THE EFFECT OF THE IMMERSION GOLD REACTION ON OXIDATION OF THE ELECTROLESS NICKEL DEPOSIT IN ENIG PLATING

摘要

Black Pad in Electroless Nickel / Immersion Gold (ENIG) plating occurs in the reaction between nickel dissolution and gold deposition in the immersion gold process step. Minimizing the corrosion of the nickel is one of the keys to providing a robust "Black pad" free ENIG. The role of the immersion gold reaction in forming corrosion products on the electroless nickel deposit is studied.Three different immersion gold systems are studied, two immersion type golds, with different chemical make-up and one semi-autocatalytic. The gold was deposited on two mid-phos electroless nickel deposits differing in phosphorus content; one with 6.5% P by weight and the other with 8.5% P by weight. The propensity to "black pad" was determined by examining the surface and the cross-section of the deposit using SEM analysis, as well as evaluating the solder joint reliability using BGA ball pull testing.