Double-sided heat dissipation power semiconductor module and manufacturing method

Abstract

The present invention discloses a double-sided heat dissipation power semiconductor module and a manufacturing method, which belongs to the field of semiconductor technology. The semiconductor module is composed of an upper insulating lining, a lower insulating lining, a power semiconductor chip, a metal gasket, an aluminum wire, a power terminal and a signal terminal; the power semiconductor chip is bonded to the lower insulating lining through a preformed solder sheet, and after the power semiconductor chip is placed above the preformed solder sheet, a prestressed pressing block is applied on the surface of the power semiconductor chip and reflow soldering is performed; the power terminal and the signal terminal are first welded to the lower insulating lining by ultrasonic bonding, and solder paste is applied around the pins of the power terminal and the signal terminal before reflow soldering. The manufacturing method of the double-sided heat dissipation power semiconductor module provided by the present invention improves the consistency of the chip height after welding, reduces the welding void rate, ensures the connection strength between the terminal and the insulating lining, and solves the problem of cracking of the ceramic layer of the insulating lining caused by the ultrasonic bonding process.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and in particular to a double-sided heat dissipation power semiconductor module and a manufacturing method thereof. Background Art

[0002] Complex and changeable operating conditions require electric vehicles to have strong power and high reliability. The power semiconductor module in the electric drive traction inverter is the main factor that determines the power output capacity and service life of electric vehicles. After decades of development, power semiconductor chips have higher current density, reliability, price advantages and lower power consumption. At the same time, due to the limited current carrying capacity of a single power semiconductor chip, multiple chips need to be packaged in parallel for use. Therefore, the packaging structure is a major factor affecting the power output capacity of electric vehicle chips and the reliability of the module.

[0003] The output power of the power semiconductor module is expressed as P = ΔT / R TH , where ΔT is the difference between the chip junction temperature and the heat dissipation environment temperature, R TH is the steady-state thermal resistance of the power module. It can be seen from the formula that the thermal resistance directly determines the power output capacity of the module; at the same time, the voltage between the chip collector (drain) electrode and the emitter (source) electrode is expressed as V CE =V DC +L·di / dt, where V DC is the bus voltage, L is the module stray inductance, and di / dt is the current change rate when the chip is turned off. From the formula, it can be seen that the high stray inductance parameter of the module will cause a large voltage overshoot between the collector (drain) and emitter (source) during the chip shutdown process, resulting in chip overvoltage damage and reduced module reliability. In summary, the power module package of electric vehicles needs to have the characteristics of low thermal resistance and low stray inductance.

[0004] The packaging forms of electric vehicle power modules are mainly divided into traditional single-sided heat dissipation welding modules and double-sided heat dissipation power modules. Since the latter can dissipate heat through the upper and lower insulating linings at the same time and has a laminated structure, it has lower thermal resistance and smaller stray inductance than the former, and has attracted widespread attention in the electric vehicle field. However, double-sided heat dissipation power semiconductor modules have at least the following problems:

[0005] 1. The manufacturing process is difficult, especially the process control of solder thickness consistency: inconsistent chip solder thickness will cause chip height differences, which will directly lead to poor contact between some chips and metal gaskets, reducing the electrical and thermal performance of the module.

[0006] 2. Since the double-sided heat dissipation module has no substrate, if the welding process parameters with larger ultrasonic energy are used, it will directly lead to the cracking of the ceramic layer of the insulating lining, resulting in a decrease in production yield; while the bonding process parameters with smaller ultrasonic energy are difficult to ensure good connection strength between the terminal and the insulating lining, reducing the module installation and operation reliability. Summary of the invention

[0007] In order to solve the problems of inconsistent chip height and low production yield of the existing double-sided heat dissipation power semiconductor module, the present invention provides a double-sided heat dissipation power semiconductor module and a manufacturing method. The lower surface of the power semiconductor chip is bonded to the lower insulating lining through a preformed solder sheet. After the power semiconductor chip is placed on the preformed solder sheet, prestressed blocks are applied to the surface of the power semiconductor chip and reflow soldering is performed, which improves the consistency of the height of the components after welding and reduces the welding void rate. At the same time, the power terminal and the signal terminal are first connected to the lower insulating lining by ultrasonic bonding, and then solder paste is applied around the connection between the power terminal and the signal terminal and the lower insulating lining for reflow soldering. Low ultrasonic energy bonding parameters are used in the bonding process, and reflow soldering is performed after solder paste and water-washed flux are applied to the terminal pins, that is, the terminal and the insulating lining are connected in a combination of ultrasonic bonding and reflow soldering, which ensures the bonding strength while avoiding the cracking of the ceramic layer of the lower insulating lining caused by excessive bonding parameters.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] An object of the present invention is to provide a double-sided heat dissipation power semiconductor module, comprising an upper insulating liner, a lower insulating liner, a power semiconductor chip, a metal gasket, a power terminal and a signal terminal;

[0010] The power semiconductor chip is arranged in the middle of the upper surface of the lower insulating liner, and is bonded to the upper surface of the lower insulating liner through a preformed solder sheet, and the gate of the power semiconductor chip is connected to the lower insulating liner through an aluminum wire; the power terminals and signal terminals are arranged on both sides of the upper surface of the lower insulating liner, and are welded to the upper surface of the lower insulating liner;

[0011] A metal gasket is provided on the lower surface of the upper insulating liner, the upper surface of the metal gasket is welded to the lower surface of the upper insulating liner, and the lower surface of the metal gasket and the upper surface of the power semiconductor chip are joined via a preformed welding sheet.

[0012] Preferably, the power semiconductor chip comprises one or more of IGBT, MOSFET or diode, the material is silicon, silicon carbide or gallium nitride, the voltage level is 650V-900V, and the current level is 150A-300A.

[0013] Preferably, the number of the power semiconductor chips is 4-8.

[0014] Another object of the present invention is to provide a method for preparing the above-mentioned double-sided heat dissipation power semiconductor module, comprising the following steps:

[0015] 1) placing a preformed solder sheet on the middle of the upper surface of the lower insulating liner, and placing a power semiconductor chip on the preformed solder sheet;

[0016] 2) applying a prestressed pressing block on the upper surface of each power semiconductor chip, moving the chip to a reflow furnace, welding the preformed solder sheet to the lower insulating liner in a formic acid environment, and welding each power semiconductor chip to the upper surface of the preformed solder sheet; after welding, removing the prestressed pressing block to form a first welding assembly;

[0017] 3) Screen-printing solder paste and flux on the lower surface of the upper insulating liner, placing a metal gasket on the solder paste, moving it to a reflow oven, and welding the metal gasket to the upper insulating liner in a formic acid environment, wherein the preheating temperature in the reflow oven is 100-180° C., the welding temperature is 200-280° C., and the welding time is 60-80 seconds; after welding, cleaning the residual flux to form a second welding assembly;

[0018] 4) placing the first welding assembly on the bonding table, and connecting the gate of the power semiconductor chip to the lower insulating liner through the bonding aluminum wire;

[0019] 5) Fix the power terminal and the signal terminal to the lower insulating liner with a clamp, and perform ultrasonic bonding welding in a vacuum system, wherein the ultrasonic welding pressure of the power terminal is 1.8-2.2 bar, the amplitude is 80%, and the bonding energy is 100-120 W·s; the ultrasonic welding pressure of the signal terminal is 1.6-1.8 bar, the amplitude is 80%, and the bonding energy is 60-80 W·s; then, apply solder paste and flux to the pins of the power terminal and the signal terminal, and put them into a reflow furnace for secondary welding in a formic acid environment;

[0020] 6) placing a preformed solder sheet on the metal gasket of the second soldering assembly, then placing the second soldering assembly upside down on the upper surface of the first soldering assembly, placing it in a reflow furnace, and soldering it in a formic acid environment, so that the lower surface of the metal gasket and the upper surface of the power semiconductor chip are bonded through the preformed solder sheet to form a double-sided heat dissipation power semiconductor module;

[0021] 7) Injecting resin material to encapsulate the double-sided heat dissipation power semiconductor module.

[0022] Furthermore, when the first welding assembly, the second welding assembly and the double-sided heat dissipation power semiconductor module are obtained in steps 2), 3) and 6), respectively, the void ratio of the assembly is detected by using X-ray and ultrasonic scanning technology, and subsequent operations are performed only after the void ratio is lower than 0.5%.

[0023] Furthermore, in the step 5), after completing ultrasonic bonding and secondary welding in the vacuum system, a thrust tester is used to detect the bonding strength, and ultrasonic scanning technology is used to check the cracking of the insulating lining. When the bonding strength meets the preset strength and there is no cracking, subsequent operations are performed; the bonding strength must meet the thrust value of the power terminal of 40kg and above, and the thrust value of the signal terminal of 35kg and above.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1) When welding power semiconductor chips, the present invention adopts a method of applying a prestressed pressing block on the upper surface of each power semiconductor chip. The area of ​​the prestressed pressing block can completely cover the surface of the power semiconductor chip. After the prestressed pressing block is applied, the pressure on the chip solder is the sum of the weight of the pressing block and the weight of the chip. Compared with the traditional technology (without applying the prestressed pressing block), the pressure on the chip solder is increased, and the distribution is more uniform, so that the high consistency of the power semiconductor chips in the prepared double-sided heat dissipation power semiconductor module is improved, and all parallel chips are ensured to have good electrical contact with the metal gasket, reduce the contact resistance, and reduce the coupling effect of the contact resistance heating on the chip junction temperature, and finally improve the power output capacity of the module; at the same time, during the long-term operation of the module, the welding voids lead to uneven heat dissipation of the module, increase the thermal resistance of the module, and reduce its life and reliability. The application of prestressed pressing blocks can promote uniform distribution of solder and reduce the welding void rate, thereby achieving an improvement in the life and reliability of the module.

[0026] 2) The present invention connects the terminal and the liner by combining ultrasonic bonding and reflow soldering. First, the power terminal and the signal terminal are ultrasonically bonded to the lower insulating liner using low ultrasonic energy bonding parameters. The smaller ultrasonic energy bonding parameters can avoid cracking of the insulating liner ceramic layer due to excessive pressure during the bonding process, thereby effectively improving the production yield and production efficiency. Thereafter, solder paste and water-washable flux are coated on the pins of the power terminal and the signal terminal, and reflow soldering is performed to further increase the connection strength between the terminal and the insulating liner, thereby ensuring the bonding strength between the terminal and the insulating liner while avoiding cracking of the insulating liner ceramic layer, thereby improving the reliability of the module. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the manufacturing method of the double-sided heat dissipation power semiconductor module of the present invention;

[0028] Figure 2 It is a schematic cross-sectional structure diagram of a double-sided heat dissipation power semiconductor module of the present invention;

[0029] Figure 3 This is a schematic diagram of a terminal positioning fixture for a double-sided heat dissipation power semiconductor module according to the present invention;

[0030] Figure 4 A schematic diagram of chip arrangement and terminal connection of a double-sided heat dissipation power semiconductor module of the present invention;

[0031] Among them: 1-upper insulating lining, 2-lower insulating lining, 3-silicon-based IGBT chip, 4-diode chip, 5-metal gasket, 6-aluminum wire, 7-power terminal, 8-signal terminal, 9-preformed solder sheet, 10-solder paste, 11-fixture. DETAILED DESCRIPTION

[0032] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0033] The present invention proposes a method for manufacturing a double-sided heat dissipation power semiconductor module, in which the power / signal terminals are welded by a "bonding + secondary welding" process, which limits the bonding parameters selected for the power / signal terminals and selects slightly smaller bonding parameters to ensure that the insulating liner will not crack due to excessive bonding parameters. The subsequent secondary welding process steps further enhance the welding strength, avoiding the cracking of the insulating liner caused by the use of high-energy bonding parameters in traditional welding processes, and requiring continuous trial and error to adjust the process parameters before producing a certain module, which costs a large amount of time and has the defect of low production yield.

[0034] The structure of the double-sided heat dissipation power semiconductor module proposed by the present invention is as follows Figure 2 As shown, it includes an upper insulating liner 1, a lower insulating liner 2, a power semiconductor chip, a metal gasket 5, a power terminal 7 and a signal terminal 8;

[0035] The power semiconductor chip is arranged in the middle of the upper surface of the lower insulating liner 2, and is joined to the upper surface of the lower insulating liner 2 through a preformed solder sheet, and the gate of the power semiconductor chip is connected to the lower insulating liner 2 through an aluminum wire; the power terminal 7 and the signal terminal 8 are arranged on both sides of the upper surface of the lower insulating liner 2 and are welded to the upper surface of the lower insulating liner 2.

[0036] A metal gasket 5 is provided on the lower surface of the upper insulating liner 1 , the upper surface of the metal gasket is welded to the lower surface of the upper insulating liner, and the lower surface of the metal gasket and the upper surface of the power semiconductor chip are joined via a preformed solder sheet.

[0037] In a specific implementation of the present invention, the arrangement of the power semiconductor chip, the power terminal 7 and the signal terminal 8 is as follows: Figure 4As shown. The power semiconductor chip includes a silicon-based IGBT chip 3 and a diode chip 4, and the number of both chips is 4, of which the diode chip 4 is evenly distributed in the middle, and the silicon-based IGBT chips 3 are distributed on both sides of the diode chip 4, with two on each side; the voltage level of each power semiconductor chip is 650V-900V, and the current level is 150A-300A. In addition, a plurality of power terminals 7 and signal terminals 8 are distributed on the lower insulating liner 2, and each terminal is welded to the upper surface of the lower insulating liner 2.

[0038] In the present invention, the lower surface of the power semiconductor chip is joined to the lower insulating lining by a preformed solder sheet, and after the power semiconductor chip is placed on top of the preformed solder sheet, a prestressed pressure block is applied to the surface of the power semiconductor chip and reflow soldering is performed. At the same time, after the power terminals and signal terminals are welded to the lower insulating lining by ultrasonic bonding, solder paste is applied around the connection between the power terminals and signal terminals and the lower insulating lining, and reflow soldering is performed. The manufacturing method of the double-sided heat dissipation power semiconductor module provided by the present invention improves the consistency of the height of the components after welding, reduces the chip welding void rate, ensures the connection strength between the terminal and the insulating lining, and solves the problem of cracking of the ceramic layer of the insulating lining caused by the ultrasonic bonding process.

[0039] The preformed solder sheet material used in the present invention is PbSn5Ag2.5 or SnSb8, the solder paste material is SnSb8, SnAgCu or SnAg, and the metal gasket material is molybdenum.

[0040] In a specific implementation of the present invention, the manufacturing method of the double-sided heat dissipation power semiconductor module is as follows: Figure 1 As shown, the specific steps include:

[0041] Step 1, place a preformed solder sheet 9 on the lower insulating liner 2, the preformed solder sheet 9 has a thickness of 100μm and is made of PbSn5Ag2.5; after placing the silicon-based IGBT chip 3 and the diode chip 4 on top of the preformed solder sheet, apply a prestressed pressure block on the surface of the silicon-based IGBT chip 3 and the diode chip 4, and put the mounted lower insulating liner 2 into a reflow furnace for welding in a formic acid environment. The placement time of the prestressed pressure block is the entire chip welding process, which can increase the gravity of the solder sheet or solder paste, thereby making the solder sheet / solder paste more evenly distributed; after welding is completed, remove the prestressed pressure block to form a first welding assembly; use X-ray and ultrasonic scanning technology to respectively detect the void rate of the welding assembly 1, and proceed with subsequent operations after the void rate is lower than 0.5%.

[0042] Step 2: screen print SAC305 solder paste 10 and water-washable flux on the upper insulating liner 1 by using a 0.30 mm thick steel screen printing method, place the metal gasket 5 on the solder paste, put the mounted upper insulating liner 1 into a reflow furnace for welding in a formic acid environment, preheating temperature 140°C, welding temperature 250°C, welding time 70s, clean the surface flux residue after welding, and form a second welding assembly; use X-ray and ultrasonic scanning technology to detect the void rate of the welding assembly 2. In a specific implementation of the present application, the metal gasket is a molybdenum sheet.

[0043] Step 3, place the first welding assembly on the bonding table, and connect the gate of the silicon-based IGBT chip 3 to the lower insulating liner 2 by bonding an aluminum wire 6 with a wire diameter of 250μm; place the first welding assembly on the machine and fix it with a vacuum system; insert the power terminal 7 and the signal terminal 8 into the fixture 11 from bottom to top, and then fix the fixture on the machine with bolts. At this time, the pins of the power terminal 7 and the signal terminal 8 are in contact with the corresponding positions on the bonding of the insulating liner; fix the power terminal 7 and the signal terminal 8 with the fixture 11, and perform ultrasonic welding. The pressure of ultrasonic welding of the power terminal 7 is 1.8bar, the amplitude is 80%, and the bonding energy is 100W·s. The pressure of ultrasonic welding of the signal terminal 8 is 1.6bar, the amplitude is 80%, and the bonding energy is 80W·s; the selection of bonding parameters is related to the size of the bonded object. The volume, mass and pin area of ​​the power terminal 7 are larger than those of the signal terminal 8. Therefore, in order to ensure sufficient bonding strength, bonding 7 requires slightly larger bonding parameters.

[0044] After that, SAC305 solder and water-wash flux are applied to the terminal pins, and the terminals are placed in a reflow oven for soldering in a formic acid environment. The bonding strength is tested using a thrust tester. After completing the "ultrasonic bonding & secondary soldering" of the terminals, the thrust value of the power terminals is 40kg or more, and the thrust value of the signal terminals is 35kg or more. Finally, ultrasonic scanning technology is used to check the cracking of the insulating liner.

[0045] In a specific implementation of the present invention, when a dispensing machine or a coating machine is used to apply solder paste to the power terminal pin, a No. 18 (inner diameter 0.92mm) or No. 20 (inner diameter 0.61mm) needle tube is used, and when applying solder paste to the signal terminal pin, a No. 23 (0.34mm) or No. 25 (0.26mm) needle tube is used, that is, needle tubes of different specifications are selected for terminals of different sizes to ensure that the solder coating position is close to the side of the welding pin so that the coating is uniform.

[0046] Step 4: Place a SnSb8 preformed solder sheet on the metal gasket 5 of the second welding assembly, the preformed solder sheet 9 has a thickness of 100 μm, and then place the second welding assembly upside down on the upper surface of the first welding assembly, put it into a reflow furnace for welding in a formic acid environment, and then rinse it with water to form a third welding assembly; use ultrasonic scanning technology to detect the void rate of the welding assembly 3, and proceed with subsequent operations after the void rate is less than 0.5%.

[0047] Step 5: Inject resin material to seal and protect the double-sided heat dissipation module, and perform edge cutting and bending according to actual needs.

[0048] In a specific implementation of the present invention, the prestressed block is a rectangular structure with a cross-sectional area of ​​1 to 1.2 times the surface area of ​​the power semiconductor chip, a thickness of 1-30 mm, a mass of 1-500 g, and the material of the prestressed block is graphite or molybdenum sheet.

[0049] This example explores the influence of the mass of the pressing block and the ultrasonic welding pressure on the welding quality. As shown in Table 1, in order to avoid the damage to the chip caused by excessive gravity of the pressing block and the inability to provide effective pressure due to too small gravity, the preferred thickness of the pressing block of the present invention is 1-30 mm and the mass is 1-500 g.

[0050] Table 1 Effect of briquetting quality on welding thickness difference

[0051]

[0052] The area of ​​the prestressed pressing block used in this embodiment is 1.2 times the upper surface area of ​​the power semiconductor chip, which can completely cover the surface of the power semiconductor chip. After applying the prestressed pressing block, the pressure on the chip solder is the sum of the gravity of the pressing block and the gravity of the chip. The pressure on the chip solder increases and is more evenly distributed, thereby achieving improved consistency in the height of the power semiconductor chips in the prepared double-sided heat dissipation power semiconductor module.

[0053] This example explores the effects of different ultrasonic welding pressure values ​​on the liner, as shown in Table 2.

[0054] Table 2 Effect of different ultrasonic welding pressure values ​​on liner

[0055] Ultrasonic welding pressure value (bar) 2.5 2.4 2.3 2.2 2.1 2.0 Whether the lining is cracked or not yes yes yes no no no

[0056] When the welding pressure value is too large, the excessive ultrasonic energy bonding parameter will cause the insulating liner ceramic layer to crack due to excessive pressure during the bonding process. The safe range is less than 2.2 bar. If the welding pressure value is too small, the bonding strength will not meet the standard. The preferred bonding pressure of the present invention is 1.6 to 2.2 bar. Since the selection of bonding parameters is related to the size of the bonded object, the volume, mass and pin area of ​​the power terminal are larger than those of the signal terminal. Therefore, in order to ensure sufficient bonding strength, the power terminal can use a slightly larger bonding parameter, and the signal terminal can use a slightly smaller bonding parameter.

[0057] The manufacturing method of the double-sided heat dissipation power semiconductor module provided by the present invention improves the consistency of chip height after welding, reduces the welding void rate, ensures the connection strength between the terminal and the insulating liner, and solves the problem of cracking of the ceramic layer of the insulating liner caused by the ultrasonic bonding process.

[0058] The above examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples, and many variations are possible. All variations that can be directly derived or associated with the contents disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for preparing a double-sided heat dissipation power semiconductor module, the double-sided heat dissipation power semiconductor module comprising an upper insulating liner (1), a lower insulating liner (2), a power semiconductor chip, a metal gasket (5), a power terminal (7) and a signal terminal (8); The power semiconductor chip is arranged in the middle of the upper surface of the lower insulating liner (2), and is bonded to the upper surface of the lower insulating liner (2) via a preformed solder sheet, and the gate of the power semiconductor chip is connected to the lower insulating liner (2) via an aluminum wire; the power terminal (7) and the signal terminal (8) are arranged on both sides of the upper surface of the lower insulating liner (2), and are welded to the upper surface of the lower insulating liner (2); A metal gasket (5) is provided on the lower surface of the upper insulating liner (1), the upper surface of the metal gasket is welded to the lower surface of the upper insulating liner, and the lower surface of the metal gasket and the upper surface of the power semiconductor chip are joined via a preformed welding sheet; It is characterized in that The preparation method comprises the following steps: 1) placing a preformed solder sheet on the middle of the upper surface of the lower insulating liner (2), and placing a power semiconductor chip on the preformed solder sheet; 2) applying a prestressed pressing block on the upper surface of each power semiconductor chip, moving the prestressed pressing block to a reflow furnace, welding the preformed solder sheet to the lower insulating liner (2) in a formic acid environment, and welding each power semiconductor chip to the upper surface of the preformed solder sheet; after welding, removing the prestressed pressing block to form a first welding assembly; the prestressed pressing block is a rectangular parallelepiped structure, with a cross-sectional area of ​​1-1.2 times the upper surface area of ​​the power semiconductor chip, a thickness of 1-30 mm, a mass of 1-500 g, and a material of graphite or molybdenum sheet; 3) Screen-printing solder paste and solder flux on the lower surface of the upper insulating liner (1), placing the metal gasket (5) on the solder paste, moving it to a reflow oven, and soldering the metal gasket (5) to the upper insulating liner (1) in a formic acid environment, wherein the preheating temperature in the reflow oven is 100-180° C., the soldering temperature is 200-280° C., and the soldering time is 60-80 seconds; after soldering is completed, cleaning the residual solder flux to form a second soldering assembly; 4) placing the first welding assembly on a bonding platform, and connecting the gate of the power semiconductor chip to the lower insulating liner (2) through a bonding aluminum wire; 5) The power terminal (7) and the signal terminal (8) are fixed on the lower insulating lining (2) by a clamp, and ultrasonic bonding welding is performed in a vacuum system, wherein the ultrasonic welding pressure of the power terminal (7) is 1.8 to 2.2 bar, the amplitude is 80%, and the bonding energy is 100 to 120 W·s; the ultrasonic welding pressure of the signal terminal (8) is 1.6 to 1.8 bar, the amplitude is 80%, and the bonding energy is 60 to 80 W·s; then, solder paste and flux are coated on the pins of the power terminal (7) and the signal terminal (8), and the terminals are placed in a reflow furnace for secondary welding in a formic acid environment; the bonding strength is detected by a thrust tester, and the cracking of the insulating lining is checked by ultrasonic scanning technology. When the bonding strength meets the preset strength and there is no cracking, subsequent operations are performed; the bonding strength needs to meet the thrust value of the power terminal (7) of 40 kg or more, and the thrust value of the signal terminal (8) of 35 kg or more; 6) placing a preformed solder sheet on the metal gasket (5) of the second soldering assembly, then placing the second soldering assembly upside down on the upper surface of the first soldering assembly, placing it in a reflow furnace, and performing soldering in a formic acid environment, so that the lower surface of the metal gasket and the upper surface of the power semiconductor chip are bonded through the preformed solder sheet, thereby forming a double-sided heat dissipation power semiconductor module; 7) Injecting resin material to encapsulate the double-sided heat dissipation power semiconductor module.

2. The method for preparing a double-sided heat dissipation power semiconductor module according to claim 1, characterized in that: The material of the preformed solder sheet is PbSn5Ag2.5 or SnSb8, and the material of the solder paste is SnSb8, SnAgCu or SnAg.

3. The method for preparing a double-sided heat dissipation power semiconductor module according to claim 1, characterized in that: The metal gasket material is molybdenum.

4. The method for preparing a double-sided heat dissipation power semiconductor module according to claim 1, characterized in that: When the first welding assembly, the second welding assembly and the double-sided heat dissipation power semiconductor module are obtained in steps 2), 3) and 6), the void ratio of the assembly is detected by using X-ray and ultrasonic scanning technology, and subsequent operations are performed after the void ratio is lower than 0.5%.

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