Thermal shock testing can avoid plating adhesion problems.

The microsection images (Figures 1 and 2) show through-hole copper plating pulling away from the laminate surface. Copper separation from the hole is uncommon, or at least, it has been for many years. Yet, it has been seen in recent years with Pb-free and new laminate materials.

Recent use of higher Tg laminates that require modification in the plating process to successfully key copper to the hole wall have been experienced. The occurrence of poor adhesion or the total lack of adhesion would increase under the higher soldering temperatures and moisture content typical of Pb-free assembly. It is necessary to examine the testing conducted for different laminate materials. Thermal shock testing on samples and microsectioning are the simplest test methods to show any improvement in the copper plating adhesion. Thermal shock testing is best conducted with a sand bath rather than a solder bath, as it makes the lack of copper adhesion easier to identify. PCD&F

Dr. Davide Di Maio is with the National Physical Laboratory Industry and Innovation division (npl.co.uk); This email address is being protected from spambots. You need JavaScript enabled to view it..

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