Issue link: https://iconnect007.uberflip.com/i/1540425
OCTOBER 2025 I PCB007 MAGAZINE 47 • Hypercorrosion that negatively impacts sol- derability: Rejectable condition. • Inspection of corrosion (including hyper corrosion): Must be performed using optical microscopy, maximum 1000x magnification. If soldering is found to be non-wetting, hyper cor- rosion should not be assumed to be the first reason, as there are many possibilities for this defect that do not include the final finish of the PCB. Consistent and low-level nickel corrosion is the best course of action to prevent any solderability failure being diagnosed as hyper corrosion and a rejected product. 2 This change gives fabricators clearer guidance and aligns ENEPIG with ENIG's proven assessment framework. A Need for Higher Gold Thickness? The updated standard allows gold thicknesses above 2.8 µin, but only for hybrid gold processes. While this can ease compliance and wire bonding concerns, committee discussions and testing show no measurable wire bond strength benefit between 2 and 4 µin deposits, even after aging. For most fabricators, more gold means more cost without proven performance gains. Conclusion IPC-4556A raises the bar for ENEPIG reliability, demanding tighter controls, better measurement capability, and more disciplined SPC. Fabricators can adapt by: • Upgrading measurement capability to meet gold tolerance without guard bands • Enforce SPC across nickel, palladium, and gold baths • Selecting stable EN chemistry to minimise percentage of phosphorous variation • Considering hybrid gold to reduce corrosion risk and process control challenges The path forward may be more demanding, but those who embrace these requirements will be well positioned to deliver the most consistent, reliable ENEPIG finishes to their customers for next-genera- tion, high-performance electronics. To speak with our experts or learn more, click here or visit our website. PCB007 References 1. "Nitride Semiconductor Light-Emitting Diodes (LEDs) (Second Edition)," by Xiaobing Luo and Run Hu, Woodhead Publishing, 2018. 2. "Achieving a Successful ENIG Finished PCB Under Revision A of IPC-4552," by Bunce, Clark, and Swanson, SMTAI 2017. Dr. Frank Xu is the global product director for final finishes at MacDermid Alpha Electronics Solutions. B ox p l ot of E N E P I G g o l d w i re b o n d p e r fo r m a n c e at b ot h 2 a n d 4 m i c ro i n c h e s of g o l d . ▼ Statistical analysis of ENEPIG gold wire bond data performance at both 2 and 4 microinches of gold. ▼ " " The path forward may be more demanding, but those who embrace these requirements will be well positioned to deliver the most consistent, reliable ENEPIG finishes to their customers for next-generation, high- performance electronics.