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48 PCB007 MAGAZINE I MARCH 2022 Fundamentals of Acid Copper Electroplating Introduction Electroplating a printed circuit board is by no means a trivial task. Higher layer counts, smaller diameter vias (through-hole and blind), as well as higher performance material sets contribute to the greater degree of diffi- culty with today's technology. So, process engi- neers pay close attention to the "soer" issues such as cathode current density, solution chemistry (copper sulfate and sulfuric acid concentration), and—sometimes—addition agent control. e concern here is that acid copper pattern plating of a printed circuit board has many crit- ical aspects that must be diligently controlled for optimum performance. ese include solu- tion agitation and filtration, anode length and placement, current distribution effects, reduc- ing electrical resistance in the plating cell, pho- toresist development, and controlled organic contamination in the plating solutions. More on these issues in a future column. Yes, electroplating or electrodeposition, as some prefer, is a complex process. A review of the fundamentals is warranted. In this month's column, the intricacies of electrodeposition technology and its function of building up the thickness of copper in the holes and on the surface will be presented in detail. In this next series of columns, the func- tion of the active ingredients in the copper plating solutions will be presented. Process control limits for the various plating solution components and the effects on deposit integ- rity will be discussed. Trouble in Your Tank by Michael Carano, RBP CHEMICAL TECHNOLOGY

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