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JUNE 2021 I DESIGN007 MAGAZINE 45 by way of chemical etching. While equipment, materials, and processes have been enhanced along the years, the etching process is inaccu- rate by its nature, leaving PCB fabricators in a continuing mission to increase its accuracy and its yield. e smaller the spacing between unexposed copper features on the board, the higher the chances that the fluid will flow non- uniformly, creating unwanted over-etching in places prone to this. Most routing tools will ensure that traces make 135-degrees turns, but fine traces in dense areas may sometimes break on these turns, too. us, in case of thin lines in dense busses, you might consider making smooth turns using arcs or curves. Every fabricator independently determines which places are prone for over-etching based on their experience. ey may identify fea- tures as problematic such as a single pad in close vicinity of a long trace, two long traces that run in parallel, and separate or non-par- allel traces that get too close to each other at a very small angle. Return to Tomorrow Are current HDI boards our industry's final frontier? No. Within our industry there is never a final frontier. We exist in an industry of efficiency and evolution. While great strides have been made in the HDI manufacturing, driven by miniaturization and computational power needs, we see additive and semi-addi- tive processes arising to overcome limitations of HDI processes. However, these processes have not yet reached their maturity, while the miniaturization and computational power demands do not stop. With more complex and denser board designs, your k nowledge of fabr ication becomes much more critical. Staying in touch with your fabricator is one of the best ways to prepare your design for optimal yields, and you don't need a fancy Star Trek communicator to do so. DESIGN007 Alex Belelovsky is software engineering manager at Siemens EDA. Are current HDI boards our industry's final frontier? No. Within our industry there is never a final frontier.