A ROOT CAUSE FAILURE MECHANISM FOR SOLDER JOINT INTEGRITY OF ELECTROLESS NICKEL / IMMERSION GOLD SURFACE FINISHES
Authors: Nicholas Biunno and Michael Barbetta Company: HADCO Corporation Date Published: 5/4/2000
Surface Finishes Forum
Abstract: Electroless Nickel / Immersion Gold is used throughout the electronics industry as a surface finish for fine pitch SMT and BGA packaged devices. Recently there has been a lot of activity trying to quantify a sporadic solder joint failure by mechanical means, but no root cause for the failure has been identified. We have identified a root cause failure mechanism for this surface finish process as a bonding failure that is induced as a result of a hyperactive corrosion effect of the nickel surface during the immersion gold plating process. Furthermore, we have designed a test that can reproduce the corrosion process. The experimental evidence will show that advanced corrosion of the nickel surface by the immersion gold chemistry is induced by an electric charge unbalance between the printed circuit board and ionic species within the immersion gold plating bath.