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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.
Date of Conference: 16-18 March 2005