Vacuum ultrasonic laser welding apparatus and method of use

Abstract

This invention relates to a vacuum ultrasonic laser welding apparatus and its method of use, belonging to the field of welding technology. The vacuum ultrasonic laser welding apparatus includes a pressure head, an ultrasonic component, a first vacuum pipe, and a laser head. The pressure head has a first through-hole for the laser to pass through. The ultrasonic component is disposed on the side of the pressure head and connected to the side wall of the pressure head. The first vacuum pipe is disposed on the side of the pressure head and communicates with the first through-hole. The bottom of the pressure head is connected to a first workpiece to press the first workpiece firmly against the surface of a second workpiece. The first workpiece seals the bottom of the first through-hole, and a protective lens is disposed at the top of the first through-hole. The pressure head can press the first workpiece firmly against the surface of the second workpiece, reducing the gap between them; the connection between the pressure head and the ultrasonic component can reduce defects such as porosity and cracks, improving the mechanical properties of the weld; the local vacuum environment formed in the first through-hole can suppress the plasma shielding effect and porosity defects during the welding process, improving the utilization efficiency of laser energy and the quality of the weld.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a vacuum ultrasonic laser welding apparatus and its method of use. Background Technology

[0002] In semiconductor power modules, copper busbar terminals typically handle high-voltage, high-current main power transmission, while pins are usually used for small signal transmission. Currently, terminals and pins are typically connected using soldering or ultrasonic welding. Soldering suffers from solder layer degradation and insufficient reliability under high-current periodic impacts and thermal cycling. Ultrasonic welding requires a welding head to connect the terminals to the substrate, resulting in intense friction between the welding head and the first workpiece, leading to rapid wear and higher material costs.

[0003] Laser welding technology utilizes a high-energy-density laser beam to directly irradiate the workpieces. The first workpiece absorbs the energy and melts instantly, then rapidly cools and crystallizes, thus achieving the welding of two workpieces. Compared to ultrasonic welding and brazing, laser welding does not directly contact the first workpiece, has a longer consumable lifespan, and offers advantages such as high welding speed, high welding precision, high connection reliability, and low connection cost.

[0004] Traditional laser welding technology, under high-power laser conditions, generates plasma that produces strong absorption, scattering, and reflection effects on the incident light, easily leading to various welding defects such as metal spatter, porosity, shrinkage cavities, and surface collapse. Furthermore, due to the influence of plasma, it is difficult to maintain consistent penetration depth across different products, making it unsuitable for processes requiring high penetration depth. Summary of the Invention

[0005] This invention provides a vacuum ultrasonic laser welding device and its usage method, which can effectively reduce laser welding defects and improve the welding effect of laser welding.

[0006] On one hand, the present invention provides a vacuum ultrasonic laser welding device, including a pressure head, an ultrasonic component, a first vacuum pipe and a laser head. The pressure head has a first through hole for the laser to pass through. The ultrasonic component is disposed on the side of the pressure head and connected to the side wall of the pressure head. The first vacuum pipe is disposed on the side of the pressure head and communicates with the first through hole. The bottom of the pressure head is connected to a first weldment to press the first weldment against the surface of a second weldment. The first weldment blocks the bottom of the first through hole, and a protective lens is disposed on the top of the first through hole.

[0007] In one embodiment, the side wall of the pressure head is further provided with a second vacuum pipe, and the inside of the pressure head is provided with a second through hole. The two ends of the second through hole are located at the bottom and the side of the pressure head, respectively. The second vacuum pipe is connected to the second through hole, and the second through hole is isolated from the first through hole.

[0008] In one embodiment, the first vacuum conduit and the second vacuum conduit are located above and below the ultrasonic component, respectively, and the first vacuum conduit and the second vacuum conduit are parallel to each other.

[0009] In one embodiment, both the ultrasonic component and the laser head are connected to a movable axis, which is capable of XYZ three-axis movement.

[0010] In one embodiment, both the first vacuum pipe and the second vacuum pipe are flexible pipes.

[0011] In one embodiment, the vacuum ultrasonic laser welding apparatus further includes a support platform, the surface of which is used to place the second weldment.

[0012] In one embodiment, the vacuum ultrasonic laser welding apparatus further includes a cleaning tank disposed on one side of the support platform.

[0013] On the other hand, a method for using a vacuum ultrasonic laser welding device is provided, comprising the following steps: S1. Fix the second weldment to the surface of the bearing platform, and apply pressure to the first weldment with the pressure head so that the first weldment presses against the second weldment and seals the bottom of the first through hole; S2. Evacuate the first vacuum pipe to create a vacuum environment inside the first through hole; S3. The ultrasonic component drives the pressure head to vibrate, and the laser head emits laser light to complete the welding of the first and second weldment parts.

[0014] In one embodiment, step S1 further includes: moving the pressure head to the first welding part loading position, causing the second vacuum pipe to be evacuated, and then moving the pressure head above the second welding part after adsorbing the first welding part.

[0015] In one embodiment, the method of using the vacuum ultrasonic laser welding device further includes step S4: the ultrasonic component and the laser head stop working, the first vacuum pipe is supplied with gas, and the pressure head is disengaged from the first workpiece.

[0016] Compared with the prior art, the advantages of the present invention are that the pressure head can press the first weldment tightly onto the surface of the second weldment, reducing the gap between them and improving the welding effect; the pressure head is connected to the ultrasonic component, and ultrasonic action can be directly applied to the first weldment through the pressure head, utilizing the cavitation effect and acoustic flow effect of ultrasound to reduce defects such as porosity and cracks, and improve the mechanical properties of the weld; the first vacuum pipe connected to the first through hole of the pressure head can form a local vacuum environment in the first through hole, which helps to suppress the plasma shielding effect and porosity defects during the welding process, and improve the utilization efficiency of laser energy and the quality of the weld. Attached Figure Description

[0017] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the structure of a vacuum ultrasonic laser welding device in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a vacuum ultrasonic laser welding device in another embodiment of the present invention; Figure 3 This is a flowchart illustrating the method of using the vacuum ultrasonic laser welding device in one embodiment of the present invention.

[0019] Figure label: 1. Pressure head; 11. First through hole; 12. Second through hole; 2. Ultrasonic component; 3. First vacuum pipe; 4. Laser head; 5. Protective lens; 6. Second vacuum pipe; 7. Support platform; 8. Cleaning tank; 100. First weldment; 200. Second weldment. Detailed Implementation

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Copper is a highly reflective metal. When a laser irradiates a copper material, the surface metal rapidly vaporizes and ionizes, generating high-density plasma. This plasma has the characteristic of strongly absorbing and scattering laser photons, causing three major processing defects: Laser energy loss: Plasma absorbs 30%~60% of the incident laser power, which greatly reduces the melting depth under the same laser output power. In order to achieve the target melting depth, the laser power can only be increased, which aggravates the thermal deformation of the workpiece. Uncontrolled penetration: The amount of plasma generated varies randomly with the oxidation of the workpiece surface, the ambient airflow, and the impurities in the incoming material. The penetration deviation of the weld seam in the same batch of products can reach 0.3~0.5mm, and some weld seams are not fully penetrated and some are damaged by melting through, damaging the DBC ceramic liner. Metal spatter and oxidation porosity: The plasma violently disturbs the molten pool, and molten copper metal is sputtered at high speed. The spatter particles adhere to the module plastic casing and pin rods, causing a decrease in insulation and short circuits in signal pins. In the atmospheric environment, the molten pool metal reacts with oxygen and nitrogen to generate oxides and nitrides, which form shrinkage cavities and internal inclusions after cooling, reducing the mechanical strength and conductivity of the weld.

[0022] While existing integrated vacuum chamber solutions can suppress plasma, their large volume and long pumping time make them unsuitable for large-scale automated production lines. Simple inert gas protection can only weakly disperse plasma and cannot eliminate splashing and porosity defects at the source.

[0023] To address the aforementioned shortcomings of existing technologies, such as Figure 1 As shown, a vacuum ultrasonic laser welding device according to an embodiment of the present invention includes a pressure head 1, an ultrasonic component 2, a first vacuum pipe 3, and a laser head 4. The pressure head 1 has a first through hole 11 for the laser to pass through. The ultrasonic component 2 is disposed on the side of the pressure head 1 and connected to the side wall of the pressure head 1. The first vacuum pipe 3 is disposed on the side of the pressure head 1 and communicates with the first through hole 11. The bottom of the pressure head 1 is connected to a first weldment 100 to press the first weldment 100 against the surface of a second weldment 200. The first weldment 100 seals the bottom of the first through hole 11. A protective lens 5 is provided at the top of the first through hole 11. The protective lens 5 seals the top of the first through hole 11 to create a vacuum environment inside the first through hole 11. When in use, the protective lens 5 allows the laser beam to pass through and irradiate the first weldment 100. A fluororubber sealing gasket is fitted around the outer ring of the protective lens 5, and a mechanical pressure ring locks and seals it, preventing external air from entering the first through hole 11.

[0024] The pressure head 1 can press the first weldment 100 tightly against the surface of the second weldment 200, reducing the gap between them and improving the welding effect. The pressure head 1 is connected to the ultrasonic component 2, and ultrasonic action can be directly applied to the first weldment 100 through the pressure head 1. The cavitation effect and acoustic flow effect of the ultrasound can be used to reduce defects such as pores and cracks, and improve the mechanical properties of the weld. The first vacuum pipe 3, which is connected to the first through hole 11 of the pressure head 1, can form a local vacuum environment in the first through hole 11, which helps to suppress the plasma shielding effect and pore defects during the welding process, and improve the utilization efficiency of laser energy and the quality of the weld.

[0025] The vacuum ultrasonic laser welding device of this embodiment generates a local vacuum environment by opening a first through hole 11 on the pressure head 1 and connecting it with a first vacuum pipe 3. Compared with the prior art, which places the entire welding device inside a vacuum chamber, this device has a simpler structure, significantly reduced manufacturing costs, and is easier to maintain. The ultrasonic component 2 is connected to the pressure head 1. The ultrasonic component 2 is not in a vacuum environment; it directly applies ultrasonic action to the first workpiece 100 through the pressure head 1. This design is simple and highly reliable.

[0026] The vacuum ultrasonic laser welding device of this embodiment abandons the large vacuum cavity of the whole machine, and directly opens the first through hole 11 inside the multi-functional pressure head 1, which coincides with the laser beam path, as an independent vacuum cavity. It forms a closed high vacuum environment only in the laser-irradiated welding area, which has multiple mechanistic advantages compared with the whole vacuum cavity: The vacuum volume is extremely small, and the pumping efficiency is greatly improved: the volume of the vacuum chamber for a single welding point is only 5~20mL, and the vacuum pump only needs 1~3s to pump to a high vacuum, while the traditional overall vacuum chamber takes 30~60s to pump. The production cycle of a single station is shortened by more than 80%. Isolation from the atmospheric medium prevents plasma generation: In a vacuum environment, there are no large numbers of air molecules participating in ionization, and the trace metal vapor generated by laser irradiation of copper is quickly extracted and cannot accumulate to form a plasma cloud. The laser energy transfer efficiency is increased by more than 50%, and the melting depth is increased by 0.2~0.4mm at the same power. The sidewall of the pressure head physically blocks spatter: the molten metal spatter generated during welding is intercepted by the inner wall of the pressure head 1 and only adheres to the lower end face of the pressure head 1. It will not splash onto the power module molding body, pin pin rod, or DBC substrate insulation area, thus preventing spatter short circuits, insulation failures, and batch defects. Vacuum environment eliminates molten pool oxidation and gas inclusions: there is no oxygen or nitrogen dissolution in the molten pool, no gas is released during the cooling process, there are no oxidation inclusions or shrinkage cavities inside the weld, the weld structure is dense and uniform, and the corrosion resistance of the joint is greatly improved.

[0027] In this embodiment, the first solder joint 100 is a copper busbar terminal in the semiconductor power module, which is responsible for the main power output.

[0028] like Figure 2 As shown, in another embodiment, the side wall of the pressure head 1 is also provided with a second vacuum pipe 6, and the inside of the pressure head 1 is provided with a second through hole 12. The two ends of the second through hole 12 are located at the bottom and the side of the pressure head 1, respectively. The second vacuum pipe 6 is connected to the second through hole 12, and the second through hole 12 is isolated from the first through hole 11, so as to realize independent control of the two vacuum paths and prevent them from interfering with each other.

[0029] In this embodiment, the first solder joint 100 is a pin in a semiconductor power module, responsible for small signal transmission. The shape of the pin differs significantly from that of the copper busbar terminal; the pin is smaller in size. The corresponding pressure head 1 also has a distinct shape, possessing not only a first through-hole 11 but also a second through-hole 12 for adsorbing the pin. When the second vacuum channel 6 is evacuated, the air pressure inside the second through-hole 12 decreases, and the pin is drawn into the second through-hole 12, simultaneously sealing the bottom of the first through-hole 11. When the first vacuum channel 3 is evacuated, a local vacuum environment is created inside the first through-hole 11 for laser welding.

[0030] Furthermore, the first vacuum pipe 3 and the second vacuum pipe 6 are located above and below the ultrasonic component 2, respectively, and the first vacuum pipe 3 and the second vacuum pipe 6 are parallel to each other, making the overall structure of the vacuum ultrasonic laser welding device more compact.

[0031] In this embodiment, both the ultrasonic component 2 and the laser head 4 are connected to a moving axis (not shown in the figure). The moving axis is set on a three-axis platform, which enables the moving axis to move in the XYZ three axes, thereby realizing the flexible movement of the pressure head 1, the ultrasonic component 2 and the laser head 4, realizing laser welding at different positions, which is suitable for mass production.

[0032] Furthermore, both the first vacuum pipe 3 and the second vacuum pipe 6 are flexible pipes to adapt to changes in the position of the pressure head 1 and ensure the vacuum level of the vacuum environment.

[0033] In this embodiment, the vacuum ultrasonic laser welding device also includes a support platform 7. The surface of the support platform 7 is used to place the second welding part 200. The support platform 7 is mounted on a rotating platform (not shown in the figure) and can rotate precisely in increments. It is suitable for synchronous welding of multiple pins and multiple terminals. The support platform 7 is made of high-hardness ceramic or tempered steel.

[0034] A cleaning tank 8 is also provided on one side of the support platform 7. The cleaning tank 8 is filled with cleaning liquid. After a certain number of samples are welded by the pressure head 1, some metal splash residue remains on the edge of the pressure head 1. By periodically inserting the pressure head 1 into the cleaning tank 8, the ultrasonic component 2 applies ultrasonic action, which can clean the metal splash residue on the side wall of the pressure head 1 nearby, thereby improving work efficiency.

[0035] Specifically, the cleaning fluid is a low-volatility, neutral, water-based metal cleaning agent. The three-axis platform can drive the lower end face of the pressure head 1 to be completely immersed in the cleaning fluid. The ultrasonic component 2 is started simultaneously, using the ultrasonic cavitation effect to peel off the metal spatter adhering to the end face of the pressure head 1. After cleaning, the pressure head 1 is raised, and the high-pressure air blowing pipeline dries the residual cleaning fluid in the pressure head 1. No liquid is brought into the welding station. The whole process is automated and requires no manual intervention.

[0036] like Figure 3 As shown, the method of using a vacuum ultrasonic laser welding apparatus according to an embodiment includes the following steps: S1. Fix the second weldment 200 to the surface of the bearing 7, and apply pressure to the first weldment 100 with the pressure head 1 so that the first weldment 100 presses the second weldment 200 and seals the bottom of the first through hole 11. S2. Evacuate the first vacuum pipe 3 to create a vacuum environment inside the first through hole 11; S3. The ultrasonic component 2 drives the pressure head 1 to vibrate, and the laser head 4 emits a laser to complete the welding of the first weldment 100 and the second weldment 200.

[0037] When the first weldment 100 is a copper busbar terminal, the corresponding pressure head 1 only needs to have a first through hole 11. The first weldment 100 and the second weldment 200 are pre-assembled on the surface of the bearing platform 7. The pressure head 1 moves above the first weldment 100 and then moves downward, thereby pressing the first weldment 100 tightly against the surface of the second weldment 200, and the first weldment 100 seals the bottom of the first through hole 11. Air is drawn out through the first vacuum pipe 3, so that a vacuum environment is formed inside the first through hole 11. The ultrasonic component 2 drives the pressure head 1 to vibrate, and the laser emitted by the laser head 4 passes through the protective lens 5 and enters the first through hole 11 and irradiates the first weldment 100, completing the welding of the first weldment 100 and the second weldment 200.

[0038] The method of using the vacuum ultrasonic laser welding apparatus in this embodiment further includes step S4: the ultrasonic component 2 and the laser head 4 stop working, the first vacuum pipe 3 is supplied with gas, and the pressure head 1 disengages from the first workpiece 100. After the first vacuum pipe 3 is supplied with gas, the vacuum environment inside the first through hole 11 is eliminated, and the pressure head 1 no longer exerts an adsorption effect on the first workpiece 100, thereby facilitating the separation of the two for subsequent workpiece welding.

[0039] When the first workpiece 100 is a pin, since the pin needs to be pre-adsorbed, a second through hole 12 needs to be added to the pressure head 1. Step S1 also includes: moving the pressure head 1 to the loading position of the first workpiece 100, evacuating the second vacuum pipe 6, and after the pressure head 1 adsorbs the first workpiece 100, moving it above the second workpiece 200. Then, the pressure head 1 is lowered to press the first workpiece 100 firmly onto the surface of the second workpiece 200 for subsequent welding work.

[0040] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A vacuum ultrasonic laser welding device, characterized in that, The device includes a pressure head, an ultrasonic component, a first vacuum pipe, and a laser head. The pressure head has a first through hole for the laser to pass through. The ultrasonic component is disposed on the side of the pressure head and connected to the side wall of the pressure head. The first vacuum pipe is disposed on the side of the pressure head and communicates with the first through hole. The bottom of the pressure head is connected to a first weldment to press the first weldment against the surface of a second weldment. The first weldment blocks the bottom of the first through hole, and a protective lens is disposed on the top of the first through hole.

2. The vacuum ultrasonic laser welding apparatus according to claim 1, characterized in that, The side wall of the pressure head is also provided with a second vacuum pipe, and a second through hole is opened inside the pressure head. The two ends of the second through hole are located at the bottom and the side of the pressure head, respectively. The second vacuum pipe is connected to the second through hole, and the second through hole is isolated from the first through hole.

3. The vacuum ultrasonic laser welding apparatus according to claim 2, characterized in that, The first vacuum pipe and the second vacuum pipe are located above and below the ultrasonic component, respectively, and the first vacuum pipe and the second vacuum pipe are parallel to each other.

4. The vacuum ultrasonic laser welding apparatus according to claim 2, characterized in that, Both the ultrasonic component and the laser head are connected to a moving axis, which can move along three axes (XYZ).

5. The vacuum ultrasonic laser welding apparatus according to claim 4, characterized in that, Both the first vacuum pipe and the second vacuum pipe are flexible pipes.

6. The vacuum ultrasonic laser welding apparatus according to claim 1, characterized in that, It also includes a base, the surface of which is used to place the second weldment.

7. The vacuum ultrasonic laser welding apparatus according to claim 6, characterized in that, It also includes a cleaning tank, which is disposed on one side of the support platform.

8. A method of using a vacuum ultrasonic laser welding device, characterized in that, Includes the following steps: S1. Fix the second weldment to the surface of the bearing platform, and apply pressure to the first weldment with the pressure head so that the first weldment presses against the second weldment and seals the bottom of the first through hole; S2. Evacuate the first vacuum pipe to create a vacuum environment inside the first through hole; S3. The ultrasonic component drives the pressure head to vibrate, and the laser head emits laser light to complete the welding of the first and second weldment parts.

9. The method of using the vacuum ultrasonic laser welding device according to claim 8, characterized in that, Step S1 further includes: moving the pressure head to the first welding part loading position, causing the second vacuum pipe to be evacuated, and then moving the pressure head above the second welding part after adsorbing the first welding part.

10. The method of using the vacuum ultrasonic laser welding apparatus according to claim 8, characterized in that, It also includes step S4: the ultrasonic component and laser head stop working, the first vacuum pipe is supplied with gas, and the pressure head is separated from the first weldment.

Images