Causes of cold welding:
（1）The temperature of the filler groove is low.
（2）The clamping speed is too high and the welding time is short.
（3）PCB does not accumulate enough heat in the pin solder spot of the element with large heat
（4）capacity during normal welding.
Cold welding solution:
（1）Raise the temperature of the filler groove.
（2）Reduce the feeding speed and control the welding time at 3-5s.
（3）Increase preheating temperature to reduce thermal shock of PCB from preheating zone to solder groove.
（4）Solder joint icicles