Processes

Properties of the electroless copper bath and deposit are highly dependent on the pretreatment (and, to a lesser degree, the post-treatment) system used. Although the plating bath is the most visible and complex-to-operate solution in the process line, a mistake commonly made is to blame any process problem on the plating chemistry itself. In a majority of cases, this is not the case. Lack of correct attention to the details of the preplate chemistry is more likely to have caused the problem.

This section concentrates on the main commercial processes for electroless copper, namely PTH, decorative POP, and EMI. Other applications employ similar processes, some of which are shown in the overall process flow summary given in Fig. 5. Note that rinse steps are not shown; unless stated otherwise it should be assumed that one or more rinse steps intervene between every two process steps. This is not to minimize the importance of adequate rinsing; the adage of "it's the water" has been proven true in many troubleshooting situations. Specific requirements of water quality for PWB plating processes have been published (Ref 52) (see also the section "Controls—Miscellaneous" in this article).

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