Elastic-Creep Finite Element Analysis of Solder Joints and Experimental Verification Using a Diffused Type Strain Gauge.

In this study, first, tensile and creep tests were carried out on two solders, 63 Sn-37 Pb and 95 Pb-5 Sn, to determine their mechanical properties. Using the measured properties, constitutive equations for the solders based on elasticity and creep were formulated. Next, an elastic-creep finite element analysis was performed on solder joint structures under thermal cycle. The solder joint structure consisted of a Si chip and a Cu plate with either 63 Sn-37 Pb or 95 Pb-5 Sn solder. The validity of the analysis was verified by the experiment using a diffused type strain gauge formed on the Si chip. The analytical results of the thermal stress on the Si chip were in good agreement with the experimental results. The analytical results showed that most of the creep strain in the solder joints occurred during the temperature change, the temperature change time hardly affected the creep strain range in solder joints, and the creep strain range for 95 Pb-5 Sn solder was higher than that for 63 Sn-37 Pb solder.