Relationship between free solder thickness to the solderability of Sn–0.7Cu–0.05Ni solder coating during soldering

Abstract

The relationships between solderability, free solder thickness and intermetallic thickness of Sn–0.7Cu–0.05Ni solder coatings on Cu substrate has been investigated. The annealing method was proposed to control free solder thickness by controlling the ratio of free solder and interfacial intermetallics (IMCs). The solderability of solder coating has investigated using a purpose-designed microwetting balance. The interfacial intermetallic microstructure was analysed and the thickness measured in the as-coated condition with aging process. Results indicate that the solderability is related to free solder thickness, where the increase of aging time and temperature thickness of the free solder is reduced by the interfacial intermetallic compound growth. Onwards, the different composition of germanium (Ge) was added into Sn–0.7Cu–0.05Ni as an antioxidant to control drossing of the molten solder. The effect on solderability of a Ge addition to the coating alloy was measured. These results may be used as a basis to obtain an optimum wettability of solder coating during soldering.