Effect of TiO<sub>2</sub> on the Formation of Primary and Interfacial Cu<sub>6</sub>Sn<sub>5</sub> in Sn-0.7wt%Cu and Sn-0.7wt%Cu-0.05wt%Ni Solder Paste during Soldering

Abstract

This paper investigates the effect of 1 wt% TiO2 on the formation of primary and interfacial Cu6Sn5 in Sn-0.7wt%Cu and Sn-0.7wt%Cu-0.05wt%Ni solder pastes soldered on a Cu substrate using a real-time synchrotron imaging technique. It was found that TiO2 had altered the nucleation time of the primary Cu6Sn5 intermetallics and increased the number of particles observed. In addition, a more planar Cu6Sn5 interfacial layer had formed in joints made with TiO2 reinforced solders. This indicated that TiO2 promotes nucleation of primary Cu6Sn5 intermetallics in the early stages of soldering while being a barrier for further growth of interfacial Cu6Sn5 intermetallics. The synchrotron imaging technique provides direct evidence of the sequence of events in the soldering reaction and how these are influenced by TiO2 reinforcement.