If possible, limit the number of flex layers to 1 or 2, for maximum mechanical flexibility and cost savings.
Pay attention to a symmetrical stack-up of the printed circuit board.
The flex layers continue within the rigid part as inner layers and can there be used for conductor routing.
Distinguish between dynamic (regular) and stable flexion (bend-to-install).
The minimum bending radius is usually between 1mm and 5mm. The dynamic bending stress can only be reliably ensured with single- and double-layer flexible printed circuit boards.
| ||Bending||Dynamic Bend||frequent||Semi-Dynamic||max. 20x||Stable Bend||„Bend-to-Install“
| ||Layers||Dynamic Bend||1-2L recommended||Semi-Dynamic||1-4L recommended||Stable Bend||1-10L possible
| ||Covering*||Dynamic Bend||PI Coverlay||Semi-Dynamic||PI Coverlay or solder-stop||Stable Bend||PI Coverlay or solder-stop
| ||Min. bending radius||Dynamic Bend||100-150 x h flex||Semi-Dynamic||> 20x h flex||Stable Bend||10 - 20 x h flex
| ||Copper type**||Dynamic Bend||RA copper||Semi-Dynamic||ED or RA copper||Stable Bend||ED or RA copper
h = height
* Flexible solde-stop may break or peel off after 5-10x bending
** RA = Rolled copper, suitable for dynamic, flexible applications; ED = Electrolytically deposited copper , only suited for stable and semi-dynamic applications