Power device and sintering method therefor

Abstract

The present application provides a power device and a sintering method therefor. The sintering method comprises: providing a heat dissipation substrate, the heat dissipation substrate having a sintering surface; printing a sintering material layer on the sintering surface of the heat dissipation substrate; performing drying of the heat dissipation substrate printed with the sintering material layer; attaching a power module onto the heat dissipation substrate having the dried sintering material layer, the power module being in contact with the sintering material; and performing pressure sintering on the heat dissipation substrate having the power module attached, so as to complete connection between the power module and the heat dissipation substrate. By means of performing drying processing on the sintering material layer and then pressure sintering, large-area reliable interconnection between the power module and the heat dissipation substrate can be achieved. Additionally, it can be ensured that the thickness of the connecting layer is controllable, without defects such as delamination, overflowing, cracking, air holes and air channels, and high heat conductivity and high long-term working temperature can be achieved.

Description

Power device and sintering method thereof Technical Field

[0001] The present application relates to the technical field of power device preparation, and in particular to a power device and a sintering method thereof. Background Art

[0002] To maximize the performance and reliability of silicon carbide power devices, interconnects within power modules have gradually evolved from soldering to sintering. In contrast, the connection between the power module and the heat sink substrate involves system-level connections, affecting not only the external connections themselves but also the completed connections within the power module. Therefore, it is subject to more constraints and presents greater challenges.

[0003] Currently, the connection between the power module and the heat dissipation substrate is limited to an area less than 500mm 2 In most cases, traditional soldering processes are still used. For large-area soldering, solder melts at high temperatures, causing fluidity and making it difficult to accurately control the thickness. This leads to numerous drawbacks, including difficulty controlling the thickness of the solder layer, the creation of numerous solder voids, solder overflow, tin bead splashing leading to insulation problems, low thermal conductivity of the connection layer, and long-term low operating temperatures. These drawbacks significantly limit the performance of silicon carbide power modules.

[0004] In contrast, if large-area connections are made using a sintering process, the goals of controllable connection layer thickness, void-free and overflow-free connection, high thermal conductivity, and high long-term operating temperature can be achieved. However, compared to small-area sintering, such as chip sintering and copper clip sintering, large-area sintering must overcome various difficulties, such as warping of the power module and heat sink substrate, large heat capacity, uneven thermal conductivity, and a narrow process window (such as temperature and pressure) for the module's internal component structures (such as chips, bonding wires, and molding compounds). Therefore, a reliable method for large-area sintering is urgently needed.

[0005] Summary of the Invention

[0006] In view of the above-mentioned problems in the prior art, the purpose of the present application is to provide a power device and a sintering method thereof, which can achieve reliable connection between a large-area power module and a heat dissipation substrate.

[0007] To achieve the above-mentioned and other related purposes, the present application provides a power device sintering method, comprising:

[0008] providing a heat dissipation substrate having a sintering surface;

[0009] printing a sintering material layer on the sintering surface of the heat dissipation substrate;

[0010] drying the heat dissipation substrate printed with the sintered material layer;

[0011] Mounting a power module on the heat dissipation substrate with the dried sintered material layer, wherein the power module is in contact with the sintered material;

[0012] The heat dissipation substrate with the power module mounted thereon is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate.

[0013] In an optional embodiment of the present application, the area of ​​the sintering surface is larger than the printing area of ​​the sintering material layer.

[0014] In an optional embodiment of the present application, the heat dissipation substrate is a copper heat dissipation substrate or an aluminum heat dissipation substrate.

[0015] In an optional embodiment of the present application, a plating layer is formed on the sintering surface of the heat dissipation substrate, and the plating layer is a silver plating layer, a nickel plating layer, a copper plating layer or a titanium plating layer.

[0016] In an optional embodiment of the present application, in the step of printing the sintering material layer on the sintering surface of the heat dissipation substrate, the printing thickness is between 30 μm and 800 μm.

[0017] In an optional embodiment of the present application, in the step of drying the heat dissipation substrate printed with the sintering material layer, the drying temperature is between 90 degrees Celsius and 170 degrees Celsius, and the drying time is 20 minutes to 100 minutes.

[0018] In an optional embodiment of the present application, the heat dissipation substrate with the power module mounted thereon is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate, including:

[0019] Preheating the heat dissipation substrate on which the power module is mounted;

[0020] The heat dissipation substrate with the power module mounted thereon after preheating is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate.

[0021] In an optional embodiment of the present application, the parameters of the preheating process include: a preheating temperature between 80 degrees Celsius and 170 degrees Celsius, and a preheating time between 3 minutes and 30 minutes;

[0022] The sintering parameters include: sintering temperature between 180 degrees Celsius and 260 degrees Celsius, sintering time between 5 minutes and 20 minutes, and sintering pressure between 6 MPa and 25 MPa.

[0023] In an optional embodiment of the present application, in the step of pressurizing and sintering the heat dissipation substrate with the power module mounted thereon to complete the connection between the power module and the heat dissipation substrate, a target sintering pressure is achieved by gradually increasing the pressure.

[0024] In an optional embodiment of the present application, the power module includes a ceramic substrate and a plurality of chips disposed on an inner metal layer of the ceramic substrate;

[0025] Printing a sintering material layer on the sintering surface of the heat dissipation substrate comprises:

[0026] According to the position of the chip in the power module, the sintering material is printed in a partitioned manner on the sintering surface of the heat dissipation substrate to form a sintering material layer including multiple independent partitions on the sintering surface of the heat dissipation substrate, wherein the position of each independent partition corresponds to the position of at least one chip of the power module.

[0027] In an optional embodiment of the present application, the boundary of each of the independent partitions avoids the internal etching groove on the internal metal layer of the ceramic substrate.

[0028] To achieve the above-mentioned purpose and other related purposes, the present application also provides a power device sintered using the above-mentioned method.

[0029] The power device sintering method of the present application comprises providing a heat dissipation substrate having a sintering surface; printing a sintering material layer on the sintering surface of the heat dissipation substrate; drying the heat dissipation substrate with the printed sintering material layer; mounting a power module on the heat dissipation substrate with the dried sintering material layer, wherein the power module is in contact with the sintering material; and pressurizing and sintering the heat dissipation substrate with the power module mounted thereon to complete the connection between the power module and the heat dissipation substrate. Before sintering, the sintering material layer coated on the sintering surface of the heat dissipation substrate is dried first, so that the organic solvent in the sintering material layer evaporates, so that the sintering material layer maintains a certain shape, and prevents the sintering material from overflowing, breaking, and other damage during the mounting process. It can also prevent the solvent from not evaporating easily in the subsequent sintering process, causing voids, airways, etc., which affect the heat dissipation performance of the connection layer. Pressure sintering is used during sintering, which can not only enhance the density of the sintered material layer after sintering and the connection strength between the heat dissipation substrate and the power module, but also prevent the heat dissipation substrate and the high-power module from warping during the sintering process, so that the sintering method of the present application can be applied to large-area reliable interconnection between the power module and the heat dissipation substrate.

[0030] The power device sintering method of the present application adopts a partitioned printing method when printing the sintering material layer on the sintering surface of the heat dissipation substrate to form a sintering material layer including multiple independent partitions on the sintering surface of the heat dissipation substrate. This not only saves the amount of sintering material and reduces the cost of large-area sintering, but also the intervals between the independent partitions can serve as volatilization channels for the solvent during the drying and sintering process, thereby reducing or avoiding the formation of holes and air channels in the sintering material layer during drying and sintering, and improving the heat dissipation performance of the connecting layer after sintering.

[0031] The power device sintering method of the present application adopts a partitioned printing method when printing a sintered material layer on the sintering surface of the heat dissipation substrate, so that when a sintered material layer including multiple independent partitions is formed on the sintering surface of the heat dissipation substrate, the boundary of each independent partition avoids the internal etched groove on the internal metal layer of the ceramic substrate, thereby preventing the stress concentration phenomenon in the overlapping area of ​​the ceramic substrate caused by the overlap of the connecting material layer and the etched groove on the internal metal layer of the ceramic substrate, thereby causing the ceramic in the ceramic substrate to crack and cause insulation failure.

[0032] In the power device sintering method of the present application, since one heat dissipation substrate can be connected to multiple power modules at the same time, sintering material layers corresponding to multiple power modules can be printed on the heat dissipation substrate at the same time, and the printing efficiency is high.

[0033] In the power device sintering method of the present application, the printing process on the heat dissipation substrate can be carried out simultaneously with the power module packaging process without any front-end or back-end relationship, which can save the production time of the assembly product, that is, the power device.

[0034] Compared with the power module after plastic encapsulation, which contains multiple sub-components such as chips and plastic encapsulation materials, the power device sintering method of the present application has a simple heat dissipation substrate structure and low unit cost. Therefore, the sintering material layer is printed on the heat dissipation substrate, and the scrapping cost is lower.

[0035] The power device sintering method of the present application prints a sintering material layer on a heat dissipation substrate, which is not affected by the complex shape of the injection-molded power module, and the printing jig of the heat dissipation substrate can be simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a flow chart of a power device sintering method according to an embodiment of the present application.

[0037] FIG. 2 a is a schematic diagram of a heat dissipation substrate provided in an embodiment of the present application.

[0038] FIG. 2 b is a schematic diagram of printing a sintering material layer on the sintering surface of the heat dissipation substrate in one embodiment of the present application.

[0039] FIG2 c is a schematic diagram of drying the heat dissipation substrate printed with the sintering material layer in one embodiment of the present application.

[0040] FIG2 d is a schematic diagram of mounting a power module on the dried sintered material layer in one embodiment of the present application.

[0041] FIG2e is a schematic diagram of pressurizing and sintering the heat dissipation substrate with the power module mounted thereon in one embodiment of the present application.

[0042] FIG3 is a schematic diagram of the structure of a power device in an embodiment of the present application.

[0043] FIG4 is a schematic diagram of printing sintering material on the sintering surface of the heat dissipation substrate in a zoned manner in one embodiment of the present application.

[0044] FIG5 is a schematic diagram of printing sintering material on the sintering surface of the heat dissipation substrate in a zoned manner in another embodiment of the present application.

[0045] FIG6 is a schematic diagram of printing sintering material on the sintering surface of the heat dissipation substrate in a zoned manner in another embodiment of the present application.

[0046] FIG7 a is a schematic diagram of the printing area.

[0047] FIG7 b is an actual post-sintering image of the printed area of ​​the sintered power device obtained by analyzing the printed area using an ultrasonic scanning microscope. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present application through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0049] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. Therefore, the illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0050] As shown in Figures 1-2, this application proposes a reliable power device sintering method. This sintering method can achieve large-area reliable interconnection between the power module and the heat dissipation substrate, ensuring a controllable thickness of the connection layer without defects such as delamination, overflow, cracking, pores, and air channels, and has high thermal conductivity and a high long-term operating temperature.

[0051] The heat dissipation substrate 10 is a substrate capable of dissipating heat that can directly contact the cooling liquid. The heat dissipation substrate 10 can be made of, for example, copper or aluminum. This means the heat dissipation substrate 10 can be a copper or aluminum heat dissipation substrate. The heat dissipation substrate 10 can be, for example, a liquid-cooled heat sink to dissipate heat from the power module 30. The liquid-cooled heat sink can be a liquid-cooled heat sink with flaps or a liquid-cooled heat sink with spoilers.

[0052] The power module 30 is an injection-molded power module 30, which has parts and connections inside to achieve certain functions, including but not limited to silicon-based chips, silicon carbide-based chips, diodes, bonding wires, copper bridges, lead frames, ceramic substrates, sensors, plastic packaging materials, gaskets and other parts and their combinations.

[0053] Among them, the ceramic substrate can be an AMB (Active Metal Brazing) substrate or a DBC (Direct Bonding Copper) substrate. Taking the copper-clad ceramic substrate as an example, it is a ceramic substrate with a copper metal layer formed on both sides, wherein the copper metal layer located inside the power module 30 is used to connect with the chip, and a circuit is etched thereon, and the copper metal layer located outside the power module 30 is used to connect with the heat dissipation substrate 10 for heat dissipation. Figure 1 shows a process flow chart of the power device sintering method of the present application, including steps S110-S150, and Figures 2a-2e provide schematic diagrams of each step. The entire sintering process will be described in detail below in conjunction with Figures 1 and 2a-2e.

[0054] In step S110 , as shown in FIG. 2 a , a heat dissipation substrate 10 is provided. The heat dissipation substrate 10 has a sintering surface 101 .

[0055] The heat dissipation substrate 10 has a sintering surface 101, which refers to the surface in direct contact with the sintering material. The sintering surface 101 can be a bare copper surface, a silver-plated surface, a nickel-plated surface, a titanium-plated surface, or a surface plated with a combination of copper, silver, nickel, aluminum, titanium, etc.

[0056] In order to improve the oxidation resistance, corrosion resistance and sintering processability of the substrate, a coating is formed on the sintering surface 101 of the heat dissipation substrate 10. The coating can be a copper-plated surface, a silver-plated layer, a nickel-plated layer or a composite coating. The coating can be implemented by chemical plating, electroplating, physical vapor deposition, etc., which is not limited here.

[0057] Taking the silver plating layer as an example, due to the chemical stability and high oxidation temperature of silver, a silver plating layer is formed on the copper-clad ceramic substrate of the power module 30 and / or on the sintering surface 101 of the heat dissipation substrate 10. During the subsequent sintering process, the silver plating layer can, on the one hand, promote the diffusion connection between the sintered material and the interface, further enhancing the interface connection strength; on the other hand, the silver plating layer can also hinder the oxidation of the copper substrate during the subsequent sintering process and during the high-temperature service of the power device, further ensuring the interface connection strength and preventing the product from interfacial oxidation during the sintering process and high-temperature service. In addition, by silver-plating the copper-clad ceramic substrate on the back of the power module 30, after sintering, the reliability between the heat dissipation substrate 10 and the power module 30 can be further improved.

[0058] As an example, the thickness of the coating is between 0.05μm and 20μm, such as 0.05μm, 0.1μm, 0.3μm, 0.5μm, 0.7μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 6μm, 9μm, 12μm, 15μm, 18μm, 20μm, etc.

[0059] In step S120 , a sintering material layer 20 is printed on the sintering surface 101 of the heat dissipation substrate 10 .

[0060] When printing the sintered material layer 20 on the sintered surface 101 of the heat dissipation substrate 10, if there are contaminants and / or oxides on the sintered surface 101, it is necessary to first perform a pretreatment process such as cleaning and drying on the sintered surface 101 of the heat dissipation substrate 10 to remove the contaminants and / or oxides on its surface, thereby improving the adhesion between the sintered material and the sintered surface 101, increasing the connection strength between the sintered material and the sintered surface 101, and increasing the reliability of the power device.

[0061] As shown in FIG2b , after pre-treating the sintering surface 101 of the heat dissipation substrate 10, a sintering material can be printed on the sintering surface 101 of the heat dissipation substrate 10 by stencil printing or dispensing to form a sintering material layer 20 (serving as a connecting layer). The sintering material can be, for example, a sintering silver paste, a sintering copper paste, or a sintering silver film. Sintering silver paste or sintering copper paste is a mixture of metal particles and an organic solvent, while a sintering silver film is a pre-formed film of sintering silver material.

[0062] During the printing process, the printing thickness and printing area should be reasonably selected according to actual needs. Among them, the printing thickness, that is, the thickness of the sintered material layer 20, should be reasonably selected according to actual needs. It should not be too thick or too thin. If the thickness is too thin, it is easy to break and delaminate, making it difficult to form an effective connection; if the thickness is too thick, it is difficult to control the thickness of the final connection layer, it is difficult to control the amount of solvent volatilization, and increase thermal resistance. As an example, the printing thickness is between 30μm and 800μm, such as 30μm, 60μm, 90μm, 120μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, and 800μm.

[0063] The printing area depends on the connection area between the power module 30 and the heat dissipation substrate 10. For example, for a large area sintering process, the printing area is between 500 mm 2 -2500mm 2 , for example 500mm 2 , 600mm 2 , 700mm 2 , 800mm 2 , 900mm 2 , 1000mm2 , 1500mm 2 , 2000mm 2 , 2500mm 2 .

[0064] Because a single heat sink substrate 10 can be connected to multiple power modules 30 simultaneously, the sintered material layers 20 corresponding to the multiple power modules 30 can be printed simultaneously on the heat sink substrate 10, resulting in high printing efficiency. Furthermore, the printing process on the heat sink substrate 10 can be performed simultaneously with the packaging process of the power modules 30, eliminating the need for a front-end or back-end process. This reduces production time for the assembled product, specifically the power device.

[0065] The current power module 30 is becoming more and more integrated, and more and more chips are used inside, resulting in the area of ​​the copper-clad ceramic substrate becoming larger and larger, that is, the area of ​​the connection between the power module 30 and the heat dissipation substrate 10 becomes larger. For the connection between the power module 30 and the heat dissipation substrate 10, the use of a sintering solution can improve the thermal conductivity and connection strength of the connection layer, and more effectively exert the performance of the chip in the power module 30. Since the sintering silver paste and sintering copper paste used for sintering are basically close to or even higher than the price of precious metals, the cost is relatively high. For the power module 30, the effective heat dissipation path is mainly concentrated directly below the chip, and the area away from the chip contributes less to the heat dissipation. Therefore, for large-area sintering such as the present application, if a printing solution that covers the entire sintering surface 101 is still used, this will not only lead to a huge consumption of sintering materials; but also a large area of ​​silver paste is not conducive to the volatilization of the solvent during the drying or sintering process, and is likely to bring more holes, airways, etc., which affect the heat dissipation performance of the connection layer.

[0066] Based on this, when printing the sintered material layer 20 on the sintering surface 101 of the heat dissipation substrate 10, the sintered material can be printed in a partitioned manner to form a sintered material layer 20 comprising multiple independent partitions on the sintering surface 101 of the heat dissipation substrate 10. The number and shape of the independent partitions can be reasonably designed according to the position of the chips in the power module 30, so that the original entire sintered material layer 20 corresponding to each power module 30 is divided into multiple independent partitions according to the position of the chips in the power module 30, so that the position of each independent partition corresponds to the position of at least one chip in the power module 30. This not only saves the amount of sintered material and reduces the cost of large-area sintering, but also the spacing between the independent partitions can serve as a volatilization channel for the solvent during the drying and sintering process, thereby reducing or avoiding the formation of holes and air channels in the sintered material layer 20 during subsequent drying and sintering, and improving the heat dissipation performance of the connection layer after sintering.

[0067] As an example, as shown in Figure 4, the sintered material is printed in a partitioned manner to form a sintered material layer 20 including two rectangular independent partitions on the sintering surface 101 of the heat dissipation substrate 10; as shown in Figure 5, the sintered material is printed in a partitioned manner to form a sintered material layer 20 including four rectangular independent partitions on the sintering surface 101 of the heat dissipation substrate 10; as shown in Figure 6, the sintered material is printed in a partitioned manner to form a sintered material layer 20 including multiple irregularly shaped independent partitions on the sintering surface 101 of the heat dissipation substrate 10.

[0068] It should be noted that when the sintered material is printed in a partitioned manner to form a sintered material layer 20 including multiple independent partitions on the sintering surface 101 of the heat dissipation substrate 10, the boundaries of each independent partition avoid the internal etched grooves on the internal metal layer of the ceramic substrate as much as possible, thereby preventing the sintered material layer 20 from overlapping with the etched grooves on the internal metal layer of the ceramic substrate, causing stress concentration in the overlapping area of ​​the ceramic substrate, and further causing ceramic cracking in the ceramic substrate to cause insulation failure.

[0069] In step S130 , the heat dissipation substrate 10 printed with the sintering material layer 20 is dried.

[0070] Small area (area less than 500mm 2 During sintering, the power module 30 and the heat dissipation substrate 10 are sintered while the sintering material is wet. If applied to a large area, the large-area power module 30 is relatively heavy, which may cause the sintering material printed on the heat dissipation substrate 10 to collapse, squeeze out, or break, making it impossible to effectively control the thickness of the sintering material layer 20. Therefore, in this embodiment, as shown in FIG2c , before sintering, the heat dissipation substrate 10 printed with the sintering material layer 20 needs to be placed in an oven 40 for drying. The purpose is to volatilize the organic solvent in the sintering material, so that the sintering material layer 20 maintains a certain shape, and prevent the sintering material from overflowing, breaking, or other damage when the power module 30 is mounted on the sintering material layer 20 in step S140. It can also prevent the organic solvent from not evaporating easily during the sintering process in step S150, thereby preventing holes, air channels, etc., which may affect the heat dissipation performance of the connection layer.

[0071] As an example, the drying temperature is between 90 degrees Celsius and 170 degrees Celsius, such as 90 degrees Celsius, 100 degrees Celsius, 110 degrees Celsius, 120 degrees Celsius, 130 degrees Celsius, 140 degrees Celsius, 150 degrees Celsius, 160 degrees Celsius, and 170 degrees Celsius; the drying time is between 20 minutes and 100 minutes, such as 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, and 100 minutes. Of course, the drying temperature and drying time can also be adjusted as long as the drying purpose can be achieved.

[0072] The drying atmosphere needs to be selected based on the material of the sintering surface 101 and the sintering material. Taking the sintering surface 101 as a silver-plated surface, a nickel-plated surface, a copper-plated surface, or a titanium-plated surface, and the sintering material as a sintered silver paste as an example, the drying atmosphere can be vacuum, nitrogen, or air. Taking the sintering surface 101 as a bare copper surface or a sintered copper paste as an example, the drying atmosphere can be vacuum or nitrogen. The oxygen content during the drying process should be less than 100ppm. It can be further limited to less than 30ppm during the drying process. The purpose is to prevent oxidation of the bare copper surface or the copper paste.

[0073] In step S140 , the power module 30 is mounted on the dried sintered material layer 20 .

[0074] As shown in Figure 2d, the heat sink substrate 10 with the dried and sintered silver paste or copper paste is mounted on the power module 30, thereby assembling the heat sink substrate 10, the sintered material, and the power module 30. The surface of the power module 30 in contact with the sintered material layer 20 can be a bare copper surface, or a coating such as copper, silver, nickel, titanium, or a combination thereof. The coating can be achieved by chemical plating, electroplating, physical vapor deposition, etc., without limitation. The mounted product can proceed to step S150 for sintering to form a power device.

[0075] In step S150 , the heat dissipation substrate 10 with the power module 30 mounted thereon is pressurized and sintered to complete the connection between the power module 30 and the heat dissipation substrate 10 , thereby forming a power device as shown in FIG. 3 .

[0076] As shown in FIG2e , the mounted product is placed in a sintering device for sintering, so that the solvent in the sintering material is further volatilized and the metal particles undergo atomic diffusion, and finally the sintering material is mechanically connected to the heat dissipation substrate 10 and the power module 30 at the same time, thereby forming a reliable system connection layer between the heat dissipation substrate 10 and the power module 30.

[0077] The sintering parameters are as follows: the sintering temperature is between 180 degrees Celsius and 260 degrees Celsius, for example, 180 degrees Celsius, 190 degrees Celsius, 200 degrees Celsius, 210 degrees Celsius, 220 degrees Celsius, 230 degrees Celsius, 240 degrees Celsius, 250 degrees Celsius, and 260 degrees Celsius; the sintering time is between 5 minutes and 20 minutes, for example, 5 minutes, 10 minutes, 15 minutes, and 20 minutes; the sintering pressure is between 6 MPa and 25 MPa, for example, 6 MPa, 8 MPa, 10 MPa, 12 MPa, 15 MPa, 20 MPa, and 25 MPa.

[0078] It should be noted that the sintering temperature is crucial during the sintering process. Too high a temperature may damage the components (chips, bonding wires, molding compound, etc.) in the power module 30, while too low a sintering temperature may prevent the sintered materials from forming effective connections.

[0079] It should be noted that when the heat dissipation substrate 10 with the power module 30 mounted thereon is pressurized and sintered to complete the connection between the power module 30 and the heat dissipation substrate 10, a fixed target sintering pressure can be used, or a stepwise pressurization method can be used to reach the target sintering pressure. After the sintering is completed, the sintering pressure can be released by gradually reducing the pressure. The pressurization rate is 0.05MPa / s-1.5MPa / s, for example, 0.05MPa / s, 0.1 MPa / s, 0.3MPa / s, 0.5MPa / s, 0.8MPa / s, 1.0MPa / s, 1.2MPa / s, 1.5MPa / s, and the pressure reduction rate is 0.05MPa / s-1.5MPa / s, such as 0.05MPa / s, 0.1MPa / s, 0.3MPa / s, 0.5MPa / s, 0.8MPa / s, 1.0MPa / s, 1.2MPa / s, 1.5MPa / s. The pressure sintering is adopted during sintering, which can not only enhance the density of the sintered material layer 20 and the connection strength between the heat dissipation substrate 10 and the power module 30 after sintering, but also prevent the heat dissipation substrate 10 and the power module 30 from warping during the sintering process, so that the sintering method of the present application can be applied to large-area reliable interconnection between the power module 30 and the heat dissipation substrate 10.

[0080] During the sintering process, the sintering atmosphere is selected based on the material of the sintering surface 101 and the sintering material. For example, if the sintering surface 101 is silver-plated, nickel-plated, or titanium-plated, and the sintering material is silver paste, the sintering atmosphere can be vacuum, nitrogen, or air. For example, if the sintering surface 101 is bare copper or copper paste, the sintering atmosphere can be vacuum or nitrogen to prevent oxidation of the bare copper surface or copper paste.

[0081] During the cooling process to room temperature after sintering, the cooling atmosphere should also be selected based on the material of the sintering surface 101 and the sintering material. For example, if the sintering surface 101 is silver-plated, nickel-plated, or titanium-plated, and the sintering material is a sintered silver paste, the cooling atmosphere can be nitrogen or air. For example, if the sintering surface 101 is a bare copper surface or a sintered copper paste, the sintering atmosphere can be nitrogen to prevent oxidation of the bare copper surface or the copper paste.

[0082] It should be noted that, in an optional embodiment, in order to improve sintering efficiency and sintering quality, the heat dissipation substrate 10 with the power module 30 mounted thereon may be preheated in a sintering atmosphere before sintering. After the preheating is completed, the heat dissipation substrate 10 with the power module 30 mounted thereon is pressurized and sintered to complete the connection between the power module 30 and the heat dissipation substrate 10. The parameters of the preheating include: a preheating temperature between 80 degrees Celsius and 170 degrees Celsius, such as 80 degrees Celsius, 90 degrees Celsius, 100 degrees Celsius, 110 degrees Celsius, 120 degrees Celsius, 130 degrees Celsius, 140 degrees Celsius, 150 degrees Celsius, 160 degrees Celsius, and 170 degrees Celsius; and a preheating time between 3 minutes and 30 minutes, such as 3 minutes, 6 minutes, 9 minutes, 12 minutes, 15 minutes, 18 minutes, 21 minutes, 24 minutes, 27 minutes, and 30 minutes.

[0083] A specific example of the power device sintering method of the present application is given below.

[0084] Example 1: A nickel-plated heat sink substrate 10 is selected, and its sintered surface 101 is silver-plated with a thickness of 0.1 μm. A printing area of ​​2500 mm is printed on the heat sink substrate 10 by screen printing. 2 The sintered silver paste is printed to a thickness of 600 μm. The paste is then dried in a vacuum oven 40 at 150°C for 80 minutes in an air atmosphere. The power module 30 is mounted on the heat sink substrate 10 with the sintered silver paste and preheated at 150°C for 20 minutes. The heat sink substrate 10 is then sintered at 250°C for 10 minutes at 20 MPa in a vacuum atmosphere, achieving a large-area connection between the heat sink substrate 10 and the power module 30.

[0085] Example 2: A silver-plated heat sink substrate 10 is selected, and its sintered surface 101 is a copper-based silver-plated surface with a coating thickness of 1 μm. A 600 mm-diameter heat sink substrate 10 is formed by applying glue on the heat sink substrate 10. 2 The sintered silver paste is applied to a thickness of 100 μm. The paste is then dried in an oven 40 at 100°C for 20 minutes in an air atmosphere. The power module 30 is mounted on the heat sink substrate 10 with the sintered silver paste. The heat sink substrate 10 is then sintered at 190°C for 5 minutes at 15 MPa in an air atmosphere, achieving a large-area connection between the heat sink substrate 10 and the power module 30.

[0086] Example 3: A nickel-plated heat dissipation substrate 10 is selected, and its sintering surface 101 is a bare copper surface. A stencil printing method is used on the heat dissipation substrate 10 to print a 2000mm 2The sintered copper paste is printed to a thickness of 300 μm. The paste is then dried in an oven 40 at 120°C for 80 minutes in a nitrogen atmosphere. The power module 30 is mounted on the heat sink substrate 10 with the sintered copper paste. The process is then sintered at 260°C for 15 minutes at 8 MPa in a nitrogen atmosphere, achieving a large-area connection between the heat sink substrate 10 and the power module 30.

[0087] Figure 7a is a schematic diagram of the printing area A, and Figure 7b is an image of the actual sintered printing area B obtained by analyzing the power device sintered in the manner of Example 1 using an ultrasonic scanning microscope. As can be seen in Figure 7b, the large-area sintered layer in printed area B is free of defects such as delamination, cracking, and air channels. The thermal conductivity of the large-area sintered connection layer, measured according to ASTM-E1461, reaches 300 W / mK at room temperature, six times that of traditional solder.

[0088] In summary, the power device sintering method of the present application is provided by providing a heat dissipation substrate having a sintering surface; printing a sintering material layer on the sintering surface of the heat dissipation substrate; drying the heat dissipation substrate with the printed sintering material layer; mounting a power module on the heat dissipation substrate with the dried sintering material layer, wherein the power module is in contact with the sintering material; and pressurizing and sintering the heat dissipation substrate with the power module mounted thereon to complete the connection between the power module and the heat dissipation substrate. Before sintering, the sintering material layer coated on the sintering surface of the heat dissipation substrate is dried first, so that the organic solvent in the sintering material layer evaporates, so that the sintering material layer maintains a certain shape, and prevents the sintering material from overflowing, breaking, and other damage during the mounting process. It can also prevent the solvent from not evaporating easily in the subsequent sintering process, causing voids, airways, etc., which affect the heat dissipation performance of the connection layer. Pressure sintering is used during sintering, which can not only enhance the density of the sintered material layer after sintering and the connection strength between the heat dissipation substrate and the power module, but also prevent the heat dissipation substrate and the high-power module from warping during the sintering process, so that the sintering method of the present application can be applied to large-area reliable interconnection between the power module and the heat dissipation substrate.

[0089] The power device sintering method of the present application adopts a partitioned printing method when printing the sintering material layer on the sintering surface of the heat dissipation substrate to form a sintering material layer including multiple independent partitions on the sintering surface of the heat dissipation substrate. This not only saves the amount of sintering material and reduces the cost of large-area sintering, but also the intervals between the independent partitions can serve as volatilization channels for the solvent during the drying and sintering process, thereby reducing or avoiding the formation of holes and air channels in the sintering material layer during drying and sintering, and improving the heat dissipation performance of the connecting layer after sintering.

[0090] In the power device sintering method of the present application, when printing the sintering material layer on the sintering surface of the heat dissipation substrate, the sintering material is printed in a partitioned manner so that when a sintering material layer including multiple independent partitions is formed on the sintering surface of the heat dissipation substrate, the boundary of each independent partition avoids the internal etched groove on the internal metal layer of the ceramic substrate, thereby preventing the ceramic substrate from having stress concentration lines in the overlapping area due to the overlap of the connecting material layer and the etched groove on the internal metal layer of the ceramic substrate, thereby preventing the ceramic in the ceramic substrate from cracking and causing insulation failure.

[0091] Compared with the power module after plastic encapsulation, which contains multiple sub-components such as chips and plastic encapsulation materials, the power device sintering method of the present application has a simple heat dissipation substrate structure and low unit cost. Therefore, the sintering material layer is printed on the heat dissipation substrate, and the scrapping cost is lower.

[0092] The power device sintering method of the present application prints a sintering material layer on a heat dissipation substrate, which is not affected by the complex shape of the injection-molded power module, and the printing jig of the heat dissipation substrate can be simpler.

[0093] In the description herein, many specific details are provided, such as examples of components and / or methods, to provide a complete understanding of the embodiments of the present application. However, those skilled in the art will recognize that embodiments of the present application can be practiced without one or more specific details or by other devices, systems, assemblies, methods, components, materials, parts, etc. In other cases, well-known structures, materials, or operations are not specifically shown or described in detail to avoid blurring the aspects of the embodiments of the present application.

[0094] Reference throughout this specification to "one embodiment," "an embodiment," or "a specific embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application, and not necessarily in all embodiments. Thus, various appearances of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" in different places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present application may be combined with one or more other embodiments in any suitable manner. It should be understood that other variations and modifications of the embodiments of the invention described and illustrated herein are possible in light of the teachings herein and are considered part of the spirit and scope of the present application.

[0095] It should also be understood that one or more of the elements shown in the figures may also be implemented in a more separate or more integrated manner, or even removed because they are inoperable in certain circumstances or provided because they may be useful depending on the application.

[0096] In addition, unless otherwise expressly indicated, any marking arrows in the drawings should be regarded as illustrative only and not limiting. Furthermore, unless otherwise indicated, the term "or" as used herein is generally intended to mean "and / or." Where a term is unclear in providing separation or combination capabilities, the combination of components or steps will also be considered as indicated.

[0097] As used in the description herein and throughout the claims that follow, “a,” “an,” and “the” include plural references unless otherwise indicated. Likewise, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless otherwise indicated.

[0098] The above description of the embodiments shown in the present application (including the content described in the abstract of the specification) is not intended to be an exhaustive list or to limit the present application to the precise form disclosed herein. Although the specific embodiments of the present application and the examples of the present application are described herein for illustrative purposes only, as those skilled in the art will recognize and understand, various equivalent modifications are possible within the spirit and scope of the present application. As noted, these modifications can be made to the present application according to the above description of the embodiments described in the present application, and these modifications will be within the spirit and scope of the present application.

[0099] Systems and methods have been generally described herein as details that are helpful for understanding the present application. In addition, various specific details have been given to provide an overall understanding of the embodiments of the present application. However, those skilled in the relevant art will recognize that the embodiments of the present application can be practiced without one or more specific details, or practiced using other devices, systems, accessories, methods, components, materials, parts, etc. In other cases, known structures, materials, and / or operations are not specifically shown or described in detail to avoid confusion in various aspects of the embodiments of the present application.

[0100] Thus, although the present application has been described herein with reference to specific embodiments thereof, freedom of modification, various changes and substitutions are also within the foregoing disclosure, and it should be understood that in some cases, some features of the present application will be adopted without the corresponding use of other features without departing from the scope and spirit of the claimed invention. Therefore, many modifications can be made to adapt a particular environment or material to the true scope and spirit of the present application. The present application is not intended to be limited to the specific terminology used in the claims below and / or the specific embodiments disclosed as the best mode contemplated for carrying out the present application, but the present application will include any and all embodiments and equivalents falling within the scope of the appended claims. Therefore, the scope of the present application will be determined solely by the appended claims.

Claims

1. A method for sintering a power device, characterized in that: include: Providing a heat dissipation substrate, wherein the heat dissipation substrate has a sintering surface; printing a sintering material layer on the sintering surface of the heat dissipation substrate; Drying the heat dissipation substrate printed with the sintering material layer; Mounting a power module on the dried sintered material layer; The heat dissipation substrate with the power module mounted thereon is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate.

2. The power device sintering method according to claim 1, characterized in that: The area of ​​the sintering surface is larger than the printing area of ​​the sintering material layer.

3. The power device sintering method according to claim 2, characterized in that: A plating layer is formed on the sintering surface of the heat dissipation substrate, and the plating layer is a silver plating layer, a nickel plating layer, a copper plating layer or a titanium plating layer.

4. The power device sintering method according to claim 1, characterized in that: In the step of printing the sintering material layer on the sintering surface of the heat dissipation substrate, the printing thickness is between 30 μm and 800 μm, and the printing area is between 500 mm 2 -2500mm 2 .

5. The power device sintering method according to claim 4, characterized in that: In the step of drying the heat dissipation substrate printed with the sintering material layer, the drying temperature is between 90 degrees Celsius and 170 degrees Celsius, and the drying time is 20 minutes to 100 minutes.

6. The power device sintering method according to claim 4, characterized in that: The heat dissipation substrate with the power module mounted thereon is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate, comprising: Preheating the heat dissipation substrate on which the power module is mounted; The heat dissipation substrate with the power module mounted thereon after the preheating treatment is subjected to pressure sintering to complete the connection between the power module and the heat dissipation substrate.

7. The power device sintering method according to claim 6, characterized in that: The parameters of the preheating treatment include: the preheating temperature is between 80 degrees Celsius and 170 degrees Celsius, and the preheating time is between 3 minutes and 30 minutes; The sintering parameters include: sintering temperature between 180 degrees Celsius and 260 degrees Celsius, sintering time between 5 minutes and 20 minutes, and sintering pressure between 6 MPa and 25 MPa.

8. The power device sintering method according to claim 1, characterized in that: In the step of pressurizing and sintering the heat dissipation substrate with the power module mounted thereon to complete the connection between the power module and the heat dissipation substrate, a stepwise pressurization method is adopted to reach the target sintering pressure.

9. The power device sintering method according to claim 1, characterized in that: The power module includes a ceramic substrate and a plurality of chips arranged on an inner metal layer of the ceramic substrate; Printing a sintering material layer on the sintering surface of the heat dissipation substrate comprises: According to the position of the chip in the power module, the sintering material is printed on the sintering surface of the heat dissipation substrate in a partitioned manner to form a sintering material layer including multiple independent partitions on the sintering surface of the heat dissipation substrate, wherein the position of each of the independent partitions corresponds to the position of at least one chip of the power module.

10. The power device sintering method according to claim 9, characterized in that: The boundary of each of the independent partitions avoids the inner etching groove on the inner metal layer of the ceramic substrate.

11. A power device, characterized in that: The power device is obtained by the sintering method according to any one of claims 1 to 10.

Images