High-Speed NIC PCBA

12–18 Layer 100G/200G/400G RoCEv2 SmartNIC for AI Cluster RDMA Fabric

Product Overview

The high-speed NIC PCBA is the network interface card powering GPU-to-GPU communication in AI training clusters via RDMA over Converged Ethernet (RoCEv2) and InfiniBand protocols. Operating at 100G, 200G, or 400G per port with dual-port configurations, this board is built on 12–18 layers of ultra-low-loss laminate with precision 100 Ω differential pair routing. Our assembly supports QSFP112/QSFP-DD and OSFP cage soldering with co-planarity below 0.1 mm for reliable 112 Gbps PAM4 optical and copper connectivity. The board incorporates advanced DPU/ASIC silicon (NVIDIA ConnectX-7, Intel IPU) with on-board HBM or DDR5 memory for in-network computing offload. Deployed in rail-optimized topologies across 1,000+ node GPU clusters requiring sub-3 µs tail latency.

Key Specifications

PCBA Assembly Challenges

High-speed NIC assembly demands precision at every stage, starting with the QSFP-DD/OSFP connector cages. These surface-mount cage assemblies have over 100 leads with coplanarity requirements below 0.08 mm across the full connector footprint — any deviation causes unreliable optical module insertion or poor ground contact, degrading signal integrity at 112 Gbps. The DPU/ASIC BGA, typically 2,500–4,000 balls at 0.8–1.0 mm pitch, sits adjacent to HBM or DDR5 memory packages, requiring optimized component placement to minimize via stub lengths on the critical memory bus. The board's 12–18 layers of dense routing and power planes create significant thermal mass; the reflow profile must achieve complete BGA wetting while protecting the QSFP cage plastic housings from thermal deformation (typically rated to 260°C peak for 10 seconds). The high-speed differential pairs running from the ASIC SerDes to the QSFP connector pads demand impedance-controlled routing with less than 0.25 dB insertion loss variation per inch — any solder mask thickness or pad geometry inconsistency in assembly can create impedance discontinuities visible on TDR. Post-reflow, all hidden BGA joints are X-ray inspected, and QSFP cage leads undergo automated optical inspection for coplanarity and solder fillet quality. Electro-static discharge (ESD) protection is paramount — all assembly steps use ionized workstations and grounded handling procedures given the extreme ESD sensitivity of 112 Gbps SerDes PHYs.

Test Strategy

NIC testing emphasizes signal integrity and protocol compliance. Flying probe ICT initially verifies all passives, power rail isolation, and QSFP connector pin continuity. High-speed SerDes testing runs PRBS31 and PRBS58 patterns at 112 Gbps PAM4 on every lane, measuring eye diagram parameters (eye height > 30 mV, eye width > 0.5 UI) and bit error rate (BER < 1E-15) across temperature corners from 0°C to 85°C. PAM4 receiver sensitivity is characterized with stressed-eye calibration per IEEE 802.3ck. Full RDMA performance validation measures throughput, IOPS, and tail latency under RoCEv2 with DCQCN congestion control enabled, confirming line-rate performance at all packet sizes from 64 bytes to 9 KB jumbo frames. PCIe Gen5 compliance testing validates link training, lane reversal, and polarity inversion at 32 GT/s. Production burn-in runs 24 hours with bidirectional 400G traffic across all ports while monitoring FEC (Forward Error Correction) symbol error counts — any port exceeding 1E-6 pre-FEC BER triggers rework.

PCB Manufacturing Difficulty

The high-speed NIC PCB demands elite fabrication capability for reliable 112 Gbps PAM4 signaling. At 12–18 layers of Megtron 7 or Tachyon-100G ultra-low-loss laminate, the dielectric material must exhibit Dk tolerance of ±0.05 and Df below 0.002 at 28 GHz to maintain signal eye opening across the full SerDes channel. Backdrilling is mandatory on all high-speed via transitions — residual stub length is controlled to under 6 mil, verified by cross-sectioning on coupon vias from every panel. Differential pair impedance targets 100 Ω ±8% for Ethernet/InfiniBand lanes, modeled with 3D full-wave solvers and verified by TDR using 20 ps rise-time pulses to capture millimeter-scale discontinuities. The QSFP-DD breakout region requires 2.5 mil trace/space routing with tight fiber-weave effect mitigation — spread-glass or low-Dk glass cloth is used to eliminate skew within differential pairs. The aspect ratio of plated through-holes reaches 10:1, requiring pulse plating for uniform copper distribution. Every finished board passes 100% automated optical inspection, flying probe electrical test, and impedance coupon verification; high-pot (HiPot) testing at 500 VDC confirms isolation between the PCIe edge connector and chassis ground before release to assembly.

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