Electromagnetic Compatibility (EMC) is one of the key indicators for evaluating the performance of 16-layer high-layer-count PCBs. For 16-layer boards integrated with a large number of high-speed chips and complex power modules, electromagnetic interference (EMI) not only affects their own signal transmission quality but may also interfere with the normal operation of surrounding devices. Therefore, optimizing EMC during the design phase is far more efficient and cost-effective than making corrections later.

**Tip 1: Plan the Grounding System Reasonably and Build Low-Impedance Grounding Paths**  

Grounding is the foundation of EMC optimization. The grounding design for 16-layer high-layer-count PCBs should follow the principle of combining "single-point grounding" and "multi-point grounding." For low-frequency signals (below 1 MHz), use single-point grounding to avoid forming ground loops. For high-frequency signals (above 10 MHz), use multi-point grounding to shorten the grounding path and reduce grounding impedance.

In the layer stackup, ensure an adequate number of ground layers, and keep these layers intact, avoiding large-area slots as much as possible. A complete ground layer acts like an "electromagnetic shield," absorbing electromagnetic radiation generated by high-speed signals while providing a stable reference plane for signals. Additionally, arrange arrays of grounding vias along the edges of the PCB to enhance connections between ground layers and reduce interlayer ground impedance.

**Tip 2: Optimize High-Speed Signal Routing to Reduce Electromagnetic Radiation**  

High-speed signal routing is one of the primary sources of EMI in 16-layer high-layer-count PCBs. The longer and faster the traces, the stronger the electromagnetic radiation. Therefore, during design, aim to shorten the routing length of high-speed signals and avoid unnecessary detours. Additionally, control the curvature radius of traces and avoid right-angle turns—right-angle routing can cause impedance discontinuities, leading to reflections and radiation. It is recommended to use 45-degree angle or curved routing.

Differential routing is an effective means of suppressing EMI. The electromagnetic radiation generated by differential signals during transmission cancels each other out. Thus, for high-speed interfaces such as PCIe and USB 3.0, prioritize differential routing. Ensure that the two traces of a differential pair are of equal length, uniformly spaced, and kept as close as possible to the reference plane. Avoid routing across layers; if crossing layers is unavoidable, add grounding vias near the transition vias to reduce signal radiation.

**Tip 3: Suppress Power Noise to Reduce Conducted Interference**  

Power noise is a major source of conducted interference in 16-layer high-layer-count PCBs. Since 16-layer boards need to supply power to multiple chips, the current fluctuations in the power layers are significant, making them prone to noise, which can be conducted to other modules through power lines.

The core of suppressing power noise lies in the "rational placement of decoupling capacitors." Decoupling capacitors are categorized into high-frequency and low-frequency capacitors. High-frequency capacitors (such as 0402-packaged ceramic capacitors) are responsible for filtering high-frequency noise and should be placed close to the chip's power pins. Low-frequency capacitors (such as tantalum capacitors) filter low-frequency noise and can be placed near the power entry point. Additionally, arrange a sufficient number of filter capacitors between the power and ground layers to form a "power filtering array," further reducing power noise.

Simultaneously, employ "power layer segmentation" techniques to separate power layers of different voltages, preventing noise coupling between different voltage domains. When segmenting, ensure clean and tidy dividing lines and avoid segmenting power layers directly beneath high-speed signal traces to prevent discontinuities in the signal reference plane.

**Tip 4: Implement Shielding Design to Block Electromagnetic Interference Propagation Paths**  

For 16-layer high-layer-count PCBs with extremely high EMC requirements, internal design optimization alone is insufficient—external shielding is also essential. Shielding can be achieved in two primary ways: First, incorporate shielding layers within the PCB to wrap sensitive signal layers or noise source layers with ground layers, blocking the propagation of electromagnetic radiation. Second, install metal shielding covers externally on the PCB, ensuring they are well-connected to the PCB's ground layers to form a complete shielding enclosure.

EMC optimization for 16-layer high-layer-count PCBs is a comprehensive task that requires attention to multiple dimensions, including grounding, signals, power, and shielding. Only by considering all these aspects during the design phase can high-quality products that meet EMC standards be developed.