Solderability of Electroless Nickel Alloys Using Wetting Balance Technique

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Abstract
Solderability of electroless nickel-alloy deposits was investigated by the wetting balance technique. The wetting time, wetting force and dewetting can be obtained from the wetting curve. Four parameters, wetting time, percentage of theoretical force, stability of wetting and solderability index, were applied to determine the effects of the soldering variables including two kinds of flux, substrates of electroless nickel-alloy deposits and their solderability. In general, wetting time decreases with an increase in soldering temperature. The rosin-activated flux has a stronger fluxing effect than organic acid. Among the investigated items, solderability index and contact angle are quite sensitive to the base metal material. The electroless Ni–Cu–P deposit and the electroless Ni–P with Au-coated deposit exhibit good wetting behavior with contact angles of 25°<θ<45° when using RA flux. On the other hand, poor wettability, with contact angles of 65°<θ<90°, was observed for the deposits investigated in this work using OA flux.