SBIR Phase I: A Novel Electroless Nickel/Immersion Gold (ENIG) Surface Finish for Better Reliability of Electronic Assemblies

This Small Business Innovation Research Phase I project will develop a cost-effective novel Electroless Nickel Immersion Gold (ENIG) surface finish to achieve robust solder joints for better reliability of electronic assemblies. Currently available ENIG surface finishes are prone to so-called "black pads", which are sites of galvanic hyper corrosion that lead to failures associated with de-wetting of solder, brittle solder joints, component disconnection, and overall malfunction of electronic assemblies. Existing substitute surface finishes are either very expensive or do not resolve the black pad defects fully, and they can compromise other key properties. The cost-effective novel ENIG to be developed will eliminate black pads, corrosion related issues, achieve robust solder joints and provide improved quality & reliability of electronic assembly products to end consumers. This will allow manufacturers to avoid major product field failures and the resulting consequences. This new technology would be a potential replacement for existing ENIG (with a market value in excess of $400 million) and other surface finishes (representing a market exceeding $1 billion). The intellectual merit of this project includes development of a cost-effective novel ENIG to eliminate black pads and achieve robust solder joints. The root cause of black pad defects has been identified as hyper corrosion activity of the immersion gold process which originates at intergranular boundaries and crevices of the nickel-phosphorous surface. Galvanic hyper-corrosion occurs between gold and nickel atoms, resulting in nickel depletion and an enrichment of phosphorous atoms in the localized area. The proposed research would use an interfacial engineering approach at the gold and nickel-phosphorous interfaces to prevent black pads and eliminate brittle solder failures in the electronic assemblies. The main objective of the proposed Phase I research is to achieve marked improvement in corrosion resistance (eliminate black pads) and attain robust solder joints (eliminate brittle solder joint failures). This will involve identifying right interfacial chemistry and process parameters. Corrosion resistance of this new process will be evaluated using electrochemical corrosion tests and acid tests. In addition, solder joint strength and properties (brittle/ductile) will be investigated using ball shear tests and cold ball pull tests.