Reliability analysis of plastic ball grid array double-bump lead-free solder joint under thermal cycle

The automatic seam tracking of overlap seams of sheet was always a particular problem in the welding field.According to the characteristics of its welding procedure,a seam tracking method for overlap sheet welding based on magneticcontrol arc sensing is proposed in this paper.By employing external alternating transverse magnetic field to control arc motion, this method acquires the real-time welding deviation through detecting the variation rules of welding currents.Wavelet threshold de-noising method is selected to process the current signals after contrastive analysis on the filtering results of the two-level second- order Butterworth filter and the wavelet filtering.Based on the analysis of characteristics of overlap sheet welding and the motion of magnetic-control arc,a control method of welding deviation correction based on the combination of unilateral-compared midpoint-divided area integral method and the torch-control method is proposed.The results of practical seam tracking experiments demonstrate that the automatic seam tracking method proposed can effectively resolve the dilemma of real-time seam tracking during overlap sheet welding.