UHDI Fundamentals: Ultra HDI Pushes PCB Manufacturing Capabilities

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Ultra high-density interconnect (UHDI) is a term used in the electronics industry to describe a cutting-edge technology that pushes the limits of fabrication capabilities for printed circuit boards (PCBs) and semiconductor devices. UHDI represents an advancement in miniaturization and integration, allowing for the creation of electronic components and systems with extremely high levels of functionality in a smaller footprint. UHDIs are sub-1-mil (0.001") line widths and spaces, which necessitate that we change the unit of measurement from mils to microns. For reference, a 1-mil trace is 25 microns. In general terms, UHDI refers to traces and spaces on a printed circuit board that are sub-25 micron. As electronics continue to shrink, so does the printed circuit board, not only in the X-axis, but also the Y-axis. Designers are challenged with reducing the form factor as well as the thickness of printed circuit boards to meet these demands. This is where UHDI comes in.

With every major advancement in technology comes manufacturing challenges. UHDI is not just a major change, it is a quantum leap in technology. It represents a change in the fundamental method of manufacturing printed circuit boards, moving from the traditional subtractive process to an additive one. UHDI technology requires not only new manufacturing methods, but new manufacturing equipment, chemistry, materials, and inspection capabilities. While there are some crossover processes, it is definitely not a plug-and-play implementation. PCB manufacturers that want to take on the challenge of producing ultra HDI boards will need to assess the more stringent requirements with regard to equipment and their manufacturing environment.

To read this entire article, which appeared in the October 2023 issue of Design007 Magazine, click here.