Development of new surface finishing technology for PKG substrate with high bondability

This paper describes the characteristics, development and application of the surface finishing technology for packaging substrate, especially electroless Ni/Pd/Au (nickel/palladium/gold). The palladium of this surface contains 5% of phosphorous and the crystal structure is minute and rigid. Both wire-bondability after high temperature storage and solderability with lead-free solder to the connecting pads applied this layer surface finishing are investigated. This surface finish has good wire bondability and excellent solderability that the conventional electrolytic nickel/gold have. Palladium layer effectively inhibits the diffusion of nickel metal from under layer. This surface finishing technology does not use plating buses, and the Ni/Pd/Au will confirm the increase of design flexibility for package substrate, downsizing of packages and decrease the electrical noises. This technology can be applied for the high performance SiP (System in a Package) and MCM (multichip module) etc.