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102 DESIGN007 MAGAZINE I OCTOBER 2021 Article by Anaya Vardya AMERICAN STANDARD CIRCUITS Introduction One of the biggest challenges facing PCB designers is not understanding the cost drivers in the PCB manufacturing process. is article is the latest in a series that will discuss these cost drivers (from the PCB manufacturer's perspective) and the design decisions that will impact product reliability. DFM Design for manufacturing (DFM) is defined as the practice of designing printed circuit boards that meet not only the capabilities of the customer's assembly manufacturing pro- cess, but also the capabilities of the board fab- rication process at the lowest possible cost. While not a substitute for early design engage- ment with the PCB fabricator, these articles will provide guidelines that will help to "design for success." Microvias One of the most important technologi- cal advancements that made HDI viable was development of the microvia: a very small hole (typically 0.006" or smaller) that only connects certain layers either as "blind" or "buried" via holes. is represents a totally new way of making electrical connections between lay- ers on a PCB. Traditional PCB technology has utilized "through-holes," which by definition, are drilled through the entire PCB connecting the two outside layers with all of the internal layers. e ability to strategically connect only certain pads on certain layers greatly reduces the real estate needed for a PCB design and allows a much greater density in a smaller foot- print. Figure 1 shows through-holes and bur- ied and blind vias. DFM 101: PCB Via Structures Figure 1: Microvias vs. through-hole vias.