Electroless plating benefits

The Electroless plating deposition (ELP) technique is based upon the controlled auto-catalyzed decomposition or reduction of meta-stable metallic salt complexes on target surfaces [75]. In the case of palladium, usually, the substrate should be pre-seeded with palladium nuclei in an activation solution in order to reduce the induction period of the autocatalytic plating reaction. For some applications, this technique provides strong benefits such as uniformity of deposits on complex shapes and hardness. Palladium and some of its alloys are among the few metals that can be deposited in this way [11]. However, this method presents some drawbacks such as difficult thickness control, costly losses of palladium in the bath, not guaranteed purity of the deposit and so on [75]. 

CuNiAu boards fabricated either with the NiAu as the Cu etch resist or by the SMOBC process followed by electrolessly plating Ni and Au can confer improved PTH reliability. There are two mechanisms for the observed improvement the enhanced rivet effect provided by the Ni and the elimination of Cu dissolution during solder shocks such as wave soldering or PGA rework. For high-aspect-ratio holes, electroless Ni confers an additional benefit because the plating thickness in the barrel is more consistent than for conventional electroplating. 

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