Continuous vacuum welding device and method for IGBT (Insulated Gate Bipolar Translator) chip

Abstract

The invention relates to the technical field of chip welding, and discloses a continuous vacuum welding device for an IGBT (Insulated Gate Bipolar Translator) chip, which comprises a working channel formed by connecting a plurality of working furnaces in series, vacuum gate valves used for sealing the space are installed at an inlet and an outlet of the working channel and the butt joint position of every two adjacent working furnaces, and the conveying mechanism is used for conveying product carriers, is installed in the working furnaces and comprises two conveying assemblies symmetrically distributed on the two sides of the axis of the working channel; the two ends of the product carrier are erected on the conveying parts of the two conveying assemblies correspondingly. The preheating furnace, the welding furnace and the cooling furnace are connected in series to form the working channel, and the vacuum gate valves are mounted at the inlets and the outlets of the cavities, so that the adjacent cavities are independently sealed, the oxygen content of each cavity is controlled in an extremely low range, the ceramic copper-clad plate is prevented from being oxidized, the welding void rate is reduced, and the interface bonding strength is improved.

Description

Technical Field

[0001] This invention relates to the field of chip welding technology, specifically to a continuous vacuum welding apparatus and method for IGBT chips. Background Technology

[0002] Insulated Gate Bipolar Transistor (IGBT) is widely used in new energy vehicles, wind power generation, frequency converters, inverter welding machines, high-speed rail, bullet trains, subways, variable frequency air conditioners, washing machines, aerospace and other fields to achieve high-efficiency, small size, low cost, high reliability and high safety energy conversion and control.

[0003] In the vacuum soldering process of IGBT chips, the ceramic copper-clad laminate, solder and IGBT chip are usually assembled together and placed in a vacuum brazing furnace. The soldering process is completed by strictly controlling parameters such as furnace temperature, furnace gas pressure, vacuum degree, soldering time and heating and cooling rate. By adjusting the process parameters during the soldering process, the air bubbles and voids in the solder layer after soldering are minimized as much as possible, so as to ensure that the IGBT chip has good heat dissipation and current carrying capacity.

[0004] However, the following problems exist in the continuous soldering process of IGBT chips and urgently need to be solved: 1. Oxidation problem of ceramic copper-clad laminate: The main material of the ceramic copper-clad laminate used in the IGBT chip welding method is copper, which is extremely sensitive to oxygen and has a high affinity at high temperatures. If the continuous vacuum welding device is not strictly sealed during the process, the ceramic copper-clad laminate will be oxidized, which will increase the void ratio of the ceramic copper-clad laminate and reduce the interfacial bonding strength. 2. The problem of uniform and rapid heating and cooling: In order to achieve rapid welding of IGBT chips during continuous vacuum welding, the device needs to have the function of rapid heating and rapid cooling. If the heating rate is slow, it will cause problems such as increased energy consumption and slow production cycle. If the cooling rate is slow, it will affect the degree of supercooling, microstructure and crystal type during phase transition, and will also affect production efficiency. At the same time, the number of products on the carrier is generally multiple, and the temperature non-uniformity in the effective area of ​​the cavity will also have an adverse effect on the consistency of parameters after vacuum welding. 3. Continuous production issues: After the IGBT chip enters the vacuum welding device, the atmosphere needs to be controlled by adjusting parameters such as the internal air pressure, inert gas content, reducing gas content, and vacuum degree. The actual temperature of the product can be controlled by adjusting the up-down and back-forward positions of the carrier and the welding time. The control of these parameters is quite complicated, and the continuous operation logic is complex.

[0005] To address the shortcomings of the existing technology, this application proposes a continuous vacuum welding apparatus and method for IGBT chips. Summary of the Invention

[0006] To address the technical problems existing in the background art, the present invention proposes a continuous vacuum welding apparatus and method for IGBT chips.

[0007] This invention proposes a continuous vacuum welding apparatus for IGBT chips, comprising a working channel formed by multiple working furnaces connected in series. A preheating-welding-cooling chamber is sequentially arranged within the working channel along the product conveying direction. Vacuum gate valves for enclosing the space are installed at the inlet and outlet of the working channel and at the junction of adjacent working furnaces. The apparatus also includes: A conveying mechanism for conveying product carriers and installing them inside a working furnace includes two conveying components symmetrically distributed on both sides of the working channel axis, with the two ends of the product carrier respectively mounted on the conveying sections of the two conveying components; The temperature control platform is located between the two conveying components and below the product carrier to regulate the temperature; The lifting mechanism is installed below the working furnace and its movable end extends upward into the working furnace, and drives the temperature control platform to lift and lower to adjust the distance between the temperature control platform and the product carrier. Specifically, there are three working furnaces, which are arranged in sequence as a preheating furnace, a welding furnace, and a cooling furnace. The heating temperature in the preheating furnace is T1, the heating temperature in the welding furnace is T2, and T2≥T1. The outer surfaces of the preheating furnace, the welding furnace, the cooling furnace, and the vacuum gate valve are all made of corrosion-resistant and high-temperature resistant metals, preferably one or more of austenitic stainless steel, duplex stainless steel, nickel high-temperature alloy, and Hastelloy. The vacuum gate valve includes a first valve body, a second valve body, a third valve body, and a fourth valve body. The first and fourth valve bodies are respectively installed at the opening ends of the preheating furnace and the cooling furnace. The second valve body is installed between the preheating furnace and the welding furnace, and the third valve body is installed between the welding furnace and the atmosphere. The gate inside the first, second, third, and fourth valve bodies is driven up and down by a cylinder or an electric cylinder, thereby achieving relative isolation between adjacent preheating furnaces and the atmosphere, between the preheating furnace and the welding furnace, between the welding furnace and the cooling furnace, and between the cooling furnace and the atmosphere. The first valve body, the second valve body, the third valve body, and the fourth valve body are equipped with cooling channels. Refrigerant is introduced into the cooling channels to ensure that the internal sealing structure can be used normally at high temperatures. The refrigerant is any one or more of deionized water, inorganic compounds, Freon, azeotropic solutions, and hydrocarbons. The inner cavities of the preheating furnace, welding furnace, and cooling furnace are each connected to a set of vacuum pumping equipment and gas inlet equipment to create a vacuum environment, inert gas environment, or reducing gas environment in the inner cavities of the preheating furnace, welding furnace, and cooling furnace. The working furnace is also designed with installation interfaces for vacuum pumping pipelines and gas inlet pipelines on both sides. The inert gas is preferably any one or a mixture of nitrogen and argon, and the reducing gas is any one of formic acid and hydrogen, preferably formic acid. The two outer walls of the preheating furnace, welding furnace, and cooling furnace are all welded with cooling channels, into which circulating coolant can be introduced to ensure that the ambient temperature is within a suitable range. The inner walls of the preheating furnace and welding furnace are equipped with reflective screens, which have 2-6 layers and are made of stainless steel, isostatic graphite, or a composite material. Both the preheating furnace and the cooling furnace are equipped with filter components above their openings. The filter components contain filter elements, and the upper end of the filter elements is connected to a negative pressure device via a pipe. When the first valve body and the fourth valve body are opened, the negative pressure device draws in the residual gas in the working channel, causing it to move upward and pass through the filter element for filtration. This prevents the residual gas from being accidentally mixed with harmful gases. The filter element includes any one or more of the following: filter cotton, non-woven fabric, polyester fiber, glass fiber, cotton fiber, nylon fiber, polyurethane sponge, and activated carbon adsorption material. Both sides of the opening ends of the preheating furnace and the cooling furnace are equipped with light curtain safety components to prevent personnel injury caused by the closure of the vacuum gate valve; To address the problems of poor sealing, slow heating and cooling, and inability to produce continuously in traditional welding equipment, this device achieves an integrated "preheating-welding-cooling" process through a three-stage series chamber. The vacuum gate valve can still reliably open and close when the pressure difference is >2000Pa. Combined with the furnace body sealing structure (pressure rise rate <50Pa / h), the oxygen content is controlled below 10ppm, preventing oxidation of the ceramic copper-clad laminate (porosity reduced to below 0.5%). The conveying mechanism adopts a double-sided symmetrical transmission to ensure smooth transport of the carrier (speed 0.1-0.5m / s). The lifting mechanism drives the temperature control platform to rise and fall (stroke 0-50mm). Precise temperature control (temperature difference ±2℃) is achieved through spacing adjustment. The reflector screen (stainless steel or graphite material) reduces heat loss, enabling the preheating furnace to heat up at a rate of 180℃ / min. The cooling furnace achieves a cooling rate of 150℃ / min through the refrigerant flow channel. The production cycle is shortened to 5-15 minutes / piece, which is 3 times more efficient than traditional intermittent equipment.

[0008] As a further optimization of the present invention, the conveying assembly includes a frame installed on the side of the working furnace cavity and extending horizontally along the length of the channel. The inner side of the frame is provided with multiple conveying wheels and multiple rotating shafts. The rotating shafts are rotatably connected to the frame and are evenly distributed along the length of the frame. The conveying wheels are installed on the shaft ends of the rotating shafts, and there is an idle rotating shaft between every two adjacent conveying wheels. The rotating shafts on two adjacent conveying assemblies are connected by a transmission shaft. The rotating shafts are driven to rotate by a drive assembly, so that the multiple conveying wheels rotate synchronously and in the same direction to convey the product carriers on them. The conveying assembly adopts an interval distribution design of "transmission wheel + rotating shaft". The drive shaft ensures synchronous transmission on both sides to avoid the vehicle from deviating. The drive assembly is driven by gear meshing, with a power transmission efficiency of 98%, which can adapt to vehicles of different weights (≤5kg). The design of the idle rotating shaft avoids interference with the synchronous rotation of two adjacent transmission wheels, which is suitable for the smooth transport of precision chip carriers.

[0009] Specifically, the drive assembly includes a spindle, a first motor, and gears. One end of the rotating shaft extends through and to the outside of the frame and is equipped with gears, with two adjacent gears meshing together. The spindle is mounted on the shaft end of one of the rotating shafts, and the spindle is driven by the first motor. The spindle is connected to the output end of the first motor via a transmission magnetohydrodynamic seal, which ensures vacuum sealing of the spindle during rotation (leakage rate < 1 × 10⁻). 7 Pa・m 3 / s), adapting to the vacuum environment inside the furnace, gear meshing transmission ensures smooth conveying and avoids chip displacement caused by carrier vibration.

[0010] Furthermore, a limiting component is installed at the upper end of the frame. The limiting component includes multiple auxiliary wheels evenly distributed along the length of the frame. The axles of the auxiliary wheels are rotatably connected to the frame, and the axis of the axle is perpendicular to the axis of the rotating shaft. The upper sides of the product carrier are respectively rolledly connected to the outer periphery of the auxiliary wheels on the adjacent frame. A limiting plate is installed on the upper end face of the frame near the opening to prevent the carrier from rising too high. The auxiliary wheels (made of polyurethane) restrict the vehicle's deviation from above, forming a "clamping" guide with the transmission wheels. The conveying deviation is ≤0.5mm. The limit plate (50mm in height) provides physical limit when the vehicle is raised or lowered, avoiding chip compression damage caused by excessive rise of the temperature control platform.

[0011] As a further optimized solution of the present invention, the temperature control platform includes a base plate, a top plate, and a temperature control element. The base plate is installed on the movable end of the lifting mechanism, the top plate is installed on the upper end surface of the base plate, and the temperature control element is installed between the base plate and the top plate. The temperature control platform is divided into a heating platform and a cooling platform. Heating platforms are set in both the preheating cavity and the welding cavity, and a cooling platform is set in the cooling cavity. The temperature control element of the heating platform is an electric heating element and is equipped with a temperature control thermocouple. The surface of the temperature control thermocouple head is silver-plated to improve its response speed. The temperature control element of the cooling platform is a cooling channel connected to an external refrigerant unit. The heating platform uses armored electric heating elements (power 5-10kW), and the temperature control thermocouple (K-scale) accuracy is ±1℃. It can stabilize T1 at 150-250℃ and T2 at 250-400℃. The cooling channel of the cooling platform (made of copper) is filled with deionized water or Freon, which, together with the refrigerant unit, achieves rapid cooling (150℃ / min). The top plate is made of oxygen-free copper with a surface flatness of ≤0.01mm to ensure uniform contact with the carrier (temperature uniformity ±2℃).

[0012] Specifically, a small hole is provided on the upper surface of the top plate of the heating platform. A temperature sensing thermocouple for monitoring the temperature of the product carrier is installed in the small hole. The temperature sensing thermocouple (E-scale) is in direct contact with the bottom of the carrier. The response time is <0.5s, and the carrier temperature is fed back in real time (accuracy ±0.5℃). When the carrier temperature is lower than the set value, the lifting mechanism drives the heating platform to rise and get closer to the carrier. When it is higher than the set value, it falls down, realizing closed-loop temperature control and avoiding chip overheating damage.

[0013] As a further optimized solution of the present invention, the lifting mechanism includes a base plate disposed below the working furnace and whose height is adjusted by the lifting assembly. A plurality of top rods are installed on the upper end surface of the base plate, and one end of the top rod extends upward into the working furnace and is fixed to the bottom end of the temperature control platform. The lifting assembly includes a base, a screw, a second motor, and guide rods. The screw is threadedly connected to the base and driven by the second motor. The base plate is threadedly sleeved with the screw, and the guide rods are symmetrically distributed on both sides of the screw. The lower end of the screw is connected to the output end of the servo motor through a bevel gear set, which can precisely adjust the distance between the temperature control platform and the carrier. The cooperation between the guide rod and the base plate prevents the platform from rotating during lifting. Multiple top rods are evenly distributed to ensure that the temperature control platform is under balanced force.

[0014] Furthermore, the lower end face of the working furnace is provided with through holes corresponding to multiple push rods. The end of the push rod away from the base plate passes through the through hole. A telescopic tube is fitted on the outside of the push rod. One end of the telescopic tube is fixed to the upper end of the base plate and is a closed design. The other end of the telescopic tube is an open design and is sealed to the through hole through a flange seal. The telescopic tube (stainless steel corrugated pipe) extends and retracts with the rise and fall of the top rod, and the flange seal (fluororubber) ensures the furnace body's airtightness and prevents vacuum leakage. This structure allows the top rod to rise and fall without disrupting the vacuum inside the furnace, adapting to the needs of continuous production.

[0015] As a further optimization of the present invention, the upper end of the working furnace is open, and an upper cover assembly is installed at the opening and sealed. The upper cover assembly is made of an integral aluminum plate with an anodized surface. An upper cover observation window for observing the morphological characteristics of the product is installed on the upper cover assembly. The main material of the upper cover observation window is borosilicate glass or quartz glass, and the upper cover observation window can be physically blocked. A knob handle is rotatably mounted on the upper end of the cover via a dynamic seal. One end of the knob handle extends to the bottom of the cover and is fitted with a baffle. When it is not necessary to observe the shape and features of the product, rotating the knob handle will cause the baffle to block the observation window of the upper cover, thereby reducing heat loss during vacuum welding. The top cover assembly includes a cover body. One side of the cover body is hinged to the edge of the opening of the working furnace via a connecting block. The other side of the connecting block is equipped with a handle and a locking handle. One end of the locking handle extends to the bottom of the cover body and is equipped with a locking block. By rotating the locking handle, the locking block is driven to rotate synchronously, so that the locking block engages with the inner wall of the opening of the working furnace, thereby locking the cover body. The upper end face of the opening of the working furnace has a circumferentially arranged annular sealing groove. A sealing ring is installed in the sealing groove. The sealing ring is made of one or more of silicone rubber, nitrile rubber, neoprene rubber, and fluororubber to ensure that the pressure rise rate of the furnace body is less than 50Pa / h. When the cover body is locked, the sealing ring seals the joint between the cover body and the opening. An outwardly extending observation tube is installed on the side of the working furnace wall. The outer end of the observation tube is fitted with a visual detection window via a flange seal, and the visual detection window is locked with a clamp. There are at least two observation tubes, symmetrically distributed at both ends of the working furnace wall side. Fiber optic sensors for detecting the real-time position of the carrier and its products inside the working furnace are installed at both visual detection windows. The visual detection windows are made of transparent glass, ensuring that the device is isolated from the outside world while the fiber optic sensors can monitor the actual position of the carrier inside the furnace. An additional observation tube is provided as a spare and is sealed with a blind flange. Formic acid collection mechanisms are installed at the bottom of both the first and second valve bodies. The two formic acid collection mechanisms are connected to the bottom of the inner cavity of the preheating furnace and the welding furnace, respectively. The formic acid collection mechanism includes a glass bottle and a manual vacuum valve. The glass bottle is connected to the bottom of the inner cavity of the preheating furnace or the welding furnace through a collection pipe, and a manual vacuum valve is installed at the end of the collection pipe near the glass bottle. When formic acid is deposited at the bottom of the inner cavity of the preheating furnace and the welding furnace, the manual vacuum valve is opened to allow the formic acid to flow into the glass bottle for recovery under gravity, thereby saving formic acid consumption and reducing processing costs.

[0016] A continuous vacuum welding method for IGBT chips, using the aforementioned welding apparatus, comprises the following steps: S1 stacks the ceramic copper-clad laminate, solder, and IGBT chip in the order of bottom, middle, and top to form a sandwich structure, and places it on the product carrier to form a whole; S2 opens the first valve body, and the conveying mechanism sends the product and product carrier into the preheating furnace. The position of the product carrier is monitored by the fiber optic sensor. When the product carrier moves to the designated position, the first valve body is closed. S3 uses a vacuum pump to control the vacuum level in the preheating furnace at 1-50 mbar, then introduces an appropriate amount of inert gas to raise the pressure in the preheating furnace to 900-1100 mbar, then restarts the vacuum pump to control the vacuum level in the preheating furnace at 1-10 mbar, and then introduces an appropriate amount of formic acid and nitrogen mixture. S4 drives the heating platform inside the preheating furnace to rise through the lifting mechanism, so that the top plate is in contact with the bottom of the product carrier and preheats the product. The heating time of the product carrier and the distance between the product carrier and the heating platform are controlled so that the product on the product carrier is fully preheated to temperature T1 in the preheating furnace and maintained for a period of time. The time for this process step is t1. S5 drives the heating platform in the preheating furnace to descend through the lifting mechanism, the second valve body opens, and the product carrier carries the product to the welding furnace through the conveying mechanism. The vacuum degree in the welding furnace is controlled at 1-50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to increase the pressure in the welding furnace to 900-1100 mbar. The vacuum equipment is started again to control the vacuum degree in the welding furnace at 1-10 mbar, and then an appropriate amount of formic acid and nitrogen mixed gas is introduced. After the product carrier leaves the preheating furnace with the product, the first valve body and the second valve body are closed, and the preheating furnace enters the flushing stage. That is, the vacuum degree in the preheating furnace is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to increase the pressure in the preheating furnace to 900 to 1100 mbar, which is repeated 1 to 3 times. S6 drives the heating platform inside the welding furnace to rise through the lifting mechanism, so that the top plate is in contact with the bottom of the product carrier and heats the product, so that the product on the product carrier is fully welded in the welding furnace and held for a period of time. The time for this process step is t2, and t2>t1. S7 drives the heating platform inside the welding furnace to descend through the lifting mechanism, the third valve body opens, the product carrier carries the product through the conveying mechanism to the cooling furnace, the vacuum degree inside the cooling furnace is controlled at 1-50mbar by the vacuum equipment, and then an appropriate amount of nitrogen is introduced. After the product carrier leaves the welding furnace with the product, the second and third valves are closed, and the welding furnace enters the flushing stage. That is, the vacuum degree in the welding furnace is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to increase the pressure in the welding furnace to 900 to 1100 mbar, which is repeated 1 to 3 times. S8 drives the cooling platform of the cooling furnace to rise through the lifting mechanism, so that the top plate is in contact with the bottom of the product carrier and the product is cooled. Through heat exchange with the refrigerant, the carrier and the product are cooled to the set temperature. Then the fourth valve is opened. After the product carrier carries the product away from the cooling furnace through the conveying mechanism, the fourth valve is closed. The time for this process step is t3, and t3>t2. After the product carrier leaves the cooling furnace with the product, the third and fourth valves are closed, and the cooling furnace enters the flushing stage. That is, the vacuum degree in the cooling furnace is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to increase the pressure in the cooling furnace to 900 to 1100 mbar, which is repeated 1 to 3 times. This method replaces residual air (oxygen content <10ppm) through a "vacuum-gas filling" cycle, uses formic acid as a reducing gas to prevent copper oxidation, reduces the welding void rate to below 0.5%, preheating (T1=200℃, t1=120s) softens the solder, welding (T2=300℃, t2=300s) ensures a dense weld layer, and cooling (t3=600s) controls the phase transformation structure. The parameters of each step are independently controlled and seamlessly connected through a conveying mechanism, enabling continuous production (capacity 120 pieces / hour), improving the yield by 40% compared to traditional methods.

[0017] The continuous vacuum welding apparatus and method for IGBT chips proposed in this invention have the following beneficial effects: (i) The multi-stage cavity works in conjunction with the vacuum gate valve to achieve continuous production and ensure sealing performance. The preheating furnace, welding furnace, and cooling furnace are connected in series to form a working channel. Vacuum gate valves are installed at the inlet and outlet of each cavity to ensure independent sealing of adjacent cavities. This keeps the oxygen content of each cavity in an extremely low range (<10ppm), effectively preventing oxidation of the ceramic copper-clad laminate, reducing welding voids, and thus improving the interfacial bonding strength. (ii) The temperature control platform works in conjunction with the lifting mechanism to achieve rapid and uniform temperature rise and fall. The heating platforms of the preheating furnace and welding furnace adopt a constant temperature design (T1=150-250℃, T2=250-400℃). The distance between the heating platform and the product carrier is adjusted (0-50mm) through the lifting mechanism. With the help of reflective screens (2-6 layers), heat loss is reduced, and the heating rate reaches 180℃ / min. The cooling platform achieves a cooling rate of 150℃ / min through the refrigerant flow channel. Actual measurements show that the temperature uniformity deviation within the effective area of ​​the cavity is ≤±2℃, and the consistency of multiple product batches is improved by 40%. This solves the problems of slow heating and cooling and uneven temperature caused by traditional equipment, resulting in low production efficiency and product differences. (iii) Precise atmosphere control and recycling design reduce costs and improve welding quality. Each chamber is independently connected to a vacuum pump and an air intake device, allowing for flexible switching between vacuum (1-50 mbar), inert gas (N2, Ar), or reducing gas (formic acid) environments. During preheating and soldering, residual air is replaced through a "vacuum-air filling" cycle (1-3 times), increasing formic acid utilization by 60%. The formic acid collection mechanism at the bottom (glass bottle + manual vacuum valve) recovers condensed formic acid, which helps save raw material costs. Moreover, this design can improve the density of the solder layer and meet the high heat dissipation requirements of IGBT chips. (iv) Symmetrical conveying mechanism and limiting components to ensure product transmission stability The conveying mechanism uses symmetrical double-sided conveyor wheels and rotating shafts to achieve synchronous transmission through the drive shaft. With the auxiliary wheels of the limit component, the product carrier is restricted from deflection. The conveying speed is adjustable, and multiple products can be carried in a single batch, which improves the production cycle and significantly increases the efficiency compared to traditional intermittent production. (v) Safety and environmental protection design to improve operational safety and reduce pollution. Light grating safety components are installed at the entrance and exit of the working channel to prevent personnel injury caused by misoperation of the vacuum gate valve. The filter component adsorbs residual harmful gases (such as formic acid vapor) through activated carbon and glass fiber filter elements, with a purification efficiency of over 95%. The cooling channel is circulated with refrigerant to keep the outer wall temperature of the cavity below 50°C, while extending the life of the seals and reducing the maintenance frequency. (vi) The device focuses on uniform preheating in a low-oxygen environment through the preheating chamber, the welding chamber focuses on the pressure and atmosphere coordination of high-temperature welding, and the cooling chamber controls the rapid cooling rate. The parameters of each link are set independently but are seamlessly connected through the conveying mechanism, which avoids the logical confusion caused by the frequent switching of parameters in traditional single chambers and achieves stable connection of continuous production. By using a conveying mechanism in conjunction with fiber optic sensors to locate the carrier position in real time, the product is accurately transferred between cavities. The vacuum gate valve can still reliably open and close when the pressure difference is >2000Pa, realizing the automated linkage of "cavity isolation - parameter adjustment - carrier transmission". This eliminates the process interruption caused by traditional manual intervention and makes the continuous operation logic clear and controllable. The welding method clearly defines the timing design of "preheating time t1 < welding time t2 < cooling time t3", and coordinates with the lifting control of the heating / cooling platform (precise temperature control through spacing adjustment) to match the parameters of each cavity with the carrier's transmission rhythm to ensure continuous operation; The device adopts a modular cavity design, which can increase or decrease the number of cavities according to production capacity requirements (such as adding two welding cavities to improve batch processing capacity). The parameters of each cavity are linked through a unified control system, eliminating the need to rewrite the logic program. This design improves the flexibility of continuous production capacity, adapts to the production needs of different batch sizes, and avoids the logic reconstruction problem of traditional fixed structures when adjusting production capacity. In summary, by segmented independent control, automated linkage, timing optimization, and modular design, the problem of "strict parameter control leading to complex continuous operation logic" has been effectively resolved, and efficient continuous production of IGBT chip vacuum welding has been achieved.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the continuous vacuum welding apparatus for IGBT chips provided by the present invention. Figure 2 This is a schematic diagram of the working furnace of the continuous vacuum welding apparatus for IGBT chips provided by the present invention. Figure 3 This is a front cross-sectional view of the working furnace of the continuous vacuum welding apparatus for IGBT chips provided by the present invention. Figure 4 This is a schematic diagram of the conveying mechanism of the continuous vacuum welding device for IGBT chips provided by the present invention. Figure 5 This is a schematic diagram of the temperature control platform of the continuous vacuum welding device for IGBT chips provided by the present invention. Figure 6 This is a schematic diagram of the lifting mechanism of the continuous vacuum welding device for IGBT chips provided by the present invention. Figure 7 This is a first-view structural schematic diagram of the cover assembly of the continuous vacuum welding device for IGBT chips provided by the present invention. Figure 8 This is a second-view structural schematic diagram of the cover assembly of the continuous vacuum welding device for IGBT chips provided by the present invention. Figure 9 This is a schematic diagram of the internal structure of the working furnace of the continuous vacuum welding apparatus for IGBT chips provided by the present invention.

[0020] Figure Descriptions: 1. Working furnace; 101. Preheating furnace; 102. Welding furnace; 103. Cooling furnace; 2. Vacuum gate valve; 21. First valve body; 22. Second valve body; 23. Third valve body; 24. Fourth valve body; 3. Conveying mechanism; 31. Frame; 32. Conveying wheel; 33. Rotating shaft; 34. Main shaft; 35. First motor; 36. Transmission magnetohydrodynamic seal; 37. Transmission shaft; 38. Limiting assembly; 39. Gear; 4. Temperature control platform; 41. Base plate; 42. Top plate; 43. Temperature control element; 44. Temperature sensing thermocouple; 5. Lifting mechanism; 51. Base 52. Plate; 53. Top rod; 54. Telescopic tube; 55. Base; 56. Screw; 57. Second motor; 58. Guide rod; 69. Sealing ring; 60. Top cover assembly; 61. Cover body; 62. Connecting block; 63. Handle; 64. Locking handle; 65. Locking block; 7. Top cover observation window; 8. Baffle; 9. Knob handle; 10. Sealing ring; 11. Visual detection window; 12. Fiber optic sensor; 13. Cooling channel; 14. Thermocouple; 15. Blind plate; 16. Glass bottle; 17. Manual vacuum valve; 18. Dynamic seal; 19. Filter assembly; 20. Light grating safety assembly. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0023] Please see Figures 1-9A continuous vacuum welding device for IGBT chips is proposed. This device addresses issues such as easy oxidation of ceramic copper-clad laminates, insufficient heating and cooling rates, and complex continuous production logic in IGBT chip welding. It adopts a "three-stage series chamber + modular functional integration" design. The preheating furnace 101, welding furnace 102, and cooling furnace 103 are sequentially and sealed together by a vacuum gate valve 2 to form a closed working channel. Each chamber is independently equipped with vacuum pumping equipment (Roots pump + mechanical pump combination, inert gas + formic acid mixed gas path in the air intake system) and a temperature control module. The carrier is continuously transported through the conveying mechanism 3. The distance between the temperature control platform 4 and the carrier is adjusted by the lifting mechanism 5 to achieve full automation of the "preheating-welding-cooling" process. Taking the application of IGBT module production line for a new energy vehicle as an example, the device can continuously process 10mm×10mm chips, carry 8 chips in a single batch, have a production cycle of 8 minutes per batch, and a solder layer void rate of ≤0.5%, which is 3 times more efficient than traditional intermittent equipment.

[0024] Specifically, the preheating furnace 101, welding furnace 102, and cooling furnace 103 are all forged from 316L austenitic stainless steel, which can withstand internal pressure of 1-1200 mbar. Water cooling channels 13 are welded on both sides and the bottom, through which 30℃ deionized water is introduced at a flow rate of 2L / min to ensure that the outer wall temperature is ≤50℃. An annular sealing groove with a depth of 5mm is opened at the top opening, and a sealing ring 10 made of fluororubber is built in. The compression is controlled at 30%. After being pressed by the upper cover assembly 6, the pressure rise rate is ≤50Pa / h, and the oxygen content is controlled below 10ppm to avoid oxidation of the ceramic copper-clad laminate.

[0025] Specifically, such as Figure 1 As shown, the vacuum gate valve 2 includes a first valve body 21 located at the inlet of the preheating furnace 101, a second valve body 22 located between the preheating furnace 101 and the welding furnace 102, a third valve body 23 located between the welding furnace 102 and the cooling furnace 103, and a fourth valve body 24 located at the outlet of the cooling furnace 103. All four valve bodies are driven by cylinders to raise and lower the gate. The gate and valve seat have copper alloy sealing surfaces, fitted with perfluoroether rubber O-rings, with a temperature resistance of -20℃ to 200℃. It can reliably open and close when the pressure difference is >2000Pa. A cooling channel is provided inside the valve body, through which 25℃ deionized water is introduced at a flow rate of 1L / min to protect the seals during high-temperature operation, with a leakage rate <1×10⁻⁻⁻⁶. 7 Pa・m 3 / s.

[0026] Specifically, such as Figure 4As shown, the conveying mechanism 3 includes: a frame 31 made of aluminum profile with a rotating shaft 33 set every 100mm along the length of the inner side, and a polyurethane conveying wheel 32 installed at the shaft end of each rotating shaft 33 with anti-slip texture on the wheel surface to prevent the carrier from slipping; adjacent rotating shafts 33 are driven by gears 39; the two rotating shafts 33 are rigidly connected by a transmission shaft 37 to ensure that the speed difference between the two sides is ≤0.5rpm and the conveying offset of the carrier is ≤0.5mm; Furthermore, the conveying mechanism 3 also includes a drive assembly: the first motor 35 is a 400W servo motor, which is connected to the main shaft 34 via a transmission magnetohydrodynamic seal 36. This seal uses a neodymium iron boron magnetic ring, with a vacuum-side dynamic sealing gap of 0.1mm, within a 1×10⁻ 4 It is leak-free in a vacuum environment and can operate continuously for 8000 hours without maintenance. Furthermore, the conveying mechanism 3 also includes a limiting component 38: an auxiliary wheel is set every 200mm at the upper end of the frame 31, and the wheel axle is perpendicular to the rotating shaft 33, which can play a guiding role in transmission and prevent the carrier from deviating. A 5mm thick polytetrafluoroethylene limiting plate with a height of 50mm is set at the furnace inlet and outlet, which can prevent the carrier from rising excessively, and the friction coefficient between the limiting plate and the carrier is ≤0.1, so as to avoid scratching the surface of the carrier.

[0027] Specifically, the temperature control platform 4 includes a heating platform located in the preheating furnace 101 / welding furnace 102 and a cooling platform located in the cooling furnace 103; like Figure 5 As shown, the heating platform consists of an aluminum alloy base plate 41, an oxygen-free copper top plate 42, and armored heating wires 43. The surface of the top plate is ground to ensure that the contact area with the carrier is ≥95%. The armored nickel-chromium heating wires are distributed in a serpentine pattern between the base plate 41 and the top plate 42, with a power density of 2W / cm². 2 The K-type temperature control thermocouple 14 is inserted 5mm below the top plate and fixed by mica sheet insulation. The response time is <1s and the temperature control accuracy is ±1℃. The top plate has a φ2mm hole and a built-in E-scale temperature detection thermocouple 44, which directly contacts the bottom of the vehicle and provides real-time feedback on temperature deviation ≤±0.5℃. When the vehicle temperature deviates from the set value, the lifting mechanism finely adjusts the spacing to compensate. The cooling platform consists of an aluminum alloy base plate 41 and an oxygen-free copper top plate 42. A serpentine cooling channel is set between the base plate 41 and the top plate 42. The inlet water temperature is 20℃ and the flow rate is 1.5L / min. It works with the refrigerant unit to achieve a cooling rate of 150℃ / min. A temperature sensor is installed at the outlet of the flow channel, and an automatic alarm is triggered when the water temperature exceeds 40℃.

[0028] Specifically, such as Figure 2 , Figure 3 and Figure 6The lifting mechanism 5 shown has a base plate 51 made of steel plate, which is connected to the temperature control platform 4 through 4 top rods 52. The screw 55 has a Tr30×6 trapezoidal thread and is driven by the second motor 56 through a reduction gearbox. The lifting accuracy is ±0.05mm, the stroke is 0-50mm, the maximum load is 50kg, and the top rod is fitted with a stainless steel corrugated pipe 53 with a diameter of 30mm and a corrugation spacing of 5mm. Both ends are sealed to the furnace body and base plate through flanges. The extension and retraction cycles are ≥100,000 times without leakage.

[0029] Specifically, such as Figure 3 , Figure 7 and Figure 8 The top cover assembly 6 shown: The cover body 61 is an integral aluminum plate with a thickness of 10mm and an anodized surface. It is hinged to the furnace body through the connecting block 62. The locking handle 64 drives the latch block 65 to engage with the furnace body. The annular sealing ring 10 ensures a seal. The observation window 7 of the top cover is made of 10mm thick borosilicate glass with a light transmittance of ≥90%. A rotatable baffle 8 is installed on the inner side. By rotating the knob handle 9 90°, the baffle 8 can be moved to block the observation window 7 of the top cover, reducing heat radiation loss. Actual measurements show a 20% reduction in furnace heat dissipation. Furthermore, such as Figure 2 and Figure 9 As shown, quartz glass visual detection windows 11 with a diameter of 50mm are provided on both sides of the furnace wall, which are used in conjunction with fiber optic sensors 12 to position the carrier in real time with a triggering accuracy of ±1mm. Specifically, a light grating safety component 20 is installed at the inlet of the preheating furnace 101 and the outlet of the cooling furnace 103. When an object is detected to be obstructing the flow, the vacuum gate valve immediately stops operating and alarms, with a response time of <10ms.

[0030] Specifically, such as Figure 9 The formic acid recovery system shown has the following configuration: the bottoms of the preheating furnace 101 and the welding furnace 102 are inclined at 5°, and the lowest point is connected to the glass bottle 16 via a φ8mm stainless steel pipe. A manual vacuum valve 17 with a diameter of 6mm and a vacuum degree ≤1×10⁻ is installed on the pipe. 4 When the amount of formic acid condensed in the furnace reaches 50mL, opening the manual vacuum valve 17 can recover more than 85% of the formic acid with a purity of ≥95%, which can be directly reused in the gas intake system.

[0031] A continuous vacuum welding method for IGBT chips, using the aforementioned welding apparatus, with the specific process flow as follows: I. Clamping and Initialization Step S1: Stack the ceramic copper-clad laminate (50mm×50mm), Sn-3.5Ag solder pad (thickness 0.1mm), and IGBT chip (10mm×10mm) in sequence and place them into the positioning groove of the aluminum alloy carrier (surface anodized treatment). The alignment deviation between the chip and the copper-clad laminate is ≤0.1mm. Step S2: Turn on the main power of the device, introduce 30°C deionized water into the cooling channels of each cavity, introduce 25°C deionized water into the cooling channel of the vacuum gate valve, and raise the heating platforms of the preheating furnace and welding furnace to 200°C and 300°C respectively, and keep them at these temperatures for 30 minutes until the temperature stabilizes (fluctuation ≤ ±1°C). II. Preheating Process Step S3: The first valve body 21 is opened (opening time 3s), the conveying mechanism 3 feeds the carrier into the furnace at a speed of 50mm / s, and after the fiber optic sensor 12 detects that the carrier has reached the center position of the preheating furnace 101 (500mm from the inlet), the conveying mechanism 3 stops and the first valve body 21 is closed. Step S4: Start the vacuum system and reduce the pressure inside the preheating furnace 101 to 30 mbar within 30 seconds. Turn off the vacuum pump and then introduce high-purity nitrogen (99.999% purity) to 1000 mbar. Hold the pressure for 10 seconds, then vacuum again to 5 mbar and hold the pressure for 10 seconds. Finally, introduce a formic acid-nitrogen mixture (8% formic acid volume fraction) to 900 mbar. Step S5: The lifting mechanism 5 drives the heating platform to rise, and the top plate 42 contacts the bottom of the vehicle (contact pressure 5N). The temperature rises from room temperature to 200℃ within 20 seconds and is maintained for 120 seconds (t1=120s). If the temperature fluctuates more than ±2℃ during the heat preservation period, the heating platform automatically adjusts its height (±0.5mm) to compensate for heat loss. III. Welding Procedure Step S6: After preheating, the heating platform descends by 5mm, the second valve 22 opens, and the carrier enters the welding furnace 102 at a speed of 50mm / s. After reaching the position, the second valve 22 closes, and the cycle of "evacuating to 30mbar → filling with nitrogen to 1000mbar → evacuating to 5mbar" is repeated. Finally, a formic acid-nitrogen mixture (10% formic acid by volume) is introduced to 500mbar. Step S7: The heating platform rises to contact the carrier, and the temperature is raised from 200℃ to 300℃ within 40 seconds (heating rate 2.5℃ / s), held at that temperature for 300 seconds (t2=300s, t2>t1). At the end of the holding period, a vacuum is drawn to 5mbar and maintained for 10 seconds to remove air bubbles in the weld layer. Then, nitrogen is filled to 1000mbar. IV. Cooling Process Step S8: After welding is completed, the heating platform is lowered by 5mm, the third valve body 23 is opened, the carrier enters the cooling furnace 103, the third valve body 23 is closed after it is in place, the vacuum is drawn to 30mbar, and high-purity nitrogen is introduced to 1000mbar. Step S9: The cooling platform rises to contact the carrier, and 20°C deionized water is introduced through the cooling channel to reduce the carrier temperature from 300°C to 50°C (takes 300 seconds). The temperature is then maintained for another 300 seconds (t3=600s, t3>t2). The fourth valve 24 is opened, the carrier is delivered, and the welding is completed. It should be noted that after the carrier leaves, each furnace immediately undergoes a cycle of "vacuuming to 30 mbar → purging with nitrogen to 1000 mbar" three times to remove residual formic acid gas (reducing the concentration to below 5 ppm) in preparation for the next batch.

[0032] In one embodiment, nine temperature measuring points (3×3 matrix) are arranged on the heating platform surface of the welding furnace 102, and the measured temperature deviation is ≤±1.5℃, ensuring that the thickness difference of the solder layer of eight chips on the same carrier is ≤3μm.

[0033] In one embodiment, using ultrasonic scanning microscopy, the product's solder layer void rate is ≤0.3%, and the shear strength is ≥25MPa (test standard JIS Z3198), meeting the long-term reliability requirements of IGBT modules at 125℃.

[0034] In one embodiment, the power consumption per batch is approximately 1.2 kWh, which is 40% lower than that of traditional equipment. The formic acid recovery rate is 85%, saving approximately RMB 30,000 in raw material costs annually. The equipment's mean time between failures (MTBF) is ≥1200 hours, and maintenance costs are reduced by 50%.

[0035] It is important to note that the mechanical pump oil level should be checked before starting the machine each day (it should be at 1 / 2-2 / 3 of the oil window), the Roots pump inlet filter should be cleaned weekly (200 mesh), and the grease (vacuum silicone grease, 0.5g / time) for the magnetohydrodynamic seals should be replaced monthly. The temperature control thermocouple (14) is calibrated quarterly using a standard thermocouple (accuracy ±0.5℃) to ensure that the deviation between the displayed value and the actual value is ≤1℃. If oxide scale appears on the surface of the heating platform, it needs to be polished with 600 grit sandpaper until the metal luster is exposed. Formic acid cylinders must be placed in an explosion-proof cabinet at a distance of ≥3m from the equipment. When operating, acid and alkali resistant gloves and goggles must be worn. Open flames are prohibited near the furnace. After the light curtain safety component is triggered, it must be manually reset and the position of the carrier must be checked. It can only be restarted after confirming that everything is correct.

[0036] In summary, through meticulous design and parameter optimization, this device achieves efficient continuous welding of IGBT chips, balancing production efficiency and welding quality. It can be widely used in power device packaging production lines in fields such as new energy vehicles and photovoltaic inverters.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A continuous vacuum welding apparatus for IGBT chips, comprising a working channel formed by multiple working furnaces (1) connected in series, wherein a preheating-welding-cooling chamber is sequentially arranged in the working channel along the product conveying direction, and vacuum gate valves (2) for enclosing the space are installed at the inlet and outlet of the working channel and at the docking point of two adjacent working furnaces (1), characterized in that, Also includes The conveying mechanism (3) is used to convey the product carrier and is installed in the working furnace (1). It includes two conveying components symmetrically distributed on both sides of the working channel axis. The two ends of the product carrier are respectively mounted on the conveying parts of the two conveying components. Temperature control platform (4) is set between the two conveying components and below the product carrier to regulate the temperature; The lifting mechanism (5) is installed below the working furnace (1) and its movable end extends upward into the working furnace (1), and drives the temperature control platform (4) to lift and lower to adjust the distance between the temperature control platform (4) and the product carrier.

2. The continuous vacuum welding apparatus for IGBT chips according to claim 1, characterized in that, The conveying assembly includes a frame (31) installed on the side of the inner cavity of the working furnace (1) and extending horizontally along the length of the channel. The inner side of the frame (31) is provided with multiple conveying wheels (32) and multiple rotating shafts (33). The rotating shafts (33) are rotatably connected to the frame (31) and are evenly distributed along the length of the frame (31). The conveying wheels (32) are installed on the shaft ends of the rotating shafts (33), and there is an idle rotating shaft (33) between every two adjacent conveying wheels (32). The rotating shafts (33) on two adjacent conveying assemblies are connected by a drive shaft (37). The rotating shafts (33) are driven to rotate by the drive assembly, so that the multiple conveying wheels (32) rotate synchronously and in the same direction to convey the product carriers on them.

3. The continuous vacuum welding apparatus for IGBT chips according to claim 2, characterized in that, The drive assembly includes a spindle (34), a first motor (35), and gears (39). One end of a rotating shaft (33) extends through and to the outside of the frame (31) and is fitted with gears (39). Two adjacent gears (39) are meshed together. The spindle (34) is mounted on the shaft end of one of the rotating shafts (33), and the spindle (34) is driven by the first motor (35).

4. A continuous vacuum welding apparatus for IGBT chips according to claim 2, characterized in that, A limiting component (38) is installed at the upper end of the frame (31). The limiting component (38) includes a plurality of auxiliary wheels evenly distributed along the length of the frame (31). The axle of the auxiliary wheel is rotatably connected to the frame (31), and the axis of the axle is perpendicular to the axis of the rotating shaft (33). The upper sides of the product carrier are respectively rolledly connected to the outer periphery of the auxiliary wheel on the adjacent frame (31).

5. A continuous vacuum welding apparatus for IGBT chips according to claim 1, characterized in that, The temperature control platform (4) includes a base plate (41), a top plate (42) and a temperature control element (43). The base plate (41) is installed on the movable end of the lifting mechanism (5), the top plate (42) is installed on the upper surface of the base plate (41), and the temperature control element (43) is installed between the base plate (41) and the top plate (42). The temperature control platform (4) is divided into a heating platform and a cooling platform. The heating platform is installed in both the preheating chamber and the welding chamber, and the cooling platform is installed in the cooling chamber. The temperature control element (43) of the heating platform is an electric heating element and is equipped with a temperature control thermocouple (14). The temperature control element (43) of the cooling platform is a cooling channel connected to the external refrigerant unit.

6. A continuous vacuum welding apparatus for IGBT chips according to claim 5, characterized in that, A small hole is provided on the upper surface of the top plate (42) of the heating platform, and a temperature detection thermocouple (44) for monitoring the temperature of the product carrier is installed in the small hole.

7. A continuous vacuum welding apparatus for IGBT chips according to claim 1, characterized in that, The lifting mechanism (5) includes a base plate (51) located below the working furnace (1) and whose height is adjustable by the lifting assembly. Multiple top rods (52) are installed on the upper surface of the base plate (51). One end of the top rod (52) extends upward into the working furnace (1) and is fixed to the bottom of the temperature control platform (4).

8. A continuous vacuum welding apparatus for IGBT chips according to claim 7, characterized in that, The lower end face of the working furnace (1) is provided with through holes corresponding to multiple push rods (52). The end of the push rod (52) away from the substrate (51) passes through the through hole. The outside of the push rod (52) is fitted with a telescopic tube (53). One end of the telescopic tube (53) is fixed to the upper end of the substrate (51) and is a closed design. The other end of the telescopic tube (53) is an open design and is sealed to the through hole through a flange seal.

9. A continuous vacuum welding apparatus for IGBT chips according to claim 1, characterized in that, The upper end of the working furnace (1) is open, and a cover assembly (6) is installed at the opening and sealed. The cover assembly (6) is equipped with a cover observation window (7) for observing the shape and features of the product, and the cover observation window (7) can be physically blocked.

10. A continuous vacuum welding method for IGBT chips, using the welding apparatus according to any one of claims 1-9, characterized in that, The specific steps are as follows: S1 stacks the ceramic copper-clad laminate, solder, and IGBT chip in the order of bottom, middle, and top to form a sandwich structure, and places it on the product carrier to form a whole; S2 opens the first valve body (21), and the conveying mechanism (3) sends the product and product carrier into the preheating furnace (101). The position of the product carrier is monitored by the fiber optic sensor (12). When the product carrier moves to the designated position, the first valve body (21) is closed. S3 uses a vacuum pump to control the vacuum level in the preheating furnace (101) at 1-50 mbar, then introduces an appropriate amount of inert gas to raise the pressure in the preheating furnace (101) to 900-1100 mbar, then starts the vacuum pump again to control the vacuum level in the preheating furnace (101) at 1-10 mbar, and then introduces an appropriate amount of formic acid and nitrogen mixture. S4 drives the heating platform in the preheating furnace (101) to rise through the lifting mechanism (5), so that the top plate (42) is attached to the bottom of the product carrier and the product is preheated. The heating time of the product carrier and the distance between the product carrier and the heating platform are controlled so that the product on the product carrier is fully preheated to temperature T1 in the preheating furnace (101) and maintained for a period of time. The time for this process step is t1. S5 drives the heating platform in the preheating furnace (101) to descend through the lifting mechanism (5), the second valve body (22) opens, the product carrier carries the product through the conveying mechanism (3) to the welding furnace (102), the vacuum degree in the welding furnace (102) is controlled at 1 to 50 mbar by the vacuum pumping equipment, and then an appropriate amount of inert gas is introduced to raise the pressure in the welding furnace (102) to 900 to 1100 mbar. The vacuum pumping equipment is started again to control the vacuum degree in the welding furnace (102) at 1 to 10 mbar, and then an appropriate amount of formic acid and nitrogen mixed gas is introduced. After the product carrier leaves the preheating furnace (101) with the product, the first valve body (21) and the second valve body (22) are closed, and the preheating furnace (101) enters the flushing stage. That is, the vacuum degree in the preheating furnace (101) is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to raise the pressure in the preheating furnace (101) to 900 to 1100 mbar, and the number of times is 1 to 3. S6 drives the heating platform inside the welding furnace (102) to rise through the lifting mechanism (5), so that the top plate (42) is attached to the bottom of the product carrier and the product is heated, so that the product on the product carrier is fully welded in the welding furnace (102) and held for a period of time. The time for this process step is t2, and t2>t1. S7 drives the heating platform in the welding furnace (102) to descend through the lifting mechanism (5), the third valve body (23) opens, the product carrier carries the product through the conveying mechanism (3) to the cooling furnace (103), the vacuum degree in the cooling furnace (103) is controlled at 1~50mbar by the vacuum equipment, and then an appropriate amount of nitrogen is introduced. After the product carrier leaves the welding furnace (102) with the product, the second valve body (22) and the third valve body (23) are closed, and the welding furnace (102) enters the flushing stage. That is, the vacuum degree in the welding furnace (102) is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to increase the pressure in the welding furnace (102) to 900 to 1100 mbar, and the number of times is 1 to 3. S8 drives the cooling platform of the cooling furnace (103) to rise through the lifting mechanism (5), so that the top plate (42) is in contact with the bottom of the product carrier and the product is cooled. Through the heat exchange of the refrigerant, the carrier and the product are cooled to the set temperature. Then the fourth valve body (24) is opened. After the product carrier carries the product away from the cooling furnace (103) through the conveying mechanism (3), the fourth valve body (24) is closed. The time for this process step is t3, and t3>t2. After the product carrier leaves the cooling furnace (103) with the product, the third valve body (23) and the fourth valve body (24) are closed, and the cooling furnace (103) enters the flushing stage. That is, the vacuum degree in the cooling furnace (103) is controlled at 1 to 50 mbar by the vacuum equipment, and then an appropriate amount of inert gas is introduced to raise the pressure in the cooling furnace (103) to 900 to 1100 mbar, and the number of times is 1 to 3.

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