Estimation of Fall Impact Strength for BGA Solder Joints

摘要

The quantity of stress and strain at BGA (Ball Grid Array) solder joints produced by fall impact was analyzed. The analysis motif is straightforward, having only a square PWB (Printed Wiring Board) on which a BGA is mounted in the center. An analysis was conducted using the detailed global model in which the entire analysis motif was particularly and elementally divided. The value of strain applied to the PWB, which was acquired through this analysis, agreed well with that of the fall impact experiment. As a result of these findings, the validity of the impact analysis was strongly confirmed. The findings show that the position supporting the maximum stress corresponded with the position of the peeled solder joints on the PWB. The study demonstrates that the most likely positions to cause peeling are predictable. A 2-step analysis method is reviewed. The method combines a detailed model, using only one solder ball and a simplified model that treats the overall motif used for acquiring the board displacement obtained near the solder balls. Using this method, it was demonstrated that the position having the maximum stress on solder joints and its maximum value can be calculated and that it takes about 1/10 of the time previously calculated.