Creep-Fatigue Life Evaluation of Sn-3.5Ag-0.5Cu-Ni-Ge Solder at Low Temperatures

Abstract

Kitachujyo, Tsubata-machi, Kahoku-gun, Ishikawa, 929-0392 Japan This paper describes creep-fatigue lives of Sn-3.5Ag-0.5Cu-Ni-Ge solder at low temperatures. Push-pull creep-fatigue tests under four types of strain wave form were carried out at 253K and 273K to study an application of creep-fatigue life evaluation method for Sn-3.5Ag-0.5Cu-Ni-Ge. There were effects of temperatures on stress amplitude, and tension stress amplitude at 253K was larger than that at 273K in fast-fast wave form test. The higher stress amplitude reduced the creep-fatigue lives. The creep-fatigue lives with slow strain rate were shorter than the creep-fatigue lives with fast strain rate. A linear damage rule and a strain range partitioning method estimated the creep-fatigue lives in a large scatter. A grain boundary sliding model was a suitable parameter for creep-fatigue life estimation for Sn-3.5Ag-0.5Cu-Ni-Ge.