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Summary
Plating small diameter through holes in thick PC boards that utilize SMT poses a difficult technical challenge. The research reported in this paper has optimized the acid copper bath inorganic and additive chemistry to enable these boards to be plated. Boards 5.8 mm thick with 18:1 aspect ratio holes were plated to give a hole:surface thickness ratio of 0.80:1 at a current density of 1.1 A/dm2. Levelling and deposit mechanical properties are excellent. Recommendations for PTH electroless and electrolytic plating processes, equipment, and controls to enable successful plating of high aspect ratio through holes are given.