Method of regulating nickel concentration in lead-free solder containing nickel
AssigneeNihon Superior Sha Co., Ltd.
InventorTetsuro Nishimura
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Abstract
A method by which the amount of nickel contained in an alloy having a composition represented by Sn—X—Ni can be regulated. The method of nickel concentration regulation comprises adding phosphorus to Sn—X—Ni in a molten state (wherein X is one or more elements selected from the group consisting of Ag, Zn, Cu, Bi, Au, Ti, Ge, Ga, Si, and Ce), holding the mixture at 250-400° C., and removing the resultant dross floating on the surface of the liquid phase and containing a P—Ni compound and a P—Sn—Ni compound. An example of X is copper, and the content thereof may be 0.3-5 wt %. The phosphorus may be added in the state of a Sn—P alloy. The upper limit of the amount of the phosphorus to be added may be about half the nickel amount in terms of atomic amount.
Claims5
A method of regulating Ni concentration, the method comprising:
- adding an amount of P to Sn—Cu—Ni comprising an excess of Ni over a desired Ni concentration while in a molten state,
- holding the mixture of P and Sn—Cu—Ni at 250-400° C. resulting in a dross floating on the surface of a liquid phase, and
- removing the resulting dross floating on the surface of the liquid phase,
- wherein the dross contains at least one of a P—Ni compound and a P—Sn—Ni compound thereby diluting the Ni concentration remaining in the molten Sn—Cu—Ni to the desired concentration;
- wherein the desired concentration of Ni is within a range of 0.04-0.1 wt %.
Dependencies are inferred from the claim text.