A final finish, which was already introduced more than ten years ago, is now receiving renewed attention because of its suitability for both Pb-free soldering and wire bonding applications, namely Electroless Nickel / Electroless Palladium / Immersion Gold (ENEPIG). Brittle fracture on BGAs is also no issue with this combination of metallic layers.
Another promising application for ENEPIG would be the replacement of the secondary image technique (SIT), which is common for HDI PCBs for cellular phones. With SIT two different final finishes are selectively coated on a panel: OSP on BGAs for soldering and ENIG on keypads for contacting. With ENEPIG the production flow would be shortened as only one final finish will be applied and no protective film to mask the pads destined for OSP during ENIG plating is necessary.
Atotech's Selective Finishing technology team develops and provides you with four options for electroless nickel / electroless palladium / immersion gold (ENEPIG), Cerabond M, Universal ASF II, Universal Finish SolderBond (UFSB) and Aurotech PEP. All ENEPIG processes deliver nickel layers with medium phosphorus content (7 to 10 wt%). CeraBond M, Universal ASF and Universal Finish SolderBond provide pure Pd layers, whereas Aurotech PEP provides a Pd layer with a phosphorus content of 4 - 6% by weight.
A process sequence without a gold plating step (ENEP) can be used for soldering and Cu-wire bonding applications.
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