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NOVEMBER 2020 I DESIGN007 MAGAZINE 85 vias are staggered is being viewed by some as a more reliable way of constructing such designs (Figure 1G). Regardless of the design approach, all have been enabled by continu- ous advances in hole formation and copper plating chemistries/technologies—the former by steady improvement in lasers of every sort used for drilling microvias. To complete the discussion, it might be worth mentioning interesting variations on the practice. One was (and is) the via-in-trace concept, which was demonstrated in the early 1980s. There was (and is) also the possibility to make vias using a photoimaging process, which could potentially greatly reduce manu- facturing complexity and increase productivity. These things are mentioned because technical approaches that were once thought long dead have a way of reentering the picture when con- ditions are right. This brief review has hopefully provided those unfamiliar with the history some appre- ciation of how we got to where we are in cir- cuit via technology and why, as well as where we might go next. FLEX007 Joe Fjelstad is founder and CEO of Verdant Electronics and an interna- tional authority and innovator in the field of electronic interconnection and packaging technologies with more than 185 patents issued or pending. To read past columns or contact Fjelstad, click here. Download your free copy of Fjelstad's book Flexible Circuit Technology, 4 th Edition, and watch his in-depth workshop series "Flexible Circuit Technology." Figure 2: An abbreviated comparison of frequently used proprietary microvia processes with that of traditional microvia processing.