Vacuum diffusion welding method and system for reducing thermal resistance of VC and cold plate interface

Abstract

The invention provides a vacuum diffusion welding method and system for reducing thermal resistance of an interface between VC and a cold plate. The vacuum diffusion welding method comprises the steps that the welding face of VC and the welding face of the cold plate are pretreated; the pretreated VC and a cold plate are aligned and attached to form a to-be-welded assembly, the to-be-welded assembly is loaded into a vacuum diffusion welding furnace, and initial pre-pressing is applied; the furnace chamber is vacuumized, then stepped heating and pressurization are carried out, the stepped heating and pressurization sequentially comprises a stress relief stage and a diffusion welding stage, and finally controllable cooling is carried out; after cooling to a preset temperature, releasing the pressure, and continuously cooling to room temperature to finish welding; through the integrated design of pretreatment, precise temperature control pressurization, stage switching and controllable cooling, VC and cold plate atomic-scale metallurgical bonding is achieved, the problems that an existing connection technology is high in thermal resistance, poor in reliability and insufficient in process controllability are solved, and the heat dissipation requirement of high-heat-flux equipment is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cold plate manufacturing, in particular to a vacuum diffusion welding method and system for reducing the interface thermal resistance between VC and a cold plate. BACKGROUND

[0002] With the rapid development of new energy vehicles, cloud computing servers, high-end chips and other industries, the power density of electronic devices continues to rise, and the heat generation per unit area grows exponentially. Traditional heat dissipation solutions have been difficult to meet the demand. Heat dissipation efficiency has become a core bottleneck restricting the performance improvement and life extension of electronic equipment, and has promoted the development of heat dissipation technology towards high efficiency and integration.

[0003] Vapor chamber (VC) combined with micro-channel cold plate with active cooling capability has become a key technology path to solve high heat flux dissipation due to its high efficiency and uniform heating characteristics, and is widely used in high-end electronic equipment. The connection quality of VC and cold plate directly determines the overall heat dissipation effect, and the interface thermal resistance is a key factor affecting the heat dissipation efficiency. Therefore, the connection technology with low interface thermal resistance, high strength and high airtightness has become the focus of industry research.

[0004] Currently, the connection methods of VC and cold plate in the industry mainly include three types: first, brazing connection, which realizes combination through filler metal filling interface. However, the thermal conductivity of filler metal is much lower than that of copper and other base materials, which will introduce additional interface thermal resistance, and the filler metal is prone to uneven flow or voids at high temperature, which seriously affects the airtightness and structural strength of the connection. Second, connection through thermal interface material (TIM), which is simple to operate. However, the thermal resistance of TIM material itself is significantly higher than that of metal, which becomes the main bottleneck in the heat dissipation path, and cannot meet the demand for ultra-low thermal resistance. Third, traditional welding technology, which is prone to problems such as false welding and thermal stress concentration, resulting in high interface thermal resistance and poor connection reliability, making it difficult to meet the long-term stable operation demand.

[0005] In addition, in the traditional diffusion welding process, the stage switching mainly uses the trigger mode of fixed time and temperature parameters, without considering the dynamic coupling effect of temperature and pressure in the actual welding process, which leads to inaccurate switching timing and easy occurrence of insufficient or excessive stress relief, affecting product consistency and welding quality.

[0006] Therefore, there is an urgent need in the art for an integrated technical solution that can achieve ultra-low interface thermal resistance, high strength and high airtightness connection, and has strong process controllability. SUMMARY

[0007] The application provides a vacuum diffusion welding method and system for reducing the interface thermal resistance of VC and a cold plate.

[0008] In one aspect, the application provides a vacuum diffusion welding method for reducing the interface thermal resistance of VC and a cold plate, comprising the following steps:

[0009] Step one: pretreating the welding surface of VC and the welding surface of the cold plate;

[0010] Step two: aligning and bonding the pretreated VC and the cold plate to form a to-be-welded assembly, loading the to-be-welded assembly into a vacuum diffusion welding furnace and applying initial pre-pressure;

[0011] Step three: vacuumizing the furnace cavity, then performing stepwise heating and pressurizing, the stepwise heating and pressurizing comprising a stress relief stage and a diffusion welding stage in sequence, and finally performing controllable cooling;

[0012] Step four: releasing the pressure after cooling to a preset temperature, and continuing to cool to room temperature to complete the welding.

[0013] In another aspect, the application provides a vacuum diffusion welding system for reducing the interface thermal resistance of VC and a cold plate, comprising a vacuum furnace body, a heating device, a pressurizing device, a vacuum module and a control module.

[0014] The vacuum furnace body provides a sealed welding chamber, and the heating device and the pressurizing device are arranged in the vacuum furnace body and are respectively used for heating the workpiece and applying pressure;

[0015] The vacuum module is connected with the vacuum furnace body and is used for extracting and maintaining high vacuum degree in the furnace;

[0016] The control module is electrically connected with the heating device, the pressurizing device and the vacuum module, pre-stores a stepwise temperature-pressure process curve and an integral value calculation program, and is used for automatically controlling the whole welding process.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] 1. The interface thermal resistance is significantly reduced, that is, the application realizes atomic metallurgical combination without filler metal, completely eliminates the thermal resistance bottleneck caused by the filler metal layer and TIM material, improves the stability of the interface thermal resistance, greatly improves the heat dissipation efficiency, and meets the heat dissipation demand of high heat flux density equipment.

[0019] 2. The connection strength and air tightness are excellent, that is, the diffusion bonding layer formed by the application has a strength close to that of the copper base material itself, can effectively resist the influence of complex working conditions such as vibration and thermal cycle, and the atomic-level bonding ensures long-term vacuum sealing of the VC cavity, avoids leakage of working fluid, and significantly improves the product reliability and service life.

[0020] 3. The organization performance and process stability are good, that is, the welding process of the application is carried out below the melting point of the metal, avoiding the grain coarsening or internal structure damage of the base material, the microstructure of the bonding zone is dense, no brittle intermetallic compound is generated, and the thermal conductivity is excellent; through the stepwise temperature-pressure curve and the preset integral model, temperature-pressure-time dynamic coupling control is realized, different specifications of components can be flexibly adapted, and the consistency and high yield of batch production are ensured.

[0021] 4. Wide application range and strong practicality, that is, the application is compatible with mainstream VC and cold plate materials such as copper and copper alloy, and can meet the manufacturing needs of heat dissipation components of electronic equipment of different power grades, and has good industrial application prospects.

[0022] The technical solutions of the application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the application, and constitute a part of the specification, together with the embodiments of the application, to explain the application, and do not constitute a limitation on the application; in the drawings:

[0024] Figure 1 is a flowchart of a vacuum diffusion welding method for reducing the thermal resistance of the interface between the VC and the cold plate provided by the embodiment of the application;

[0025] Figure 2 is a structural schematic diagram of a vacuum diffusion welding system for reducing the thermal resistance of the interface between the VC and the cold plate provided by the embodiment of the application. DETAILED DESCRIPTION

[0026] The preferred embodiments of the application will be described below with reference to the accompanying drawings, and it should be understood that the preferred embodiments described herein are only used to illustrate and explain the application, and do not limit the application;

[0027] Example 1:

[0028] The embodiment of the application provides a vacuum diffusion welding method for reducing the thermal resistance of the interface between the VC and the cold plate, please refer to Figure 1 , which comprises the following steps:

[0029] Step 1, pretreating the welding surface of the VC and the welding surface of the cold plate;

[0030] Step two, align and attach the pretreated VC with the cold plate to form a to-be-welded assembly, load the to-be-welded assembly into a vacuum diffusion welding furnace and apply initial pre-pressure;

[0031] Step three, vacuumize the furnace cavity, then perform stepwise heating and pressurization, which includes a stress relief stage and a diffusion welding stage in sequence, and finally perform controlled cooling;

[0032] Step four, release the pressure after cooling to a preset temperature, and continue to cool to room temperature to complete the welding.

[0033] Specifically, the embodiment improves the adaptability of the welding surface of the VC and the cold plate through pretreatment, and realizes atomic-level diffusion bonding under the stepwise heating and pressurization process in a vacuum environment, thereby reducing the interface thermal resistance; the entire process forms a closed-loop control from surface treatment to final cooling, ensuring the stability and reliability of the welding quality.

[0034] In one embodiment, the pretreatment of step one includes surface treatment and cleaning activation. The surface treatment is to precisely polish the welding surface to make the surface flatness ≤0.1 and the surface roughness ≤Ra0.8. The cleaning activation uses ultrasonic cleaning and plasma cleaning in sequence to remove oil stains and oxide layers on the welding surface.

[0035] Specifically, the surface treatment uses a diamond grinding wheel for precise polishing, and the surface flatness is ensured to be controlled within 0.1 through a laser interferometer, and the roughness is measured to be below Ra0.8 through a white light interferometer, so as to increase the actual contact area of the welding surface; in the cleaning activation, the ultrasonic cleaning uses ethanol solution as the medium, and the oil stains are removed by cleaning for 15 minutes at a frequency of 40 kHz; the plasma cleaning uses argon as the working gas, the power is set to 300 W, and the processing time is 5 minutes, so as to completely remove the surface oxide layer and activate the metal surface activity, providing a clean contact interface for subsequent diffusion welding.

[0036] In one embodiment, the pressure value of the initial pre-pressure in step two is 1-5 MPa, and the pressure is transmitted to the to-be-welded assembly through a graphite jig plate, so that the uneven contact points of the welding surface form preliminary physical contact.

[0037] Specifically, the initial pre-pressure is applied by a hydraulic device, and the pressure value is selected according to the size of the VC and the cold plate. For example, for a welding surface with an area of 100 cm 2 , the initial pre-pressure is set to 3 MPa; the graphite jig plate is selected from high-density graphite material (density ≥1.8 g / cm 3), which has a thermal expansion coefficient close to that of copper material, can avoid uneven pressure distribution caused by thermal deformation during the pressing process, ensure that the contact points of each area of the welding surface are uniformly stressed and form a preliminary fit, and lay the foundation for pressure transmission in the subsequent stage. During the pressing process, the graphite jig plate is pressed by the hydraulic device, and the pressure is transmitted to the welded workpiece, so that the contact points of the uneven surface form a preliminary physical contact. Under continuous pressure, the material surface undergoes plastic deformation and high-temperature creep, breaks the oxide film and expands the atomic contact area. The present embodiment ensures the sealing of the chamber by atomic-level bonding to prevent working fluid leakage, and operates below the melting point of the metal to reduce deformation and maintain the precision of the internal structure.

[0038] In one embodiment, the process of vacuumizing the furnace chamber in step three is to vacuumize the furnace chamber to less than or equal to 5x10 -3 Pa, and the vacuum degree is maintained by the vacuum module until the end of the welding process.

[0039] Specifically, the vacuum module is composed of a mechanical pump and a molecular pump. First, the mechanical pump is used to vacuumize the furnace chamber to below 1 Pa, and then the molecular pump is started to continue vacuumizing to below 5x10 -3 Pa. The entire vacuumizing process lasts for 30-40 minutes. The vacuum degree is monitored in real time by an ionization vacuum gauge, and the control module automatically adjusts the power of the molecular pump according to the monitoring data to ensure that the vacuum degree in the furnace chamber is always maintained within the set threshold from the warming-up stage to the cooling to room temperature, avoiding the reaction between impurities such as oxygen and water vapor in the air and the high-temperature metal surface to form a new oxide layer, affecting the interface bonding quality.

[0040] In one embodiment, the process parameters of the stress relief stage in step three are as follows:

[0041] The warming-up rate is 10-15℃ / min, the first temperature T1 is 450-550℃, the holding time is 10-30 minutes, and the first pressure P1 is 5-10 MPa, so as to eliminate internal stress and make the contact surface micro area plastic deformation.

[0042] Specifically, the warming-up rate of the stress relief stage is precisely controlled by a program-controlled temperature system. For example, for a cold plate with a thickness of 5mm, a warming-up rate of 12℃ / min is selected to avoid thermal shock. The first temperature T1 is set according to the material properties. For VC and cold plate of red copper material, T1 is preferably 500℃. The first pressure P1 applied during the holding process is realized by a segmented pressing method. Within the initial 10 minutes, the initial pre-pressing is gradually increased to the set value (such as 8 MPa), which ensures that the plastic deformation of the micro convex body of the contact surface occurs, fills the surface pits, and releases the residual stress generated by the pretreatment of the welding surface, so that the interface contact rate is increased to more than 80%.

[0043] In one embodiment, the process parameters of the diffusion welding stage in step three are as follows:

[0044] The temperature increasing rate is 5-10℃ / min, the temperature is increased to the second temperature T2=850-950℃, the holding time is 60-120 minutes, and the second pressure P2=10-20MPa is applied to make the atoms at the contact interface sufficiently diffuse to form a metallurgical bond.

[0045] Specifically, the temperature increasing rate in the diffusion welding stage is preferably 8℃ / min to reduce the accumulation of thermal stress, the second temperature T2 is preferably 900℃ for copper materials (about 0.83 times of the melting point of copper 1083℃), at which the atomic diffusion coefficient is significantly improved; the second pressure P2 is preferably set to 15MPa to promote plastic flow at the interface by continuous pressure to further expand the contact area. The holding time is determined according to the size of the welding surface. For a welding surface of 100cm 2 , the holding time is 90 minutes to ensure that the copper atoms at the interface sufficiently diffuse to form a diffusion layer with a thickness of ≥5μm, achieve a metallurgical bond, and significantly reduce the interface thermal resistance.

[0046] In one embodiment, step three further comprises calculating an integral value Ψ by a preset integral model, and switching from the stress relief stage to the diffusion welding stage when the Ψ reaches a preset threshold value Ψ c ;

[0047] The formula of the preset integral model is:

[0048]

[0049] Wherein, T m is the melting point of the base material, T(τ) is the temperature at time τ, P(t) is the pressure at time τ, t is the time from the first stage, and β is a constant with a value range of 15-25.

[0050] Specifically, T mTm refers to the melting point of VC and the base material of the cold plate (such as red copper), which is expressed in Kelvin (K), and for red copper, Tm is 1356K (i.e. 1083℃ + 273), which is obtained by consulting a material manual or experimental measurement, and is a basic physical parameter reflecting the atomic diffusion activity of the material; T(τ) refers to the actual temperature in the furnace at any time τ during the stress relief stage, which is expressed in Kelvin (K), and is collected in real time by a thermocouple arranged near the assembly to be welded, directly reflecting the strength of the thermal action in the welding area, and the higher the temperature, the more intense the atomic thermal motion, which is more conducive to the plastic deformation and stress release of the interface micro area; P(t) refers to the actual pressure applied to the assembly to be welded at any time τ during the stress relief stage, which is expressed in megaPascal (MPa), and is monitored in real time by a pressure sensor, reflecting the effect of external force on the interface contact state, and the greater the pressure, the more it can promote the plastic flow of the micro convex body of the contact surface and improve the actual contact area; t refers to the duration of the stress relief stage, which is expressed in minutes (min), and is the upper limit of the integral variable, reflecting the cumulative effect of the time dimension on the stress relief; the value of the constant β ranges from 15 to 25, which is a correction coefficient determined by multiple orthogonal experiments, and its physical meaning is to balance the weight of temperature and pressure on the interface, and for the welding of copper VC and cold plate, β is preferably 20, which can be adjusted slightly according to specific material combinations (such as when the VC is a copper alloy);

[0051] In this model, the exponential term reflects the ratio of the actual temperature to the melting point, and the larger the ratio (i.e. the higher the temperature), the closer the value of the exponential term to 1, indicating that the contribution of temperature to stress relief is stronger; on the contrary, when the temperature is low, the value of the exponential term decreases, reflecting the weakening of the thermal action at low temperature; the pressure term P(t) directly quantifies the external force, and after being multiplied by the exponential term, it comprehensively reflects the instantaneous stress relief effect under the temperature-pressure coupling; the integral operation accumulates the above instantaneous effect in the time dimension, and the integral value Ψ represents the total amount of stress relief in the stress relief stage, which is a comprehensive quantitative index of the plastic deformation degree of the interface micro area, the residual stress release amount and the initial contact area improvement;

[0052] The preset threshold value Ψ c needs to be determined according to the welding surface size (such as area, thickness) and material hardness of the VC and the cold plate, and is set by the following method:

[0053] For a specific specification of the assembly to be welded (such as a 100mm x 100mm copper VC and cold plate), multiple comparison experiments are conducted, and the interface contact rate (which needs to be ≥ 90%) and residual stress (which needs to be ≤ 50MPa) after switching to the diffusion welding stage under different Ψ values are recorded;

[0054] The minimum Ψ value that meets the above index is selected as the initial Ψ c for this specification;​

[0055] Adjust the initial Ψ in proportion (positively correlated with the welding surface area) for different specifications of components c Finally, through 3-5 verification experiments, for example, for a 100mm×100mm copper component, Ψ c Preferably 500MPa·min (calculated in units of pressure multiplied by time);

[0056] When the real-time calculated Ψ reaches the preset threshold Ψ c , it indicates that the stress relief stage has achieved the expected goal (sufficient interface contact and stress release), at which point switching to the diffusion welding stage can ensure that subsequent atomic diffusion proceeds efficiently, avoiding interface defects caused by insufficient or excessive stress relief.

[0057] Further, the preset integral model is used for stage switching, which can be used alternatively with the above-mentioned fixed parameter stage switching, or can be used together; the process of using together includes:

[0058] After the stress relief stage is started, the control system runs two monitoring logics at the same time; on the one hand, the integral value Ψ is continuously calculated according to the preset integral model through real-time acquisition of temperature T(τ) and pressure P(τ) data; on the other hand, it is simultaneously monitored whether the fixed parameter condition is met, i.e. “the temperature is stable at T1±5℃ and the duration reaches the preset fixed holding time (such as 20 minutes), and the pressure is stable at P1±0.5MPa”;

[0059] When the integral value Ψ first reaches the threshold Ψ c , the control system pauses the timing and triggers an auxiliary verification to check whether the fixed parameters have met (or within the allowable deviation range): if the fixed parameters meet the standard, switching is immediately performed; if the fixed parameters do not meet the standard (such as the holding time has not arrived but Ψ has met the standard), the stress relief stage is extended until the fixed parameters meet the standard before switching, avoiding misjudgment of Ψ caused by instantaneous parameter fluctuations;

[0060] When the fixed parameters first meet (such as the preset holding time is reached), but the integral value Ψ has not reached Ψ c , the control system continues to maintain the stress relief stage while speeding up the calculation frequency of Ψ (such as from 1 time per second to 5 times per second), until Ψ reaches the threshold before switching, to ensure that the actual stress relief effect of the interface meets the standard, avoiding switching too early due to fixed time setting deviation;

[0061] If the integral value Ψ and the fixed parameter judgment results conflict (such as Ψ far exceeds Ψ c but the fixed time has not arrived, or the fixed time has arrived but Ψ is far lower than Ψ c), the control system automatically starts the abnormality diagnosis, whether the sensor failure or parameter fluctuation abnormality exists is judged through the history curve of temperature and pressure, if the data is confirmed to be effective, the judgment result of Ψ is used as the reference, and the deviation value is recorded for subsequent process optimization;

[0062] Through the above-mentioned cooperative process, the accurate quantification ability of the preset integral model to the interface state is reserved, and the experiential bottom safeguard is provided with the help of the fixed parameters, the accuracy and reliability of the switching control are considered, and it is especially suitable for the consistency control of different batches of components to be welded in batch production.

[0063] In one embodiment, the controllable cooling mode in step three is air cooling and / or water cooling, the cooling speed is controlled by adjusting the fan flow and / or the water cooling system flow, and the pressure is released after cooling to below 300 DEG C.

[0064] Specifically, the cooling stage can first use water cooling mode, circulating cooling water is introduced through the water cooling pipeline on the wall of the furnace body, the cooling rate is controlled to be 50-80 DEG C / min, when the temperature drops to 500 DEG C, it is switched to air cooling, inert gas (such as argon) is introduced into the furnace through the adjustable speed fan, and the cooling rate is reduced to 20-30 DEG C / min, to avoid thermal stress cracking caused by rapid cooling; when the temperature in the furnace drops to below 300 DEG C, the pressure is slowly released through the hydraulic system (the pressure release rate is less than or equal to 1 MPa / min), to prevent interface peeling caused by sudden pressure drop, and then naturally cooled to room temperature, to complete the whole welding process.

[0065] Embodiment 2:

[0066] The embodiment of the present application provides a vacuum diffusion welding system for reducing the interface thermal resistance of VC and a cold plate, please refer to Figure 2 , comprising a vacuum furnace body, a heating device, a pressurizing device, a vacuum module and a control module;

[0067] The vacuum furnace body provides a sealed welding chamber, the heating device and the pressurizing device are arranged in the vacuum furnace body, and are respectively used for heating and applying pressure to the workpiece;

[0068] The vacuum module is connected with the vacuum furnace body, and is used for extracting and maintaining high vacuum degree in the furnace;

[0069] The control module is electrically connected with the heating device, the pressurizing device and the vacuum module, pre-stores a stepwise temperature-pressure process curve and an integral value calculation program, and is used for automatically controlling the whole welding process.

[0070] This embodiment is based on the above-mentioned embodiment 1, and will not be described further.

[0071] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A vacuum diffusion welding method for reducing the thermal resistance at the interface of a VC and a cold plate, characterized by, The method comprises the following steps: Step one, pretreatment of the welding surface of the VC and the welding surface of the cold plate; Step two, aligning and bonding the pretreated VC and the cold plate to form a welding assembly, loading the welding assembly into a vacuum diffusion welding furnace and applying initial pre-pressure; Step three, vacuumizing the furnace cavity, then performing stepwise heating and pressurizing, which comprises a stress relief stage and a diffusion welding stage in sequence, and finally performing controlled cooling; Step four, releasing the pressure after cooling to the preset temperature, and continuing to cool to room temperature to complete the welding.

2. The vacuum diffusion welding method of claim 1, wherein, The pretreatment of step one comprises surface treatment and cleaning activation, the surface treatment is precision polishing of the welding surface to make the surface flatness ≤0.1 and the surface roughness ≤Ra0.8, and the cleaning activation uses ultrasonic cleaning and plasma cleaning in sequence to remove oil stains and oxide layers on the welding surface.

3. The vacuum diffusion bonding method of claim 1, wherein, The pressure value of the initial pre-pressure in step two is 1-5 MPa, the pressure is transmitted to the welding assembly through a graphite fixture plate to form preliminary physical contact at uneven contact points of the welding surface.

4. The vacuum diffusion bonding method of claim 1, wherein, The process of vacuuming the furnace cavity in step three is to vacuum the furnace cavity to a vacuum level less than or equal to 5 x 10 -3 Pa, which is maintained by the vacuum module until the end of the welding process.

5. The vacuum diffusion bonding method of claim 1, wherein, The process parameters of the stress relief stage in step three are as follows: The heating rate is 10-15 ℃ / min, the temperature is raised to the first temperature T1=450-550 ℃, the holding time is 10-30 minutes, and the first pressure P1=5-10 MPa is applied to eliminate internal stress and make the contact surface micro zone plastic deformation.

6. The vacuum diffusion bonding method of claim 1, wherein, The process parameters of the diffusion welding stage in step three are as follows: The heating rate is 5-10 ℃ / min, the temperature is raised to the second temperature T2=850-950 ℃, the holding time is 60-120 minutes, and the second pressure P2=10-20 MPa is applied to make the contact interface atoms fully diffuse to form metallurgical bonding.

7. The vacuum diffusion bonding method of claim 1, wherein, The controlled cooling in step three is air cooling and / or water cooling, the cooling speed is controlled by adjusting the fan flow and / or the water cooling system flow, and the pressure is released after cooling to below 300 ℃.

8. A vacuum diffusion bonding system for reducing the thermal resistance at the interface of a VC and a cold plate, based on the method of any one of claims 1-7, characterized in that, It comprises a vacuum furnace body, a heating device, a pressurizing device, a vacuum module and a control module; The vacuum furnace body provides a sealed welding chamber, the heating device and the pressurizing device are arranged in the vacuum furnace body and are used for heating and applying pressure to the workpiece respectively; The vacuum module is connected with the vacuum furnace body and is used for extracting and maintaining high vacuum degree in the furnace; The control module is electrically connected with the heating device, the pressurizing device and the vacuum module, pre-stores the stepwise temperature-pressure process curve and the integral value calculation program, and is used for automatically controlling the whole welding process.

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