Flexible PCB design mirrors rigid PCB principles with nuances: accommodate wider wires for heat dissipation, use rectangular shapes, round inner corners, minimize wire width, and space, and ensure gradual transitions to mitigate stress. For durability, favor single-sided flexible PCBs for extensive bending, avoid pad placement in bend-prone areas, and use teardrop-shaped pads. In mass production, integrate flexible PCBs with rigid laminated stiffeners for cost-effectiveness, considering spatial optimization, broader tolerance range, longer wings, assembly strategies, smaller circuits, strict tolerance adherence, limited bonding areas, stiffeners over rigid-flex circuits, specified binder thickness, and omitting shielding for cost savings.