20-Layer Rigid-Flex Board

A high-density rigid-flex PCB with 20 rigid layers, 4 flex layers, and 5-stage HDI build-up on the rigid sections, targeted at the most space-constrained foldable and wearable assemblies. The 5-stage HDI stack uses sequential laser microvias to deliver ultra-fine BGA breakout and the routing density required by application processors, RF front-ends, and high-speed memory in a single integrated assembly. The 4-layer flex bridge enables the board to fold across the hinge region of foldable smartphones, the camera-module-to-mainboard transition, key array areas, and RF module interconnects. Typical applications include foldable phones, advanced wearables, compact telecom RF units, and aerospace electronics where every cubic millimeter of internal volume is contested. Manufacturing requires multiple sequential lamination cycles, registration accuracy across all stages, and tightly controlled flex-bend reliability.