Low-temperature soft soldering process and system for IGBT (Insulated Gate Bipolar Translator) module

Abstract

The invention relates to an IGBT (Insulated Gate Bipolar Translator) module low-temperature soft soldering process and system, and belongs to the technical field of power semiconductor device packaging. In the process, the soldering temperature is strictly controlled in a softening interval lower than the melting point of soldering flux, and under the combined action of pressure and temperature, the soldering connection is realized in a soldering flux softening and non-melting state; and the problem of substrate deformation caused by high temperature is thoroughly eliminated. And then vacuum nitrogen protection and synchronous ultrasonic vibration are combined, so that the welding thermal stress is obviously reduced. In addition, nitrogen is adopted to replace reducing gas to serve as a single protective medium, oxidation is avoided, meanwhile, a process system is simplified, the problems of poor contact and thermal resistance rise caused by thermal expansion coefficient difference in a traditional process are solved, and the welding reliability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power semiconductor device packaging, and in particular relates to a low-temperature soft soldering process and system for an IGBT module. Background Art

[0002] IGBT modules (Insulated Gate Bipolar Transistor Modules) are core components in the power electronics field. The quality of their packaging and soldering directly impacts the module's reliability and heat dissipation performance. Currently, mainstream soldering processes include traditional soldering and low-temperature connection technologies such as silver sintering.

[0003] Traditional soldering processes achieve connections by melting solder, requiring a high temperature environment and relying on a reducing atmosphere to shield the solder. For example, vacuum reflow soldering is used to connect various electrical components, such as chips, ceramic substrates, and the DBC (Direct Bonded Copper) substrate, the core component of IGBT modules. Common solders used in soldering are typically two-phase or three-phase alloy systems, often in the form of solder paste or solder sheets. Solder paste soldering requires the addition of flux and post-soldering cleaning, but this method is susceptible to moisture. In contrast, soldering with solder sheets typically eliminates the need for flux and post-soldering cleaning, resulting in a more uniform solder layer. However, during soldering, the solder undergoes a process of heating, melting the high-temperature alloy, and cooling, forming a metallic compound layer at the interface, interconnecting the chip, ceramic substrate, and substrate. The significant differences in thermal expansion coefficients between these materials can cause irregular deformation of the substrate, leading to poor contact with the heat sink, increased thermal resistance, and compromised module reliability.

[0004] Silver sintering is a representative low-temperature joining technology. Compared to conventional solder layers, silver sintering layers are thinner, only about 50% to 80% of the thickness of ordinary solder layers. They also possess high electrical and thermal conductivity, resulting in a silver sintering layer with excellent power and temperature cycling capabilities. While silver sintering technology can improve thermal performance, its complex process, high material costs, and difficulty in controlling parameters hinder widespread industrial application. Therefore, improvements to the soldering process are still necessary. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a low-temperature soldering process and system for IGBT modules. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0006] The present invention provides a low-temperature soft soldering process for an IGBT module, comprising:

[0007] Placing a soldering sheet and a DBC substrate in sequence to form an assembly to be welded, and placing the assembly to be welded in a vacuum furnace;

[0008] Evacuate the vacuum furnace, and then inject nitrogen into the vacuum furnace;

[0009] Preheat the component to be welded by heating the component and maintain the temperature for at least 5 minutes;

[0010] The heating component is used to continuously heat the vacuum furnace until the temperature reaches (0.6-0.8)×T m , soften the soldering sheet and maintain the temperature for at least 10 minutes; wherein, T m is the melting point of the soldering sheet;

[0011] Continuously applying vertical pressure to the assembly to be welded by a pressure component, and simultaneously applying ultrasonic vibration by an ultrasonic component until the welding of the assembly to be welded is completed;

[0012] The heating component, the pressure component and the ultrasonic component are stopped, and the mixture is cooled to room temperature in a nitrogen atmosphere. The welded component to be welded is taken out, and the low-temperature soft soldering of the IGBT module is completed.

[0013] In one embodiment of the present invention, the melting point of the soldering sheet is higher than 300°C.

[0014] In one embodiment of the present invention, evacuating the vacuum furnace and then injecting nitrogen into the vacuum furnace includes: evacuating the vacuum furnace to a cavity pressure of 5 to 10 mbar, injecting nitrogen into the vacuum furnace at a flow rate of 50 sl / min until the cavity pressure reaches 950 mbar, re-evacuating the vacuum furnace to a cavity pressure of 1 to 5 mbar, and maintaining the pressure for 5 to 10 seconds; and re-injecting nitrogen into the vacuum furnace at a flow rate of 50 sl / min until the cavity pressure reaches 950 to 1000 mbar.

[0015] In one embodiment of the present invention, the component to be welded is preheated by a heating component and maintained at the temperature for at least 5 minutes, comprising: heating the component at a heating rate of 35 to 40°C / min until the temperature in the vacuum furnace reaches (0.3 to 0.5) × T m After that, keep the temperature for at least 5 minutes.

[0016] In one embodiment of the present invention, the heating component is continuously heated until the temperature in the vacuum furnace reaches (0.6-0.8)×T m , softening the solder sheet and maintaining the temperature for at least 10 minutes, comprising: heating the temperature in the vacuum furnace at a heating rate of 30 to 35°C / min by the heating component until the temperature reaches (0.6 to 0.8)×Tm Afterwards, the solder sheet is softened and kept at the temperature for at least 10 minutes.

[0017] In one embodiment of the present invention, continuously applying vertical pressure to the component to be welded by a pressure component includes: continuously applying a vertical pressure of 0.5 to 5 MPa to the component to be welded by the pressure component.

[0018] In one embodiment of the present invention, ultrasonic vibration is applied simultaneously by an ultrasonic component, including: while continuously applying vertical pressure to the component to be welded by a pressure component, ultrasonic vibration is applied by the ultrasonic component at an oscillation frequency of 20 to 30 kHz and a power of 300 to 500 W.

[0019] The present invention also provides an IGBT module low-temperature soldering system for realizing the above-mentioned IGBT module low-temperature soldering process. The system includes: a vacuum furnace, a heating component, a pressure component and an ultrasonic component, wherein a nitrogen inlet is provided on one side of the vacuum furnace and a vacuum component is provided on the other side; the component to be welded is provided on the pressure component, the heating component is provided in the vacuum furnace, and the heating component is provided around the component to be welded, and the ultrasonic component is provided below the pressure component.

[0020] In one embodiment of the present invention, the heating assembly includes: an annular copper tube, which is arranged around the central area of ​​the vacuum furnace, an induction coil is arranged on the outer sleeve of the annular copper tube, and a cooling water channel is arranged inside the annular copper tube.

[0021] In one embodiment of the present invention, the pressure assembly includes: a lower pressure head, an upper pressure head, a force transmission rod and a pneumatic assembly, wherein the lower pressure head is arranged opposite to the upper pressure head, and the pneumatic assembly is connected to the upper pressure head through the force transmission rod and can drive the upper pressure head relatively close to or away from the lower pressure head.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The low-temperature soft soldering process for IGBT modules of the present invention achieves a soldering connection by strictly controlling the soldering temperature within a softening range below the solder melting point. Through the combined effects of pressure and temperature, the solder is softened and non-melted, completely eliminating the problem of substrate deformation caused by high temperature. Combined with vacuum nitrogen protection and synchronous ultrasonic vibration, welding thermal stress is significantly reduced. Furthermore, the use of nitrogen instead of reducing gas as the sole protective medium simplifies the process system while avoiding oxidation, solving the problems of poor contact and increased thermal resistance caused by differences in thermal expansion coefficients in traditional processes, and improving welding reliability.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a method for low-temperature soldering of an IGBT module provided by an embodiment of the present invention;

[0026] Figure 2 1 is a schematic structural diagram of a low-temperature soldering system for an IGBT module provided by an embodiment of the present invention;

[0027] Figure 3 It is a structural schematic diagram of a heating component provided by an embodiment of the present invention.

[0028] Figure numerals: 1-vacuum furnace body; 11-vacuum component; 12-nitrogen inlet; 2-heating component; 3-pressure component; 31-lower pressure head; 32-upper pressure head; 33-force transmission rod; 34-air pressure component; 4-ultrasonic component; 10-component to be welded. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a low-temperature soft soldering process and system for IGBT modules proposed in accordance with the present invention, in conjunction with the accompanying drawings and specific embodiments.

[0030] The aforementioned and other technical contents, features, and effects of the present invention are clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a deeper and more specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the technical solutions of the present invention.

[0031] Example 1

[0032] IGBT module welding technology is mainly divided into soft soldering and low-temperature connection. Low-temperature connection technology represented by silver sintering is complex and has high equipment and raw material costs, making it difficult to popularize in industrial products. The traditional soft soldering process uses soft solder sheets to perform high-temperature soft soldering in a vacuum environment. The connection is achieved by forming a metal compound layer by melting the solder. However, after soldering, the base plate is prone to irregular deformation, resulting in poor contact with the heat sink. The root cause is that the traditional soft soldering process requires the soldering temperature to be raised to a range above the melting point of the solder and the continuous introduction of reducing gas to prevent oxidation. Due to the large difference in thermal expansion coefficients between different materials when the solder melts at high temperature, irregular deformation of the base plate occurs. The typical fatigue effect in the solder layer also has a significant impact on reliability.

[0033] In view of this, the first aspect of the present invention provides an IGBT module low temperature soldering process, such as Figure 1 As shown, Figure 1 This is a flow chart of a method for low-temperature soft soldering of an IGBT module provided by an embodiment of the present invention.

[0034] In this embodiment, the low-temperature soldering process for the IGBT module includes:

[0035] Step 1: Place the soldering sheet and DBC substrate in sequence to form an assembly to be welded, and place the assembly to be welded in a vacuum furnace;

[0036] Step 2: Evacuate the vacuum furnace and then inject nitrogen into the vacuum furnace.

[0037] In an optional embodiment, step 2 includes:

[0038] Step 2.1: Evacuate the vacuum furnace to a chamber pressure of 5-10 mbar. Then, inject nitrogen into the vacuum furnace at a flow rate of 50 sl / min until the chamber pressure reaches 950 mbar. Evacuate the chamber again to a chamber pressure of 1-5 mbar and maintain this pressure for 5-10 seconds.

[0039] Step 2.2: Reinject nitrogen into the vacuum furnace at a flow rate of 50 sl / min until the pressure in the chamber is 950-1000 mbar.

[0040] The principle is to use vacuum as system protection. Before heating, the vacuum furnace body is first evacuated and filled with N2, and then re-evacuated. This effectively reduces the oxygen content in the welding furnace cavity, thereby preventing the components to be welded from oxidizing during the welding process, avoiding the use of reducing gas, simplifying the process system and improving reliability.

[0041] Step 3: Preheat the components to be soldered by heating the assembly and maintain the temperature for at least 5 minutes.

[0042] In an optional embodiment, step 3 includes: heating the vacuum furnace to a temperature of (0.3-0.5)×T at a heating rate of 35-40°C / min by heating the component. m After that, keep the temperature for at least 5 minutes.

[0043] Step 4: Continue heating the vacuum furnace by heating the components until the temperature reaches (0.6-0.8)×T m , soften the soldering sheet and keep the temperature for at least 10 minutes; where T m The melting point of the solder sheet.

[0044] In an optional embodiment, step 4 includes: heating the vacuum furnace to a temperature of (0.6-0.8)×T at a heating rate of 30-35°C / min by heating the component. m Afterwards, soften the soldering sheet and keep the temperature for at least 10 minutes.

[0045] The principle is to adopt a step-by-step heating strategy, including preheating at a rate of 35-40 ° C / min to (0.3-0.5) × T m Keep warm for at least 5 minutes, then heat at a rate of 30-35°C / min to (0.6-0.8)×T m And keep it warm for at least 10 minutes to ensure that the components to be welded are heated evenly, reduce irregular deformation caused by thermal stress accumulation, soften the soft soldering sheet but not melt it, and eliminate the problem of difference in thermal expansion coefficient of materials caused by high temperature.

[0046] Step 5: Continuously apply vertical pressure to the components to be welded by the pressure component, and simultaneously apply ultrasonic vibration by the ultrasonic component until the welding of the components to be welded is completed;

[0047] In an optional embodiment, step 5 includes:

[0048] Step 5.1: Continuously apply a vertical pressure of 0.5 to 5 MPa to the assembly to be welded through the pressure assembly.

[0049] Step 5.2: While continuously applying vertical pressure to the assembly to be welded through the pressure assembly, ultrasonic vibration is applied through the ultrasonic assembly at a starting frequency of 20 to 30 kHz and a power of 300 to 500 W.

[0050] The principle is that the pressure component uses air pressure to drive the upper pressure head to apply 0.5 to 5 MPa of vertical pressure. The pressure is precisely applied without damaging the surface of the DBC substrate by utilizing the high-temperature resistant polytetrafluoroethylene contact surface between the lower and upper pressure heads. This promotes the plastic flow and atomic diffusion of the solder, achieving a close contact interface, improving the connection strength, and preventing fatigue failure of the solder layer. While applying vertical pressure, the ultrasonic component vibrates at a frequency of 20 to 30 kHz and a power output of 300 to 500 W, accelerating the diffusion movement of atoms at the interface, promoting and activating the formation of metallic bonds, and thus forming a highly dense connection layer, significantly shortening the soldering time.

[0051] Step 6: Stop the heating component, pressure component and ultrasonic component, cool to room temperature in a nitrogen atmosphere, take out the welded components to be welded, and complete the low-temperature soft soldering of the IGBT module.

[0052] It is worth noting that for the traditional soft soldering process of solder pieces, the soldering temperature is T m +(20℃~30℃). Due to the high soldering temperature, in order to prevent the solder from oxidizing at high temperature, a mixture of formic acid, H2 or NH3 is used as a reducing agent to reduce metal oxides through chemical reaction, thereby improving the soldering quality. The low-temperature soldering process of the IGBT module in this embodiment can use solder sheets with a melting point above 300℃. Compared with the traditional soldering process, it has a temperature advantage by using a temperature lower than the melting point of the solder, about (0.6~0.8)×T m , which softens the solder but does not melt it. Therefore, no reducing gas is needed during the welding process, only N2 needs to be introduced. Because the welding temperature is lower than the melting point of the solder, the irregular deformation of the base plate caused by the large difference in thermal expansion coefficients between different materials in the traditional welding process is eliminated. In addition, in order to achieve rapid displacement of the activated interface of the contact surface, ultrasonic energy is applied during the welding process to accelerate the diffusion movement of atoms, promote interface bonding, and achieve rapid welding. It is understandable that solder with a melting point below 300°C can also be used, and low-temperature soft soldering can also be achieved in the softening range below the melting point of the solder.

[0053] The low-temperature soft soldering process for IGBT modules of the present invention achieves a soldering connection by strictly controlling the soldering temperature within a softening range below the solder melting point. Through the combined effects of pressure and temperature, the solder is softened and non-melted, completely eliminating the problem of substrate deformation caused by high temperature. Combined with vacuum nitrogen protection and synchronous ultrasonic vibration, welding thermal stress is significantly reduced. Furthermore, the use of nitrogen instead of reducing gas as the sole protective medium simplifies the process system while avoiding oxidation, solving the problems of poor contact and increased thermal resistance caused by differences in thermal expansion coefficients in traditional processes, and improving welding reliability.

[0054] Based on the same inventive concept, the second aspect of the present invention provides an IGBT module low-temperature soldering system for implementing the IGBT module low-temperature soldering process of the first aspect. The preparation method provided by the present invention is described in detail below with reference to the accompanying drawings. Figure 2 and Figure 3 As shown, Figure 2 1 is a schematic structural diagram of a low-temperature soldering system for an IGBT module provided by an embodiment of the present invention; Figure 3 It is a structural schematic diagram of a heating component provided by an embodiment of the present invention.

[0055] In this embodiment, the IGBT module low-temperature soft soldering system includes: a vacuum furnace 1, a heating component 2, a pressure component 3 and an ultrasonic component 4, wherein a nitrogen inlet 12 is provided on one side of the vacuum furnace 1, and a vacuum component 11 is provided on the other side; the component to be welded 10 is provided on the pressure component 3, the heating component 2 is provided in the vacuum furnace 1, and the heating component 2 is provided around the component to be welded 10, and the ultrasonic component 4 is provided below the pressure component 3 and connected to the lower pressure head 31.

[0056] In one optional embodiment, the heating assembly 2 comprises an annular copper tube disposed around the center of the vacuum furnace 1. The tube is encased in an induction coil and contains a cooling water channel for rapid temperature control via liquid cooling. This arrangement, surrounding the component to be welded, enables uniform induction heating and rapid temperature control, optimizing heat distribution, preventing local overheating, improving welding efficiency, and reducing thermal stress.

[0057] In an optional embodiment, the pressure assembly 3 includes: a lower pressure head 31, an upper pressure head 32, a force transmission rod 33 and a pneumatic assembly 34, wherein the lower pressure head 31 is arranged opposite to the upper pressure head 32, the pneumatic assembly 34 is connected to the upper pressure head 32 through the force transmission rod 33, and can drive the upper pressure head 32 relatively close to or away from the lower pressure head 31.

[0058] For example, the contact position between the lower pressing head 31 and the upper pressing head 32 may be made of high-temperature resistant polytetrafluoroethylene (PTFE) to avoid rigid contact between the metal part and the assembly to be welded 10, so as to avoid damaging the surface of the DBC substrate.

[0059] The principle is that in order to form a welding surface, the two surfaces to be welded must be in close contact without melting the metal, so that the attractive force between the atoms can reach the range of (1 to 5) x 10 -8 Therefore, the pressure is pneumatically applied by the pressure component 3 at a pressure between 0.5 and 5 MPa. Under the action of the external pressure, the softened solder first undergoes plastic deformation. Under the action of continuous pressure, the contact area gradually expands, and finally achieves reliable contact of the entire welding surface. Through the mutual diffusion of atoms, a strong welding layer is formed.

[0060] In this embodiment, the working process of the IGBT module low-temperature soft soldering system is as follows: the component to be welded 10 is placed on the lower pressure head 31 through the placement machine, and the vacuum furnace body 1 is sealed; the vacuum component 11 first quickly evacuates the cavity to a low pressure (such as 5 to 10 mbar), injects nitrogen (such as 950 mbar) through the nitrogen inlet 12, and then evacuates to an ultra-low pressure (such as 1 to 5 mbar) again. The oxygen content in the welding furnace cavity can be effectively reduced by multiple vacuuming and nitrogen filling, and under the premise that the total vacuuming time remains unchanged, increasing the number of vacuuming times is better than a single long-term vacuuming effect. The heating component 2 is activated, and the induction coil surrounds the component to be welded 10 and heats it to 0.3 to 0.5 times the melting point of the solder and keeps it warm. Then, the heating component 2, pressure component 3, and ultrasonic component 4 are triggered synchronously, and the heating component 2 continues to heat it to 0.6 to 0.8 times the melting point of the solder to soften the solder. The heating is divided into two steps. The first step is the preheating stage, in which the temperature rises to 0.3 to 0.5 times the melting point of the solder to ensure uniform heating of the component to be welded 10. The second step is the heating stage, in which the temperature rises to 0.6 to 0.8 times the melting point of the solder to soften the solder. At this time, external pressure is applied by the air pressure component 34, and welding is achieved through the mutual diffusion of atoms. The air pressure component 34 drives the force transmission rod 33 to drive the upper pressure head 32 to apply vertical pressure, and the ultrasonic component 4 outputs high-frequency vibration. After 10 to 30 minutes, the heating component 2, air pressure component 34, and ultrasonic component 4 are stopped, and the component to be welded 10 is cooled to room temperature in a nitrogen atmosphere. Finally, the welded component to be welded 10 is removed to achieve a high-reliability connection.

[0061] Notably, the low-temperature soldering system for IGBT modules, according to the second aspect of the present invention, achieves uniform plastic flow and atomic diffusion of the solder under sustained pressure by optimizing the pressure conduction structure and the induction heating layout of the annular heating assembly 2. Ultrasonic vibration accelerates interface activation, forming a highly dense connection layer and eliminating the fatigue failure risk of conventional soldering layers. A pneumatically driven pressure assembly 3, combined with a flexible contact pressure head, ensures precise application of pressure without damaging the DBC substrate. The entire system integrates vacuum temperature control, pressure, and ultrasonic energy, significantly improving solder interface reliability while reducing equipment costs.

[0062] It should be noted that the low-temperature soldering system for IGBT modules provided in the second aspect of the present invention can be used to implement the low-temperature soldering process for IGBT modules provided in the first aspect, and therefore has similar beneficial effects as the method embodiment of the first aspect. For technical details not disclosed in the apparatus embodiment of the present invention, please refer to the description of the method embodiment for an understanding.

[0063] It should be noted that, in this document, relational terms such as first and second are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device comprising the element. Terms such as "connected" or "connected" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. References to orientations or positional relationships, such as "upper," "lower," "left," and "right," are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the description of the present invention. They do not indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention.

[0064] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A low-temperature soldering process for IGBT modules, characterized in that: include: Placing a soldering sheet and a DBC substrate in sequence to form an assembly to be welded, and placing the assembly to be welded in a vacuum furnace; Evacuate the vacuum furnace, and then inject nitrogen into the vacuum furnace; Preheat the component to be welded by heating the component and maintain the temperature for at least 5 minutes; The heating component is used to continuously heat the vacuum furnace until the temperature reaches (0.6-0.8)×T m , soften the soldering sheet and maintain the temperature for at least 10 minutes; wherein, T m is the melting point of the soldering sheet; Continuously applying vertical pressure to the assembly to be welded by a pressure component, and simultaneously applying ultrasonic vibration by an ultrasonic component until the welding of the assembly to be welded is completed; The heating component, the pressure component and the ultrasonic component are stopped, and the mixture is cooled to room temperature in a nitrogen atmosphere. The welded component to be welded is taken out, and the low-temperature soft soldering of the IGBT module is completed.

2. The IGBT module low temperature soldering process according to claim 1, characterized in that: The melting point of the soldering sheet is higher than 300°C.

3. The low-temperature soldering process for IGBT modules according to claim 1, characterized in that: The vacuum furnace is evacuated, and nitrogen is then injected into the vacuum furnace, comprising: The vacuum furnace was evacuated to a chamber pressure of 5 to 10 mbar, and nitrogen was injected into the vacuum furnace at a flow rate of 50 sl / min until the chamber pressure reached 950 mbar. The vacuum furnace was re-evacuated to a chamber pressure of 1 to 5 mbar and maintained for 5 to 10 seconds. Nitrogen was re-injected into the vacuum furnace at a flow rate of 50 sl / min until the pressure in the chamber was 950-1000 mbar.

4. The low-temperature soldering process for IGBT modules according to claim 1, characterized in that: Preheat the components to be soldered by heating the assembly and maintain the temperature for at least 5 minutes, including: The heating component is used to increase the temperature at a rate of 35-40°C / min until the temperature in the vacuum furnace reaches (0.3-0.5)×T m After that, keep the temperature for at least 5 minutes.

5. The low-temperature soldering process for IGBT modules according to claim 1, characterized in that: The heating component is used to continuously heat the vacuum furnace until the temperature reaches (0.6-0.8)×T m , softening the soldering sheet and maintaining the temperature for at least 10 minutes, comprising: The heating component is used to increase the temperature at a rate of 30-35°C / min until the temperature in the vacuum furnace reaches (0.6-0.8)×T m Afterwards, the solder sheet is softened and kept at the temperature for at least 10 minutes.

6. The IGBT module low temperature soldering process according to claim 1, characterized in that: Continuously applying vertical pressure to the assembly to be welded by a pressure component includes: continuously applying a vertical pressure of 0.5 to 5 MPa to the assembly to be welded by the pressure component.

7. The low-temperature soldering process for IGBT modules according to claim 1, characterized in that: At the same time, ultrasonic vibration is applied by the ultrasonic component, including: while continuously applying vertical pressure to the component to be welded by the pressure component, ultrasonic vibration is applied by the ultrasonic component at an oscillation frequency of 20 to 30 kHz and a power of 300 to 500 W.

8. A low-temperature soldering system for IGBT modules, characterized in that: For realizing the low-temperature soft soldering process of the IGBT module according to any one of claims 1 to 7, the system comprises: a vacuum furnace, a heating component, a pressure component and an ultrasonic component, wherein: A nitrogen inlet is provided on one side of the vacuum furnace, and a vacuum component is provided on the other side; the component to be welded is provided on the pressure component, the heating component is provided in the vacuum furnace, and the heating component is provided around the component to be welded, and the ultrasonic component is provided below the pressure component.

9. The IGBT module low temperature soldering system according to claim 8, characterized in that: The heating assembly includes an annular copper tube, which is arranged around the central area of ​​the vacuum furnace, an induction coil is arranged on the outer shell of the annular copper tube, and a cooling water channel is arranged inside the annular copper tube.

10. The IGBT module low temperature soldering system according to claim 8, characterized in that: The pressure assembly includes: a lower pressure head, an upper pressure head, a force transmission rod and a pneumatic assembly, wherein the lower pressure head is arranged opposite to the upper pressure head, and the pneumatic assembly is connected to the upper pressure head through the force transmission rod and can drive the upper pressure head to be relatively close to or away from the lower pressure head.

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