The cathode current efficiency of flip-chip solder bump plating

Flip chip solder bumps were produced on various bump pad dimensions by electroplating to investigate their current efficiency. The bump pad dimensions range from 60 x 60 mum to 250 x 250 mum. Bump heights are in the range of 80-150 mm. The bump height achieved is very uniform across a 4 in. wafer. The growth of bump height follows a parabolic trend with respect to plating time. Experimental results showed that the cathode current efficiency increases with increasing pad size. The cathode current efficiency also increases with respect to plating time and approaches a constant level after 30 min of deposition. (C) 2003 The Electrochemical Society.