Electroplating method

Abstract

A cycle of electroplating is repeated in an electroplating bath containing at least one metal ion selected from cobalt, nickel and iron, a buffering agent and a conducting agent by use of a soluble anode. The concentration of the conducting agent in an initially prepared electroplating bath is set at 70 to 95% of a saturated concentration. The electroplating is repeated in such a way that a first replenishment solution containing a buffering agent and a conducting agent at concentrations of 0.5 to 1.2 times the concentrations in the initially prepared electroplating bath and free of the metal ion is added so as to replenish the agents that have been reduced in amount during the course of the electroplating and a concentration of the conducting agent in the electroplating bath after the replenishment of the first replenishment solution is adjusted to 70 to 95% of a saturated concentration thereof. According to the invention, the electroplating can be repeated while keeping the electroplating bath over a long time in a good condition sufficient to provide a plated film having high throwing power and a good appearance, so that there can be stably obtained plated films over a long time without frequent regeneration such as by electrolysis for lowering the concentration of a metal ion in the plating bath, thus being good at economy.

1 . An electroplating method wherein a cycle of electroplating a substrate for plating is repeated by use of a soluble anode in an electroplating bath containing at least one metal ion selected from those of cobalt, nickel and iron, a buffering agent, and a conducting agent, the method comprising:
 setting a concentration of said conducting agent in an initially prepared electroplating bath at a level within a range of 70 to 95% of a saturated concentration; replenishing said buffering agent and said conducting agent, each reduced in amount during the repetition of the electroplating, by adding, to said electroplating bath, a first replenishment solution that contains a buffering agent and a conducting agent each at a concentration of 0.5 to 1.2 times the concentration contained in the initially prepared electroplating bath and is free of said at least one metal ion; and   adjusting the concentration of said conducting agent in said electroplating bath after the replenishment of said first replenishment solution to 70 to 95% of a saturated concentration under which the electroplating is repeated.   
   
   
       2 . The method according to  claim 1 , wherein said buffering agent and said conducting agent used in said first replenishment solution are, respectively, the same as those used in said initially prepared electroplating bath. 
   
   
       3 . The method according to  claim 1 , wherein said electroplating bath further comprises a halide ion, and the electroplating is carried out in such a way that a halide ion in the electroplating bath reduced in amount during the course of the repetition of the plating is replenished by adding, to said electroplating bath, said first replenishment solution that further comprises a halide ion at a concentration of 0.5 to 1.2 times the concentration in the initially prepared electroplating bath. 
   
   
       4 . The method according to  claim 3 , wherein said halide ion used in said first replenishment solution is the same as said halide ion used in said initially prepared electroplating bath. 
   
   
       5 . The method according to  claim 1 , wherein said electroplating bath further comprises an organic brightener, and the electroplating is carried in such a way that said organic brightener reduced in amount during the course of the repetition of the electroplating in said electroplating bath is replenished by adding, to said electroplating bath, said first replenishment solution further comprising an organic brightener at a concentration of 0.5 to 1.2 times that in the initially prepared electroplating bath. 
   
   
       6 . The method according to  claim 5 , wherein said organic brightener used in said first replenishment solution is the same as said organic brightener used in said initially prepared electroplating bath.