Analysis of BGA soldering failure under cold thermal shock

Using cold thermal shocking method,the reliability of lead-free BGA soldering position was tested with the temperature change rate of 90 ℃/min,-65-+125 ℃and the stay time of 15 min in the high and low temperatures.The analyses of the test results were performed by metallographic microscope,SEM and EDS.The results show that the failure spots of BGA are mostly concentrated between the solder and the solder pad.The main reasons caused the BGA soldering position failure are that the coefficients of thermal expansion(CTE) of IMC,the solder and solder pad mismatch and IMC get oxidized.