Under the wave of artificial intelligence (AI), high-performance computing (HPC), and large-scale data analytics, the computational demands of data centers are growing exponentially at an unprecedented rate. To overcome the bottlenecks of traditional packaging, the industry has turned to heterogeneous integration solutions centered around chiplets, with NVIDIA's NVLink-C2C (Chip-to-Chip) technology being the pinnacle of this trend. It achieves ultra-high bandwidth and ultra-low latency interconnects between chips, but this places extreme demands on the printed circuit boards (PCBs) that carry it. This article delves into the core design and manufacturing challenges of NVLink-C2C PCBs and explains how specialized manufacturers like Highleap PCB Factory (HILPCB) can help clients navigate this complex field.

As processors like GPUs, CPUs, and DPUs grow larger and more complex, monolithic die designs are approaching physical limits. NVLink-C2C technology allows multiple chiplets to be connected via high-density organic substrates or PCBs, forming a logical "super chip." This architecture not only improves yield and flexibility but also pushes data transfer rates to new heights. However, this transformative advancement means that the NVLink-C2C PCB, as the physical carrier of all components, must achieve unprecedented levels of signal integrity, power integrity, thermal management, and manufacturing precision.

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What Revolutionary Requirements Does NVLink-C2C Technology Impose on PCB Design?

NVLink-C2C is a parallel, energy-efficient die-to-die (D2D) interconnect standard designed to deliver multiple TB/s of bandwidth over extremely short physical distances. Compared to traditional board-level or system-level interconnects like PCIe or Ethernet, its demands on PCBs are fundamentally different, primarily in the following aspects:

1. Extremely High Routing Density: The NVLink-C2C interface features thousands of I/O channels that must be fanned out under the BGA (Ball Grid Array) area of the chip package. This requires PCBs with ultra-fine line width/spacing (e.g., below 2/2 mil) and microvias, achievable only with advanced HDI (High-Density Interconnect) or substrate-like PCB (SLP) technologies.

2. Stringent Signal Integrity: With data rates reaching 100Gbps/pin or higher, signals are highly susceptible to loss and interference during transmission on PCB traces. This means NVLink-C2C PCBs must use ultra-low-loss dielectric materials and maintain extremely precise impedance control (typically within ±7% or even ±5%).

3. Robust Power Delivery Network (PDN): Processors integrating multiple high-performance chiplets can consume thousands of watts, with dynamic current demands. The PCB must provide a stable, low-impedance PDN to handle instantaneous current surges and prevent voltage drops that could disrupt chip operation.

4. Integrated Thermal Management: The enormous power density generates significant heat. The PCB itself must become part of the thermal path, incorporating thick copper layers, thermal via arrays, or embedded heat sinks to efficiently conduct heat from the chips to the cooler.

These requirements collectively form a complex multi-physics problem, where any oversight can lead to system failure.

How to Achieve Ultimate Signal Integrity in NVLink-C2C PCBs?

Signal integrity (SI) is critical for ensuring high-speed digital signals remain undistorted during transmission, and for NVLink-C2C PCBs, this is the foremost challenge. When signal rates leap from 16GT/s in PCIe Gen4 PCBs and 32GT/s in PCIe Gen5 PCBs to NVLink-C2C's 100Gbps level, physical effects become exceptionally sensitive.

First, material selection is foundational. Traditional FR-4 materials exhibit excessive loss at high frequencies and cannot meet the requirements. Designers must opt for materials with extremely low dielectric constant (Dk) and dissipation factor (Df), such as Megtron 6/7/8 or Tachyon 100G. These high-speed PCB materials minimize signal attenuation and dispersion.

Second, precise impedance control is crucial. Impedance mismatches cause signal reflections, severely degrading eye diagrams. HILPCB achieves differential impedance tolerances within ±5% through advanced manufacturing processes and strict process control. This requires precise management of trace width, dielectric thickness, and copper weight, supported by field solver software for modeling and simulation. Once again, via optimization is a critical step. In thicker multilayer PCBs, traditional through-holes create unnecessary stubs, which can resonate at high frequencies and become signal killers. Back-drilling technology precisely removes these stubs, significantly improving signal quality. For extremely dense areas, blind/buried vias in HDI technology must be employed to shorten paths and reduce parasitic effects.

Finally, crosstalk management. In high-density routing, electromagnetic coupling between adjacent traces can cause crosstalk. Increasing trace spacing, adopting stripline structures, and optimizing ground via layouts can effectively suppress crosstalk, ensuring the independence of each channel.

Why is Power Integrity (PDN) Key to NVLink-C2C PCB Success?

If signal integrity is the highway, then power integrity (PI) is the energy network that powers this highway. A processor integrating multiple powerful chiplets can consume over 2000W, with current fluctuations reaching hundreds of amperes within nanoseconds during operation. Poor PDN design can cause core voltage droops, leading to computational errors or even system crashes.

Designing a robust PDN requires systematic thinking:

• Low-impedance paths: The entire current path from VRM (Voltage Regulator Module) to chip packaging must have minimal impedance. This is typically achieved in NVLink-C2C PCBs through multiple continuous, uninterrupted power and ground planes. Heavy copper technology (e.g., 3oz or higher) effectively reduces DC resistance (IR Drop).
• Hierarchical decoupling: Different types of capacitors are needed to suppress noise at various frequencies. PDN designs employ hierarchical decoupling strategies, placing bulk electrolytic capacitors near VRMs and numerous small, low-ESL (Equivalent Series Inductance) ceramic capacitors around chip packaging to form a broadband low-impedance network covering kHz to GHz ranges.
• Planar capacitance: The PCB's power and ground planes themselves act like massive parallel-plate capacitors, providing decoupling at extremely high frequencies. Reducing the dielectric thickness between power and ground planes significantly enhances this intrinsic capacitance, which is critical for suppressing high-frequency noise.

As an experienced PCB manufacturer, HILPCB's engineering team collaborates closely with clients through DFM (Design for Manufacturability) reviews to ensure PDN designs are physically perfected—optimizing capacitor placement, ensuring sufficient power vias, etc.

How Does Advanced PCB Stackup Design Balance Signals, Power, and Thermal Management?

Stackup design is the soul of NVLink-C2C PCBs, defining the physical structure for signals, power, ground, and thermal management. An excellent stackup achieves the optimal balance between performance, cost, and manufacturability.

For NVLink-C2C PCBs typically exceeding 20 layers, stackup design must consider:

1. Signal layer isolation: High-speed differential pairs typically route as striplines (sandwiched between two ground layers) or microstrips (above a ground layer). Striplines offer superior EMI shielding and crosstalk prevention, making them the preferred choice for NVLink-C2C and other high-speed signals.
2. Power/ground plane pairing: Tightly coupling power and ground planes leverages planar capacitance to enhance PDN performance.
3. Material hybridization: For cost optimization, hybrid stackups can be used—employing expensive ultra-low-loss materials for core high-speed signal layers while using cost-effective materials for power and low-speed signal layers.
4. Symmetrical structure: To prevent warping during manufacturing and assembly due to uneven thermal stress, stackup designs must maintain top-bottom symmetry.

This complex stackup design not only serves current NVLink-C2C needs but also lays a solid foundation for future interconnect technologies like PCIe Gen7 PCBs under development. These future standards will demand even lower loss and higher density, making today’s NVLink-C2C PCB experience invaluable.

What Severe Thermal Management Challenges Does NVLink-C2C PCB Face?

Heat is the number one enemy of high-performance computing. An AI accelerator module equipped with NVLink-C2C interconnects can easily exceed a total design power (TDP) of 1500W, with this heat concentrated in an extremely small area, creating astonishing thermal flux density. If the heat cannot be removed promptly and effectively, chip temperatures will rise rapidly, leading to performance degradation (throttling), computational errors, or even permanent damage.

NVLink-C2C PCB plays a dual role in thermal management: it is both a carrier of heat sources and a critical link in the heat dissipation path. Effective PCB-level thermal management strategies include:

• Thermal Vias: Densely arranging numerous thermal vias beneath the chip to directly conduct heat from the chip to the other side of the PCB, where large heat sinks are typically connected. These vias are filled with conductive paste or directly plated to maximize thermal conductivity.
• Copper Coin: For hotspot areas, a solid copper block can be embedded directly during PCB manufacturing. Copper's thermal conductivity is far higher than that of PCB substrates, serving as an efficient "thermal highway" to spread heat laterally and conduct it vertically.
• High Thermal Conductivity Materials: Choosing PCB substrates with higher thermal conductivity (Tc), though not as effective as direct metal conduction, still benefits overall heat distribution and reduces temperature differences within the board.
• Collaboration with System Cooling Solutions: PCB design must closely align with the server's cooling solution (e.g., air or liquid cooling). For example, precise installation positions and contact surfaces must be reserved for liquid cooling system cold plates to ensure continuity in the heat transfer path.

These thermal management techniques are not only applicable to current computing chips but are also crucial for future Optical Interconnect PCB or Linear Optics PCB integrated into server motherboards, as optical modules and related driver chips are also highly temperature-sensitive.

From Design to Manufacturing: What Role Does DFM Play in NVLink-C2C PCBs?

A theoretically perfect design is a failure if it cannot be manufactured economically and reliably. Design for Manufacturability (DFM) serves as the bridge between design and manufacturing, and its importance is magnified for extremely complex boards like NVLink-C2C PCBs.

Collaborating early with experienced manufacturers like HILPCB for DFM reviews can prevent costly modifications and project delays later. Key DFM checkpoints include:

• Microvia Process Capability: Laser drilling aspect ratios, via wall quality, and filling processes all impact reliability. Manufacturers must confirm whether the design falls within their process window.
• Lamination Alignment Accuracy: For multilayer HDI PCBs, alignment accuracy between each layer is critical. Minor deviations can lead to via connection failures.
• Copper Thickness Uniformity: During electroplating, large copper planes and small traces may exhibit uneven copper thickness, affecting impedance control and current-carrying capacity.
• Warpage Control: Asymmetric stack-up designs or uneven copper distribution can cause PCB warping under thermal shocks like reflow soldering, impacting BGA soldering quality.

HILPCB offers free DFM analysis services. Our engineers leverage professional CAM software and extensive manufacturing experience to help clients identify and address potential manufacturing risks before production, ensuring a smooth transition from PCIe Gen4 PCBs to NVLink-C2C PCBs.

How Does HILPCB Ensure the Manufacturing and Assembly Quality of NVLink-C2C PCBs?

Producing a qualified NVLink-C2C PCB is just the first step; high-quality assembly is equally essential. As a provider of one-stop turnkey assembly services, HILPCB understands that every step from bare PCB to fully functional PCBA must be executed with precision.

On the manufacturing side, we possess industry-leading equipment and process capabilities:

• Advanced Imaging & Etching Technology: Ensures fine traces of 1.5/1.5 mil to meet high-density routing requirements.
• High-Precision Lamination Equipment: Guarantees dimensional stability and interlayer alignment accuracy through strict control of temperature, pressure, and time.
• Plasma Desmear & Electroplating Fill: Ensures the conductive reliability of microvias, which is the foundation for long-term stability of HDI boards.
• Comprehensive Inspection Methods: We use Automated Optical Inspection (AOI), X-Ray Inspection, and cross-section analysis to monitor 100% of critical parameters during production.

On the assembly side, we are equally capable of handling complex server motherboards:

• High-Precision SMT Assembly Lines: Capable of handling large BGA packages (e.g., 100mm x 100mm) and tiny components like 01005.
• 3D X-Ray Inspection: For BGA packages, solder joints are hidden beneath the chip and cannot be inspected optically. 3D X-Ray can non-destructively detect the quality of each solder ball, identifying potential defects like cold solder, bridging, or voids.
• Strict Temperature-Controlled Reflow Soldering: For thick server motherboards and complex component combinations, we customize optimized reflow profiles to ensure all components are soldered under safe and reliable conditions.
• Functional Testing (FCT): Based on customer requirements, we set up test environments to conduct comprehensive functional tests on assembled boards, ensuring every delivered PCBA meets specifications 100%. Whether it's manufacturing PCIe Gen5 PCBs with stringent requirements or Linear Optics PCBs with special demands for cleanliness and precision, HILPCB's quality management system (certified by ISO 9001 and IATF 16949) ensures the highest standards.

Conclusion

NVLink-C2C PCBs are not just circuit boards; they are the physical embodiment of modern data center computing power, a product of semiconductor innovation and advanced manufacturing technology. From the selection of ultra-low-loss materials to sub-micron manufacturing precision, from complex signal and power co-design to efficient multi-physics thermal management, every step is filled with challenges.

To overcome these challenges, you need a partner with not only advanced equipment but also deep technical expertise and extensive industry experience. Highleap PCB Factory (HILPCB), with over a decade of specialization in high-speed, high-density, and high-layer-count PCBs, along with its one-stop service from manufacturing to assembly, is ready to tackle the opportunities and challenges presented by NVLink-C2C PCBs. We are committed to transforming your cutting-edge design concepts into stable, reliable, and high-performance hardware products, driving the advent of the AI and HPC era.

Contact HILPCB's expert team today to start your next high-performance server PCB project.

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Related links

• high-speed PCB
• multilayer PCBs
• HDI PCBs
• one-stop turnkey assembly services