As-supplied component residues are often the culprit.

This month we look at dewetting on the surface of solder mask or components in manufacture.

FIGURES 1 and 2 show the impact of dewetting on the surface of plastic components in conformal coating. Figure 2 illustrates dewetting on solder mask. In both cases if the coating does not cover all the critical areas of the assembly, it must be reworked. It is up to the quality and design departments to agree what level, if any, of dewetting is acceptable to the product and the customer, rather than just quoting a standard. In some cases, the position or level of the problem may not affect the product operation or reliability.

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