The elimination of Lead from electronic devices, as mandated by RoHS (Restriction of Hazardous Substance), is changing the playing field for companies that manufacture and supply electronic assemblies globally. Lead-free SAC solder (Sn/Ag/Cu alloys) are the new solders of choice that enable RoHS compliance but these solders suffer from poor joint strength when used with classic Gold or Nickel metalizations.
In the ENEPIG metalization scheme, the Palladium inhibits Nickel diffusion into the Gold layer, promoting long term shelf life (before assembly) benefits. During SAC soldering, the Electroless Palladium provides excellent solderability and can withstand multiple rework cycles. The solder strength of SAC solders to ENEPIG is very high. Both Gold and Aluminum wire bonding can be performed on ENEPIG.
UltraSource has developed a thin film based ENEPIG process that now combines low cost sputtering, traditional thin film photolithography and etching, and plating with ENEPIG. The process is well suited to volume applications. Because the ENEPIG finish is plated and contains very small amounts of precious metal, it is intrinsically less expensive than traditional thin film choices for providing wirebonding and soldering on the same circuit.