A compression IGBT module based on phase change material

Abstract

The application provides a crimping IGBT module based on a phase change material, which comprises, from top to bottom, a collector copper plate, a collector molybdenum sheet, an IGBT chip, an emitter molybdenum sheet, a silver gasket, a gate probe, a PEEK support, a gate PCB plate, a boss and an emitter copper plate; a plurality of grooves are formed on one side of the collector molybdenum sheet close to the collector copper plate, each groove is filled with a phase change material, and an inner wall of each groove in contact with the phase change material is coated with a graphene layer. The application forms a plurality of grooves on the collector molybdenum sheet for filling the phase change material and coats the inner wall of the groove with the graphene layer, so that the IGBT module has high transient thermal capacity properties, the heat transfer performance of the power chip is strengthened, the response speed of the phase change material is extremely short, and the reliability of the crimping IGBT module is improved and the service life thereof is prolonged.

Description

Technical Field

[0001] This invention relates to the field of electronic device technology, and in particular to a press-fit IGBT module based on phase change material. Background Technology

[0002] With the rapid development of renewable energy, press-fit modules are widely used in rail transit, new energy power generation, electric vehicles and other fields. In their respective application scenarios, the power of the system is constantly changing. For example, the acceleration and deceleration of electric vehicles, the starting and braking of rail and subway systems, and the power fluctuations of new energy power generation systems will cause fluctuations in the junction temperature inside the power module.

[0003] The press-fit IGBT module consists of multiple parallel sub-modules. Due to manufacturing process, circuit parasitic parameters and thermal coupling issues, there is uneven pressure and temperature distribution inside the device. Under the effect of electrothermal coupling, there is uneven current distribution between chips. At the same time, the redistribution of current further affects the temperature distribution, resulting in excessive stress in local positions inside the device and reducing device reliability.

[0004] In electronic systems, chips generate heat loss. This heat is transferred to the ceramic casing through molybdenum plates, copper pillars, copper sheets, and copper plates. This heat is dissipated through active or passive cooling. Typically, the junction temperature of the chips within the module does not exceed the maximum allowable temperature (150°C for silicon devices, and 125°C for continuous operation). In electrical systems, system power is generally constantly changing, such as the acceleration and deceleration of electric vehicles, the start-up and shutdown of rail transit, and changes in wind speed in wind power generation systems. This manifests as junction temperature fluctuations within the power module.

[0005] Traditional press-fit IGBT modules consist of multiple layers of components, from top to bottom: collector copper plate, collector molybdenum sheet, IGBT chip, emitter molybdenum sheet, silver pad, gate probe, PEEK bracket, gate PCB board, boss, and emitter copper plate. Each layer is fixed in position by the PEEK bracket, and external pressure creates a stable connection between them. When the chip temperature fluctuates, stress arises between the components due to their different coefficients of thermal expansion, thus affecting the reliability of the press-fit IGBT module.

[0006] To reduce junction temperature fluctuations in press-fit IGBTs and improve power module lifespan, existing technologies typically combine phase change materials (PCMs) with heat sinks. A certain proportion of PCM is filled between the fins of a traditional heat sink to reduce junction temperature fluctuations in applications with high impulse power and low duty cycle. However, the excessively long temperature response time limits the cooling effect of the PCMs. Therefore, existing technologies cannot quickly and effectively reduce junction temperature fluctuations in power modules, resulting in low reliability of press-fit IGBT modules. Summary of the Invention

[0007] The present invention aims to provide a press-fit IGBT module based on phase change material to solve the above-mentioned technical problems, thereby improving the reliability of the press-fit IGBT module.

[0008] To address the aforementioned technical problems, this invention provides a press-fit IGBT module based on phase change material, comprising, from top to bottom, a collector copper plate, a collector molybdenum sheet, an IGBT chip, an emitter molybdenum sheet, a silver pad, a gate probe, a PEEK bracket, a gate PCB board, a boss, and an emitter copper plate.

[0009] The current collector molybdenum sheet has multiple grooves on the side near the current collector copper plate. Each groove is filled with a phase change material, and the inner wall of each groove in contact with the phase change material is coated with a graphene layer.

[0010] Furthermore, the plurality of grooves are uniformly formed on the side of the molybdenum collector sheet that is close to the copper collector plate, according to a preset arrangement rule.

[0011] Furthermore, the plurality of grooves includes a central groove located in the central region of the current collector molybdenum sheet, and at least four edge grooves evenly distributed around the central groove.

[0012] Furthermore, the geometric center of the central region coincides with the geometric center of the current collector molybdenum sheet.

[0013] Furthermore, a channel for the phase change material to flow is formed between adjacent edge grooves.

[0014] Furthermore, the melting point of the phase change material filled in the central groove is higher than that of the phase change material filled in the edge groove.

[0015] Furthermore, the number of edge grooves is eight.

[0016] Furthermore, the central groove and the eight edge grooves are evenly arranged in a three-row, three-column pattern on the side of the molybdenum collector sheet that is close to the copper collector plate.

[0017] Furthermore, the current collector molybdenum sheet extends with at least two branches in each of the grooves, and the at least two branches in the same groove are not connected to each other.

[0018] Furthermore, each of the grooves is elliptical in shape.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By creating multiple grooves on the molybdenum collector plate to fill with phase change material and coating the inner wall of the grooves with a graphene layer, the IGBT module has high transient heat capacity properties, which enhances the heat transfer performance of the power chip. This results in an extremely short response speed of the phase change material, improving the reliability of the press-fit IGBT module and increasing its service life. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the molybdenum collector sheet structure of the press-fit IGBT module based on phase change material provided by the present invention;

[0022] Figure 2 This is a side view of the relative positions of the molybdenum sheet and the collector copper sheet of the press-fit IGBT module based on phase change material provided by the present invention;

[0023] Figure 3 This is a schematic diagram of the manufacturing process of the press-fit IGBT module based on phase change material provided by the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that research indicates the lifespan of a power module is related to its average temperature and junction temperature fluctuations, a relationship that can be represented by the Coffin-Manson-Arrhenius power module lifespan model. This model shows that, under the same junction temperature fluctuation, a 20°C decrease in average temperature increases the number of failure cycles by 2-5 times; while at the same average temperature, a 20°C decrease in junction temperature fluctuation can increase the number of failure cycles by 5-10 times. The impact of junction temperature fluctuation on the number of failure cycles is greater than that of average temperature. Therefore, reducing junction temperature fluctuations in power modules is crucial for improving module reliability in applications with frequent power fluctuations.

[0026] Phase change materials (PCMs) are materials that change their state of matter while maintaining a constant temperature. The material's temperature remains almost constant until the phase change is complete, at which point the PCM absorbs or releases a large amount of latent heat. The phenomenon of a PCM's crystal structure transforming from one state to another during a temperature rise or fall is called a phase change, and the temperature at which the phase change begins is called the phase change temperature (Tpcm).

[0027] Because phase change materials absorb heat while maintaining a constant temperature during phase change, this process can be equated to the infinite heat capacity of the phase change material. If this is introduced into the field of power modules, it will bring beneficial changes. It can not only control the rise in junction temperature during normal operation of power modules and simplify heat sink design, but also enable optimized modules to have a certain degree of short-term overload capacity.

[0028] In electronic systems, system power is generally constantly changing. Press-fit IGBT modules are made of stacked different materials. When they operate in a system with constantly changing power for a long time, high junction temperature fluctuations will occur inside the module. Due to the different coefficients of thermal expansion (CTE) of each layer of material, thermal stress will be generated between adjacent layers. Under long-term thermal stress, many reliability problems may occur.

[0029] To reduce junction temperature fluctuations in press-fit IGBTs and improve power module lifespan, researchers have combined phase change materials (PCMs) with heat sinks. Filling the space between the fins of traditional heat sinks with a certain proportion of PCM reduces junction temperature fluctuations in applications with high impulse power and low duty cycle. However, the excessively long temperature response time limits the cooling effect of the PCMs to some extent. One researcher proposed a novel module structure that fills a molybdenum sheet with PCM, utilizing the latent heat absorption property of PCMs during phase change. While this has some effect on reducing junction temperature fluctuations, the long response time of the PCMs in the molybdenum sheet of this structure increases the junction thermal resistance of the module, preventing the full utilization of the PCM's capabilities.

[0030] Current research results are not ideal in improving junction temperature fluctuations, failing to achieve an effective combination of temperature response speed, junction temperature fluctuation timescale, and junction temperature suppression amplitude. Therefore, this invention focuses on the structure of a molybdenum sheet, aiming to enhance its heat transfer capacity. A molybdenum sheet with a special structure was designed and fabricated, and the layout of the phase change material was optimized to more quickly and effectively reduce junction temperature fluctuations in power modules and improve their lifespan.

[0031] The purpose of this invention is to fundamentally reduce the junction temperature fluctuation of press-fit IGBT modules under conditions of large power fluctuations, thereby reducing the probability of module failure, improving module reliability, and extending module lifespan for better application in practical situations. Addressing the common drawbacks of traditional phase change material (PCM) filling methods, such as uneven heating of the integrally slotted PCM, slow response time, and increased thermal resistance, this invention proposes a highly integrated press-fit IGBT module based on PCM. This module integrates a thermally conductive molybdenum sheet structure and a high-thermal-conductivity PCM, enabling it to respond to power fluctuations. When power increases, it can quickly respond to suppress excessively rapid junction temperature increases; when power decreases, it can effectively suppress excessively rapid junction temperature decreases, thus effectively reducing junction temperature fluctuations in the power module.

[0032] Please see Figure 1 This invention provides a press-fit IGBT module based on phase change material, comprising, from top to bottom, a collector copper plate, a collector molybdenum sheet, an IGBT chip, an emitter molybdenum sheet, a silver pad, a gate probe, a PEEK bracket, a gate PCB board, a boss, and an emitter copper plate.

[0033] The current collector molybdenum sheet has multiple grooves on the side near the current collector copper plate. Each groove is filled with a phase change material, and the inner wall of each groove in contact with the phase change material is coated with a graphene layer.

[0034] It should be noted that all the grooves are of the same shape to improve the reliability of heat dissipation. By coating one or more layers of graphene, the phase change material can have a good dynamic response to the temperature of the semiconductor chip, thereby reducing the internal temperature difference of the phase change material and improving its sensitivity.

[0035] In this embodiment of the invention, the plurality of grooves are further formed uniformly on the side of the molybdenum collector sheet near the copper collector plate according to a preset arrangement rule.

[0036] It should be noted that, in order to improve heat dissipation performance, multiple grooves need to be evenly opened on one side of the molybdenum sheet. The preset arrangement rule can be a horizontal and vertical alignment, or a vertical alignment and horizontal staggered arrangement, so that the molybdenum sheet can transfer heat evenly.

[0037] In this embodiment of the invention, the plurality of grooves further includes a central groove located in the central region of the current collector molybdenum sheet, and at least four edge grooves uniformly arranged around the central groove.

[0038] In this embodiment of the invention, the geometric center of the central region coincides with the geometric center of the current collector molybdenum sheet.

[0039] In this embodiment of the invention, a channel for the phase change material to flow is further provided between adjacent edge grooves.

[0040] In this embodiment of the invention, the melting point of the phase change material filled in the central groove is higher than that of the phase change material filled in the edge groove.

[0041] It should be noted that the grooves on the molybdenum sheet are divided into grooves in the middle area and grooves in the remaining areas. Since the temperature in the middle of the chip is high and the temperature around the edges is low, the grooves in the middle area can be used to fill high-melting-point phase change materials, while the grooves around the edges can be used to fill low-melting-point phase change materials (generally, a melting point above 108℃ is considered a high melting point, and a melting point below 80℃ is considered a low melting point).

[0042] In this embodiment of the invention, the number of edge grooves is further eight.

[0043] In this embodiment of the invention, the central groove and the eight edge grooves are evenly arranged in a three-row, three-column pattern on the side of the molybdenum collector sheet that is close to the copper collector plate.

[0044] In a further embodiment of the present invention, the current collector molybdenum sheet extends with at least two branches in each of the grooves, and the at least two branches in the same groove are not connected to each other.

[0045] It should be noted that the extended branches are used to increase the contact area between the molybdenum sheet and the phase change material, which is beneficial to improving heat transfer performance.

[0046] In this embodiment of the invention, each of the grooves is further elliptical in shape.

[0047] It should be noted that, unlike slotted structures such as rectangles, rhombuses, and triangles, elliptical shapes do not have sharp corners, which facilitates the flow of phase change material within the slot, resulting in more uniform heat transfer of the molybdenum sheet.

[0048] To better illustrate the press-fit IGBT module based on phase change material provided in the embodiments of the present invention, the following specific examples are provided in detail:

[0049] In this embodiment of the invention, a suitable phase change material is selected so that its phase change temperature (Tpc) can effectively reduce the junction temperature fluctuation of the press-fit IGBT module under conditions of large power fluctuations. When the system power increases, the rising temperature causes the phase change material to melt and absorb heat, inhibiting the rapid increase of junction temperature; when the system power decreases, the decreasing temperature causes the phase change material to change from liquid to solid again and release heat, inhibiting the sharp drop in junction temperature. By controlling the temperature variation range of the chip as small as possible, the temperature fluctuation ΔT of the highly integrated press-fit IGBT module based on the phase change material can be reduced, thereby extending its lifespan.

[0050] When a semiconductor chip heats up, its internal temperature distribution is uneven, with higher temperatures in the center and lower temperatures around the edges. Therefore, selecting different phase change materials (PCMs) for different parts of the chip can more effectively suppress junction temperature fluctuations in press-fit IGBT modules. The heat transfer process within the PCM is transient, with a temperature difference existing within the PCM at every moment. Traditional techniques involve creating a square groove above a molybdenum sheet to fill with the PCM, but the inner wall lacks any conductive material. This results in a long response time for the PCM, increasing the module's thermal resistance and hindering the efficient utilization of the PCM. Rectangular, rhomboid, and triangular groove structures, due to their sharp corners, impede the flow of the PCM within the groove, leading to uneven heating. Elliptical groove structures effectively solve these problems.

[0051] It is understandable that adding a layer of graphene, a material with excellent thermal conductivity, between the molybdenum sheet and the phase change material in the temperature control device allows the phase change material to have a good dynamic response to the temperature of the semiconductor chip, thereby reducing the internal temperature difference of the phase change material and improving its sensitivity. Graphene is a two-dimensional material with a single atomic layer thickness, and its thermal conductivity can reach up to 5300 W / m². -1 K -1 Its thermal conductivity is higher than that of bulk graphite and diamond, making it the highest known material in terms of thermal conductivity. Furthermore, the thermal conductivity of graphene decreases with increasing graphene layer thickness, while its heat flux increases with rising ambient temperature. Therefore, simply adding a single layer of graphene between the added phase change material and the molybdenum sheet is sufficient to achieve both temperature uniformity and heat conduction.

[0052] The molybdenum sheet with an elliptical groove structure in this embodiment of the invention is as follows: Figure 1 As shown, the molybdenum sheet has a hollow internal structure, divided into several elliptical regions. These regions are interconnected to reduce the number of times the phase change material is filled (the groove in the central region and the surrounding grooves are independent of each other). To enhance heat transfer, branches extend from each elliptical region to increase the contact area between the molybdenum sheet frame and the phase change material. The branches are not connected to each other to reduce the number of times the phase change material is filled. Furthermore, the inner walls of each partition are coated with graphene material to enhance heat transfer.

[0053] The fabrication flowchart of a highly integrated press-fit IGBT module based on phase change materials is as follows: Figure 3 As shown. First, an elliptical slotted molybdenum sheet is fabricated, as shown. Figure 1 As shown in the diagram. Then, the phase change material is injected into each set of phase change tanks at high temperature. After the phase change material cools, the collector copper plate, collector molybdenum sheet, IGBT chip, emitter molybdenum sheet, silver pad, gate probe PEEK bracket, gate PCB board, boss, and emitter copper plate are fixed from top to bottom using a PEEK bracket. The collector copper plate, located above the molybdenum sheet, also serves as a top cover for the molybdenum sheet. A side view of the relative positions of the molybdenum sheet and the collector copper plate is shown in the diagram. Figure 2 As shown. Then, external pressure is used to form a stable connection between the components, and then the electrodes are brought out, thus completing the fabrication.

[0054] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0055] Traditional techniques involve creating a square groove on top of a molybdenum sheet to fill it with phase change material (PCM). However, the inner wall lacks any good thermal conductivity material, resulting in a long PCM response time, which increases the module's thermal resistance and hinders the effective utilization of the PCM. Addressing these drawbacks, this invention provides a highly integrated press-fit IGBT module based on PCM. This module structure features high transient thermal capacity, enhanced heat transfer from the power chip, and extremely short PCM response times, thereby improving system stability and extending the lifespan of the press-fit IGBT module.

[0056] It should be noted that the press-fit IGBT module based on phase change material provided in this embodiment of the invention has the following characteristics:

[0057] 1. Molybdenum sheets have a grooved cavity structure, which is divided into two types of areas to be filled with different phase change materials. The central area is filled with high-melting-point phase change material, and the remaining areas are filled with low-melting-point phase change material (generally, a melting point above 108℃ is considered a high melting point, and a melting point below 80℃ is considered a low melting point).

[0058] 2. The internal structure is an elliptical structure;

[0059] 3. Each group is interconnected through channels to reduce the number of phase change material injections;

[0060] 4. The elliptical structure extends into branches, increasing its contact area with the phase change material, resulting in faster heat transfer and a faster response time for the phase change material.

[0061] 5. Branches are not interconnected to avoid structural segmentation, thereby reducing the number of phase change material injections;

[0062] 6. The inner walls of the partitions in each area are coated with single or multiple layers of graphene material to enhance heat transfer.

[0063] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A press-fit IGBT module based on phase change material, characterized in that, It includes, from top to bottom, a collector copper plate, a collector molybdenum sheet, an IGBT chip, an emitter molybdenum sheet, a silver pad, a gate probe, a PEEK bracket, a gate PCB board, a boss, and an emitter copper plate. The current collector molybdenum sheet has multiple grooves on the side near the current collector copper plate. Each groove is filled with a phase change material, and the inner wall of each groove in contact with the phase change material is coated with a graphene layer. The current collector molybdenum sheet extends with at least two branches within each groove, and the at least two branches within the same groove are not connected to each other; each groove is elliptical; the plurality of grooves are uniformly arranged on the side of the current collector molybdenum sheet near the current collector copper plate according to a preset arrangement rule; the plurality of grooves include a central groove located in the central region of the current collector molybdenum sheet, and at least four edge grooves uniformly arranged around the central groove; the geometric center of the central region coincides with the geometric center of the current collector molybdenum sheet; a channel for the phase change material to flow is formed between adjacent edge grooves; the melting point of the phase change material filled in the central groove is higher than the melting point of the phase change material filled in the edge grooves.

2. The press-fit IGBT module based on phase change material according to claim 1, characterized in that, The number of edge grooves is eight.

3. The press-fit IGBT module based on phase change material according to claim 2, characterized in that, The central groove and the eight edge grooves are evenly arranged in a three-row, three-column pattern on the side of the molybdenum collector sheet closest to the copper collector plate.

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