Gradient type copper-molybdenum alloy ratio pressure-equalizing and soaking method for crimping type power module

Abstract

The invention discloses a pressure-equalizing and soaking method for a crimping type power module based on gradient copper-molybdenum alloy ratio, and belongs to the field of pressure-equalizing and soaking of crimping type power modules, which comprises the following steps: dividing the crimping type power module into an internal area, a middle area and an external area according to the spatial distribution of a plurality of chips in the crimping type power module; according to the division results of the internal region, the middle region and the external region, copper-molybdenum alloy layers are arranged on the collector side and the emitter side of each region respectively; forming a copper content gradient which linearly changes from an internal area to an external area according to the setting result of the copper-molybdenum alloy layer; and according to a forming result of the copper content gradient, establishing a pressure-equalizing and heat-equalizing structure of the crimping type power module. According to the invention, a gradient copper-molybdenum alloy proportioning scheme is introduced, so that the heat dissipation capability of the central chip, which is not easy to dissipate heat, of the crimping module is improved, and the thermal coupling effect between the chips is reduced.

Description

Technical Field

[0001] This invention belongs to the field of pressure equalization and heat equalization technology of press-fit power modules, and particularly relates to a pressure equalization and heat equalization method for press-fit power modules with gradient copper-molybdenum alloy ratio. Background Technology

[0002] Currently, press-fit IGBT power modules are widely used in flexible DC transmission. They employ pure molybdenum sheets as stress buffer and heat-conducting layers at both ends of the IGBT chip. The thermal expansion coefficient of pure molybdenum is close to that of silicon chips, which can alleviate the problem of thermal stress accumulation in multi-layer structures. At the same time, external pressure is used to achieve vertical interconnection between the collector and emitter protrusions, meeting the requirements of multi-chip parallel connection in high-voltage and high-current scenarios (e.g., 36 chips connected in parallel to achieve a 4500V / 3000A module).

[0003] The shortcomings of existing technologies: Pure molybdenum sheets have low thermal conductivity and high Young's modulus, resulting in poor heat dissipation in the central area of ​​the module and severely uneven heat distribution, leading to thermal coupling effects between chips. Simultaneously, large-area protrusions generate uneven contact pressure under external pressure, causing an imbalance in the distribution of interlayer contact thermal resistance. The synergistic effect of uneven thermal and mechanical distribution accelerates chip cracking and interconnect material aging and failure, significantly reducing the long-term reliability of press-fit power modules. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a pressure equalization and heat equalization method for press-fit power modules with a gradient copper-molybdenum alloy ratio, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for equalizing pressure and heat in a press-fit power module with a gradient copper-molybdenum alloy ratio, comprising:

[0006] Based on the spatial distribution of multiple chips in the press-fit power module, the press-fit power module is divided into an internal region, a middle region, and an external region.

[0007] Based on the division of the internal region, the middle region and the external region, copper-molybdenum alloy layers are provided on the collector side and the emitter side of each region respectively;

[0008] Based on the configuration of the copper-molybdenum alloy layer, a copper content gradient is formed that linearly varies from the inner region to the outer region.

[0009] Based on the formation of the copper content gradient, a pressure equalization and heat equalization structure for the press-fit power module is established.

[0010] Preferably, the step of dividing the press-fit power module into an internal region, a middle region, and an external region includes:

[0011] Based on the distance between the chip and the center of the press-fit power module, the chip is divided into an internal region, a middle region, and an external region;

[0012] Based on the grouping results, the number of chips and their relative positions in each region are determined.

[0013] Preferably, the step of forming copper-molybdenum alloy layers on the collector side and emitter side of each region includes:

[0014] Based on the chip location in the internal region, the collector molybdenum sheet and emitter molybdenum sheet in the internal region are replaced with a first copper-molybdenum alloy layer;

[0015] Based on the chip position in the intermediate region, the collector molybdenum sheet and emitter molybdenum sheet in the intermediate region are replaced with a second copper-molybdenum alloy layer;

[0016] Based on the chip location in the external region, the collector molybdenum sheet and emitter molybdenum sheet in the external region are retained as pure molybdenum layers.

[0017] Preferably, the copper content of the first copper-molybdenum alloy layer is higher than that of the second copper-molybdenum alloy layer, and the copper content of the second copper-molybdenum alloy layer is higher than that of the pure molybdenum layer.

[0018] Preferably, the step of forming a copper content gradient that changes linearly from the inner region to the outer region includes:

[0019] Based on the copper-molybdenum alloy layers in the inner, middle, and outer regions, the copper content is set as a linear gradient decreasing from the inner region to the outer region.

[0020] Preferably, the steps for establishing a pressure- and heat-equalizing structure include:

[0021] Based on the copper content gradient, a multi-layer structure of the press-fit power module is constructed. The multi-layer structure sequentially includes a collector boss, a collector molybdenum sheet, a first nano-sintered layer, a chip, a second nano-sintered layer, an emitter molybdenum sheet, and an emitter boss.

[0022] Preferably, the chip is an IGBT chip or a MOSFET chip, and the chip is connected to a copper-molybdenum alloy layer through a nano-sintered material.

[0023] Preferably, the method further includes:

[0024] Based on the aforementioned pressure-equalizing and heat-equalizing structure, a finite element simulation model is established;

[0025] Based on the finite element simulation model, the chip temperature distribution path and stress distribution path are extracted;

[0026] The temperature and stress uniformity of the press-fit power module are evaluated based on the temperature and stress distribution paths described.

[0027] Preferably, the steps for extracting the chip temperature distribution path and stress distribution path include:

[0028] The chip temperature distribution is obtained based on the steady-state thermal analysis module in the finite element simulation model.

[0029] The temperature distribution results are inherited into the static structural analysis module of the finite element simulation model to obtain the chip stress distribution.

[0030] Preferably, the temperature distribution path and stress distribution path are respectively arranged along the chip edge to the center symmetrical plane of the press-fit power module, and there are three paths, corresponding to the first row of chips, the second row of chips and the third row of chips of the press-fit power module.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] This invention provides a method for equalizing pressure and heat in a press-fit power module with a gradient copper-molybdenum alloy ratio, comprising the following steps: First, based on the spatial distribution of multiple chips in the press-fit power module, the press-fit power module is divided into an internal region, a middle region, and an external region; second, based on the division of the internal, middle, and external regions, copper-molybdenum alloy layers are respectively set on the collector side and emitter side of each region; then, based on the setting of the copper-molybdenum alloy layers, a copper content gradient that linearly changes from the internal region to the external region is formed; finally, based on the formation of the copper content gradient, a pressure equalization and heat equalization structure for the press-fit power module is established.

[0033] This invention introduces a gradient copper-molybdenum alloy ratio scheme to improve the heat dissipation capacity of the central chip in press-fit modules, which is prone to heat dissipation. This reduces the thermal coupling effect between chips, preventing heat accumulation in the middle and thus avoiding stress accumulation and warping behavior caused by large-area bumps. It also prevents further uneven contact thermal resistance and uneven heat distribution between chips, which can lead to aging and failure of the press-fit power module. Depending on actual needs, this invention can be extended to press-fit power modules with different numbers of chips connected in parallel to further improve module reliability. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a complete structural schematic diagram of the press-fit IGBT power module according to an embodiment of the present invention;

[0036] Figure 2This is a schematic diagram of the multi-layer structure of each sub-module unit of the press-fit IGBT power module according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the gradient copper-molybdenum alloy ratio division region of the press-fit IGBT power module according to an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the temperature and stress distribution of the IGBT power chip in the finite element steady-state thermal simulation of the press-fit IGBT power module according to an embodiment of the present invention; wherein, (a) is the steady-state thermal distribution diagram of the IGBT with pure molybdenum scheme, (b) is the steady-state stress distribution diagram of the IGBT with pure molybdenum scheme, (c) is the steady-state thermal distribution diagram of the IGBT with the Mo70in_Mo85mid_Mo100out copper-molybdenum ratio scheme, and (d) is the steady-state stress distribution diagram of the IGBT with the Mo70in_Mo85mid_Mo100out copper-molybdenum ratio scheme.

[0039] Figure 5 This is a schematic diagram illustrating the extraction of temperature and stress results from the finite element simulation of the steady-state thermal distribution of the press-fit IGBT power module according to an embodiment of the present invention.

[0040] Figure 6 This is a schematic diagram of the steady-state temperature and steady-state stress distribution of the IGBT power chip along path 1 in an embodiment of the present invention, where the third region is pure molybdenum and the first and second regions have different gradient distributions of copper-molybdenum ratios; wherein, the left figure is a schematic diagram of the steady-state temperature distribution and the right figure is a schematic diagram of the steady-state stress distribution.

[0041] Figure 7 This is a schematic diagram of the steady-state temperature and steady-state stress distribution of the IGBT power chip along path 2 in an embodiment of the present invention, where the third region is pure molybdenum and the first and second regions have different gradient distributions of copper-molybdenum ratios; wherein, the left figure is a schematic diagram of the steady-state temperature distribution and the right figure is a schematic diagram of the steady-state stress distribution.

[0042] Figure 8 This is a schematic diagram of the steady-state temperature and steady-state stress distribution of the IGBT power chip along path 3 in an embodiment of the present invention, where the third region is pure molybdenum and the first and second regions have different gradient distributions of copper-molybdenum ratios; wherein, the left figure is a schematic diagram of the steady-state temperature distribution and the right figure is a schematic diagram of the steady-state stress distribution.

[0043] Figure 9 This is a bar and broken line double Y-axis schematic diagram comparing the temperature and stress imbalance of the IGBT power chip along paths 1 to 3 in a pure molybdenum scheme and four different copper-molybdenum alloy ratios of the press-fit IGBT power module according to an embodiment of the present invention.

[0044] Among them: 1. Collector boss; 2. Emitter boss; 3. Collector molybdenum sheet; 4. First nanometer sintered layer; 5. IGBT power chip; 6. Second nanometer sintered layer; 7. Emitter molybdenum sheet. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the steps shown in Embodiment 1 can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in Embodiment 1, in some cases the steps shown or described may be executed in a different order than that shown here.

[0047] Example 1

[0048] This embodiment aims to address the uneven temperature and pressure distribution of the chip in traditional press-fit structures with pure molybdenum sheets, which leads to accelerated device aging, failure, and short lifespan, thus improving the reliability of press-fit power modules. Based on actual needs, this embodiment can be extended to optimize the reliability of various press-fit power semiconductor devices, providing a solution for improving the operational reliability of power electronic equipment.

[0049] This embodiment provides a method for equalizing pressure and heat in a press-fit power module with a gradient copper-molybdenum alloy ratio. By changing the materials of the collector and emitter molybdenum plates above and below the IGBT chip (or the drain and source molybdenum plates above and below the MOSFET chip), pure molybdenum material is replaced with an alloy material with a corresponding copper-molybdenum ratio according to a gradient scheme, thereby improving its reliability. The structure of the replaced press-fit IGBT power module submodule is as follows: collector copper-molybdenum alloy, second nano-sintered layer 6, IGBT power chip 5, nano-sintered material, and emitter copper-molybdenum alloy. Specifically, it includes:

[0050] S1. Based on the spatial distribution of multiple chips in the press-fit power module, the press-fit power module is divided into an internal region, a middle region, and an external region.

[0051] Furthermore, the step of dividing the press-fit power module into an internal region, a middle region, and an external region includes:

[0052] S101. Based on the distance between the chip and the center of the press-fit power module, the chip is divided into an internal region, a middle region, and an external region.

[0053] S102. Based on the grouping results, determine the number of chips and their relative positions in each region.

[0054] S2. Based on the division results of the internal region, the middle region and the external region, copper-molybdenum alloy layers are provided on the collector side and the emitter side of each region respectively;

[0055] Furthermore, the step of depositing copper-molybdenum alloy layers on the collector side and emitter side of each region includes:

[0056] S201. Based on the chip position in the internal region, replace the collector molybdenum sheet and emitter molybdenum sheet in the internal region with a first copper-molybdenum alloy layer.

[0057] S202. Based on the chip position in the intermediate region, replace the collector molybdenum sheet and emitter molybdenum sheet in the intermediate region with a second copper-molybdenum alloy layer.

[0058] S203. Based on the chip position in the external region, the collector molybdenum sheet and emitter molybdenum sheet in the external region are retained as pure molybdenum layers.

[0059] In this embodiment, the copper content of the first copper-molybdenum alloy layer is higher than that of the second copper-molybdenum alloy layer, and the copper content of the second copper-molybdenum alloy layer is higher than that of the pure molybdenum layer.

[0060] S3. Based on the setting result of the copper-molybdenum alloy layer, a copper content gradient that changes linearly from the inner region to the outer region is formed;

[0061] Furthermore, the steps for forming a copper content gradient that varies linearly from the inner region to the outer region include:

[0062] Based on the copper-molybdenum alloy layers in the inner, middle, and outer regions, the copper content is set as a linear gradient decreasing from the inner region to the outer region.

[0063] Specifically, the copper-molybdenum alloy ratio for the collector and emitter is determined based on the submodule's position within the complete press-fit IGBT power module. The copper-molybdenum alloy ratio is as follows: the multi-chip press-fit IGBT power module is divided into three regions. Taking a 36-chip press-fit IGBT power module as an example, the inner region consists of 6 chips in the center ring, the middle region has 12 chips in the outer ring, and the outer region has 18 chips in the outermost ring. This division of the press-fit power module into different copper-molybdenum alloy ratio regions is not strictly defined; the overall division is based on the symmetry of the chips and their distance from the center. The aim is to improve local heat dissipation and reduce thermal coupling effects between chips by setting different copper-molybdenum alloy ratios for different regions.

[0064] S4. Based on the formation result of the copper content gradient, establish a pressure equalization and heat equalization structure for the press-fit power module.

[0065] Furthermore, the steps for establishing a pressure- and heat-equalizing structure include:

[0066] Based on the copper content gradient, a multi-layer structure of the press-fit power module is constructed. The multi-layer structure includes, in sequence, a collector boss 1, a collector molybdenum sheet 3, a first nano-sintered layer 4, an IGBT power chip 5, a second nano-sintered layer 6, an emitter molybdenum sheet 7, and an emitter boss 2.

[0067] In this embodiment, the chip is an IGBT chip or a MOSFET chip, and the chip is connected to a copper-molybdenum alloy layer through a nano-sintered material.

[0068] like Figure 1 As shown in the diagram, this embodiment provides a complete structural schematic of a press-fit power module, which consists of: a collector boss 1, an emitter boss 2, and a collector molybdenum sheet 3. This press-fit power module is a press-fit IGBT power module with 36 chips connected in parallel. This embodiment can be extended to press-fit modules with other numbers of parallel chips. The collector boss 1 is pressed onto the collector molybdenum sheet 3 via hard pressing; this diagram is only an exploded view. Further details regarding the collector molybdenum sheet in this example are described below. Figure 2 .

[0069] like Figure 2 The diagram shows a multi-layer structure of each sub-module unit of a press-fit power module provided in this embodiment. From top to bottom, the structure consists of: collector boss 1, collector molybdenum sheet 3, first nano-sintered layer 4, IGBT power chip 5, second nano-sintered layer 6, emitter molybdenum sheet 7, and emitter boss 2. This example uses a double-sided nano-silver sintered press-fit IGBT power module. Depending on actual needs, this embodiment can be extended to various single-sided welded, weldless, or other welded hard-press-fit power module structures.

[0070] Considering the copper-molybdenum ratios used in practice, the comparison scheme is as follows: the first internal region is the inner layer of the module, represented by "in"; the second internal region is the middle layer of the module, represented by "mid"; and the third internal region is the outer layer of the module, represented by "out". Specifically, four schemes are compared: Mo40in_Mo70mid_Mo100out, Mo70in_Mo85mid_Mo100out, Mo100in_Mo70mid_Mo40out, and Mo100in_Mo85in_Mo70out. Taking Mo40in_Mo70mid_Mo100out as an example, in this example, the current collector molybdenum sheet and the emitter molybdenum sheet in the first internal region are both Mo40Cu60 copper-molybdenum alloy, the current collector molybdenum sheet and the emitter molybdenum sheet in the second internal region are both Mo70Cu30 copper-molybdenum alloy, and the current collector molybdenum sheet and the emitter molybdenum sheet in the third internal region are both pure molybdenum sheets. The gradient copper-molybdenum alloy ratio scheme is distributed in a linear gradient manner. By exploring the optimal copper-molybdenum ratio gradient, it was determined whether the copper-molybdenum alloy with increased copper content should be placed inside or outside, thereby improving the pressure equalization and heat equalization performance of the press-fit power module.

[0071] like Figure 3 The diagram illustrates the region division of a gradient copper-molybdenum alloy ratio-based pressure and heat equalization method provided in this embodiment. The first region represents the innermost ring of modules, the second region represents the middle ring of modules, and the third region represents the outermost ring of modules. By replacing the collector molybdenum sheet and emitter molybdenum sheet in each region with a copper-molybdenum alloy, and selecting appropriate copper-molybdenum alloy ratios in the first to third regions according to a suitable gradient, the uneven pressure and heat distribution of multi-chip parallel press-fit power modules can be effectively reduced.

[0072] S5. Based on the aforementioned pressure-equalizing and heat-equalizing structure, establish a finite element simulation model;

[0073] S6. Based on the finite element simulation model, extract the chip temperature distribution path and stress distribution path.

[0074] Furthermore, the steps for extracting the chip temperature distribution path and stress distribution path include:

[0075] The chip temperature distribution is obtained based on the steady-state thermal analysis module in the finite element simulation model.

[0076] The temperature distribution results are inherited into the static structural analysis module of the finite element simulation model to obtain the chip stress distribution.

[0077] S7. Evaluate the temperature uniformity and stress uniformity of the press-fit power module based on the temperature distribution path and stress distribution path.

[0078] Furthermore, the temperature distribution path and stress distribution path are respectively arranged along the chip edge to the center symmetrical plane of the press-fit power module, and there are three paths, corresponding to the first row of chips, the second row of chips and the third row of chips of the press-fit power module.

[0079] Specifically, the finite element simulation software used was ANSYS Workbench 2023R1, and the simulation modules were the Steady-State Thermal analysis module and the Static Structural module. The finite element simulation steps were as follows: material properties were set for different structural components of the press-fit IGBT power module, and meshing was performed. Internal heat generation of the chip was set, the initial temperature was set, and the convective heat transfer coefficient at the boundaries was set as a heat dissipation condition. Contact thermal resistance was also set between each layer, calculated using a microscopic contact model and external pressure, contact materials, and the area of ​​each layer. Finite element simulation was then performed, and the steady-state thermal distribution of the press-fit IGBT power module was obtained through post-processing of the results.

[0080] like Figure 4 The figure shows the temperature and stress distribution of the IGBT power chip in the steady-state thermodynamic model of the press-fit power module based on the finite element analysis. Among them, Figure 4 (a) and Figure 4 (b) shows the temperature and stress distribution of the IGBT power chip when both the collector and emitter molybdenum sheets are pure molybdenum sheets; Figure 4 (c) and Figure 4 Figure (d) shows the temperature and stress distribution of the IGBT power chip when both the collector and emitter molybdenum sheets are replaced with copper-molybdenum alloy, with a copper-molybdenum ratio of Mo70in_Mo85mid_Mo100out. The results show that, from the perspective of the overall module temperature distribution, the gradient copper-molybdenum alloy ratio method provided in this embodiment can reduce the center temperature of the IGBT power chip and the maximum module temperature is reduced by approximately 1 degree Celsius, improving temperature uniformity. Furthermore, from the perspective of the overall module stress distribution, the traditional multi-chip parallel module using a uniform pure molybdenum sheet results in a large stress difference between the second and third regions, forming significant stress concentration and uneven pressure phenomena. This overall uneven pressure state easily leads to accelerated local aging failure. In contrast, from... Figure 4 As shown in (d), the gradient copper-molybdenum alloy proportioning scheme of Mo70in-Mo85mid-Mo100out can significantly balance the stress distribution, reducing the stress difference between the middle and edge regions, thus greatly reducing stress concentration and demonstrating a very obvious improvement in stress distribution. In summary, the gradient copper-molybdenum alloy proportioning method provided in this embodiment has excellent pressure and heat equalization capabilities, effectively alleviating temperature concentration and significantly reducing stress concentration.

[0081] like Figure 5 As shown in the diagram, this embodiment provides a schematic diagram of three paths extracted along the chip's edge from the module's edge to its center in a press-fit power module. The purpose is to further illustrate the effect of the gradient copper-molybdenum alloy ratio method on pressure and heat equalization along each path, thus demonstrating that the gradient copper-molybdenum alloy ratio improves performance on each path and on an overall average basis. Since the module is approximately symmetrically distributed, only one-quarter of the extraction paths need to be considered to reflect the temperature and stress distribution in other areas. The heights of the three temperature extraction paths are all set at the chip's volume center, and the heights of the three stress extraction paths are all set at the chip's emitter surface. This is to reflect the volume average temperature and the stress distribution at the contact surface, respectively, which in turn reflects the module's thermal resistance distribution. Path 1 is the path from the edge of the first row of chips to the module's center symmetry plane, path 2 is the path from the edge of the second row of chips to the module's center symmetry plane, and path 3 is the path from the edge of the third row of chips to the module's center symmetry plane.

[0082] After obtaining the overall temperature distribution of the press-fit IGBT power module, the temperature distribution was inherited into the static structure analysis module using the result inheritance function of ANSYS Workbench. Mechanical structural constraints, namely fixed bottom surface constraints, were set to prevent the module structure from moving during the simulation, which could lead to simulation non-convergence. Subsequently, static structural finite element simulation was performed to obtain the stress distribution on the emitter surface of the IGBT chip in the multi-chip parallel module.

[0083] In press-fit power modules, the emitter surface of the IGBT has a smaller area and greater contact thermal resistance than the collector surface, and the obtained stress distribution is more indicative of the pressure and heat equalization.

[0084] In order to further compare the temperature and stress distribution at the edge and center of the module, it is necessary to extract the IGBT emitter surface path stress and IGBT chip volume average path temperature of the press-fit IGBT power module in the post-processing of the finite element simulation results. The specific steps are as follows: take the position of the lower surface of the outermost chip in each row as the new coordinate axis, and set the path to start from the midpoint of the side length of the outermost chip and continue to the symmetry plane of the module center.

[0085] Since the overall modules are symmetrically distributed, only the temperature and stress paths of the IGBT chips in one-quarter of the modules need to be extracted.

[0086] like Figure 6 The figure shows a comparison of temperature and stress for three copper-molybdenum alloy ratios in path 1 of the press-fit power module; the left figure is a schematic diagram of steady-state temperature distribution, and the right figure is a schematic diagram of steady-state stress distribution. Figure 6As can be seen, when the copper content in the copper-molybdenum alloy in the first region gradually increases from 0% to 30% to 60%, the temperature decreases and the temperature unevenness also decreases. Meanwhile, the surface stress of the emitter of the second chip along path 1 increases slowly, but the degree of unevenness remains basically unchanged. Therefore, the gradient copper-molybdenum alloy ratio scheme can reduce the temperature of the chip in path 1 while keeping the degree of unevenness basically unchanged. This is because the collector and emitter molybdenum sheets in path 1 are still pure molybdenum sheets, but the decrease in the center temperature promotes the temperature diffusion from the center to the periphery.

[0087] like Figure 7 The figure shows a comparison of temperature and stress for three copper-molybdenum alloy ratios in path 2 of the press-fit power module; the left figure is a schematic diagram of steady-state temperature distribution, and the right figure is a schematic diagram of steady-state stress distribution. Figure 7 As can be seen, when the copper content in the copper-molybdenum alloy in the first region gradually increases from 0% to 30% to 60%, the temperature decreases and the temperature unevenness also decreases, while the chip stress in path 2 increases significantly. When the copper-molybdenum alloy ratio of the collector and emitter in the first region changes from Mo70in to Mo40in, the stress increases by 48.1%, and the unevenness first decreases and then increases. The Mo70in_Mo85mid_Mo100out copper-molybdenum alloy ratio scheme brings the lowest stress unevenness. Therefore, the Mo70in_Mo85mid_Mo100out gradient copper-molybdenum alloy ratio scheme can reduce the chip temperature in path 2 and also significantly reduce the stress unevenness. However, if the Mo40in_Mo70mid_Mo100out copper-molybdenum alloy ratio scheme is used, the stress will increase significantly, and the stress unevenness will increase considerably.

[0088] like Figure 8 The figure shows a comparison of temperature and stress for three copper-molybdenum alloy ratios in path 3 of the press-fit power module; the left figure is a schematic diagram of steady-state temperature distribution, and the right figure is a schematic diagram of steady-state stress distribution. Figure 8As can be seen, when the copper content in the copper-molybdenum alloy in the first region gradually increases from 0% to 30% to 60%, the temperature decreases and the temperature unevenness also decreases, while the chip stress in path 3 increases significantly. When the collector and emitter copper-molybdenum alloy ratio in the first region changes from Mo70in to Mo40in, the stress increases by 35.5%, and the unevenness also decreases first and then increases. The Mo70in_Mo85mid_Mo100out copper-molybdenum alloy ratio scheme provides the lowest stress unevenness. Therefore, the Mo70in_Mo85mid_Mo100out gradient copper-molybdenum alloy ratio scheme can reduce the chip temperature in path 3 and also significantly reduce the stress unevenness. However, if the Mo40in_Mo70mid_Mo100out copper-molybdenum alloy ratio scheme is used, the stress will increase significantly, and the stress unevenness will increase considerably.

[0089] like Figure 9 The figure shows a bar chart and a polygonal line diagram illustrating the comparison of temperature and stress imbalance of IGBT power chips along paths 1-3 in a pure molybdenum scheme and four different copper-molybdenum alloy ratios for a press-fit power module. From... Figure 9 As can be seen, the temperature imbalance is comparable across the five schemes, with a standard deviation of only about 2.1 for temperature distribution along the three paths and almost equal mean values. This indicates that changing the copper-molybdenum ratio can slightly optimize heat dissipation or keep it essentially unchanged. However, in terms of stress imbalance, the Mo100in_Mo85mid_Mo70out and Mo100in_Mo70mid_Mo40out schemes exhibit higher stress imbalance along the three paths than the pure molybdenum scheme. Furthermore, as the copper proportion in the copper-molybdenum alloy in the third region gradually increases, the degree of uneven pressure also gradually increases. Therefore, this example does not adopt the scheme of increasing the copper proportion in the third region, but rather the scheme of increasing the copper proportion in the first region. That is, the copper proportion should be appropriately increased closer to the center of the press-fit power module. Specifically, from Figure 9It can be seen that the Mo70in_Mo85mid_Mo100out formula can significantly reduce stress imbalance and achieve synergistic optimization of heat and pressure equalization. Therefore, the gradient copper-molybdenum ratio scheme for multi-chip parallel press-fit power modules, which uses a Mo70Cu30 copper-molybdenum alloy in the first region, a Mo85Cu15 copper-molybdenum alloy in the second region, and a pure Mo100Cu0 molybdenum alloy in the third region, can reduce single-path temperature imbalance by up to 7.11% and single-path stress imbalance by up to 14.14%; the average temperature imbalance across the three paths is reduced by 6.24%, and the average stress imbalance across the three paths is reduced by 2.83%. This simple yet effective gradient copper-molybdenum alloy ratio method for press-fit power modules can significantly reduce pressure imbalance while slightly reducing temperature and heat imbalance, which is crucial for improving the long-term reliability of press-fit power module devices.

[0090] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for equalizing pressure and heat in a press-fit power module with a gradient copper-molybdenum alloy ratio, characterized in that, Includes the following steps: Based on the spatial distribution of multiple chips in the press-fit power module, the press-fit power module is divided into an internal region, a middle region, and an external region. Based on the division of the internal region, the middle region and the external region, copper-molybdenum alloy layers are provided on the collector side and the emitter side of each region respectively; Based on the configuration of the copper-molybdenum alloy layer, a copper content gradient is formed that linearly varies from the inner region to the outer region. Based on the formation of the copper content gradient, a pressure equalization and heat equalization structure for the press-fit power module is established.

2. The method according to claim 1, characterized in that, The steps of dividing the press-fit power module into an internal region, a middle region, and an external region include: Based on the distance between the chip and the center of the press-fit power module, the chip is divided into an internal region, a middle region, and an external region; Based on the grouping results, the number of chips and their relative positions in each region are determined.

3. The method according to claim 2, wherein the step of depositing copper-molybdenum alloy layers on the collector side and emitter side of each region respectively comprises: Based on the chip location in the internal region, the collector molybdenum sheet and emitter molybdenum sheet in the internal region are replaced with a first copper-molybdenum alloy layer; Based on the chip position in the intermediate region, the collector molybdenum sheet and emitter molybdenum sheet in the intermediate region are replaced with a second copper-molybdenum alloy layer; Based on the chip location in the external region, the collector molybdenum sheet and emitter molybdenum sheet in the external region are retained as pure molybdenum layers.

4. The method according to claim 3, wherein the copper content of the first copper-molybdenum alloy layer is higher than that of the second copper-molybdenum alloy layer, and the copper content of the second copper-molybdenum alloy layer is higher than that of the pure molybdenum layer.

5. The method according to claim 4, wherein the step of forming a copper content gradient that linearly varies from the inner region to the outer region comprises: Based on the copper-molybdenum alloy layers in the inner, middle, and outer regions, the copper content is set as a linear gradient decreasing from the inner region to the outer region.

6. The method according to claim 1, wherein the step of establishing a pressure-equalizing and heat-equalizing structure includes: Based on the copper content gradient, a multi-layer structure of the press-fit power module is constructed. The multi-layer structure sequentially includes a collector boss, a collector molybdenum sheet, a first nano-sintered layer, a chip, a second nano-sintered layer, an emitter molybdenum sheet, and an emitter boss.

7. The method according to claim 6, wherein the chip is an IGBT chip or a MOSFET chip, and the chip is connected to the copper-molybdenum alloy layer through a nano-sintered material.

8. The method according to claim 6, further comprising: Based on the aforementioned pressure-equalizing and heat-equalizing structure, a finite element simulation model is established; Based on the finite element simulation model, the chip temperature distribution path and stress distribution path are extracted; The temperature and stress uniformity of the press-fit power module are evaluated based on the temperature and stress distribution paths described.

9. The method according to claim 8, wherein the step of extracting the chip temperature distribution path and stress distribution path includes: The chip temperature distribution is obtained based on the steady-state thermal analysis module in the finite element simulation model. The temperature distribution results are inherited into the static structural analysis module of the finite element simulation model to obtain the chip stress distribution.

10. The method according to claim 8, wherein the temperature distribution path and the stress distribution path are respectively arranged along the chip edge to the center symmetrical plane of the press-fit power module, and the number of paths is three, corresponding to the first row of chips, the second row of chips and the third row of chips of the press-fit power module respectively.

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