Abstract
Under the goal of prolonging lifetime of an electroless-copper-plating solution, a new method for supplying Cu2+ ions to the solution, copper-ball dissolution method was developed. The effect of the developed method was examined by comparing with conventional methods: CuO-particle dissolution method and CuSO4-supply method. Studies on copper-ball dissolution reactions clarified that Cu2+ ion could be supplied to the plating solution by dissolving copper ball in the oxygen-supplied solution. Compared with CuSO4-supply method, copper-ball dissolution method prevents salts from being accumulated in the solution, which can potentially double the lifetime of the solution, similar to CuO-particle dissolution method. The films obtained by copper-ball dissolution method contain fewer impurities than those deposited by CuO-particle dissolution. As a result, the mechanical properties of the deposited film and the reliability of through-hole connection are improved. It is concluded that copper-ball dissolution method is an effective method for prolonging the lifetime of an electroless copper-plating solution, leading to reduction in environmental loads.
