Plating of 60/40 Tin/lead solder for head termination metallurgy

Current head termination metallurgy consists of plated copper studs followed by plated gold pads. Gold wires are then ultrasonically bonded to the gold pads. This presentation shows the feasibility of plating tin/lead (60/40) as a replacement for the gold. This solder alloy can be laser-sonically bonded to the wires. The thickness uniformity of the plated studs as a function of applied current is determined from the alpha step measurements. The maximum uniformity and smoothness of these studs are obtained at current densities between 60 and 80 mA/cm 2 . The changes in thickness, uniformity, profile, and roughness of films deposited with direct and pulsed current are consistent with the expectations for pulsed plating to overcome the mass transport.