Apparatus for controlling electroless plating bath

摘要

A method and an apparatus for controlling the content of an electroless plating bath such as an electroless nickel plating bath such that the bath is useable for an extended period of time without remaking are disclosed. The method comprises the steps of: continuously or intermittently measuring the concentration of at least one consumable ingredient of the electroless plate bath, and automatically adding to the plating bath a first replenishing composition essentially consisting of the consumable ingredient after detecting that the measured value has reached a predetermined concentration; while continuously or intermittently measuring one physical property of the electroless plating bath to determine the degree of aging of the bath, and automatically discharging a predetermined volume of the plating solution and automatically adding to the plating bath a second replenishing composition containing unconsumable ingredients in an amount essentially corresponding to the lost amount by the discharging after detecting that the measured value has reached a predetermined value of the physical property.