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60 PCB007 MAGAZINE I MARCH 2025 Writing about surface finishes brings a feel- ing of nostalgia. You see, one of my first jobs in the industry was providing technical support for surface cleaning processes and finishes to enhance dry film adhesion to copper surfaces. I'd like to take this opportunity to revisit the basics, indulge in my nostalgia, and perhaps provide some insight into why we do things the way we do them in the here and now. In 1974, most circuit boards were double- sided, plated through-hole panels, although some people were still using eyelets to connect the sides of the board. ese were small, hollow copper tubes pushed through the drilled holes and soldered or crimped to the surface copper to provide communications between the sides. Multilayer production was just beginning, mostly limited to three or four layers. Alkaline etchants had just been introduced (an anni- versary I do not celebrate except to remind myself that the alternatives were worse). Fully aqueous dry film photoresists were also rela- tively new and replaced the first solvent-based dry films because, even in 1974, people recog- nized that the solvents were not good for you. e problem was fully aqueous resists did not adhere to the copper nearly as well as the sol- vent-based dry films. en, as now, copper foil was produced by plating it onto a smooth, stainless-steel roller; the thickness of the foil was controlled by the speed of rotation through the plating bath. The Chemical Connection Feature Column by Don Ball, CHEMCUT Surface Finishes for PCBs