CONSTITUTIVE RELATIONS FOR TIN-BASED SOLDER JOINTS

This paper presents extensive data on 62Sn36Pb2Ag, 60Sn40Pb, 96.5Sn3.5Ag, 97.5Pb2.5Sn, and 95Pb5Sn solder. All of the data were collected on actual soldered assemblies to properly account for the effects of grain size and intermetallic compound distribution. Tensile and shear loading were employed in the strain rate range between 10(-8) and 10(-1) s-1 and the temperature range between 25 and 135-degrees-C. It is remarkable to note that all of the data can be fit to the same general form of constitutive relations; i.e., only the constants depend on the solder alloy. The derived constitutive relations are used to predict solder joint response under thermal cycling. Based on the calculated hysteresis loops, it is apparent that each solder will have a different acceleration factor between field use cycling and accelerated test cycling.