IMC Growth Study on Ni-P/Pd/Au Film and Ni-P/Au Film Using Sn/Ag/Cu Lead Free Solder

摘要

The surface finishes Ni-P/Pd/Au (hereafter referred to ENEPIG) and Ni-P/Au (hereafter referred to ENIG) were prepared on ball grid array (BGA) circuit boards by electroless/immersion plating method. The IMCs (Inter metallic compounds) of Sn37Pb and Sn3.0Ag0.5Cu solder with these finishes were compared using TEM (Transmission Electron Microscope). It was found that the IMC crystal lattice is dependant on solder material and the solder joint reliability is dependant on both the solder material as well as the surface finish. In using Sn3.0Ag0.5Cu solder, the Pd in the ENEPIG finish limits the Ni diffusion and exhibits excellent solder joint reliability. In the combination of Sn/Pb solder and ENEPIG, the Ni diffusion is accelerated and solder joint reliably is compromised.