Patent ID: 6245389
Filing Date: 2001-06-12
Classification: B01D,B01J,C23C,Y02A

Abstract:
A method of circulating an electroless nickel plating solution, which method comprises the following sequential process steps:(A) electrolessly plating nickel by use of a plating solution having nickel hypophosphite contained as a chief chemical material for supplying a plating metal ion Ni.sup.2+, and a hypophosphorous acid ion H.sub.2 PO.sub.2.sup.- acting as a reducing agent;(B) removing HPO.sub.3.sup.2- from the plating solution that has aged in step (A);(C) separating a mother liquor from step (B), and then desalting the mother liquor separated in step (B) by passing it through an electrodialysis cell, cation exchange resin or reverse osmosis membrane; and(D) adjusting the components of the treated plating solution of step (C) and then circulating them back into step (A) for electroless nickel plating,wherein, in step (B), the pH of the plating solution having aged in step (A) is adjusted to 6-9 with a calcium salt to cause calcium phosphite to precipitate, and the precipitate is thereafter separated and removed.