Interfacial reactions between In 10Ag solders and Ag substrates

The morphology and growth kinetics of intermetallic compounds formed during the reaction of liquid In 10Ag on Ag substrates in the temperature range between 250°C and 375°C are studied. The results indicate that the Ag₂In intermetallic compounds that appear at the interface are in the columnar shape, enveloped by thin AgIn₂ shells. The growth kinetics of intermetallic compounds are parabolic, indicating that the reaction is diffusion-controlled. The Arrhenius reaction activation energy was found to be 44.9 kJ/mol. Also, the wetting behavior of the In10Ag on Ag substrates was studied. The results show that there exists a transient plateau of the contact angle variation. Such a phenomenon can be explained by the intermetallic compound precursor halo formation preceding the edge of the solder drop.