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Acid Copper Plating for High Aspect Ratio and Via Fill

Newer products focused on form factor (size, weight, and portability) as well as high reliability, coupled with new developments in plating technology, offer designers options that were not available a few years ago. Among these are deposited copper via fill and very high aspect ratio through-hole plating. The former meets HDI requirements and the latter, high-layer-count (40+ layers) boards like backplanes and chip tester boards. Both of these are high-value-added products that are attractive to manufacturers who specialize in leading-edge technology.

These requirements can only be met with two distinctive plating systems. The high aspect ratio plating is based on low electrolyte concentration with a specialized additive package specifically designed for this low current density plating application and an optimized plating cell setup. Via fill, on the other hand, requires a very high concentration of electrolyte with a specific additive package and a specific cell design.

To meet these specification requirements, the board shop is forced to seek new and advanced processes in every department in the manufacturing process. Acid copper plating comes under heavy scrutiny, as it is the process that forms the traces and the through-hole connectivity that conveys the signal from end-to-end of the final device.

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Editor's Note: This article originally appeared in the May 2013 issue of The PCB Magazine.