IMPROVEMENT IN LEVELING OF PULSE-PLATED M ETAL DEPOSIT

An electric potential field in an electrolytic bath that contains elec trodes of various geometric shapes for pulse plating was numerically a nalyzed by using the finite element method, and dimensionless thicknes s distribution of metal deposit on the cathode was estimated from the potential distribution in the bath. Relations between the potential di stribution in the bath and the thickness distribution of metal deposit were investigated on the basis of both calculated results and experim ental data for pulse plating of copper. Moreover, an improvement in le veling of the pulse-plated metal deposit was discussed. The calculated results of dimensionless thickness distributions of metal deposit on the cathode agreed with the experimental ones, showing the validity of the numerical analysis employed in this work. Relations between the t hickness distributions of metal deposit and the geometric factors such as distance between the electrodes, size and shape of the electrodes were quantitatively clarified by the present numerical analysis. Furth ermore, by including cutoff plates near the cathode, the electric pote ntial field in the bath could be controlled, and leveling of the pulse -plated metal deposit was also improved effectively.