Pb-free surface-finishing on electronic components' terminals for Pb-free soldering assembly

Pb-free solderable surface finishing is essential to implement Pb-free sold er assembly in order to meet with the growing demand of environmental consc iousness to eliminate Pb from electronic products. Two types of widely appl icable Pb-free surface finishing technologies are developed. One is the mul tilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enable s whole-surface-plating on to leadframe before IC-assembling process. The o ther is the double-layer-system with low-melting-point-materials, for examp le, thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy's defects of harmful reactivity along with substrate metal and mechan ical brittleness with keeping its advantages of solder-wettability and no w hisker.