Shelf-Life Study of Ag/NiNiP-Plated Cu Leadframes Without Anti-Tarnish Coating

An Ag spot/full nickel and nickel phosphorus (NiNiP)-plated Cu leadframe without the anti-tarnish layer was used for aluminum wire bonding in power packages. Two periods of shelf-life, namely 7 months and 13 months, of the leadframe were studied in terms of processability (die attachment and wire bonding) and package reliability. It was found that the leadframe with 7-month shelf-life showed positive results for both processability and package reliability. The leadframe with 13-month shelf-life showed positive results for processability. However, it showed delamination at the leads between the NiNiP leadframe surface and the molding compound interface after high-temperature storage for 1000 h. Further analysis showed that the delamination is related to Ni diffusion into the interface of the NiP/molding compound and S in the molding compound during the reliability test.