1) in the case of penetration, solder joint surface laser spot welding has obvious collapse. With the increase of laser power and the duration of the collapse of solder joint surface depth increased, the duration or the gap size is large, the surface will appear concave.
2) with the increase of clearance, the overall deformation of solder joints, joints and the concave center is very obvious, and the fusion surface shrinkage and strength decreased quickly. At present, the welding resistance, battery and electronic field commonly used at the same time two points of welding process, usually using two laser light source design.
3) with the increase of laser power, the surface diameter of the solder joint fluctuates, and the diameter of the fusion surface and the diameter of the lower surface of the surface increase slowly. The shape of the cross section is not obvious. And with the increase of the duration, the solder joint size grows very fast, the change rate of the fusion surface diameter is greater than the change rate of the upper and lower surface diameter. The influence of the variation of the off focus amount on the solder joint size is very large. It directly changes the spot diameter and laser power density, and the combined effect of these two factors determines the size of the solder joint.