Soft soldering process and device for IGBT module terminal

Abstract

The invention discloses an IGBT module terminal soft soldering process and device, solves the problems that in the prior art, a heating plate needs to set higher temperature, a small-area terminal bonding pad needs to be welded, the welding process time is prolonged, and the production efficiency is reduced, and achieves heat concentration, short heating time, small heat affected area, small welding deformation and high welding efficiency. The process comprises the following steps: feeding a DBC substrate assembly assembled with a terminal into a heating cavity, vacuumizing, filling nitrogen, cleaning the cavity, and integrally preheating; and the diamond drill bit on the top is driven to move to a welding pin area, rotary pressing and synchronous wire feeding are conducted, and welding wires are melted through friction heat to form eutectic welding seams. And then air hole defoaming treatment is conducted, and finally the workpiece is conveyed to a cooling cavity to be cooled.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device manufacturing technology, and in particular to a soft soldering process and apparatus for IGBT module terminals. Background Technology

[0002] Power terminals and signal terminals (collectively referred to as "terminals") are the interfaces for power conversion in Insulated Gate Bipolar Transistor (IGBT) modules. There are generally two methods for their formation: one is to directly solder copper-based or nickel-based metal terminals to the metal layer of the Direct Bonded Copper (DBC) substrate; the other is to form the DBC metal layer through epitaxy and bending. Because the second process significantly increases the processing difficulty of the DBC, it is not widely used. Currently, terminals are generally connected to the DBC using ultrasonic welding or soft soldering techniques to achieve current conduction. In applications, terminals combine force and current receiving, generating thermal and mechanical stresses that affect the lifespan of the IGBT module. Therefore, the welding strength of the power terminals has become an important indicator for evaluating the performance of IGBT modules.

[0003] Ultrasonic welding uses high-frequency ultrasonic energy to cause metal atoms to diffuse between two materials at the interface, ultimately forming a high-strength bond. The process is simple and fast, with low contact resistance and high bond strength, better meeting the requirements of IGBT terminals for low resistance and high strength. It eliminates the need for solder, achieving solid-state metallurgical bonding through high-frequency vibration, avoiding oxidation and contamination problems during solder melting. However, due to the small size of IGBT module welding terminals and the fragility of the DBC insulating ceramic substrate, the welding requirements are more precise. Welding requires strict control of parameters such as welding force, amplitude, deformation, and energy to ensure weld consistency. Ultrasonic welding is suitable for high-reliability, high-power-density automotive-grade IGBT modules, such as the three-electric systems of new energy vehicles.

[0004] For general industrial applications where cost is critical or process requirements are not stringent, terminal soldering technology is widely adopted. This technology primarily utilizes vacuum reflow soldering, and the solder can be either solder paste or solder pads. When using solder paste, flux is required, and cleaning is necessary after soldering, making it susceptible to the effects of humid environments. In contrast, solder pad soldering typically requires no flux, eliminates the need for cleaning after soldering, and results in a more uniform solder layer.

[0005] The existing temperature control system of a vacuum reflow soldering furnace mainly consists of a heating power supply, heating resistance wire, heating plate, cooling water pipes, cooling plate, temperature sensor, and temperature controller, and includes an over-temperature protection device. During operation, the heating plate maintains a constant temperature. The heating rate is controlled by adjusting the distance between the heating plate and the process tray, and the cooling rate is controlled by adjusting the distance between the cooling plate and the process tray. Therefore, existing vacuum reflow soldering is more suitable for large-area soldering. For point-contact terminal soldering, the heat from the heating plate passes through the process tray, the base plate, the solder layer on the base plate, and the DBC (Diamond-Cooled Base) before reaching the terminal. Therefore, the heating plate needs to be set to a higher temperature. Soldering small-area terminal pads increases the soldering time and reduces production efficiency. Summary of the Invention

[0006] This invention provides a soft soldering process and apparatus for IGBT module terminals, which solves the problems in the prior art where the heating plate needs to be set to a higher temperature, the soldering of small-area terminal pads is longer, and the production efficiency is reduced. It achieves concentrated heat, short heating time, small heat-affected zone, small welding deformation, and high welding efficiency.

[0007] In a first aspect, the present invention provides a soft soldering process for IGBT module terminals, comprising: S1: Assemble the base plate assembly and terminals after welding the DBC to the base plate into a workpiece, and transport the workpiece to the heating chamber; S2: Perform vacuuming and nitrogen filling operations on the heating chamber to complete the chamber cleaning; S3: Preheat the workpiece inside the heating chamber as a whole; S4: Drive the diamond drill bit located at the top of the heating chamber to move above the welding pin area of ​​the terminal, control the diamond drill bit to rotate at high speed along a concentric circle trajectory and feed downwards, and at the same time start the welding wire feeding mechanism to deliver the welding wire; use the heat energy generated by the friction between the diamond drill bit and the welding pin to melt the welding wire, so that the molten solder fills and covers the welding area, and forms a eutectic bond with the welding pin; S5: In the heating chamber, the molten solder in the terminal welding pin area is subjected to a degassing treatment to remove air bubbles; S6: Transport the workpiece to the cooling chamber for cooling.

[0008] In conjunction with the first aspect, in one possible implementation, the process of performing vacuuming and nitrogen purging on the heating chamber to complete the chamber cleaning includes: The heating chamber is evacuated to a pressure of 5-10 mbar and held for 2-5 seconds. Then, nitrogen is injected at a flow rate of 50 sl / min until the pressure inside the chamber reaches 950 mbar and held for 2-5 seconds. The evacuation is then continued to a pressure of 1-5 mbar and held for 5-10 seconds.

[0009] In conjunction with the first aspect, in one possible implementation, the overall preheating of the workpiece within the heating chamber includes: The heating plate is first heated to 150~200℃ and held for 5~10s. Then, NH mixed gas is injected into the heating chamber at a flow rate of 50sl / min until the pressure inside the chamber reaches 950mbar.

[0010] In conjunction with the first aspect, in one possible implementation, the process of performing a degassing treatment on the molten solder in the terminal welding pin area within the heating chamber includes: The heating chamber is subjected to multiple cycles of slow vacuuming and NH gas filling, with the flow rate of NH gas filling decreasing in each cycle.

[0011] In conjunction with the first aspect, in one possible implementation, the flow rates of the NH mixed gas are successively 80~90 sl / min, 50~60 sl / min, 30~40 sl / min, 20~25 sl / min, and 10~15 sl / min, with each flow rate condition maintained for 20~30 seconds.

[0012] Secondly, the present invention provides an IGBT module terminal soft soldering device for implementing the IGBT module terminal soft soldering process, comprising: a heating chamber 10, wherein a heating plate 11, a diamond drill bit, and a welding wire feeding mechanism 12 are disposed inside the heating chamber 10; the heating plate 11 is used to support and preheat the workpiece; the diamond drill bit and the welding wire feeding mechanism 12 are used to perform friction heating on the terminal leads; The control unit 50 is electrically connected to the heating plate 11, the diamond drill bit, and the welding wire feeding mechanism 12, respectively, and is used to control the preheating temperature, the drill bit movement, and the welding process. A vacuum and atmosphere control system, connected to the control unit 50 and the heating chamber 10, is used to regulate the pressure and gas environment inside the chamber. A cooling chamber 20, located downstream of the heating chamber 10, is used to cool the welded workpiece; and a conveying mechanism 30 is used to sequentially convey the process tray 2 of the assembled workpiece through the heating chamber 10 and the cooling chamber 20.

[0013] In conjunction with the second aspect, in one possible implementation, the vacuum and atmosphere control system includes: Vacuum pump 14 is used to evacuate the heating chamber 10; The inflation valve 19 is used to selectively inject nitrogen or NH mixture into the heating chamber 10; Pressure sensor 15 is used to detect the pressure inside the heating chamber 10; Solenoid valve 13 serves as a throttle valve in the vacuum pipeline; The vacuum pump 14, the inflation valve 19, and the solenoid valve 13 are all controlled by the control unit 50. The control unit 50 adjusts the working status of each valve and the vacuum pump according to the feedback signal from the pressure sensor 15.

[0014] In conjunction with the second aspect, one possible implementation also includes: Displacement sensor 18 is used to detect the position of the diamond drill bit in the X, Y, and Z directions; A contact sensor 16 is disposed at the workpiece entry position in the heating chamber 10 to detect whether the workpiece has reached the designated work station; The lifting sensor 17 is used to monitor and provide feedback on the lifting position of the heating plate 11 or related actuator.

[0015] In conjunction with the second aspect, in one possible implementation, the control unit 50 is configured to execute the following control logic: A control signal S30 is output to the conveying mechanism 30 to control the cycle feed of the process tray 2 and the opening and closing of the input port 31 and the output port 32; Upon receiving the detection signal S16 from the contact sensor 16 and confirming that the workpiece is in place, the welding process is initiated. A heating control signal S11 is output to the heating plate 11, and a welding control signal S12 is output to the diamond drill bit and welding wire feeding mechanism 12.

[0016] In conjunction with the second aspect, in one possible implementation, the cooling cavity 20 is provided with a cooling plate 21, and the cooling method of the cooling plate 21 is a combination of water cooling and air cooling.

[0017] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention assembles the substrate assembly and terminals after welding the DBC to the base plate into a workpiece, and then transports the workpiece to the heating chamber. Automated transport provides a foundation for precise positioning and efficient production for subsequent welding. The heating chamber is evacuated and filled with nitrogen to clean it, effectively removing oxygen and impurities and creating a clean, oxygen-free environment for welding, preventing oxidation of the weld surface. S3: The workpiece in the heating chamber is preheated uniformly to a suitable welding temperature, reducing thermal shock during subsequent welding and preventing accidental melting of the existing solder layer. The diamond drill bit, located at the top of the heating chamber, is driven to move above the welding pin area of ​​the terminal. The drill bit is controlled to rotate at high speed along a concentric circular trajectory and feed downwards, while the welding wire feed is initiated. The mechanism feeds the welding wire; the instantaneous high heat generated by the friction between the diamond drill bit and the welding pin melts the welding wire, allowing the molten solder to fill and cover the welding area, forming a strong eutectic bond with the welding pin. This method features extremely concentrated heat, short action time, and a small heat-affected zone, effectively protecting the surrounding fragile DBC ceramic substrate. Inside the heating chamber, the molten solder in the terminal welding pin area undergoes a degassing treatment. Through multiple cycles of vacuuming and filling with reducing gas, the internal pores of the solder are completely eliminated, significantly improving the density and long-term reliability of the welding interface. The workpiece is then transported to the cooling chamber for cooling, using a combination of water cooling and air cooling to achieve rapid and uniform cooling, solidifying the solder joints and stabilizing the structure, further ensuring the welding strength and overall performance of the module. Attached Figure Description

[0018] Figure 1 A flowchart of the IGBT module terminal soft soldering process steps provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the working area of ​​the diamond drill bit and terminal welding area provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the welding wire feeding mechanism provided in an embodiment of the present invention; Figure 4 This is a structural diagram of the control system of the soft soldering device provided in an embodiment of the present invention; Figure 5 A flowchart of the IGBT module terminal soft soldering process provided in an embodiment of the present invention.

[0019] Reference numerals: 1-Workpiece; 2-Process tray; 10-Heating chamber; 11-Heating plate; 12-Diamond drill bit and welding wire feeding mechanism; 13-Solenoid valve; 14-Vacuum pump; 15-Pressure sensor; 16-Contact sensor; 17-Lifting sensor; 18-Displacement sensor; 19-Inflation valve; 20-Cooling chamber; 21-Cooling plate; 30-Conveying mechanism; 31-Input port; 32-Output port; 40-Operating interface; 50-Control unit; 60-N2 / NH mixed gas path. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] In a first aspect, the present invention provides a soft soldering process for IGBT module terminals, see [link to relevant documentation]. Figure 1 This includes the following steps S1 to S6.

[0022] S1: Assemble the base plate assembly and terminals after welding the DBC to the base plate into a workpiece, and transport the workpiece to the heating chamber; S2: Perform vacuuming and nitrogen purging operations on the heating chamber to complete the chamber cleaning; Here, the heating chamber is evacuated and filled with nitrogen to complete the cleaning process, including: evacuating the heating chamber to a pressure of 5~10 mbar and holding for 2~5 seconds, then injecting nitrogen at a flow rate of 50 sl / min until the pressure inside the chamber reaches 950 mbar and holding for 2~5 seconds, and then evacuating to 1~5 mbar and holding for 5~10 seconds.

[0023] S3: Preheat the workpiece in the heating chamber as a whole; Here, the workpiece inside the heating chamber is preheated as a whole, including: The heating plate is first heated to 150~200℃ and held for 5~10s. Then, NH mixed gas is injected into the heating chamber at a flow rate of 50sl / min until the pressure inside the chamber reaches 950mbar.

[0024] S4: Drive the diamond drill bit located at the top of the heating chamber to move above the welding pin area of ​​the terminal, control the diamond drill bit to rotate at high speed along a concentric circle trajectory and feed downwards, and at the same time start the welding wire feeding mechanism to deliver the welding wire; use the heat energy generated by the friction between the diamond drill bit and the welding pin to melt the welding wire, so that the molten solder fills and covers the welding area, and forms a eutectic bond with the welding pin; S5: In the heating chamber, the molten solder in the terminal welding pin area is subjected to degassing treatment; Here, in the heating chamber, the molten solder in the terminal welding pin area is subjected to a degassing treatment, which includes: performing multiple slow vacuuming and NH mixed gas filling cycles in the heating chamber, with the flow rate of NH mixed gas decreasing in each cycle.

[0025] Specifically, the flow rates of the NH mixture were 80~90 sl / min, 50~60 sl / min, 30~40 sl / min, 20~25 sl / min, and 10~15 sl / min, respectively, and each flow rate condition was maintained for 20~30 seconds.

[0026] S6: Transport the workpiece to the cooling chamber for cooling.

[0027] In a specific embodiment of this invention, the terminal soldering process proposed in this invention eliminates the need for pre-processing of the solder. After the DBC and the base plate are vacuum reflow soldered into a semi-finished product, they are assembled with terminals using a tooling fixture to form workpiece 1, which then enters the terminal soldering device proposed in this invention. The device's heating plate 11 heats the semi-finished product after the DBC and base plate are soldered to 150-200°C. A diamond drill bit and a wire feeding mechanism 12 located at the top of the cavity are responsible for performing the soldering. After the workpiece is preheated, the diamond drill bit moves above the terminal soldering pins, rotates at high speed along a concentric circle trajectory, and feeds downwards. Simultaneously, the wire feeding mechanism begins feeding the wire. The instantaneous high heat generated by friction melts the solder wire, and the molten solder forms a eutectic bond with the copper pins. This process features extremely concentrated heat, a short action time, and a small heat-affected zone, effectively preventing thermal damage to surrounding components, such as the DBC ceramic substrate.

[0028] See Figure 5 This is a flowchart of the IGBT module terminal soft soldering process of the present invention. The process begins with the workpiece 1 assembled with the process tray, and the workpiece is sequentially fed into the heating chamber via a conveying mechanism. Upon entering the heating chamber, a chamber cleaning step is first performed: vacuuming to low pressure, filling with nitrogen, and then vacuuming again to remove oxygen and impurities from the chamber. Subsequently, the heating plate is activated to preheat the workpiece to the set temperature; simultaneously, the diamond drill bit and welding wire feeding mechanism at the top of the heating chamber begin operation. After preheating, the diamond drill bit moves according to the program to above the terminal soldering pins, rotates at high speed along a concentric circle trajectory, and presses down, while the wire feeding mechanism feeds out the welding wire; frictional heat melts the welding wire, filling the soldering area and forming a eutectic bond. After all terminals are soldered, the solder is degassed through multiple alternating vacuuming and NH3 gas filling cycles to eliminate internal porosity. Finally, the workpiece is sequentially fed into the cooling chamber, where it is cooled using a combination of water cooling and air cooling, completing the entire soldering process. The process embodies continuous automated control of preheating, friction welding, degassing, and cooling, ensuring consistent and reliable welding quality.

[0029] The terminal soldering process proposed in this invention is as follows: Figure 4 As shown.

[0030] S001: After workpiece 1 is assembled with the process pallet, it is moved onto the process pallet track 2, the input port 31 is opened, and workpiece 1 is fed in cycles.

[0031] S002: Input port 31 is closed, workpiece 1 enters the designated position of heating chamber 10, the chamber is evacuated, N2 is filled, vacuum is drawn again, and the chamber cleaning action is completed.

[0032] Vacuum the heating chamber 10 until the internal pressure is 5-10 mbar, hold for 2-5 seconds, then inject nitrogen into the heating chamber 10 at a flow rate of 50 sl / min until the internal pressure reaches 950 mbar, hold for 2-5 seconds, and continue evacuating until the internal pressure is 1-5 mbar, and hold for 5-10 seconds.

[0033] S003: Heating plate 11 operates to preheat workpiece 1 to 150~200℃, maintain for 5~10s, and then inject NH mixed gas into the heating chamber at a flow rate of 50sl / min until the pressure inside the chamber reaches 950mbar. Diamond drill bit and welding wire feeding mechanism 12 starts and enters standby state.

[0034] S004: Under the command of the control unit, the diamond drill bit moves to the designated terminal position, and performs high-speed rotation and downward feed according to the program settings, while the wire feeding mechanism feeds the wire. After welding a single terminal is completed using frictional heat, it moves to the next terminal and repeats the operation until all terminals are welded, and then the mechanism resets.

[0035] S005: Degassing of pores in solder is achieved by vacuuming and filling with NH mixed gas. The process involves: slow vacuuming, filling with NH mixed gas at a flow rate of 80-90 sl / min for 20-30 seconds; slow vacuuming, filling with NH mixed gas at a flow rate of 50-60 sl / min for 20-30 seconds; slow vacuuming, filling with NH mixed gas at a flow rate of 30-40 sl / min for 20-30 seconds; slow vacuuming, filling with NH mixed gas at a flow rate of 20-25 sl / min for 20-30 seconds; and slow vacuuming, filling with NH mixed gas at a flow rate of 10-15 sl / min for 20-30 seconds. Degassing of pores is then complete.

[0036] S006: The cooling chamber 20 door is opened, and workpiece 1 is fed in a cycle. The cooling method is water cooling + air cooling.

[0037] Secondly, the present invention provides an IGBT module terminal soft soldering device for implementing the IGBT module terminal soft soldering process, comprising: a heating chamber 10, wherein a heating plate 11, a diamond drill bit and a welding wire feeding mechanism 12 are disposed inside the heating chamber 10; the heating plate 11 is used to support and preheat the workpiece; the diamond drill bit and the welding wire feeding mechanism 12 are used to perform friction heating on the terminal pins; The control unit 50 is electrically connected to the heating plate 11, the diamond drill bit and the welding wire feeding mechanism 12 respectively, and is used to control the preheating temperature, the drill bit movement and the welding process; Here, the control unit 50 is configured to execute the following control logic: output a control signal S30 to the conveying mechanism 30 to control the cycle feed of the process tray 2 and the switching of the input port 31 and the output port 32; receive the detection signal S16 from the contact sensor 16, and start the welding process after confirming that the workpiece is in place; output a heating control signal S11 to the heating plate 11, and output a welding control signal S12 to the diamond drill bit and welding wire feeding mechanism 12.

[0038] A vacuum and atmosphere control system, connected to the control unit 50 and the heating chamber 10, is used to regulate the pressure and gas environment inside the chamber; Here, the vacuum and atmosphere control system includes: a vacuum pump 14 for evacuating the heating chamber 10; an inflation valve 19 for selectively filling the heating chamber 10 with nitrogen or NH mixture; a pressure sensor 15 for detecting the pressure inside the heating chamber 10; and a solenoid valve 13 as a throttling valve in the vacuum pipeline. The vacuum pump 14, inflation valve 19, and solenoid valve 13 are all controlled by a control unit 50, which adjusts the operating status of each valve and the vacuum pump based on the feedback signal from the pressure sensor 15.

[0039] The cooling chamber 20 is located downstream of the heating chamber 10 and is used to cool the welded workpiece; and the conveying mechanism 30 is used to sequentially convey the process tray 2 of the assembled workpiece through the heating chamber 10 and the cooling chamber 20.

[0040] Here, the cooling chamber 20 is equipped with a cooling plate 21, and the cooling method of the cooling plate 21 is a combination of water cooling and air cooling.

[0041] The IGBT module terminal soldering device also includes: a displacement sensor 18 for detecting the position of the diamond drill bit in the X, Y, and Z directions; a contact sensor 16, located at the workpiece entry position of the heating chamber 10, for detecting whether the workpiece has reached the designated position; and a lifting sensor 17 for monitoring and providing feedback on the lifting position of the heating plate 11 or related actuators.

[0042] In a specific embodiment provided by the present invention, see [link to specific embodiment]. Figure 2 , Figure 2 See the schematic diagram of the working area where the diamond drill bit and terminal are soldered. Figure 3 , Figure 3 This is a schematic diagram of the welding wire feeding mechanism; see [link / reference]. Figure 4 , Figure 4The control system of the terminal soldering device shown includes: a conveying structure 30, an operating interface 40, a control unit 50, an N2 / NH mixed gas path 60, a heating chamber 10, a heating plate 11, a diamond drill bit and welding wire feeding mechanism 12, a solenoid valve 13, a vacuum pump 14, a pressure sensor 15, a contact sensor 16, a lifting sensor 17, a displacement sensor 18, an air filling valve 19, a cooling chamber 20, and a cooling plate 21, in order to control the heating chamber 10, the cooling chamber 20, and the conveying mechanism 30.

[0043] The terminal soldering device proposed in this invention is equipped with a heating chamber 10 and a cooling chamber 20 starting from the input port 31, and performs cycle-feeding of the workpiece 1 so that the workpiece 1 passes through the heating chamber 10 and the cooling chamber 20 to reach the output port 32.

[0044] The conveying mechanism 30 is connected to the control unit 50. After the workpiece 1 is assembled with the process tray, it is transported to the process tray track 2. The control unit 50 sends a control signal S30 to the conveying mechanism 30, the input port 31 opens, and the workpiece 1 is fed in cycles. After welding is completed, the control unit 50 sends a control signal S30 to the conveying mechanism 30, the output port 32 opens, and the workpiece 1 is output in cycles.

[0045] The heating plate 11 is connected to the control unit 50. The control unit 50 outputs a heating control signal S11 to the heating plate 11. The heating control signal S11 is used to heat the heating plate 11 to a specified temperature.

[0046] The lifting sensor 17 is connected to the control unit 50. The control unit 50 outputs a lifting control signal S17 to the lifting sensor 17. The lifting control signal S17 is used to raise or lower the heating plate to maintain a constant set temperature.

[0047] The diamond drill bit and welding wire feeding mechanism 12 is connected to the control unit 50. The control unit 50 outputs a heater control signal S12 to the diamond drill bit and welding wire feeding mechanism 12. The heater control signal S12 is a composite signal of the diamond drill bit's start, stop, rotation speed, feed speed, and motion trajectory, as well as the welding wire feeding mechanism's wire feeding timing and speed.

[0048] The displacement sensor 18 is connected to the control unit 50. The control unit 50 outputs a displacement control signal S18 to the displacement sensor 18 and receives its feedback signal to precisely control the diamond drill bit to move linearly along the X, Y, and Z directions, thereby achieving accurate positioning.

[0049] Solenoid valve 13 is connected to control unit 50. Solenoid valve 13 serves as a throttle valve for vacuum control. Control unit 50 outputs a solenoid valve control signal S13 to solenoid valve 13 to control the valve opening degree of solenoid valve 13.

[0050] Vacuum pump 14 is connected to control unit 50. The vacuum pump is capable of both rapid and slow vacuuming. Control unit 50 outputs a vacuum pump control signal S14 to vacuum pump 14. Vacuum pump control signal S14 is used to control the output of vacuum pump 14.

[0051] Contact sensor 16 is connected to control unit 50. Contact sensor 16 outputs contact detection signal S16 to control unit 50 to detect whether workpiece 1 has reached heating chamber 10.

[0052] Pressure sensor 15 is connected to control unit 50. Pressure sensor 15 generates pressure detection signal S15. Pressure detection signal S15 is a signal indicating the pressure inside heating chamber 10. As pressure sensor 15, thermocouple vacuum gauge, Penning vacuum gauge, Pirani vacuum gauge, etc. can be used.

[0053] The inflation valve 19 is used to supply N2 or NH mixture to the cavity, and the flow rate of the N2 or NH mixture can be adjusted. The self-control unit 50 outputs an inflation valve control signal S19 to the inflation valve 19 for controlling the inflation valve 19. Here, N2 is an inactive gas; the NH mixture is an active gas used for reduction.

[0054] The cooling chamber 20 is connected to the control unit 50. The control unit 50 outputs a cooling control signal S20 to the cooling chamber 20. The cooling method of the cooling chamber 20 is water cooling + air cooling.

[0055] The various embodiments described in this specification are presented in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. All or part of this invention can be used in numerous general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, mobile communication terminals, multiprocessor systems, microprocessor-based systems, programmable electronic devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A soft soldering process for IGBT module terminals, characterized in that, include: S1: Assemble the base plate assembly and terminals after welding the DBC to the base plate into a workpiece, and transport the workpiece to the heating chamber; S2: Perform vacuuming and nitrogen filling operations on the heating chamber to complete the chamber cleaning; S3: Preheat the workpiece inside the heating chamber as a whole; S4: Drive the diamond drill bit located at the top of the heating chamber to move above the welding pin area of ​​the terminal, control the diamond drill bit to rotate at high speed along a concentric circle trajectory and feed downwards, and at the same time start the welding wire feeding mechanism to deliver the welding wire; use the heat energy generated by the friction between the diamond drill bit and the welding pin to melt the welding wire, so that the molten solder fills and covers the welding area, and forms a eutectic bond with the welding pin; S5: In the heating chamber, the molten solder in the terminal welding pin area is subjected to a degassing treatment to remove air bubbles; S6: Transport the workpiece to the cooling chamber for cooling.

2. The IGBT module terminal soft soldering process according to claim 1, characterized in that, The process of performing vacuuming and nitrogen purging on the heating chamber to complete the chamber cleaning includes: The heating chamber is evacuated to a pressure of 5-10 mbar and held for 2-5 seconds. Then, nitrogen is injected at a flow rate of 50 sl / min until the pressure inside the chamber reaches 950 mbar and held for 2-5 seconds. The evacuation is then continued to a pressure of 1-5 mbar and held for 5-10 seconds.

3. The IGBT module terminal soft soldering process according to claim 1, characterized in that, Place The method of preheating the workpiece within the heating chamber includes: The heating plate is first heated to 150~200℃ and held for 5~10s. Then, NH mixed gas is injected into the heating chamber at a flow rate of 50sl / min until the pressure inside the chamber reaches 950mbar.

4. The IGBT module terminal soft soldering process according to claim 1, characterized in that, The process of performing a degassing treatment on the molten solder in the terminal welding pin area within the heating chamber includes: The heating chamber is subjected to multiple cycles of slow vacuuming and NH gas filling, with the flow rate of NH gas filling decreasing in each cycle.

5. The IGBT module terminal soft soldering process according to claim 4, characterized in that, The flow rates of the NH mixed gas were 80~90 sl / min, 50~60 sl / min, 30~40 sl / min, 20~25 sl / min, and 10~15 sl / min, respectively, and each flow rate condition was maintained for 20~30 seconds.

6. An IGBT module terminal soldering apparatus for implementing the IGBT module terminal soldering process according to any one of claims 1 to 5, characterized in that, include: A heating chamber (10) is provided inside which a heating plate (11), a diamond drill bit, and a welding wire feeding mechanism (12) are provided; the heating plate (11) is used to support and preheat the workpiece; the diamond drill bit and the welding wire feeding mechanism (12) are used to perform friction heating on the terminal pins; The control unit (50) is electrically connected to the heating plate (11), the diamond drill bit and the welding wire feeding mechanism (12) respectively, and is used to control the preheating temperature, the drill bit movement and the welding process; A vacuum and atmosphere control system, connected to the control unit (50) and the heating chamber (10), is used to regulate the pressure and gas environment inside the chamber; A cooling chamber (20) is located downstream of the heating chamber (10) and is used to cool the welded workpiece. And a conveying mechanism (30) for sequentially conveying the process tray (2) of the assembled workpiece through the heating chamber (10) and the cooling chamber (20).

7. The IGBT module terminal soldering apparatus according to claim 6, characterized in that, The vacuum and atmosphere control system includes: A vacuum pump (14) is used to evacuate the heating chamber (10); A gas filling valve (19) is used to selectively fill the heating chamber (10) with nitrogen or NH mixture; A pressure sensor (15) is used to detect the pressure inside the heating chamber (10); Solenoid valve (13) serves as a throttle valve in the vacuum pipeline; The vacuum pump (14), the inflation valve (19) and the solenoid valve (13) are all controlled by the control unit (50), which adjusts the working status of each valve and the vacuum pump according to the feedback signal of the pressure sensor (15).

8. The IGBT module terminal soldering apparatus according to claim 6, characterized in that, Also includes: Displacement sensor (18) is used to detect the position of the diamond drill bit in the X, Y, and Z directions; A contact sensor (16) is installed at the workpiece entry position of the heating chamber (10) to detect whether the workpiece has reached the designated work station; A lifting sensor (17) is used to monitor and provide feedback on the lifting position of the heating plate (11) or related actuator.

9. The IGBT module terminal soldering apparatus according to claim 8, characterized in that, The control unit (50) is configured to execute the following control logic: Output control signal (S30) to the conveying mechanism (30) to control the cycle feed of the process tray (2) and the opening and closing of the input port (31) and output port (32); After receiving the detection signal (S16) from the contact sensor (16) and confirming that the workpiece is in place, the welding process is started. A heating control signal (S11) is output to the heating plate (11), and a welding control signal (S12) is output to the diamond drill bit and welding wire feeding mechanism (12).

10. The IGBT module terminal soldering apparatus according to claim 6, characterized in that, The cooling chamber (20) is equipped with a cooling plate (21), and the cooling method of the cooling plate (21) is a combination of water cooling and air cooling.

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