The combination of appearance after wetted with solder, solder coverage, and wetting time can well describe the wettability for electroless deposits.The wettability decreases with an increase of phosphorus in the electroless nickel-phosphorus-based alloy deposits. Tin does not greatly affect the wettability with only a slightly favored effect either for nickel-tin-phosphorus or nickel-tin-copper-phosphorus deposits. Copper greatly improves the wettability of nickel-phosphorus-based alloy deposits.A new kind of electroless amorphous alloy deposit, nickel-tin-copper-phosphorus, with very close wettability to the amorphous nickel-boron deposit, can be a replacement for gold deposits. The electroless nickel-tin-phosphorus deposits, which have fair to good wettabilities, can be used for replacement of gold deposits to a certain extent.Tin greatly reduces the H_v of the nickel-phosphorus deposits because of its softness compared to that of nickel. Copper does not reduce the H_v of the nickel-phosphorus deposits too much. The H_v of nickel-tin-copper-phosphorus deposits is larger than that of nickel-tin-phosphorus deposits because copper is harder than tin and the alloying effect in the quaternary nickel-tin-copper-phosphorus alloy deposits stronger than that of the ternary nickel-tin-phosphorus deposits.
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