In general, the copper adhesion in flexible circuit boards is worse than in circuit boards with standard FR4 material. It is therefore recommended to make the pads / annular rings as large as possible. To improve adhesion, anchors and teardrops can be used.
In order to increase the stability of vias on flexible circuit boards, you can implement the following measures:
- Give anular rings the maximum size
- Bind vias using teardrops
- Use anchors to increase the film adhesion
- Do not place any vias in the bending area