A Novel & Cost-Effective Electroless Nickel Immersion Gold (ENIG) Surface Finish for Better Reliability of Electronic AssembliesAuthors: Kunal Shah, Ph.D.
Date Published: 10/14/2018 Conference: SMTA International
The root cause of black-pad defects has been identified as hyper corrosion activity at gold and nickel-phosphorous interface which involves nickel depletion and an enrichment of phosphorous in localized areas. Interfacial engineering approach had been used to successfully eliminate black pads by achieving marked improvement in corrosion resistance. Corrosion tests have been conducted using Potentiodynamic Polarization method and Tafel plots were generated between novel ENIG and conventional ENIG. The results show 10x improvement in corrosion resistance. Also, interfacial engineering led to smoother topography of Ni-P surface, low gold thickness and small thickness distribution. Also, it has also led to improved intermetallics at the solder joints leading to robust solder joints and elimination of brittle failures. Ball Shear and Ball Pull Tests (Industry Standard based testing: JEDEC Standard) were conducted on novel ENIG based solder joints and conventional ENIG based solder joints. No solder joints (intermetallics) failures found with novel ENIG compared to 80% of failures found at the solder joints with conventional ENIG. Also, the force to induce failure increased by more than about 50% with novel ENIG compared to conventional ENIG. A novel ENIG is eco-friendly and cost-effective with high corrosion resistance and robust solder joints for better reliability of electronic assemblies.
Electroless Nickel/Immersion Gold, gold layer thickness distribution, solder joints reliability, black pads (hyper-corrosion).
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