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With the continuous deepening of laser welding technology research, laser welding has also made great breakthroughs in terms of technology, process processing, and defect solutions. During the laser welding process of the PACK module, virtual welding often occurs, which seriously affects the service life of the battery.
False welding: that is, the welding strength between the two (multi-layer) tabs or between the bus bar and the tab is insufficient, or even no penetration is formed. This form of defect mainly affects the stable performance of the battery's electrical performance, and the consequences are relatively serious. Often, the entire battery pack cannot work normally due to the virtual welding of a solder joint, and it is often an invisible defect that is exposed after the customer has used it for a period of time.
Welding conditions required for laser welding of lithium battery PACK modules:
1. Avoid short circuits during assembly or welding
2. The influence of temperature on the cell body during the welding process should not exceed 60 degrees Celsius
3. The oxidation area of the welding area is small, which does not affect the conductivity of the tabs
4. Automatic mass production can be realized
5. There is a structure of superimposed welding of multi-layer thin material tabs, and there may be welding of copper and aluminum dissimilar materials
6. When single-layer welding, the depth of the welding layer should be controllable and cannot be welded through.
Factors affecting the welding effect of laser welding PACK module:
1. Contamination of material surface
In general, when using a laser welding machine for welding, pay attention to whether there is dirt on the surface of the material. If the material with dirt is put into the welding area, the surface of the material will not be crystallized normally or insufficiently crystallized, which is one of the factors that directly affect the instability of the laser welding machine;
2. The welding speed is too fast
Users often mistakenly believe that the faster the welding speed, the faster the production and the better the product when using a laser welding machine. In fact, when the laser welding machine acts on material processing, the longer the processing time between the laser and the workpiece, the more sufficient the welding, not the faster the better; otherwise, the faster.
3. Materials and welding power do not match
The power of laser welding machines is not suitable for all materials. The power used to weld different materials is not the same. If the power used by the user is low, the welded material is not strong; for some highly reflective materials, we can increase the welding power and slow down the welding process parameters such as the welding speed.
4. Tables and Fixtures
Tables and fixtures are used to hold materials. If the material is not fastened firmly enough, it may not be able to successfully weld, resulting in poor welds and missing welds, such as nanosecond laser welding equipment, which requires the two weldments to be fully fitted, otherwise it is prone to false welding. And for difficult welding, we need to customize the fixture to meet the welding needs.
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