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26 PCB007 MAGAZINE I MARCH 2020 Feature by Graham Lee, David Chun, Albert Tseng, Charles Bae, Smith Han, Jordan Kologe, and Bill Bowerman MACDERMID ALPHA ELECTRONICS SOLUTIONS Abstract Electronics manufacturers have chosen car- bon-based direct metallization systems over electroless copper processes due to lower cost of ownership and easier-to-maintain equip- ment. Today, hundreds of high-volume, carbon- based direct metallization lines are in produc- tion around the world. The well-documented savings due to lower water usage, less waste generation, a smaller equipment footprint, and lower power consumption are why these sys- tems became popular. In addition to this, these systems do not require precious metals such as palladium to activate printed circuit structures for electroplating, offering significant opera- tions savings. In the latest generation of smartphone tech- nology, high-density interconnect (HDI) tech- nology has pushed the line width and spac- ing to require the use of ultra-thin copper foils as a starting point. This thin-foil technology requires exacting precision in controlling the copper etch budget during the formation of copper interconnects. Direct metallization pro- cesses, like the latest generation of Blackhole, have begun production on 3-micron copper foils for modified semi-additive processing, im- proving the process overall. In this article, we walk through a history of how the technology has evolved to this point, including the new breakthroughs in equipment technology that allow this process to create the extremely fine lines and spaces being imple- mented in flagship mobile designs today. The History of Carbon Direct Metallization Carbon direct metallization processes have been widely used in the circuit board indus- try for more than 35 years. Widely utilized processes in the industry include Blackhole, Eclipse, and Shadow. The original Blackhole direct metallization technology was patented in 1984 and quickly became a commercial suc- cess as a horizontal process for seeding FR-4 through-hole panels for copper electroplating. Since Blackhole is a coating process rather than a redox process like electroless copper, the technology is less sensitive to the surface energy of the different dielectric materials, contributing to its adoption for difficult-to- plate materials. Because of this, these types of The Co-Evolution of Carbon-based Direct Metallization Alongside HDI Technology Members of the MacDermid Alpha team, including some of the authors.

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