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24 The PCB Magazine • January 2017 Figure 12: Cross-section examination of the intermetallic formed after wetting balance test, 7500x. A - Reduction assisted thick immersion gold B - Standard immersion thick immersion gold C - High-efficiency thick immersion gold Conclusions Solder wetting balance tests showed that the reduction assisted immersion gold process yielded the fastest wetting times while the stan- dard displacement immersion gold showed slightly lower wetting times. All final wetting forces were excellent regardless of heat expo- sure from 3x reflows. Wire bond testing showed very good results from all six samples with higher standard devia- tion observed for the standard displacement im- mersion gold with thick deposit. Average wire bond values were well above the 3-gram mini- mum with average readings all above 9 grams. Cross section analysis of the plated samples showed some small corrosion spikes in the stan- dard displacement and high efficiency immer- sion gold with no such corrosion spikes seen in the reduction assisted gold deposit. It is thought that the corrosion spikes, if present in higher amounts, would affect solder wetting and wire bond results and could be used a process check for production considerations. Future data presentations will include the performance of the three immersion gold types with gold thicknesses at the high end of the new IPC ENIG specification. Solder testing and cross-section analysis will be performed. PCB References 1. Yukinori Oda, Masayuki Kiso, Akira Oka- da, Kota Kitajima, Shigeo Hashimoto, George Milad, Don Gudeczauskas, 41st International Symposium on Microelectronics, Providence, RI, Nov 2008. 2. Donald Gudeczauskas et al, 39th Interna- tional Symposium on Microelectronics, October 8–12, 2006, San Diego. 3. Snugovsky, P., Arrowsmith, P. & Romansky, M., Journal of Electronic Materials (2001) 30: 1262. doi:10.1007/s11664-001-0159-z. This paper was originally presented at SMTA International 2016 in Rosemont, IL, USA, and pub- lished in the proceedings. Don Gudeczauskas is vice president, Uyemura's technical center in Southington, CT USA. Albin Gruenwald is technical service representative, Uyemura's technical center in Southington, CT USA. George Milad is national accounts manager for Technology, Uyemura's technical center in Southington, CT USA. STUDY OF IMMERSION GOLD PROCESSES USED FOR BOTH ENIG AND ENEPIG