Thermal fatigue behavior of J-lead solder joints

Thermal cycling environments were applied to test specimens with J-lead eutectic Sn-Pb solder joints to assess the effect of lead and package material selection. Metallographic examination and finite element analysis were used to evaluate the effect of thermal cycling environments on solder joints. Matching the coefficient of thermal expansion (CTE) of the lead and solder was found to be crucial to reducing thermal cycling damage for the J-lead solder joints examined. Matching the CTE of the package and the board was substantially less important. The number of thermal cycles 1.9 nucleate cracks in the J-lead solder joints correlated reasonably well with the number of cycles to produce a 50% drop in the load range in isothermal strain controlled mechanical fatigue tests on Sn/Pb solder