Design Guidance

2022-11-08 BEST

Flex Vias & Rigid-Flex Vias

Via Design

Vias are at greater risk for peeling on flex designs. To reduce this risk:

• Make annular rings as large as possible.

• Vias should be tear-dropped.

• Adding tabs or anchors to vias, as shown, will also help prevent peeling.

Add Tabs To Vias-Design Guide

Via Locations

• Vias are not reliable in areas that will be flexed.

• In a dynamic application, flexed vias can crack very quickly.

• Vias are okay over a stiffener (reinforcements), but vias just off the edge of a stiffener (reinforcements) are at risk for cracking.

Rigid-Flex Vias

• For rigid-flex designs, hole to flex distance is important. That is, the distance between vias and the rigid-flex transition area.

• Avoid going below 50 mils for high reliability applications.

• Keep in mind the rule most broken in rigid-flex designs: most manufacturers will not allow less than 30 mils for commercial applications.