Back to Basics Part 22 - Design Features for Flexible Circuit Coatings

摘要

Those who read the last installment of this series will recall it was focused on flexible circuit coatings, which included: cover layers, cover costs, and cover films. There is inevitably a need to access features through the coating regardless of the type used, and this topic was discussed earlier in some detail for both surface mount land design and through-hole component terminations. The sizing of cover-layer openings will, of course, vary in accord with pad design features and the presence or absence of a plated through-hole structure associated with the termination. As before, the key area of concern relative to termination access design features in the flex circuit is with single metal layer flex circuits. The primary concern is related to the possibility of pad lift during assembly or use, and, with the elevated temperatures of lead free, the problem is a more urgent concern than just a few short years ago.