16-Layer Back-Drilled PCB

A 16-layer PCB on IT-9681TC low-loss laminate at 2.2±0.22mm thickness with ENIG finish, fabricated with controlled-depth back drilling to remove via stubs on high-speed signal paths. Stub removal extends usable bandwidth above 25Gbps NRZ and 56G/112G PAM4 by reducing impedance discontinuities and resonance peaks at multi-gigahertz frequencies. The IT-9681TC laminate is engineered for low Df and stable Dk over the operating temperature range, supporting tight insertion-loss budgets in telecom and datacenter line cards. Typical use cases include 5G transport network cards, optical module hosting boards, switch fabric backplanes, AI training accelerator carrier boards, and high-speed test equipment. Production demands precise back-drill depth control measured against the target reference plane, controlled stub-length yield monitoring, and copper plating uniformity to maintain consistent impedance across all back-drilled vias.