Temperature-induced effect and control of Cu3Sn on the rotation of orientation-preferred Cu6Sn5 crystals at Sn-3.0Ag/(001)Cu interface

Abstract

Crystal rotation of the orientation-preferred Cu6Sn5 formed on (001)Cu usually happens in soldering, and its rotation rate depends on the temperature closely. In this work, the evolutions of intermetallic orientation, phase and thickness at Sn-3.0Ag/(001)Cu interface were systematically investigated under temperatures of 230 °C, 250 °C and 300 °C. Results illustrate that the nucleation of orientation-preferred Cu6Sn5 on (001)Cu can be realized at any temperature above the solder melting point, but subsequently crystal rotation from <112¯0> to 〈0001〉 in ND happens as well. High temperature was found to greatly maintain the initial orientation of Cu6Sn5 crystals as well as facilitate the formation and growth of Cu3Sn, which can effectively reduce the driving force of Cu6Sn5 rotation and consequently inhibiting the rotation of Cu6Sn5 crystals. Finally, a theoretical model of Cu6Sn5 crystal rotation based on interfacial thermodynamic calculation was established and a two time reflow profile of 300 °C–230 °C was designed to furthest inhibit the rotation of Cu6Sn5 crystals and maintain the preferred orientation of Cu6Sn5 texture according to our proposed theory. The results are of great significance for the intermetallic orientation control in soldering.