Apparatus for automatically replenishing an electroless plating bath

Claim 1

Apparatus for maintaining the consumable components of an electroless plating solution at predetermined concentration in a plating tank containing said plating solution while workpieces are being processed in the tank, said consumable components comprising plating metal ions, pH adjustor and reducing agent, said apparatus comprising in combination: means for withdrawing a sample stream of plating solution at a predetermined rate from the plating tank and passing the same through a sequence of analyzing stations to a point of discharge; a first station consisting of means for analyzing the metal ion content of the sample stream and means operatively connected to and actuated by said metal ion analyzng means to meter plating metal ions to said electroless plating solution so as to replenish said solution with said ions; means for introducing into said sample stream a source of plating solution poison in an amount capable of preventing metal from plating from said solution, said means being located after said first station; a second station located after said means for introducing poison into said sample stream consisting of a pH analyzing station having means for measuring the pH of the sample stream, and means operatively connected to and actuated by said pH measuring means to meter pH adjustor to said electroless plating solution so as to replenish said solution with said adjustor; and a third station consisting of a reducing agent analyzing station having means for measuring the concentration of reducing agent, and means operatively connected to and actuated by said means for measuring reducing agent concentration to meter reducing agent to said electroless plating solution so as to replenish said solution with said reducing agent.