IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1545404
JUNE 2026 I I-CONNECT007 MAGAZINE 91 Key Points • Next-generation Ethernet is moving to 224G signaling, enabling the transition to 1.6 terabit Ethernet. • Higher data rates demand modulation schemes with greater spectral efficiency. • As bit rates surpassed 32 Gbps, PAM4 signal- ing has become the standard. • At these speeds, routing must evolve from controlled impedance traces into engineered electromagnetic structures. • Skip-layer routing is a coaxial-like waveguide formed by a differential pair sandwiched be- tween two reference planes and surrounded by a via fence. • The via pitch must be ≤ λ/8 (0.37 mm) at the highest frequency. • Rough copper dramatically increases skin- effect loss, introduces phase-delay variation, and drives additional mode conversion, all of which collapse PAM4 eye height. • Skip-layer routing uses blind skip-vias to jump directly to the appropriate stripline layer, eliminating unnecessary layer transi- tions, via stubs, antipad discontinuities and reference plane changes. • For 224G PAM4, only ultra low loss dielec- trics with Df = 0.002 and tightly controlled Dk (3.2–3.4) are suitable. I-CONNECT007 Resources • Beyond Design by Barry Olney: Balancing Trade- Offs for Optimal PCB Design, Substrate Integrated Waveguides • Skip-Layer Routing for High Bandwidth Channels, Interference Technology • Will Skip-Layer Routing Work Past 56 GHz? • Accelerating Hyperscale Data Centers w/ 224G SerDes Ethernet, Synopsys Blog • 224G Ethernet PHY IP, Synopsys • 224 Gbps PAM4 end to end channel solutions, Intel Barry Olney is managing director of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board-level simulation. The company developed the iCD Design Integrity software incorporating the iCD Stackup, PDN, and CPW Planner. The software can be downloaded at www.icd.com.au. To read past columns, click here. Figure 4: 224G long-reach ultra-low-loss stackup. (Source: iCD Stackup Planner) Figure 5: 224G PAM4 test platform. (Source: Synopsys) B E YO N D D ES I G N