Investigation of the interfacial reactions between Sn-3.0 wt%Ag-0.5 wt%Cu solder and Cu[sbnd]Ti alloy (C1990HP)

Abstract

The interfacial reactions between Sn-3.0 wt%Ag-0.5 wt%Cu (SAC) solder and CuTi alloy (C1990HP) using the solid/liquid reaction couple technique reflowed at 240, 255, and 270 °C for 10 min to 20 h was first investigated. The results revealed that the Cu6Sn5 phase and the precipitated Ti2Sn3 and Ag3Sn phases with a small grain size were formed and no Cu3Sn phase was observed in the SAC/C1990HP couple when the reflowing time was longer than 30 min. In addition, the Ti2Sn3 phase was observed among the upper the Cu6Sn5 phase. Comparing the SAC/Cu reaction couple, the thicker intermetallic compound (IMC) layers were observed in the SAC/C1990HP reaction couple. It was also shown that the massive spalling of the Cu6Sn5 phase in the SAC/C1990HP reaction couple for the prolonged reflowing time. Meanwhile, the Sn-rich layer was observed between the upper and lower Cu6Sn5 phases. When the reaction temperatures and times were increased, the small grain of the Cu6Sn5 phase was merged and ripened each other, and then spread over to the SAC solder. The hexagonal prism-shaped Cu6Sn5 phase was found when the Cu6Sn5 layer detached at the SAC/C1990HP interface. The IMC growth mechanism was diffusion controlled.