5℃ / min~10℃ / min, T1 is set to 80℃~100℃, the temperature T1 is higher than the upper limit of the decomposition temperature of ammonium bicarbonate and lower than the liquidus temperature of the solder alloy powder. Hold for 10 to 20 minutes. During this holding period, ammonium bicarbonate decomposes completely, generating NH3, CO2 and water vapor. The solder alloy powder remains in solid particle form, and the decomposition gas diffuses along the initial interparticle pores inside the composite solder preform and is discharged from the welding interface under vacuum.

5. The method for installing a modular power component heat sink according to claim 3, characterized in that, Specifically, S52 includes: Continue heating to the second preset temperature T2, which is 240℃~260℃, higher than the liquidus temperature of the solder alloy powder of 217℃, and hold for 60s~120s, so that the solder alloy powder is completely melted into molten solder. While the solder remains in a molten state, a pulsed current is applied to the power terminal of the power module through the feed electrode of the vacuum welding furnace. The current direction is configured such that the power module is connected to the positive terminal and the sub-heat sink is connected to the negative terminal, so that the electron flow is directed from the heat sink to the power module. Under the action of the pulsed current, electrons move in a directional manner in the molten solder to form an electron wind, which drives metal atoms to undergo electromigration along the direction of electron flow. This causes the molten solder to produce a uniform overall directional flow, and pushes the bubbles in the welding interface to the edge of the welding interface along the direction of solder flow. The edge of the welding interface is in a vacuum low-pressure environment. After the bubbles arrive, they burst or are extracted by the vacuum system. At the same time, the molten solder is driven to spread evenly to the edge of the welding interface.

6. The method for installing a modular power component heat sink according to claim 5, characterized in that, In S52, the pulse current parameters are: current density 8A / mm²~15A / mm², pulse width 1s~2s, duty cycle 20%~40%, and total application duration 60s~90s.

7. The method for installing a modular power component heat sink according to claim 3, characterized in that, S53 specifically includes: After the pulsed current stops, the solder remains molten. Static pressure is applied to the power module through the vacuum welding fixture. The pressure value is 1MPa to 2.5MPa, and the holding time is 60s to 90s.

8. The method for installing a modular power component heat sink according to claim 3, characterized in that, Specifically, S54 includes: Stop heating and remove static pressure, then cool to 202°C under vacuum conditions at a cooling rate of 2°C / min to 4°C / min; subsequently, fill the vacuum welding furnace with high-purity argon gas to atmospheric pressure, and cool to room temperature at a cooling rate of 6°C / min to 8°C / min.

9. The method for installing a modular power component heat sink according to claim 3, characterized in that, Specifically, S7 includes: Two adjacent power component heat sink assemblies are fixedly connected by a tenon-and-mortise interlocking structure, and multiple power component heat sink assemblies are spliced ​​together to form a closed modular power component heat sink.

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