ITRI project on electroless nickel/immersion gold joint cracking

A problem exists with electroless nickel/immersion gold (E.Ni/I.Au) board surface finish on some pads, on some boards, that causes the solder joint to separate from the nickel surface, causing an open circuit. The solder joint cracks and separates when put under stress or when it experiences a shock. An ITRI (Interconnect Technology Research Institute) project to investigate this E.Ni/I.Au problem was initiated about a year‐and‐a‐half ago. Since the electroless nickel/immersion gold board finish performs satisfactorily most of the time, a 24 variable experiment was developed to investigate which parts of the chemical matrix are satisfactory to use and which need to be avoided. This paper describes some of the activities that have occurred on the ITRI consortium, from the design of the test vehicle to building hundreds of BGA assemblies, then pulling those BGA assemblies apart and inspecting the results.