Abstract
Different diameter Sn/Cu pillars varying from 30 to 1 μm have been made by focus ion beam, and the solid state reaction to form Cu6Sn5 in these pillars has been studied. An increased Cu-Sn reaction rate to form Cu6Sn5 was observed as the pillar diameter decrease from 20 to 1 μm when annealed at 185 and 195 °C. With the shrinking of pillar size, surface diffusion becomes important as compared to grain boundary and lattice diffusion in the Cu-Sn interfacial reaction. Also, surface diffusion induced Kirkendall voids was observed to locate at the peripheral area just above Cu of the Cu-Sn pillars. A simple kinetic model of surface diffusion controlled intermetallic compound growth of Cu6Sn5 is proposed for pillars with diameter below 5 μm. What is essential in the model is that we assume a rapid interstitial diffusion of Cu in Sn, and we are able to calculated surface diffusivity of Cu on Cu6Sn5. At 185 °C, the surface diffusivity is about 3.1 × 10−7 cm2/s and the activation energy is about 0.2 ± 0.1 eV/atom.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
