Scanning electron microscopy (SEM) image obtained after etching of a supercooled tin deposit with a nickel underlayer. The selective de-tinning performed by acid etching reveals the Ni3Sn4 intermetallics (dark phase on the image) that form as a result of the diffusion of nickel in the tin layer.
About the author: Thiam ABDOULAYE recently defended his PhD on solderless connection process (pressfit).