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64 PCB007 MAGAZINE I SEPTEMBER 2022 Complex build-up HDI technologies con- tinue to expand in applications. Copper elec- troplating of vias has been perfected but the process is yet another electroplating solution to maintain and can sometimes be a lengthy process. Current conductive paste fills are not as conductive as solid copper but provide reduced cycle time, are still highly conductive, and are cost effective. Introduction Karl Dietz wrote on this topic several times in his Tech Talk series. No less than five sepa- rate columns were devoted to nanotechnology and conductive via-fill. e via-fill Tech Talk columns are titled: Nano-Cu Paste for Microvias • "e Dilemma of Innovation" (CircuiTree, October 2000) • "Processes For HDI" (CircuiTree, December 2000) • "Via Fill" (CircuiTree, July 2006) • "Nano-particles in Electronics" (CircuiTree, October 2008) • "Conductive Pastes and Inks" (e PCB Magazine, September 2011) Metallizing Pastes e metal-filled pastes have been around a long time. First used in the early 1960s for conductive jumpers and to connect double- sided non-plated through-hole (PTH) printed circuit boards with silver inks, their use has Happy's Tech Talk #12 by Happy Holden, I-CONNECT007