40-Layer Rigid PCB

A 40-layer FR-4 rigid PCB with green solder mask, white silkscreen, and full-board electroplated gold at 1.27um. The 15.88:1 thickness-to-aperture ratio is the dominant manufacturing constraint—plating uniform copper into a deep, narrow hole on a 40-layer stack requires controlled hole-wall preparation, additive plating chemistry, and pulse plating to keep the throwing power high. Inter-layer offset is held to micron-level tolerance to keep impedance, antipad clearance, and via-to-pad spacing inside the design rules. Full-board electroplated gold gives consistent contact resistance and bondability across hundreds of pads. Typical uses are AI-server compute and accelerator backplanes, switch and router central cards, telecom backplane assemblies, mil-aero high-density boards, and any motherboard where layer count and routing density push beyond what 20-layer technology can deliver.