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74 PCB007 MAGAZINE I APRIL 2019 Article by Mustafa Özkök, Sven Lamprecht, Akif Özkök, Dolly Akingbohungbe, Moody Dreiza, ATOTECH DEUTSCHLAND GMBH, Alex Stepinski, GREENSOURCE FABRICATION LLC The electronics industry is further progress- ing in terms of smaller, faster, smarter, and more efficient electronic devices. This contin- uously evolving environment caused the de- velopment of various electrolytic copper pro- cesses for different applications over the past several decades. This article describes the reasons for devel- opment and a roadmap of dimensions for cop- per-filled through-holes, microvias, and other copper-plated structures on PCBs. It will also discuss aspect ratios, dimensions, and results of plated through-holes used today in high-vol- ume manufacturing for microvia and through- hole filling with electroplated copper. Further- more, this article will also show feasibility studies of new electroplated structures for fu- ture applications, such as copper pillar plating on IC substrates. Four Main Drivers Four main drivers forced the chemical sup- ply industry to introduce new electrolytic cop- per processes with the new feature of "filling" capability over the years. The first driver is the continuous miniaturization of electronics. The first blind microvias were introduced with HDI technology in the late 1980s and early 1990s. In 1996, the IC substrate market started to fill the microvias. "Plugging" technologies were introduced to stack the microvias to save space or create via- in-pad structures. This plugging technology with conductive paste is very expensive be- cause of the additional process steps required. In addition, this technology faced several dis- advantages, such as "blow out," outgassing, smear, and other quality concerns. To achieve the necessary miniaturization benefits, the in-

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