Investigation of the wetting properties of Cu6Sn5 intermetallic compound

The intermetallic compound (IMC) layers formed during the soldering processes of electronic products are commonly agreed to have poor wetting properties but there are several studies which came to an opposite conclusion. The present study aims at basic, systematic experimental investigations to gain experience on the wetting properties of the intermetallic compounds. Intermetallic layers with different morphology were generated by multiple reflow cycles. The samples were analyzed by scanning electron microscopy and cross-sectioning. SAC305 solder balls were reflowed on the surface of Cu6Sn5 layer. The wetting property of the IMC layer was concluded from the spreading of the solder balls. It was found that the surface of intermetallic structure has indeed poor wetting properties, regardless of the morphology of the surface.