Optimization of the Copper Plating Process Using the Taguchi Experimental Design Method: I. Microvia Filling by Copper Plating Using Dual Levelers

Abstract

Copper electroplating formulas composed of CuSO4, H2SO4, chloride ions, polyethylene glycol (PEG), bis (3-sulfopropyl) disulfide (SPS), and different levelers for microvia filling of a printed circuit board (PCB) were studied. The influence of the copper electroplating parameters, accelerator and leveler concentrations and cathodic current density on the microvia filling performance was explored using the Taguchi experimental design method. An L9 orthogonal array with four controlling factors at three levels was employed in the experimental design method. Variance analyses of the mean filling performance and the signal-to-noise ratio of the controlling factors showed that the most significant factor for the microvia filling performance was the leveler concentration. The other factors exhibited little to no effect on the microvia filling performance. The contribution of levelers to the filling performance was characterized using galvanostatic measurement and linear sweep voltammetry (LSV) with a working electrode at different rotational speeds. The experimental results indicated that the inhibiting effect of the levelers on the copper deposition was related to forced convection, which is a key physicochemical interaction for exhibiting good filling performance.