Studies of copper deposition for high aspect ratio printed circuit boards

SummaryThe effects of temperature, current density, electrolyte composition and additive content on the electrodeposition of copper from acidic sulphate solutions have been investigated. Wagner numbers (Wa) were calculated from fundamental electrochemical studies at a rotating disc electrode. These were used to predict the throwing power of the system and to optimise plating conditions. Correlation betwen plating tests carried out on boards of 8:7 aspect ratio and fundamental results was excellent. Current density and solution conductivity were found to be the major influences on deposit uniformity and optimum conditions to obtain a 1:1 surface to hole ratio were established.