High Phosphorus ENIG – highest resistance against corrosive environment

Over the past years there has been consistent growth in the use of electroless nickel / immersion gold (ENIG) as a final finish. The finish is now frequently being used for PBGA, CSP, QFP and COB and more recently gathered considerable interest as a low cost under-bump metallization for flip chip bumping application. One of the largest users for this finish has been the telecommunication industry, were millions of square meters of PCBs with ENIG have been successfully used. The nickel layer offers advantages such as multiple soldering cycles and hand reworks without copper dissolution being a factor. The nickel also acts as a reinforcement to improve through-hole and blind micro via thermal integrity. In addition the nickel layer offers advantages such as co-planarity, Al-wire bondability and the use as contact surface for keypads or contact switching. Especially those pads, which are not covered by solder need a protective coating in corrosive environment – such as high humidity or pollutant gas....