THERMAL FATIGUE BEHAVIOR OF J-LEAD SOLDER JOINTS

Thermal cycling environments were applied to test specimens with J-lea d eutectic Sn-Pb solder joints to assess the effect of lead and packag e material selection, Metallographic examination and finite element an alysis were used to evaluate the effect of thermal cycling environment s on solder joints, Matching the coefficient of thermal expansion (CTE ) of the lead and solder was found to be crucial to reducing thermal c ycling damage for the J-lead solder joints examined, Matching the CTE of the package and the board was substantially less important. The num ber of thermal cycles to nucleate cracks in the J-lead solder joints c orrelated reasonably well with the number of cycles to produce a 50% d rop in the load range in isothermal strain controlled mechanical fatig ue tests on Sn/Pb solder.