Rigid-Flex PCB Recess Structure for Fold-Boundary Stress Relief

The patent applies local quality by creating a recessed portion specifically at the boundary region between the flexible and rigid parts. This localized structural modification allows the circuit board to have different mechanical properties in different regions: the recessed area provides stress relief and flexibility where needed, while the rest of the rigid part maintains its full surface area for component placement. This resolves the contradiction by addressing the reliability issue locally rather than requiring a global increase in flexible part length.

The recessed portion acts as a pre-designed stress relief structure that cushions the bending moment before it reaches the vulnerable boundary region. By anticipating the high stress concentration that occurs during tight bending, the patent预先 creates a geometric feature that redistributes and reduces this stress, allowing the circuit board to be tightly bent for compact device design without excessive damage risk.

The patent segments the circuit board structure into three distinct regions: the flexible part, the boundary region with the recessed portion, and the rigid part. This segmentation allows each region to perform its specific function optimally. The recessed portion at the boundary acts as a transition zone that improves bending moment distribution, while the rigid part maintains sufficient length and area for component placement. This resolves the contradiction by creating a multi-functional segmented structure rather than a simple trade-off between flexible and rigid part lengths.