UCLA

Sn/Cu pillar structure in diameter of 1, 5, 10, 20, and 30 um are fabricated by focused-ion-beam (FIB). After solid state reaction at 175oC, 185oC, and 195oC, the growth of intermetallic compound (IMC) has been studied in this thesis. With the decrease of the pillar diameter, especially below 20 um, the formation rate of IMC will increase. Through FIB slice-and-view study, several Kirkendall voids can be observed at the circumference area of the pillar. Based on the results, it is concluded that surface diffusion has more influence on small-sized pillarr can be concluded. Owing to different dominant diffusion path in small-sized pillar, the kinetic model used for lattice diffusion analysis has been modified by adding terms to represent surface and grain boundary diffusion term. For 1um pillar case, with only single grain inside, a simple model has been built by ignoring lattice and grain boundary diffusion. UsingBy this simple model, the surface diffusivity of Cu onin Cu6Sn5 is able to be acquired, which is at 185oC.