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42 The PCB Magazine • February 2015 Final finishes can be subdivided into metal- lic and organic finishes. For the purpose of this article, the focus will be on the metallic finishes using the combinations of nickel (Ni) and/or palladium (Pd) and/or gold (Au). Variations on this theme are used extensively in the electron- ics market of today. The Ni/Pd/Au mutations are the inevitable result of technical require- ment changes coupled with true and perceived acceptance within the industry. One such opti- mization is the phosphorus contents in the Ni and Pd layers. This subtlety will not be focused on in this article as the impact on the key topics is negligible. This subgroup of metallic final finishes can also be further divided by their application bias. Traditional ENIG processes are biased towards using a protection layer to ensure extended life- time reliability by protecting the base copper. by Rick Nichols AtOtECh dEUtSChLAnd GMBh The Future of Nickel in Nickel/ Palladium/Gold Final Finishes • Electroless Nickel/Immersion Gold (ENIG) —the work horse • Electroless Nickel/Electroless Palladium (pure palladium and phosphor containing palladium)/Immersion Gold (ENEPIG)—the all-purpose solution The next-generation surface finishes need to be biased towards satisfying lifetime require- ments in combination with enhanced technical performance. • Electroless Palladium/Autocatalytic Gold (EPAG)—fine-line, high-frequency, solder and bonding application This broad segregation implies the inclusion or exclusion of Ni. This Ni protection layer (4–7 µm) has a physical impact on line and space capability whilst simultaneously having a nega- tive impact on high-frequency applications. The symbiotic relationship between tech- nology influences and the resultant require- feature

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