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20 PCB007 MAGAZINE I FEBRUARY 2022 Article by Jordan Kologe and Leslie Kim MACDERMID ALPHA ELECTRONICS SOLUTIONS Introduction As the electronics supply chain contends with the struggles of moving out of the pan- demic and into a new normal, it is increasingly obvious that a new normal will be one with sustainability and resource conservation as the top priority. Over the past year, we have seen printed circuit board manufacturers encounter challenges associated with environmental reg- ulations, water and power outages, and pres- sures from the supply chain to reduce environ- mental footprints. From the perspective of a board fabr icator, especially one that spe- cializes in HDI, a highly resource-intensive step in the process of making a printed circuit board is the primar y metalli- zation step. All circuit boards that have mul- tiple layers go through such a primary metalliza- tion, which is either elec- troless copper or direct metallization (DM). e main difference between a direct metallization process and the more traditional electroless copper plating process is that the former deposits a paint-like conductive The Carbon Footprint of HDI: Direct Metallization vs. Electroless Copper coating through absorption onto the surface, while the latter deposits a copper coating from solution through chemical reduction. e DM coatings are most typically a carbon or graph- ite, and this kind of board manufacturing has been done reliably for nearly four decades. Electroless copper processes have a larger carbon footprint than direct metallization for several reasons. Compared to direct met- allization, electroless copper is more water and energy intensive, has a higher variety and amount of chemical ingredients, and has higher process variation. When looking at the compar- ison from the perspective of HDI, the impact of all of this becomes even more critical. Figure 1: Process steps for two commercial direct metallization processes compared to electroless copper.