Comparison of creep behavior for lead free solders Sn-3.5Ag, SAC305 and SAC387

Abstract

Numerous lead-free solder compositions were developed recently to substitute the conventional lead-tin solder due to its environmental hazards. As an example, lead-free solders with tin-silver-copper (SAC) compositions are frequently used with various weigh percentage of the alloying elements. Beside the electronic properties of these solders, the mechanical behavior is of great interest, due to the time dependent nature arising from these low melting point materials operating at thermal-mechanical loads. In this paper, the thermal-mechanical creep behavior is analyzed for three lead-free solders of Sn-3.5Ag; SAC305 and SAC387. A simple structural configuration of an electronic package containing a solder joint is modeled in finite elements, where the applied load was thermal cycling. The Anand material model was employed for the creep behavior of the solder. Stress and strain analyses of the structural behavior was performed and compared for the tree different lead-free solders. Results are presented for the mechanical response of the different compositions.