What is High-speed PCB Design? Helpful Guidelines

As time goes on, signal frequencies and data rates keep rising, making it difficult for engineers to maintain signal integrity and performance. High-speed PCB design has become a really important solution for modern devices.

OurPCB is committed to making sure you have the best guidelines for high-speed PCBs. Let's get into what these PCBs are, some design guidelines to get you started, and more.

What is a High-Speed PCB Design?

High-speed PCB design is a specific way of creating printed circuit boards that can effectively handle high-frequency signals and fast digital transitions.

When compared to traditional PCB design, the main difference is that high-speed PCB design focuses on maintaining signal integrity and controlling impedance. It also minimizes electromagnetic interference (EMI) in circuits operating at frequencies typically above 50 to 100 MHz or with rise times below 1 nanosecond.

Key Parts of High-Speed PCB Design

There are a few key parts of high-speed PCBs to keep in mind:

• Careful consideration of PCB stackup design
• Proper use of the ground plane and power planes
• Controlled impedance traces
• Management of signal reflections and crosstalk
• Attention to return path and transmission line effects

Applications of High-Speed Circuit Boards

You can use these PCBs in a number of design project options. High-speed PCBs have an important role to play for a variety of applications:

• High-performance computing
• Telecommunications equipment
• Advanced networking devices
• High-definition video systems
• Radar and RF applications

High-Speed PCB Design Guidelines

With our PCB design tips, you can ensure you get optimal performance out of your device. Here are the most important high-speed board design guidelines:

Reference Planes

One of the most essential tips for high-speed PCB designs is to use continuous ground and power planes. This will provide low-impedance return paths for high-speed signals.

Be sure to keep the signal layers adjacent to reference planes to stay at controlled impedance. Avoid splitting reference planes under high-speed traces at all costs to prevent discontinuities.

Board Stackup

You’ll need to design a proper PCB stackup with alternating signal and plane layers. Use symmetrical stackups to stop the board from warping during manufacturing. Additionally, you might want to use high-frequency PCB dielectric materials for critical layers.

Here's an example of a 6-layer high-speed PCB stackup:

Controlled Impedance Traces

It's important to maintain consistent trace impedance throughout the board. Use impedance calculators and PCB design software to figure out the proper trace width and spacing. Moreover, work with a PCB manufacturer like OurPCB to meet controlled impedance requirements.

Trace Length and Routing

Keep high-speed traces as short as possible to reduce signal degradation. You should use length matching for differential pairs and parallel bus signals. Notably, avoid using right-angle bends in traces; it's best to use 45° bend or curved corners.

Spacing and the 3W Rule

Keep enough spacing between traces to reduce crosstalk, and always follow the 3W rule. The 3W design rule dictates that you must keep the space between adjacent traces at least three times the trace width. Additionally, increase your spacing for critical or sensitive signals.

Differential Pair Routing

You should route differential pairs close together and parallel to retain common-mode noise rejection. Be sure to maintain consistent spacing between the pair throughout the route. You should also steer clear from splitting differential pairs across different layers if possible.

High-Speed PCB Design Considerations

If you're working on a high-speed PCB design or PCB layout, there are a few things you need to keep in mind. Here are some important considerations for your high-speed design:

• Signal Integrity: Keep a close eye on your signal quality through the PCB and monitor it carefully. You can use simulation tools to analyze signal integrity before fabrication.
• EMI/EMC: Create your design using proper shielding and grounding techniques, and remember to keep electromagnetic compatibility in mind.
• Transmission Line Effects: Watch the transmission line behavior in a high-speed signal trace. It's important to think about reflections, ringing, and signal distortion.
• Power Distribution Network (PDN): Design a reliable PDN to provide clean power to all components on your board layout. Use decoupling capacitors carefully to reduce power supply noise.
• Layer Stackup: Optimize the PCB stackup for signal integrity and impedance control. Consider the PCB dielectric materials for high-speed applications, and also be careful with your PCB material choice.
• Component Placement: Place your components on your circuit design carefully to cut down PCB trace lengths. Group related components together to improve your digital signal integrity.
• Thermal Management: Take heat dissipation into account for high-speed designs, and use proper thermal management techniques.
• Manufacturing and Testing: Create your advanced PCB design specifically for manufacturability and testability. You might want to consider impedance testing and signal integrity verification methods.

Keeping all of these design considerations in mind will help ensure your board is reliable and performs better. Refer back to this list as you make your design to get the best results!

How do I know If I Need a High-Speed Design?

You might be wondering how you would know if you need a high-speed PCB layout for its enhancing design performance properties. Here are a couple of pointers to find out:

High-Speed Interfaces

If you have high-speed interfaces such as PCI-e, DDR, or even video interfaces like DVI and HDMI, you might need a high-speed circuit board layout. All of these interfaces require you to follow high-speed design rules.

Trace Length and High-Speed Signal Wavelength

If the wavelength of your signals is comparable to the trace length, then your board will definitely need a high-speed design. Some standards like DDR need traces that must be length matched to minimal tolerances.

Wireless Interfaces

If your board has an antenna directly on the board or through the connector, it needs a digital design for high-speed signals. Onboard antennas also require close impedance matching and length tuning.

Boards with SMA connectors or something similar would need the traces going to the connector to be of a specific impedance value, so you're going to need a high-speed PCB design and layout.

OurPCB: Specialized PCB Manufacturing Services

High-speed PCB designs are built to handle high-frequency signals and fast digital transitions with ease. They are a great product for demanding environments with a focus on maintaining signal integrity and controlling impedance.

With the right manufacturer as your partner, you can relax knowing that your designs will be created into physical products with absolute precision.

OurPCB is a multinational PCB manufacturing and PCB assembly company that provides global service and support. We handle the challenges of high-speed design and ensure you get a high-quality product. For more information, reach out to our friendly team!

What is High-speed PCB Design? Helpful Guidelines FAQs

What is considered a high-speed circuit?

A high-speed circuit is usually one that runs with clock frequencies above 50 to 100 MHz or with signal rise times below 1 nanosecond. These circuits need special design rules to maintain signal integrity and prevent electromagnetic interference.

What is the difference between high-speed and low-speed signals?

High-speed signals have faster rise times and higher frequencies than low-speed signals. This leads to more complicated behavior on the PCB. Low-speed signals are simple point-to-point connections, whereas high-speed signals are transmission lines with impedance control and careful PCB routing.

What are the top three important steps in the PCB design and layout process?

The top three important steps in PCB design and layout process are proper component placement, careful stackup design, and efficient routing of traces. These steps can optimize signal flow, ensure proper impedance control, and take care of possible signal integrity and EMI issues.

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