Laser welding method and system for dissimilar metal films

Abstract

The present invention provides a laser welding method and system for dissimilar metal films, wherein the welding shape and area are set according to the welding requirements, and the laser welding route is determined; the metal films to be welded are stacked up and down, wherein the metal film with a high melting point is located at the top and the metal film with a low melting point is located at the bottom; the thickness of the metal film with a high melting point is less than or equal to 100 μm; the laser parameters are set so that the laser is irradiated on the metal film with a high melting point and scanned according to the welding route; a short pulse width and high frequency laser is used, and the laser peak energy obtained at the same time enables the metal film with a high melting point to be instantly heated and melted without being broken down, and the residual heat of the laser is conducted downward to melt the metal film with a low melting point, and the melted parts of the two metal films form a molten pool, thereby completing the welding. The present invention can effectively reduce the bending of the upper metal film due to heat, and finally realize the welding of dissimilar metal films.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser welding of metal films, and in particular relates to a laser welding method and system for dissimilar metal films. Background Art

[0002] In the industrial field, aluminum and copper are both good conductive materials. Since aluminum has a lower density than copper (the density of aluminum is only 1 / 3 of that of copper), it is cheap and has abundant resources. Therefore, it can be used instead of copper in many cases, which not only reduces costs and reduces product quality, but also makes rational use of resources. However, the resistivity of aluminum is 60% higher than that of copper, so the conductivity of aluminum is worse than that of copper, and its strength is lower, so there are certain disadvantages in replacing copper with aluminum. In order to make full use of the excellent properties of copper and aluminum, it is usually necessary to connect copper and aluminum together to form a composite structure of copper and aluminum, so that it can be widely used in the fields of ocean, petroleum, chemical industry, electronics, etc. In actual production, brazing, diffusion welding, pressure welding, etc. are widely used to achieve their connection.

[0003] 1. Traditionally, copper and aluminum are welded by tinning and melting. This method has poor molding and lacks good strength. Since tin has a low melting point and cannot be welded on workpieces working at high temperatures, this process is only suitable for small workpieces under low temperature conditions (only suitable for welding of multi-strand copper wires and small-sized aluminum enameled wires), and it is difficult to apply to the production of other products.

[0004] 2. When welding copper and aluminum using fusion welding, friction welding, cold pressure welding, explosion welding, electron beam welding, ultrasonic welding and other welding methods, the welded joints are brittle, prone to cracks and pores in the welds. The welded workpieces are inevitably broken, which may cause the conductor to break and the pipeline to leak, so the required effect in actual production is often not achieved.

[0005] 3. Use brazing (usually flame brazing, furnace brazing and high-frequency brazing, etc.) to weld copper and aluminum together. The brazing process uses the brazing filler metal as an intermediate medium to weld copper and aluminum together (actually a metallurgical reaction occurs, and the brazing filler metal penetrates into the molecular structure of copper and aluminum materials through capillary action). After welding, the joint has good forming, tensile and shear resistance, electrical conductivity and corrosion resistance. It is a commonly used copper-aluminum welding method. The brazing filler metals that can be used for copper-aluminum welding on the market include copper-aluminum welding wire, copper-aluminum solder paste, etc. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a laser welding method and system for dissimilar metal films, which can well weld dissimilar metals together.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a laser welding method for dissimilar metal films, the method comprising the following steps:

[0008] S1. Set the welding shape and area according to welding requirements and determine the laser welding route;

[0009] S2, stacking the metal films to be welded up and down, wherein the metal film with a high melting point is located on the upper side, and the metal film with a low melting point is located on the lower side; the thickness of the metal film with a high melting point is less than or equal to 100 μm;

[0010] S3. Setting laser parameters so that the laser irradiates and scans the metal film with a high melting point along the welding route; wherein, a short pulse width and high frequency laser is used, and the laser peak energy obtained at the same time is large enough to heat and melt the metal film with a high melting point instantaneously without being broken down, and the residual heat of the laser is conducted downward to melt the metal film with a low melting point, and the melted parts of the two metal films form a molten pool, thereby completing the welding.

[0011] According to the above method, the laser welding route includes at least one welding point, and the laser welding line of each welding point is a spiral line from the inside to the outside or from the outside to the inside, uninterrupted and without overlapping points, and the maximum diameter of the spiral line is the welding point diameter; the minimum diameter range of the welding point is 0.5-1.5mm, and the spacing between adjacent spiral lines is 0.1-0.5mm; direct jump welding is performed between welding points.

[0012] According to the above method, in S2, the metal films to be welded are in a negative pressure state, so that the stacked metal films are in contact with each other.

[0013] According to the above method, the laser parameters in S3 include pulse width, frequency and scanning speed; wherein, the metal film with a high melting point is a copper film, and the corresponding laser pulse width is 2-20ns, the frequency is 500-1000KHz, and the scanning speed is 30-100mm / s.

[0014] According to the above method, the method of adsorption from below is adopted, and at the same time, the area of ​​the metal film with a high melting point is larger than that of the metal film with a low melting point, so that the metal films are more closely attached to each other under negative pressure.

[0015] According to the above method, the method further includes S4, according to the welding requirements, the excess metal film with a high melting point is laser cut, and the same laser is used for laser cutting, and the laser parameters can be adjusted.

[0016] A laser welding system for implementing the laser welding method of dissimilar metal films, the system includes a workbench for supporting the metal film, a laser that meets the laser parameter requirements, a scanning mechanism for scanning the laser along the laser welding route, and a controller for controlling the opening and closing of the laser and the movement of the scanning mechanism according to the laser welding method.

[0017] According to the above system, the workbench is provided with a negative pressure adsorption mechanism, so that the metal film to be welded is in a negative pressure state for better adhesion.

[0018] According to the above system, the laser is an infrared pulsed mopa laser.

[0019] According to the above system, the controller is also used to adjust the laser parameters of the laser and control the scanning mechanism to make the laser scan along the cutting route, thereby cutting off the excess metal film.

[0020] According to the above system, the system also includes a CCD camera for positioning, and the controller is also used to determine the processing route according to the positioning to ensure the accuracy of the laser welding route.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention arranges a metal film with a high melting point on the top and a metal film with a low melting point on the bottom, and adjusts the pulse width and frequency of the laser so that the peak energy of the laser can melt the upper metal layer, and the residual heat melts the lower metal layer to form a molten pool for welding; the use of short pulse width and high frequency laser can, on the one hand, ensure that the peak energy of the output laser is increased when the spot overlap is large enough, thereby making it easier to form a molten pool and improve the welding process effect; on the other hand, since the upper metal film is thin, the short pulse width has a large peak energy and a short action time, which can effectively reduce the bending of the upper metal film due to heat, and finally achieve the welding of dissimilar metal films with a thickness of less than or equal to 100μm.

[0023] 2. Using a spiral path for welding can, on the one hand, reduce the number of over-welding and cold welding at the beginning and end caused by the first pulse of the laser or the delay of the laser start / end, and on the other hand, ensure the continuity of welding.

[0024] 3. Because the upper metal film is thin, and a very high temperature is required to form a molten pool, the upper metal film is easily bent by heat during the welding process, resulting in a cold weld or over-welding. Therefore, the metal film to be welded is placed in a negative pressure state, and vacuum adsorption is used below, which can effectively reduce the bending of the upper metal film during the welding process and avoid the formation of a cold weld or over-welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the welding pattern of Example 1.

[0026] Figure 2 This is the spiral welding route of the single welding point in Example 1.

[0027] Figure 3 This is the overall welding route of Example 1.

[0028] Figure 4 This is the welding pattern of Example 2.

[0029] Figure 5 The welding pattern and welding route between welding points in the second embodiment.

[0030] Figure 6 This is the welding point setting of Example 3.

[0031] Figure 7 This is a photo of the welding effect of Example 3.

[0032] In the figure: 1-copper solder joint, 2-aluminum film. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific examples and drawings.

[0034] The present invention provides a laser welding method for dissimilar metal films, the method comprising the following steps:

[0035] S1. Set the welding shape and area according to the welding requirements, and determine the laser welding route. The laser welding route includes at least one welding spot, and the laser welding line of each welding spot is a spiral line from inside to outside or from outside to inside, uninterrupted and without overlapping points, and the maximum diameter of the spiral line is the welding spot diameter; the minimum diameter range of the welding spot is 0.5-1.5mm, and the spacing between adjacent spiral lines is 0.1-0.5mm; direct jump welding between welding spots.

[0036] S2. Stack the metal films to be welded up and down, with the metal film with a high melting point located on the top and the metal film with a low melting point located on the bottom; the thickness of the metal film with a high melting point is less than or equal to 100 μm.

[0037] S3. Setting laser parameters, including pulse width, frequency and scanning speed, so that the laser irradiates and scans the metal film with a high melting point according to the welding route; wherein, a short pulse width and high frequency laser is used, and the laser peak energy obtained at the same time enables the metal film with a high melting point to be instantly heated and melted without being broken down, and the residual heat of the laser is conducted downward to melt the metal film with a low melting point, and the melted parts of the two metal films form a molten pool, thereby completing the welding. The pulse width and frequency of the laser can be set according to the melting point of the metal film with a high melting point. For example, if the metal film with a high melting point is a copper film, the corresponding laser pulse width is 2-20ns, the frequency is 500-1000KHz, and the scanning speed is 30-100mm / s.

[0038] Furthermore, in order to make the upper and lower metal films fit better and facilitate the downward conduction of residual heat to form a molten pool, in S2, the metal film to be welded is placed in a negative pressure state, that is, a vacuum adsorption method is adopted from below.

[0039] The area of ​​the metal film with a high melting point is larger than that of the metal film with a low melting point. In this arrangement, when adsorbed from below, the negative pressure provided can make the two metal films fit more closely.

[0040] Then optionally, the method may further include S4, according to the welding requirements, laser cutting the excess metal film with a high melting point, the same laser may be used for laser cutting, and the laser parameters may be adjusted, so that welding and cutting can be performed continuously without switching equipment. Of course, other cutting methods may also be used here.

[0041] The present invention also provides a laser welding system for implementing the laser welding method of dissimilar metal films. The system includes a workbench for supporting the metal film, a laser that meets the laser parameter requirements, a scanning mechanism that scans the laser along the laser welding route, and a controller for controlling the opening and closing of the laser and the movement of the scanning mechanism according to the laser welding method.

[0042] Preferably, the workbench is provided with a negative pressure adsorption mechanism, so that the metal film to be welded is in a negative pressure state for better bonding. At the same time, the area of ​​the metal film located on the upper layer is larger than that of the metal film located on the lower layer, and when adsorbed from below, a better bonding effect can be achieved.

[0043] Further preferably, the laser is an infrared pulsed mopa laser, which meets the requirements of high frequency and short pulse width.

[0044] The controller is also used to adjust the laser parameters of the laser and control the scanning mechanism to make the laser scan along the cutting route, thereby cutting off the redundant metal film.

[0045] The system also includes a CCD camera for positioning, and the controller is also used to determine the processing route according to the positioning to ensure the accuracy of the laser welding route.

[0046] The present invention is further described below by taking a copper film (a metal film with a high melting point) and an aluminum film (a metal film with a low melting point) as examples.

[0047] Embodiment 1:

[0048] On the aluminum film 2, a plurality of circular solder joints are formed with the copper film at intervals. The thickness of the copper film and the aluminum film 2 are 20 μm and 80 μm respectively. The length of the aluminum film is 250 mm and the width is 200 mm. A plurality of copper solder joints 1 with a diameter of 4 mm are formed on the aluminum film 2.

[0049] The steps are:

[0050] S1. Set the laser welding route according to the welding shape and area of ​​the copper film and the aluminum film.

[0051] The welding route of a welding point is a spiral welding route from inside to outside or from outside to inside, such as Figure 2 As shown, its minimum diameter is between 0.5-1.5 mm, the maximum diameter is 4 mm, and the spacing between adjacent spiral lines is 0.1-0.5 mm.

[0052] After one welding point is completed, jump to other welding points for welding, such as Figure 3 As shown, in this embodiment, the process jumps to adjacent welding points for welding in sequence.

[0053] S2. Stack the copper film and aluminum film to be welded.

[0054] The area of ​​the copper film is larger than that of the aluminum film, and the two are placed on the negative pressure adsorption table from bottom to top, and the negative pressure is turned on to make the copper film and the aluminum film fit better and the contact surface flat.

[0055] S3. Set laser parameters, irradiate and scan the copper film according to the welding route from inside to outside or from outside to inside, and perform welding.

[0056] Specifically, the laser scanning speed is set to 30-100 mm / s, the laser repetition frequency is set to 500-1000 KHz, the laser pulse width is set to 2-20 ns, and the laser power is set to 20-50% of the total power.

[0057] Specifically, the laser used for laser welding is a short pulse width, high frequency pulse laser; more preferably, the welding is an infrared pulse mopa laser.

[0058] S4 cuts off the excess copper film according to welding requirements.

[0059] For details, see Figure 1 The copper film and the aluminum film form a plurality of solder joints, and the copper film outside the solder joints is cut. Specifically, a laser is used to scan along the outer edge of the solder joint to cut the copper film. When cutting, the negative pressure is released to reduce the residual heat conductivity.

[0060] The laser is still the MOPA laser mentioned above, and there are no special requirements for the parameters.

[0061] Finally, remove the excess copper film.

[0062] Embodiment 2:

[0063] The principle, method and structure of this embodiment are basically the same as those of the first embodiment, except that: Figure 4 and Figure 5 As shown, the copper soldering point 1 is a square soldering point with a side length of 4 mm. The soldering route of a single soldering point is a square spiral line.

[0064] Embodiment three:

[0065] The principle, method and structure of this embodiment are basically the same as those of the first embodiment, except that: Figure 6 As shown, the entire copper film is welded on the aluminum film. The welding points are arranged as circular welding points arranged in an array. The size of the welding points is 4 mm, the spacing between adjacent welding points is 27 mm, and the edge of the outermost welding point is 13.875 mm away from the edge of the copper film.

[0066] When S4 cuts the excess copper film, it can be cut along the outer edge of the aluminum film. Figure 7 shown.

[0067] Embodiment 4:

[0068] The principle, method and structure of this embodiment are basically the same as those of the first embodiment, except that the selected welding parameters are a speed of 30 mm / s, a frequency of 500 KHz and a pulse width of 20 ns.

[0069] Embodiment five:

[0070] The principle, method and structure of this embodiment are basically the same as those of the first embodiment, except that the selected welding parameters are a speed of 100 mm / s, a frequency of 1000 KHz and a pulse width of 2 ns.

[0071] Embodiment six:

[0072] The principle, method and structure of this embodiment are basically the same as those of the first embodiment, except that the selected welding objects are aluminum and stainless steel.

[0073] Comparative Example 1

[0074] This comparative example is similar to the first embodiment, except that the welding pattern is not spiral, but concentric circles. The diameter of the smallest concentric circle is between 0.5-1.5 mm, the largest diameter is 4 mm, and the spacing between adjacent concentric circles is 0.1-0.5 mm.

[0075] Comparative Example 2

[0076] This comparative example is similar to the first embodiment, except that the negative pressure is not turned on, and the copper film and the aluminum film are pressed together in the following order from bottom to top: metal plane - aluminum film - copper film - weld point hollow rubber pad - weld point hollow metal plate.

[0077] Comparative Example 3

[0078] This comparative example is similar to the first embodiment, except that the laser is a continuous laser.

[0079] Results comparison

[0080]

[0081]

[0082] See Table 1 and Figure 1 , Figure 2 , Figure 3 , respectively, are the welding performance effects of Example 1 and Comparative Examples 1, 2, and 3.

[0083] Compared with the traditional methods of tinning and melting tin to weld copper and aluminum, laser welding is not limited by ambient temperature; compared with welding copper and aluminum by melting welding, friction welding, cold pressure welding, explosion welding, electron beam welding, ultrasonic welding and other welding methods, it is non-contact welding, with good appearance and no contact damage; compared with the traditional brazing method of welding copper and aluminum, it eliminates the medium of intermediate brazing material, which is simple, clean and pollution-free; laser welding has higher software controllability, higher welding accuracy and high degree of automation.

[0084] The present invention arranges a metal film with a high melting point on the top and a metal film with a low melting point on the bottom, and adjusts the pulse width and frequency of the laser so that the peak energy of the laser can melt the upper metal layer, and the residual heat melts the lower metal layer to form a molten pool for welding; the use of short pulse width and high frequency laser can, on the one hand, ensure that the peak energy of the output laser is increased when the spot overlap is large enough, thereby making it easier to form a molten pool and improve the welding process effect; on the other hand, since the upper metal film is thin, the short pulse width has a large peak energy and a short action time, which can effectively reduce the bending of the upper metal film due to heat, and finally achieve the welding of dissimilar metal films with a thickness of less than or equal to 100μm.

[0085] The present invention adopts a spiral path for welding, which can reduce the number of over-welding and cold welding at the beginning and end caused by the first pulse of the laser or the start / end delay of the laser on the one hand, and on the other hand, can ensure the continuity of welding; vacuum adsorption is adopted (because the copper film is thin, and a very high temperature is required to form a molten pool. During the welding process, the copper film is easily bent by heat, thereby forming cold welding or over-welding. The commonly used upper pressure method cannot solve the bending degree well. The use of vacuum adsorption from below can effectively reduce the bending of the copper film due to heat during the welding process).

[0086] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A laser welding method for dissimilar metal films, characterized in that: The method includes: S1. Set the welding shape and area according to the welding requirements, and determine the laser welding route; the laser welding route includes at least one welding point, and the laser welding line of each welding point is a spiral line from inside to outside or from outside to inside, uninterrupted and without overlapping points; S2. Stack the metal films to be welded up and down, wherein the metal film with a high melting point is located at the top and the metal film with a low melting point is located at the bottom; the thickness of the metal films with a high melting point and the metal film with a low melting point are both less than or equal to 100 μm; the metal films to be welded are in a negative pressure state, so that the stacked metal films fit together; the method of adsorption from below is adopted, and at the same time, the area of ​​the metal film with a high melting point is larger than that of the metal film with a low melting point, so that the metal films fit more closely under the negative pressure state; S3, setting laser parameters so that the laser irradiates and scans the metal film with a high melting point along a welding route; wherein a short pulse width and high frequency laser is used, and the laser peak energy obtained at the same time is large enough to heat and melt the metal film with a high melting point instantly without being broken down, and the residual heat of the laser is conducted downward to melt the metal film with a low melting point, and the melted parts of the two metal films form a molten pool, thereby completing the welding; The metal film with a high melting point is a copper film, and the metal film with a low melting point is an aluminum film.

2. The laser welding method according to claim 1, characterized in that: The maximum diameter of the spiral line is the diameter of the welding spot; the minimum diameter range of the welding spot is 0.5-1.5mm, and the spacing between adjacent spiral lines is 0.1-0.5mm; the welding is directly skipped between the welding spots.

3. The laser welding method according to claim 1, characterized in that: The laser parameters in S3 include pulse width, frequency and scanning speed; wherein, the metal film with a high melting point is a copper film, and the corresponding laser pulse width is 2-20ns, the frequency is 500-1000KHz, and the scanning speed is 30-100mm / s.

4. The laser welding method according to claim 1, characterized in that: The method further comprises S4, cutting the excess metal film with a high melting point by laser according to welding requirements, using the same laser for laser cutting and adjusting the laser parameters.

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