Power device and sintering method thereof

Abstract

The invention provides a power device and a sintering method thereof, and the method comprises the steps: providing a heat dissipation substrate which is provided with 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 heat dissipation substrate with the dried sintering material layer, wherein the power module is in contact with the sintering material; and carrying out pressure sintering on the heat dissipation substrate on which the power module is mounted so as to complete connection between the power module and the heat dissipation substrate. By means of the mode that the sintering material layer is subjected to pressure sintering after being dried, large-area reliable interconnection between the power module and the heat dissipation substrate can be achieved, meanwhile, it is guaranteed that the thickness of a connecting layer is controllable, the defects of layering, overflowing, cracking, air holes, air channels and the like do not exist, and high heat conductivity and high long-term working temperature are achieved.

Description

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] In order to better utilize the performance of silicon carbide power devices and improve their reliability, the interconnection inside the power module has gradually evolved from welding process to sintering process. In contrast, the connection between the power module and the heat dissipation substrate involves system-level connection, which not only affects the external connection itself, but also affects the completed connection inside the power module. Therefore, it is subject to more constraints and greater challenges.

[0003] Currently, the connection between the power module and the heat sink is limited to an area less than 500mm 2 In the case of large-area welding, the traditional welding process is still used. For large-area welding, the solder melts at high temperature, flows, and the thickness cannot be accurately controlled. There are many disadvantages, such as difficult to control the thickness of the solder layer, easy to produce a large number of solder layer voids, overflow tin, tin beads splashing leading to insulation problems, low thermal conductivity of the connection layer, and low long-term operating temperature. These have greatly limited the performance of silicon carbide power modules.

[0004] In contrast, if the sintering process is used for large-area connection, the goal of controllable connection layer thickness, no voids, no overflow, high thermal conductivity, and high long-term operating temperature can be achieved. However, compared with small-area sintering, such as chip sintering and copper clip sintering, large-area sintering needs to overcome the difficulties of power module and heat dissipation substrate warping, large heat capacity, uneven thermal conductivity, and narrow process window (such as temperature and pressure) of the internal structure of module parts (such as chips, bonding wires, plastic packaging materials, etc.). Therefore, it is urgent to find a reliable method to achieve large-area sintering. Summary of the invention

[0005] 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.

[0006] To achieve the above-mentioned purpose and other related purposes, the present application provides a power device sintering method, comprising:

[0007] Providing a heat dissipation substrate, wherein the heat dissipation substrate has a sintering surface;

[0008] printing a sintering material layer on the sintering surface of the heat dissipation substrate;

[0009] Drying the heat dissipation substrate printed with the sintering material layer;

[0010] 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;

[0011] 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.

[0012] 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.

[0013] In an optional embodiment of the present application, the heat dissipation substrate is a copper heat dissipation substrate or an aluminum heat dissipation substrate.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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:

[0018] Preheating the heat dissipation substrate on which the power module is mounted;

[0019] 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.

[0020] In an optional embodiment of the present application, the parameters of the preheating process include: the preheating temperature is between 80 degrees Celsius and 170 degrees Celsius, and the preheating time is between 3 minutes and 30 minutes;

[0021] 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.

[0022] In an optional embodiment of the present application, in the step of pressurizing and sintering the heat dissipation substrate mounted with the power module to complete the connection between the power module and the heat dissipation substrate, a stepwise pressurization method is used to reach the target sintering pressure.

[0023] 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;

[0024] Printing a sintering material layer on the sintering surface of the heat dissipation substrate comprises:

[0025] 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.

[0026] In an optional embodiment of the present application, the boundary of each of the independent partitions avoids an internal etching groove on the internal metal layer of the ceramic substrate.

[0027] In order to achieve the above-mentioned purpose and other related purposes, the present application also provides a power device sintered by the above-mentioned method.

[0028] The power device sintering method of the present application comprises the following steps: 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 printed with the 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 is volatilized, so that the sintering material layer maintains a certain shape, and prevents the sintering material from overflowing, breaking and other damages during the mounting process. It can also prevent the solvent from not volatilizing easily in the subsequent sintering process and causing voids, airways, etc. that 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.

[0029] The power device sintering method of the present application adopts a partitioned manner to print the sintering material when printing the sintering material layer on the sintering surface of the heat dissipation substrate, so as 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 also serve as volatilization channels for the solvent during the drying and sintering process, thereby reducing or avoiding the formation of holes and airways in the sintering material layer during drying and sintering, and improving the heat dissipation performance of the connecting layer after sintering.

[0030] The power device sintering method of the present application adopts a partitioned manner to print the sintered material when printing the 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 ceramic substrate from having stress concentration 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 causing the ceramic in the ceramic substrate to crack and cause insulation failure.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The power device sintering method of the present application prints a sintering material layer on a heat dissipation substrate, which may not be affected by the injection-molded power module with a complex shape, and the printing jig of the heat dissipation substrate may be simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Flow chart of a power device sintering method in one embodiment of the present application.

[0036] Figure 2a A schematic diagram of a heat dissipation substrate is provided in one embodiment of the present application.

[0037] Figure 2b It 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.

[0038] Figure 2c It is a schematic diagram of drying the heat dissipation substrate printed with a sintering material layer in one embodiment of the present application.

[0039] Figure 2d It is a schematic diagram of mounting a power module on a sintered material layer after drying in one embodiment of the present application.

[0040] Figure 2eIt 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.

[0041] Figure 3 This is a schematic diagram of the structure of a power device in one embodiment of the present application.

[0042] Figure 4 It 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.

[0043] Figure 5 This 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.

[0044] Figure 6 This 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] Figure 7a Schematic diagram of the printing area.

[0046] Figure 7b Actual post-sintering images of the printed area obtained by ultrasonic scanning microscopy analysis for the sintered power device. DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 without conflict.

[0048] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present application in a schematic manner, and therefore the illustrations only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0049] like Figure 1 -2, the present application proposes a reliable power device sintering method. The sintering method can realize large-area reliable interconnection between the power module and the heat dissipation substrate, and ensure that the thickness of the connection layer is controllable, without defects such as delamination, overflow, cracking, pores, airways, etc., and has high thermal conductivity and high long-term operating temperature.

[0050] The heat dissipation substrate 10 is a substrate with heat dissipation function that can be in direct contact with the cooling liquid. Its material can be copper or aluminum, for example. That is, the heat dissipation substrate 10 can be a copper heat dissipation substrate or an aluminum heat dissipation substrate. The heat dissipation substrate 10 can be, for example, a liquid cooling radiator to achieve heat dissipation of the power module 30. The liquid cooling radiator can be a liquid cooling radiator with flaps or a liquid cooling radiator with spoilers.

[0051] 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.

[0052] The ceramic substrate may 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 copper metal layers 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 The process flow chart of the power device sintering method of the present application is shown, including steps S110-S150, Figure 2a-2e A schematic diagram of each step is given. Figure 1 , Figure 2a-2e To explain the entire sintering process in detail.

[0053] In step S110, Figure 2a As shown, a heat dissipation substrate 10 is provided, wherein the heat dissipation substrate 10 has a sintering surface 101 .

[0054] The heat dissipation substrate 10 has a sintering surface 101, which refers to the surface in direct contact with the sintering material, and can be a bare copper surface, or a silver-plated surface, a nickel-plated surface, a titanium-plated surface, or a combination of copper, silver, nickel, aluminum, titanium, etc.

[0055] 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 may be a copper-plated surface, a silver-plated layer, a nickel-plated layer or a composite coating. The coating may be implemented by chemical plating, electroplating, physical vapor deposition, etc., which is not limited here.

[0056] Taking the silver-plated layer as an example, due to the chemical stability and high oxidation temperature of silver, a silver-plated 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. In the subsequent sintering process, the silver-plated layer can promote the diffusion connection between the sintered material and the interface, further enhancing the interface connection strength; on the other hand, the silver-plated layer can also hinder the oxidation of the copper matrix during the subsequent sintering process and the high-temperature service process of the power device, further ensuring the connection strength of the interface and preventing the interface oxidation of the product during the sintering process and the high-temperature service process. And 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.

[0057] 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 and so on.

[0058] In step S120 , a sintering material layer 20 is printed on the sintering surface 101 of the heat dissipation substrate 10 .

[0059] When printing the sintered material layer 20 on the sintered surface 101 of the heat dissipation substrate 10, if there are pollutants 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 pollutants 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.

[0060] like Figure 2b As shown, after pre-processing the sintering surface 101 of the heat dissipation substrate 10, the sintering material can be printed on the sintering surface 101 of the heat dissipation substrate 10 by steel screen printing or dispensing to form a sintering material layer 20 (as a connecting layer). The sintering material can be, for example, sintering silver paste, sintering copper paste, sintering silver film, etc. The sintering silver paste or sintering copper paste is a mixture of metal particles and an organic solvent, and the sintering silver film is a preformed film-shaped sintering silver material.

[0061] 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, and it is 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-800μm, such as 30μm, 60μm, 90μm, 120μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm.

[0062] 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, for example, between 500 mm 2 -2500mm 2 , for example 500mm 2 , 600mm 2 , 700mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 , 1500mm 2 , 2000mm 2 , 2500mm 2 .

[0063] Since a heat dissipation substrate 10 can be connected to multiple power modules 30 at the same time, the sintering material layers 20 corresponding to the multiple power modules 30 can be printed on the heat dissipation substrate 10 at the same time, and the printing efficiency is high. In addition, the printing process on the heat dissipation substrate 10 can be carried out simultaneously with the packaging process of the power module 30, without the relationship between the front and back processes, which can save the production time of the assembly product, that is, the power device.

[0064] The current power module 30 has a higher and higher degree of integration, and more and more chips are used inside, resulting in an increasing area of ​​the copper-clad ceramic substrate, that is, the area where the power module 30 and the heat dissipation substrate 10 are connected becomes larger. For the connection between the power module 30 and the heat dissipation substrate 10, the sintering scheme 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 the large-area sintering of the present application, if the printing scheme covering the entire sintering surface 101 is still adopted, this will not only lead to a great consumption of sintering materials; but also the large area of ​​silver paste is not conducive to the volatilization of the solvent during the drying or sintering process, and it is easy to bring more holes, airways, etc., which affect the heat dissipation performance of the connection layer.

[0065] Based on this, when printing the sintering material layer 20 on the sintering surface 101 of the heat dissipation substrate 10, the sintering material can be printed in a partitioned manner to form a sintering material layer 20 including a plurality of 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 chip in the power module 30, so that the original sintering material layer 20 corresponding to each power module 30 is divided into a plurality of independent partitions according to the position of the chip in the power module 30, so that the position of each independent partition corresponds to the position of at least one chip of the power module 30, which can not only save the amount of sintering material and reduce the cost of large-area sintering, but also the intervals between the independent partitions can also be used as volatilization channels for solvents during drying and sintering, thereby reducing or avoiding the formation of holes and airways in the sintering material layer 20 during subsequent drying and sintering, and improving the heat dissipation performance of the connection layer after sintering.

[0066] As an example, Figure 4 As shown, the sintering material is printed in a partitioned manner to form a sintering material layer 20 including two rectangular independent partitions on the sintering surface 101 of the heat dissipation substrate 10; Figure 5 As shown, the sintering material is printed in a partitioned manner to form a sintering material layer 20 including four rectangular independent partitions on the sintering surface 101 of the heat dissipation substrate 10; Figure 6 As shown, the sintering material is printed in a partitioned manner to form a sintering material layer 20 including a plurality of independent partitions of irregular shapes on the sintering surface 101 of the heat dissipation substrate 10 .

[0067] 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 groove 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 groove 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.

[0068] In step S130 , the heat dissipation substrate 10 printed with the sintering material layer 20 is dried.

[0069] Small area (area less than 500mm 2 ) During sintering, the power module 30 and the heat dissipation substrate 10 are sintered in a wet state. If applied to a large area, the large area power module 30 is relatively heavy, which will cause the sintering material printed on the heat dissipation substrate 10 to collapse, squeeze out or break, and the thickness of the sintering material layer 20 cannot be well controlled. Therefore, in this embodiment, Figure 2c As shown, 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 prevents the sintering material from overflowing, breaking, etc. 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 volatilizing easily during the sintering process in step S150, resulting in holes, airways, etc., which affect the heat dissipation performance of the connecting layer.

[0070] 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.

[0071] The drying atmosphere needs to be selected according to 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, and the oxygen content during the drying process should be less than 100ppm. It can be further limited that the oxygen content during the drying process should be less than 30ppm, the purpose of which is to prevent oxidation of the bare copper surface or the copper paste.

[0072] In step S140 , the power module 30 is mounted on the dried sintered material layer 20 .

[0073] like Figure 2d As shown, the heat dissipation substrate 10 with the dried sintered silver paste or sintered copper paste is mounted on the power module 30, so that the heat dissipation substrate 10, the sintered material and the power module 30 are assembled. 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 plating, silver plating, nickel plating, titanium plating or a combination thereof. The coating can be achieved by chemical plating, electroplating, physical vapor deposition, etc., which is not limited here. The mounted product can enter step S150 for sintering to form a power device.

[0074] In step S150, the heat dissipation substrate 10 mounted with the power module 30 is pressurized and sintered to complete the connection between the power module 30 and the heat dissipation substrate 10, thereby forming a heat dissipation substrate 10 as shown in FIG. Figure 3 The power devices shown.

[0075] like Figure 2e As shown, 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.

[0076] 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 min and 20 min, for example, 5 min, 10 min, 15 min, and 20 min; 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.

[0077] It should be noted that the sintering temperature is very important during the sintering process. Too high a temperature may damage the components (chips, bonding wires, plastic packaging materials, etc.) in the power module 30, while too low a sintering temperature may cause the sintered materials to fail to form effective connections.

[0078] It should be noted that when the heat dissipation substrate 10 mounted with the power module 30 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 step-by-step pressurization method can be used to reach the target sintering pressure. After the sintering is completed, the sintering pressure can be released by a step-by-step pressure reduction method. 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 the large-area reliable interconnection between the power module 30 and the heat dissipation substrate 10.

[0079] During the sintering process, the sintering atmosphere needs to be selected according to the material of the sintering surface 101 and the sintering material. For example, if the sintering surface 101 is a silver-plated surface, a nickel-plated surface or a titanium-plated surface, and the sintering material is a sintered silver paste, the sintering atmosphere can be vacuum, 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 vacuum or nitrogen to prevent oxidation of the bare copper surface or the copper paste.

[0080] During the cooling process to room temperature after sintering, the choice of cooling atmosphere also needs to be selected according to the material of the sintering surface 101 and the sintering material. For example, if the sintering surface 101 is a silver-plated surface, a nickel-plated surface or a titanium-plated surface, 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.

[0081] It should be noted that, in an optional embodiment, in order to improve the sintering efficiency and sintering quality, before sintering, the heat dissipation substrate 10 mounted with the power module 30 may be preheated in a sintering atmosphere; after the preheating is completed, the heat dissipation substrate 10 mounted with the power module 30 is pressurized and sintered to complete the connection between the power module 30 and the heat dissipation substrate 10. The parameters of the preheating treatment include: the preheating temperature is 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; the preheating time is 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.

[0082] A specific example of the power device sintering method of the present application is given below.

[0083] Embodiment 1: A nickel-plated heat dissipation substrate 10 is selected, and its sintering surface 101 is a silver-plated surface with a coating thickness of 0.1 μm. A printing area of ​​2500 mm is printed on the heat dissipation substrate 10 by steel screen printing. 2 The sintered silver paste is printed with a thickness of 600 μm. Then it is dried in a vacuum oven 40 at 150 degrees Celsius for 80 minutes, and the drying atmosphere is air. The power module 30 is mounted on the heat dissipation substrate 10 with the sintered silver paste and preheated at 150 degrees Celsius for 20 minutes, and then sintered at 250 degrees Celsius for 10 minutes, 20 MPa, and vacuum atmosphere, thereby obtaining a large-area connection between the heat dissipation substrate 10 and the power module 30.

[0084] Embodiment 2: A silver-plated heat sink substrate 10 is selected, and its sintered surface 101 is a copper-plated silver-plated surface with a coating thickness of 1 μm. A 600 mm-diameter heat sink substrate 10 is formed by dispensing glue on the heat sink substrate 10. 2 The sintered silver paste is applied with a dot coating thickness of 100 μm. Then it is dried in an oven 40 at 100 degrees Celsius for 20 minutes in an air atmosphere. The power module 30 is mounted on the heat dissipation substrate 10 with the sintered silver paste, and then sintered at 190 degrees Celsius, 5 minutes, 15 MPa, and air atmosphere, thereby obtaining a large-area connection between the heat dissipation substrate 10 and the power module 30.

[0085] Embodiment 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 2000 mm 2The sintered copper paste is printed with a thickness of 300 μm. Then it is dried in an oven 40 at 120 degrees Celsius for 80 minutes in a nitrogen atmosphere. The power module 30 is mounted on the heat dissipation substrate 10 with the sintered copper paste, and then sintered at 260 degrees Celsius, 15 minutes, 8 MPa, and a nitrogen atmosphere, thereby obtaining a large-area connection between the heat dissipation substrate 10 and the power module 30.

[0086] Figure 7a is a schematic diagram of printing area A. Figure 7b This is an image of the actual sintered printed area B obtained by analyzing the power device sintered in the manner of Example 1 using an ultrasonic scanning microscope. Figure 7b It can be seen that the large-area sintered layer at the printing area B has no defects such as delamination, cracking, and air channels. The thermal conductivity of the connection layer after large-area sintering can reach 300W / mK at room temperature according to the ASTM-E1461 standard, which is 6 times that of traditional solder.

[0087] In summary, the power device sintering method of the present application is provided by providing a heat dissipation substrate with 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 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 is volatilized, so that the sintering material layer maintains a certain shape, and prevents the sintering material from overflowing, breaking and other damages during the mounting process. It can also prevent the solvent from not volatilizing easily in the subsequent sintering process and causing voids, airways, etc. that 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.

[0088] The power device sintering method of the present application adopts a partitioned manner to print the sintering material when printing the sintering material layer on the sintering surface of the heat dissipation substrate, so as 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 also serve as volatilization channels for the solvent during the drying and sintering process, thereby reducing or avoiding the formation of holes and airways in the sintering material layer during drying and sintering, and improving the heat dissipation performance of the connecting layer after sintering.

[0089] 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 etching 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 etching groove on the internal metal layer of the ceramic substrate, thereby preventing the ceramic in the ceramic substrate from cracking and causing insulation failure.

[0090] 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.

[0091] The power device sintering method of the present application prints a sintering material layer on a heat dissipation substrate, which may not be affected by the injection-molded power module with a complex shape, and the printing jig of the heat dissipation substrate may be simpler.

[0092] In the description herein, many specific details are provided, such as examples of parts and / or methods, to provide a complete understanding of the embodiments of the present application. However, those skilled in the art will recognize that the embodiments of the present application can be practiced without one or more specific details or by other devices, systems, components, methods, parts, materials, parts, etc. In other cases, 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.

[0093] References throughout the specification to "one embodiment," "an embodiment," or "a specific embodiment" mean that a particular feature, structure, or characteristic described in conjunction 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 the specification do not necessarily refer to the same embodiment. In addition, 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 may be possible in accordance with the teachings herein and are to be considered part of the spirit and scope of the present application.

[0094] 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.

[0095] In addition, unless otherwise explicitly indicated, any marking arrows in the drawings should be regarded as exemplary only and not limiting. In addition, unless otherwise indicated, the term "or" used herein is generally intended to mean "and / or". In the case where the term is not clear because it is anticipated that the ability to separate or combine is provided, the combination of components or steps will also be regarded as indicated.

[0096] 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.

[0097] The above description of the embodiment shown in the application (including the content described in the abstract of the specification) is not intended to be exhaustive or to limit the application to the precise form disclosed herein. Although the specific embodiment of the application and the example of the application are described herein for the purpose of illustration only, as those skilled in the art will recognize and understand, various equivalent modifications can be within the spirit and scope of the application. As pointed out, these modifications can be made to the application according to the above description of the embodiment described in the application, and these modifications will be within the spirit and scope of the application.

[0098] This paper has generally described systems and methods as details that are helpful for understanding the application. In addition, various specific details have been given to provide an overall understanding of the embodiments of the application. However, those skilled in the relevant art will recognize that the embodiments of the application can be put into practice without one or more specific details, or put into practice using other devices, systems, accessories, methods, assemblies, materials, parts, etc. In other cases, known structures, materials and / or operations are not particularly shown or described in detail to avoid confusion in various aspects of the embodiments of the application.

[0099] 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 above disclosure, and it should be understood that in some cases, some features of the present application will be adopted without corresponding use of other features without departing from the scope and spirit of the proposed invention. Therefore, many modifications may be made to adapt specific environments or materials to the substantial scope and spirit of the present application. The present application is not intended to be limited to the specific terms used in the claims below and / or the specific embodiments disclosed as the best mode 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. Thus, 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.

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