Effects of Electroplating Process Parameters on Properties of Co-electroplated Au-Sn alloy

With the development of flip-chip packaging technology in high powered light-emitting diode (LED), the size of bump which plays a vital role to maintain the reliability of interconnects continues to decrease. Au-30at.%Sn eutectic alloy is one of the most promising lead-free solders, which has been widely used in LED packaging, owing to its excellent mechanical property and thermal conductivity. In the present work, a relatively stable non-cyanide electroplating solution was obtained. The co-electrodeposited films with bright silver surface and fine crystal grains were obtained, when the peak current density was between 25 mA/cm
²
and 30 mA/cm
²
. Chronopotentiometry analysis indicated that the irregular and coarsened particles appeared under a relatively low current density. The optimal co-electroplating temperature of Au-Sn alloy was between 30 °C and 40 °C, at which the co- electrodeposited film has a nearly eutectic composition with a bright silver surface and fine crystal grains. The cathodic polarization curve showed the effect of different plating temperature on the co-deposition Au-Sn alloy. When the plating temperature was between 20 °C and 60 °C, the coelectrodeposition of Au-Sn alloy were occurred at -797 mV.