Study the contact angle measurement and characterization of Sn-Cu lead-free solder on copper substrates

In this study, the contact angles of Sn-Cu and Sn-Cu-Zn lead-free solder were measured on the copper copper substrates of different temperatures. Measurements were performed using the SEM and optical microscope. Contact angles ranging from 30̊ to 60̊ after wetting with no fluxes and 10̊ to 60̊ with midly rosin activated ( RA) fluxes were obtained. Sn-Cu exhibited lowest contact angles, indicating improved wettability with the addition of Zinc for all soldering alloys. Then, the lower contact angles were observed using the flux intermetallic formed at the solder or copper substrates interface were identified as Cu6Sn5 adjacent to the solder and Cu3Sn adjacent to copper substrates. The effect of temperature on contact angle was dependent on the type of flux used.