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26 PCB007 MAGAZINE I OCTOBER 2024 the new IPC criteria. However, out-of-com- pliance situations are an ongoing threat, and the many variations that produce these failures are not always monitored as closely as needed. e implementation of an RAIG immersion gold bath provides a significant enhancement in gold thickness uniformity on a variety of pad sizes and configurations. is tight distribu- tion is evidenced in Figure 1 and the graphs in Figures 2 and 3, where a mean of 2.0 µin with a standard deviation of only 0.226 µin was estab- lished. 2. Limitations on immersion gold thickness. To prevent excess nickel corrosion, the IPC specification requires immersion gold thick- tions of conventional immersion gold electro- lytes: 1. Tight control of immersion gold thickness. Conventional immersion gold electrolytes operating under less than ideal process con- trol can produce plated gold that is suscepti- ble to electroless nickel corrosion; in extreme cases this corrosion results in "black pad" reli- ability failures. ENIG black pad failures are a serious reliability concern and should be pre- vented at all costs. e IPC 4552 Rev B speci- fication for ENIG limits immersion gold thick- ness, and includes expanded cross-section measurements inspection to avoid this sce- nario. For the most part, companies have met Figure 1: Reduction-assisted immersion gold vs. standard displacement. Figure 3: Gold thickness distribution vs. pad ID-ENIG. Figure 2: RAIG performance/deposit variance.