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50 The PCB Magazine • August 2014 by Michael Carano oMg electronIc cheMIcals Controlling the ENIG Process for Optimum Efficiency and Performance c o l u M n trouble iN your taNk Introduction In last month's Trouble in Your Tank, differ- ent levels of corrosion in the nickel deposit were presented. In addition, the suggestion was made that mid-phosphorous content EN process was more beneficial with respect to solderability, as opposed to a high phos content nickel deposit. Certainly, concerns with corrosion of the nickel (with lower phos) were allayed as long as the proper process controls were in place. Ideally, the ENIG process must provide the optimum in solder joint reliability while operating at the highest level of cost efficiency. All too often, process parameters that have the most influ- ence on these critical attributes are poorly un- derstood. An example of poor control is shown in Figure 1. The gold deposit has been removed in order to expose the electroless nickel surface. It is very difficult to discern any anomalies in the nickel deposit without removing the gold. figure 1: the top two photos show the severe corrosion in the nickel deposit. the bottom photo is the surface with the gold deposit over the nickel.

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