Incomplete data supervisor control for electroless nickel plating

In control practice for the electroless nickel plating through holes board, the pH-index is controlled in dependence on the metal turnover, while the nickel percentage is kept at constant level. In this paper, the state of the process is estimated by several electrochemical parameters by which the required pH-index and nickel percentage is evaluated in dependence on the current state. The desired parameters of the product - thickness of the plating film and phosphorous content - are ensured by supervisor control of the pH-index and nickel percentage at target set-points tracked from the chemical equilibrium of the system. The bath loading, which has a strong effect on the deposition process, is estimated and its variation compensated by control.