Influence of an immersion gold plating layer on reliability of a lead-free solder joint

Electroless Ni/Au plating is often performed oil a surface of a Cu pad to improve the wettability of lead-free solders on such a pad. Generally, electroless All plating is performed by all immersion plating method. Since a substitution reaction of Ni and Au occurs selectively on the surface of a Ni layer in immersion plating, the All layer does not uniformly form oil the Ni layer and microvoids or inicrocracks easily form at the Ni/Au interface. Such defects induce void formation at the joint interface in soldering. and consequently degrade the reliability of the lead-free solder joint. In this study, the influences of immersion plating time on microvoid formation at the joint interface and the reliability of a solder ball joint with a Sn-3 mass%Ag-0.5 niass%Cu lead-free solder were investigated.