in the january edition of the pcb magazine, engineers from macdermid enthone electronics solutions explored electroplated copper filling of through-holes in high-density interconnect constructions on thin ic and led substrates in order to avoid surface copper buildup and to provide efficient thermal management despite circuit miniaturization.

the engineers explain a two-step method for filling through-holes. (wikimedia commons)

the acid copper plating process that the engineers discuss has two steps. the first uses periodic pulse reverse (ppr) electroplating to create a conductive copper bridge across the middle of a through-hole. secondly, direct current electroplating fills the vias created by step one.

one of the examples that the authors highlighted was an led application where using this technique for through-hole filling lowered the operating temperature of the device from 126°c to 92°c.

the article read, “the copper through-hole plating process provides a versatile two-step process consisting of a periodic pulse reverse step with specialized waveforms that allow the middle of a through-hole to be bridged and sealed, forming two micro-vias that can subsequently be filled with dc-based via fill chemistries.”

the engineers concluded, “when designing a substrate for the utilization of copper through-hole plating, the design engineer must choose a suitable substrate and thickness and incorporate hole sizes and layouts that will minimize output variations. in this way, a robust, reliable copper through-hole process can be realized.”

read the detailed white paper at http://iconnect007.uberflip.com/i/770652-pcb-jan2017/46.