Flex Circuit Tips
Use hatched polygons. You may find that sometimes carry a power on a flex circuit is necessary. Though use solid copper pours is okay, it might greatly reduce the board flexibility. Generally it’s best to use hatched polygons to retain a high level of flexibility, but a normal hatched polygon still has heavily biased copper stresses in 0°, 90°, and 45° angle direction. Actually, a more statistically optimal hatch pattern would be hexagonal which could be done by using a negative plane layer and an array of hexagonal anti-pads.
Add support for PADs. Copper on a flex circuit is more likely to detach from a polyimide substrate because of the repeated stresses. Thus it is extremely important to provide support for exposed copper. Vias are inherently supported because the through-hole plating offers a suitable mechanical anchor from one flex layer to another. For this reason, additional through-hole plating of up to 1.5 mils for rigid-flex and flex circuits is mostly recommended. Surface mount pads and non-plated-through pads are referred to as unsupported, and SMT component pads are among the most vulnerable.