Positioning fixture and mounting method suitable for pressure sintering of TPAK device

Abstract

The application provides a positioning clamp and mounting method suitable for pressure sintering of TPAK devices, which comprises a carrier, two guide plates, a supporting plate, two positioning pins and two supporting rings; the application can realize accurate positioning and stable mounting of each boss of the TPAK device and the heat sink through clamp design in the absence of special TPAK device mounting equipment, and lays a foundation for high-quality pressure sintering. The application can save the cost of TPAK mounting equipment, is suitable for research and small-batch production, and is simple to assemble, has a wide range of applications, and can be used for mounting of various heat sink structures and multiple TPAK devices in parallel.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor device (packaging) technology, and more specifically to a positioning fixture and mounting method suitable for pressure sintering of TPAK devices. Background Technology

[0002] Currently, Tesla uses a SiC-type TPAK device sintering scheme in the main drive inverter of the Model 3, and connects the TPAK power devices to the aluminum heat sink through a pressure silver sintering process to form a power module capable of power conversion. The TPAK device structure is as follows: Figure 1 As shown.

[0003] Compared to thermal grease and high-temperature lead-free solder, the sintered connection layer of silver sintering technology is composed of silver, which has excellent electrical and thermal conductivity. Because silver has a melting point as high as 961℃, it will not exhibit the typical fatigue effects seen in soft soldering layers with melting points below 300℃, resulting in extremely high reliability. Furthermore, its sintering temperature is comparable to that of traditional soft solder. Using silver sintering technology can increase the lifespan of power modules by 5-10 times, with the sintered layer thickness being 60-70% thinner than the solder layer, and thermal conductivity increasing by 3 times.

[0004] Currently, no mature, mass-producible TPAK sintering module has been developed in China.

[0005] TPAK devices have a pressure sintering process, such as... Figure 2 As shown, printing involves using a screen printing machine to print silver paste onto the heatsink. Baking involves placing the printed heatsink in an oven to evaporate the organic matter in the silver paste, at which point the silver paste solidifies. Surface mounting involves using a dedicated surface mount machine to mount the components onto the silver paste corresponding to the heatsink's bosses. The surface mount machine provides a certain temperature and pressure, resulting in a pre-sintering state between the components and the heatsink, ensuring the TPAK components are securely mounted. Sintering involves placing the mounted TPAK modules into a sintering device. The sintering temperature is typically between 230-250℃, and pressure is applied to the surface of the TPAK components using a pressure head, achieving a connection between the TPAK components and the heatsink through pressure sintering.

[0006] Current methods for mounting TPAK devices involve using equipment, such as Tesla's. However, the technology of silver sintering TPAK devices with heat sinks is a high-cost approach, and domestically, there are no mature, mass-producible TPAK sintering modules yet developed; the domestic market is still in the experimental research stage. Therefore, for research institutes and companies conducting small-batch pilot research, purchasing dedicated TPAK device mounting equipment undoubtedly increases R&D costs. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a positioning fixture and mounting method suitable for pressure sintering of TPAK devices. In situations where dedicated TPAK device mounting equipment is unavailable, the fixture design enables precise positioning and secure mounting of the TPAK device to the heatsink's bosses, laying the foundation for high-quality pressure sintering. This invention allows for manual mounting of TPAK devices to the heatsink, reducing costs.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A positioning fixture suitable for pressure sintering of TPAK devices includes a carrier, two guide plates, a support plate, two positioning pins, and two support rings;

[0010] The carrier is used to support the heat sink and is designed according to the structure of the heat sink; the guide plate is used for manual positioning and support of the TPAK device and is installed in the track groove in the carrier; the support plate is used to support the TPAK device; the support ring is used to prevent the support plate from being squeezed out after pressure sintering; the guide plate is provided with positioning teeth, the spacing and number of which depend on the number of parallel TPAK devices, for precise positioning and fixing of the TPAK devices; the guide plate is fixed to the guide groove of the carrier with M3 hexagon socket screws with a length of less than 6mm; the upper sides of the support plate are chamfered at 30° to support the TPAK device, so that the TPAK device remains stable under the pressure applied during the sintering process.

[0011] Furthermore, the length of the guide plate is designed based on the overall length of the heat sink, the height is designed based on the height of the heat sink and the silver paste printed on its surface, and the positioning teeth on the guide plate are designed based on the number of TPAK devices connected in parallel and the parallel spacing.

[0012] Furthermore, we define h1 as the height of the support plate, h2 as the height of the support ring, h3 as the height of the heat sink boss, h4 as the reference device height, h5 as the thickness of the silver paste after baking, and h6 as the height of the boss to the bottom surface. The above parameters satisfy the following relationship: h1+h2=h3+h4+h5+h6. For heat sinks of any height and silver paste thickness, by adjusting the height of the support ring, we can achieve precise and stable chip mounting and highly reliable pressure sintering.

[0013] Furthermore, the length of the support plate is designed according to the length of the heat sink, and the height is designed as a constrained fixed value.

[0014] Furthermore, the diameter of the positioning pin is designed according to the diameter of the radiator opening.

[0015] Furthermore, the height of the support ring has a functional relationship with the height of the TPAK device and the height of the support plate.

[0016] Furthermore, the separate design of the support ring and support plate facilitates the removal of the support plate after pressure sintering.

[0017] This invention also provides a mounting method for a positioning fixture suitable for pressure sintering of TPAK devices, comprising: first, placing the baked heat sink in a carrier in a certain direction; then, placing two guide plates in the track grooves in the carrier and fixing them to the carrier with hexagonal screws of 6mm or less; then, placing the support ring on the positioning holes on both sides of the heat sink; then, placing the support plate on the support ring in a certain direction; then, positioning and fixing the support plate, support ring, and heat sink with positioning pins; finally, placing the TPAK devices in a certain direction sequentially on the corresponding bosses of the heat sink through the positioning teeth of the guide plates.

[0018] The present invention has the following beneficial effects:

[0019] 1) This invention does not utilize equipment for mounting; precise alignment of the sintered area of ​​the TPAK device with the corresponding sintered area on the heat sink surface can be achieved through manual mounting. This manual mounting method is applicable to heat sinks of different shapes and to n TPAK devices connected in parallel.

[0020] 2) A well-designed fixture can ensure a stable contact between the TPAK device and the heat sink, thereby avoiding device displacement or even breakage caused by pressure during sintering.

[0021] 3) The design of the support ring avoids the problem of the support plate not being able to be pulled out after pressure sintering.

[0022] This invention reduces the cost of TPAK mounting equipment, is suitable for research and small-batch production, and features simple assembly and wide applicability (not limited to the example size). It can be used for various heat sink structures and parallel mounting of multiple TPAK devices. Only the dimensions of the positioning plate and support plate, and the number of positioning teeth need to be changed. Furthermore, it is applicable to different sintering layer thicknesses (silver paste printing), requiring only changes to the size and thickness of the support ring. This invention enables precise positioning and stable mounting of TPAK devices to heat sinks, thereby ensuring pressure sintering quality and improving efficiency. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the TPAK device;

[0024] Figure 2 This is a process flow diagram for pressure sintering of TPAK devices;

[0025] Figure 3 This is a circuit topology diagram of the TPAK sintering module in an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram of a positioning fixture suitable for pressure sintering of TPAK devices according to an embodiment of the present invention;

[0027] Figure 5 This is a diagram of the carrier structure.

[0028] Figure 6 This is a diagram of the radiator structure.

[0029] Figure 7 A diagram of a TPAK three-phase module attached to the surface of a heatsink boss.

[0030] Figure 8 Here is a structural diagram of the guide plate;

[0031] Figure 9 This is a structural diagram of the support plate;

[0032] Figure 10 This is a schematic diagram illustrating the precise positioning and fixation of TPAK devices via the positioning teeth of a guide plate.

[0033] Figure 11 This is a side view of the positioning fixture, where h1 is the height of the support plate, h2 is the height of the support ring, h3 is the height of the heat sink boss, h4 is the height of the reference device, h5 is the thickness of the silver paste after baking, and h6 is the height from the boss to the bottom of the heat sink.

[0034] Figure 12 This is a flowchart of the mounting method of the present invention, wherein Figures a-f represent different steps. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] This invention provides a positioning fixture and mounting method for pressure sintering of TPAK devices, enabling precise positioning and stable mounting of TPAK devices to heat sinks, thus ensuring the quality of the pressure silver sintering process. Furthermore, this method is suitable for heat sink structures of any shape and for parallel applications of n TPAK devices.

[0037] like Figure 3The diagram shown is a circuit topology of the TPAK sintering module in an embodiment of the present invention. In this embodiment, it is a three-phase structure, with N being 3 TPAK devices connected in parallel in each phase arm, meaning each phase arm consists of 3 TPAK devices connected in parallel. The rated current carrying capacity of a single TPAK device is 300A, therefore the current carrying capacity of the system module is 900A. In other cases, the number of devices connected in parallel can be increased to increase system power. This invention is applicable to any number of TPAK devices connected in parallel. Figure 4 In this diagram, P represents the positive busbar, and N represents the negative busbar. U represents the U-phase bridge arm, V represents the V-phase bridge arm, and W represents the W-phase bridge arm.

[0038] like Figure 4 , Figure 6 , Figure 7 , Figure 9 As shown, a positioning fixture suitable for pressure sintering of TPAK devices according to the present invention includes a carrier 1, two guide plates 4, a support plate 5, two positioning pins 7, and two support rings 6.

[0039] The carrier 1 is used to support the heat sink 2 and is designed according to the structure of the heat sink 2. The guide plate 4 is used for manual positioning and support of the TPAK device 3, and is installed in the track groove in the carrier 1, such as... Figure 5 As shown. The support plate 5 is used to support the TPAK device 3. The support ring 6 can prevent the support plate 5 from being squeezed out after pressure sintering.

[0040] like Figure 8 , Figure 10 As shown, the guide plate 4 incorporates positioning teeth, the spacing and number of which depend on the number of parallel TPAK devices 3, enabling precise positioning and fixation of the TPAK devices 3. The guide plate 4 is fixed to the guide rail groove of the carrier 1 using M3 hexagonal screws with a length less than 6mm. The length of the guide rail groove is consistent with the length of the guide plate 4. The groove is machined within the carrier 1 using a milling machine to form a recessed groove, facilitating the placement of the guide plate for precise positioning and installation.

[0041] The upper sides of the support plate 5 are chamfered at 30° to support the TPAK device 3, which can keep the TPAK device 3 stable under the pressure applied during the sintering process.

[0042] The length of the guide plate 4 can be slightly greater than the overall length of all parallel TPAK devices on one side of the heat sink 2. Its height is the sum of the overall height of the heat sink, the height of the silver paste, and the reference height of the bottom of the TPAK devices. The number of positioning teeth on the guide plate 4 is designed based on the number of parallel TPAK devices 3. The optimal mathematical relationship is: number of positioning teeth = (n+1)*3, where n is the number of TPAK devices in parallel for each half-bridge. Furthermore, the spacing between adjacent positioning teeth in each phase is consistent with the width of the TPAK device. The length of the support plate 5 can be consistent with the length of the heat sink 2. The positions of the positioning holes on both sides must be coaxial with the positioning holes on both sides of the heat sink. Its height can be designed as a fixed value, generally less than the height of the boss of the heat sink 2. The diameter of the positioning pin 7 is designed based on the opening diameter of the heat sink 2. The height of the support ring 6 can be flexibly designed according to different heat sink heights and silver paste heights. It has a functional relationship with the height of the TPAK devices 3 and the height of the support plate 5, specifically h2 = h3 + h4 + h5 + h6 - h1. h1 is the height of the support plate, h2 is the height of the support ring, h3 is the height of the heat sink boss, h4 is the height of the reference device, h5 is the thickness of the silver paste after baking, and h6 is the height of the boss to the bottom surface.

[0043] The edge of the support plate 5 that contacts the TPAK device 3 is chamfered at 30° to support the TPAK device 3, thereby firmly fixing the TPAK device 3 and ensuring that the device remains stable under the pressure applied during the sintering process, thus guaranteeing pressure balance during sintering. The support ring 6 and the support plate 5 are designed separately, making it easy to remove the support plate 5 after pressurized sintering.

[0044] like Figure 11 As shown, the specific parameters of the positioning fixture include: h1 is the height of the support plate, h2 is the height of the support ring, h3 is the height of the heat sink boss, h4 is the height of the reference device, h5 is the thickness of the silver paste after baking, and h6 is the height of the boss to the bottom surface. These parameters satisfy the following relationship: h1 + h2 = h3 + h4 + h5 + h6. Therefore, for heat sinks 2 of any height and silver paste thickness, precise and stable mounting and highly reliable pressure sintering can be achieved by adjusting the height of the support ring 6.

[0045] like Figure 12 As shown, the mounting method of the present invention includes the following steps: Figure 12 As shown in Figure a, the baked radiator 2 is first placed in the carrier 1 in a certain direction. Figure 12 As shown in b, next, place the two guide plates 4 according to the track grooves in the carrier 1, and fix them to the carrier 1 with hexagonal screws of 6mm or less. Figure 12 As shown in c, the support ring 6 is then placed on the positioning holes on both sides of the radiator 2. Figure 12 As shown in d, the support plate 5 is then placed on the support ring 6 in a certain direction. Figure 12As shown in Figure e, the support plate 5, support ring 6, and radiator 2 are then positioned and fixed using the positioning pin 7. Figure 12 As shown in f, the TPAK device 3 is finally placed on the corresponding boss of the heat sink 2 in a certain direction through the positioning teeth of the guide plate 4.

[0046] After mounting, the TPAK module is placed in a sintering apparatus for pressure sintering. After sintering, it is removed and cooled. The subsequent disassembly process is as follows: First, pull out the positioning pin and remove the support ring; the support plate will fall off, allowing it to be pulled out. Next, remove the guide plates on both sides. Finally, remove the sintered TPAK module interface. Without the support ring design, the support plate may be squeezed by the TPAK device after pressure sintering, making it impossible to pull out.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A positioning fixture suitable for pressure sintering of TPAK devices, characterized in that, It includes a carrier, two guide plates, a support plate, two positioning pins, and two support rings; The carrier is used to support the heat sink and is designed according to the structure of the heat sink. The guide plate is used for manual positioning and support of the TPAK device and is installed in the track groove in the carrier. The support plate is used to support the TPAK device, and the support ring is used to prevent the support plate from being squeezed out after pressure sintering. The guide plate is provided with positioning teeth. The spacing and number of the positioning teeth depend on the number of parallel TPAK devices and are used for precise positioning and fixing of the TPAK devices. The guide plate is fixed to the track groove of the carrier with M3 hexagon socket screws with a length of less than 6mm. The upper part of the support plate is chamfered at 30° on both sides to support the TPAK device and keep the TPAK device stable under the pressure applied during the sintering process. The length of the track groove is the same as the length of the guide plate and its structure is machined in the carrier by a milling machine to form a groove.

2. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 1, characterized in that, The length of the guide plate is designed based on the overall length of the heat sink, and the height is designed based on the sum of the height of the heat sink and the silver paste printed on its surface. The positioning teeth on the guide plate are designed based on the number of TPAK devices connected in parallel and the parallel spacing.

3. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 2, characterized in that, definition h 1 represents the height of the support plate. h 2 represents the height of the support ring. h 3 represents the height of the radiator boss. h 4 represents the reference device height. h 5 represents the thickness of the silver paste after baking. h 6 represents the height of the boss from the bottom surface; the above parameters satisfy the following relationship: h 1+ h 2= h 3+ h 4+ h 5+ h 6. For heatsinks of any height and silver paste thickness, precise and stable mounting and highly reliable pressure sintering can be achieved by adjusting the height of the support ring.

4. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 1, characterized in that, The length of the support plate is designed according to the length of the heat sink, and the height is designed as a constrained fixed value.

5. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 1, characterized in that, The diameter of the positioning pin is designed according to the diameter of the radiator opening.

6. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 1, characterized in that, The height of the support ring is functionally related to the height of the TPAK device and the height of the support plate.

7. A positioning fixture suitable for pressure sintering of TPAK devices according to claim 1, characterized in that, The separate design of the support ring and support plate facilitates the removal of the support plate after pressure sintering.

8. A mounting method for a positioning fixture suitable for pressure sintering of TPAK devices according to any one of claims 1-7, characterized in that, include: First, place the baked heat sink in the carrier in a certain direction; then, place the two guide plates in the track grooves in the carrier and fix them to the carrier with hex screws of 6mm or less; then, place the support ring on the positioning holes on both sides of the heat sink; then, place the support plate on the support ring in a certain direction; then, fix the support plate, support ring and heat sink in a certain position with positioning pins; finally, place the TPAK devices in a certain direction on the corresponding bosses of the heat sink through the positioning teeth of the guide plate.

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