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70 DESIGN007 MAGAZINE I FEBRUARY 2024 Coverlay and Resist Coating on PCBs Finally, be sure to remove coverlay and resist around the leads and bonding area to apply optimum bonding pressure during thermal compression. Figures 9 and 10 show compari- sons between a preferred design and one that is not. Summary Rigid-flex circuits have become almost ubiq- uitous, and they're now found in all kinds of everyday electronic devices. Designing and attaching a flexible circuit to a rigid PCB pres- ents a variety of challenges, but designers who follow the guidelines in this article should have very few issues. As always, speak to your flex fabricator before you begin the design pro- cess; they can probably help you save time and money on your rigid-flex circuits. DESIGN007 Chris Keirstead is a sales manager with PFC Flexible Circuits. Figure 8: Two examples of problematic designs. Figure 9: A preferred design with coverlay and resist removed from space around leads and bonding area. Figure 10: An example of a non-preferred design showing the results when coverlay and resist are not removed correctly.