Micro-Replication: Precision Metal parts from Electronformed Master Molds

The possibility of using through-mask electrodeposition to fill features with active sidewalls was investigated. Both metal (Ni) and conductive substrates were employed; the demolding of electroformed Ni metal parts from metal substrates was difficult despite the use of various lubricants. Because of damage to the electrodeposited parts during the demolding process, conductive plastic substrates appear more feasible than metal substrates. Direct current was capable of filling features with low aspect ratios ({approx}2) with only minor voiding. For higher aspect ratio features ({approx}7), pulsed deposition and direct current with the leveling agent coumarin appeared to be more effective than pulsed reverse deposition. Since the characteristic diffusion time constant varies with the square of the feature depth, chloride ions are necessary to prevent passivation during the long pulse off-times required for uniform feature filling through a thick mask. It is shown that although thick masks require long pulse off-times, the recommended deposition rate for uniform filling (available in the literature) should not depend on the mask thickness (although the total deposition time will)