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48 The PCB Magazine • February 2015 ENIG Thousands of words have already been writ- ten about the work horse, ENIG, and many panels have been processed successfully using it. This is an established process that fulfils the requirements of many existing and past ap- plications but falls short of the requirements promised in the future. As such this process will not feature further in this article unless to make a comparison. ENEPIG with Thin Ni Although in terms of words and produc- tion, the above is equally true for the 'the all- purpose solution' (ENEPIG) process, this is the most promising of the Ni inclusive processes. In addition to performing well generically there a frequent question is raised within the industry: Why can't this process fulfil future require- ments by employing a thin Ni layer? Ni is employed as a barrier layer due to its dense crystal formations. The surface morphol- ogy, in turn is created by thicker Ni plating. This is the background for the IPC (4552 – ENIG and 4556 – ENEPIG), minimum thickness require- ment of 3µm. Higher Ni thicknesses positively influence the integrity of solder joints. By reducing the Ni layer to conform to dimensions dictated by EPAG, dramatic quality issues are encountered. Early indications of this can be found by ex- amining the intermetallic compound (IMC) by SEM. Whilst the IMC created using EPAG has no detrimental impact to the solder joint, the IMC created using EN (low thickness) EPIG dis- plays evidence of demarcation lines. Figure 5: how the ni morphology is influenced by the layer thickness. THE FUTURE OF NICKEL IN NICKEL/PALLADIUM/GOLD FINAL FINISHES continues feature