1 Evaluation of Nickel/Palladium-Finished ICs With Lead-Free Solder Alloys

A nickel/palladium (Ni/Pd) lead finish for integrated circuits (IC) was introduced in 1989. In 1998, solderability test results were published on Ni/Pd-finished components using a Sn/Ag/Cu/Sb lead-free (Pb-free) solder paste and printed wiring board (PWB) pads coated with organic solderability preservative (OSP). Since then, a number of other Pb-free solder alloys have been introduced. This evaluation shows soldering and reliability performance of Ni/Pd-finished components with the leading Pb-free solder alloys now being considered by the electronics industry. The ICs tested were 20-pin small-outline integrated circuit (SOIC) and 56-pin shrink small-outline package (SSOP) gull-wing leaded devices finished with four-layer Ni/Pd. The solder alloys were Sn/Pb/Ag (control), Sn/Ag/Cu, Sn/Bi, Sn/Ag/Cu/Sb, Sn/Zn/Bi, and Sn/Zn. The land pads on the test PWB were coated with an OSP. Using Pb-free Ni/Pd-finished components, a Pb-free solder alloy, and an OSP coating, a Pb-free assembly was achieved and evaluated. Additionally, Ni/Pd/Au-finished IC leads were soldered using the Sn/Ag/Cu paste. Evaluations of each alloy included visual appearance, lead pull before and afte