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DECEMBER 2019 I DESIGN007 MAGAZINE 65 without consulting your chosen fabricator to see what impact they will have on the design. The last thing an engineer or designer wants to hear after they have done the layout is that the part is not possible. For the want of a nail… Thanks for reading. DESIGN007 Mark Thompson, CID+, is in engineering support at Prototron Circuits. To read past columns or contact Thompson, click here. Thompson is also the author of The Printed Circuit Designer's Guide to… Producing the Perfect Data Package. Visit I-007eBooks.com to download this book and other free, educational titles. ricator is not aware of (maximum space to in- gress and egress out of a given fine-pitch com- ponent), please communicate this information to the fabricator. A typical stackup that works the best for a fabricator does not work well for tight trace and space geometries to meet the desired impedance. If I give you a trace width of 0.021" to meet 50 ohms based on a standard 0.062" four- layer board, I will hear a lot of coughing at the other end of the phone, as the design- er says, "We have no room for a trace that wide." Try to have an idea or a range that a trace width should be before consulting with the fabricator. Third, as we have learned from the afore- mentioned examples, do not change things Figure 7: The same trace after changing material and solder mask color. Figure 8: Results after changing starting and finished copper weights.