Thermal Fatigue of Low-Temperature Solder Alloys in Insertion Mount Assembly

Abstract

Thermal fatigue resistance was investigated for insertion mount solder joints, manufactured with 58Bi-42Sn (wt. %), 43Sn-43Pb-14Bi, 52In-48Sn and 40In-40Sn-20Pb low-temperature alloys. Accelerated thermal cycling was used in conjunction with metallographic analysis to determine the fatigue resistance and to elucidate the failure mode for each solder composition. Additionally, the behavior of each solder alloy was compared to that of 63Sn-37Pb solder, tested under identical conditions. A two-phase microstructure with lamellar morphology was observed in 58Bi-42Sn, whereas a globular morphology was prevalent in the remaining alloys. The Bi-containing solders demonstrate fatigue resistance comparable to 63Sn-37Pb, but greater than the In-bearing alloys. These differences and microstructure changes prior to and during thermal fatigue testing are discussed.