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14 PCB007 MAGAZINE I MARCH 2025 high solution flow is present. However, mixed reaction baths with a high autocatalytic reac- tion enable the formation of a defect-free ENIG layer. In layers plated with a mixed reac- tion type featuring a lower autocatalytic por- tion, the number of corrosive events is mini- mal, and the penetration depth in the nickel usually remains below 40% of the nickel layer depth. is is also the result of numerous data points according to the IPC-4552A and B methods. It could be concluded that gold elec- trolytes with a high autocatalytic portion yield excellent results in terms of ENIG corrosion. So, is an autocatalytic gold bath overall bet- ter than its more immersion-like counter- parts? No, or it depends. Autocatalytic gold baths have certain limitations when compared to fully immersion-type baths. Both strengths and limitations should be considered when selecting the appropriate electrolyte for the final finish. Table 2 provides a brief overview of the key plating properties of the three types of electrolytes, which could help elucidate the choice. No matter what gold bath type is used—I, II, or III—IG is used as naming in the table for simplification. e fully immersion type bath offers several benefits, particularly in terms of its potential for low gold content, extended bath life, and ease of handling and maintenance. is makes it an attractive option for those seeking efficiency and cost-effectiveness. Conversely, baths with a high autocatalytic portion demand more effort in handling and maintenance. However, they deliver a corrosion-free finish and are versatile enough to plate not only ENIG but also palla- dium/gold (Pd/Au) and nickel/palladium/gold (Ni/Pd/Au) finishes with substantial gold thick- ness. is makes them suitable for applications requiring high durability and quality. Is the Type of Gold Everything? is point was raised in a technical paper by Schafsteller et al 2 . To compare the same elec- trolytes at different PCB sites, the authors used nickel corrosion for benchmarking. e evaluation method was based on IPC-4552A, whereas slightly harsher criteria were used at the same time to get valuable distinguishments. erefore, 10 through-holes were investigated per condition and seven locations per through- hole. Four levels of corrosion were defined to provide a clear comparison between different locations and the electrolytes used: • Level 0: No corrosion events detected • Level 1: Fewer than 10 events, with all events not deeper than 20%, or a single event less than 40% deep Table 2: Plating properties based on gold bath electrolytes 1