Abstract
The wettability of Sn-Cu and Sn-Pb solder platings accelerated by pressure cooker test and high temperature shelf test was evaluated through meniscograph and the platings were surface analyzed through XPS, SEM and EDX for the determination of main factors to reduce the wettability. The surface of Sn-Cu platings has a stable oxide layer, SnO2, which is thicker for the samples kept in higher humidity atmosphere. Wettability of Sn-Cu platings does not decrease even in high temperature atmosphere, but that of thin (1μm) Sn-Pb platings reduced. Both of Sn-Cu and Sn-Pb platings do not show remarkable change in the wettability by the component of solder bath. It is suggested that the diffused Cu atoms from the brass substrate and Ni atoms from the plating under the solder plating does not effectively obstruct the wettability. Thus, the main factor for wettability reduction is concluded to be the surface oxide layer and its thickness.
