Circuit Substrate Ground Wiring Positioning for Crack Suppression

The patent applies local quality by positioning ground wirings specifically at the boundaries between flexible and rigid parts where cracks are most likely to occur. This localized reinforcement provides targeted protection without requiring changes to the entire substrate structure, allowing the flexible parts to maintain their bending capability while specific critical areas gain enhanced crack resistance.

The ground wirings act as an intermediary protective layer between the flexible and rigid parts. This intermediary structure absorbs and distributes stress at the boundary interface, preventing crack propagation into the signal and power source wirings. The ground wiring layer serves as a mechanical buffer that maintains electrical integrity while accommodating the differential movement between flexible and rigid sections.

The ground wirings serve multiple functions simultaneously: they provide electrical grounding, act as a mechanical reinforcement layer to suppress cracks, and serve as a stress-distribution structure at the flexible-rigid boundaries. This multi-functionality allows the same wiring structure to address both electrical and mechanical reliability concerns without requiring additional separate protective structures.

The patent implements local quality by concentrating ground wirings specifically at the critical boundary regions between flexible and rigid parts, rather than uniformly distributing them across the entire substrate. This localized approach provides maximum crack suppression where it is most needed while minimizing the overall wiring complexity and material usage.