4 Layer PCB Stackup

By Frank, Senior Electronics Engineer, USA

When it comes to designing printed circuit boards, the stackup - the way the different layers of copper and insulation are arranged, is crucial. Moving from a basic 2-layer board to a 4-layer design offers significant benefits in signal integrity, noise reduction, and power stability.

Drawing from my years of experience, I want to share practical insights about 4-layer PCB stackups that can help you achieve reliable, high-performing designs.

In simple terms, a 4-layer PCB sandwiches two signal layers on the outside with internal layers dedicated to power and ground. This arrangement helps control electromagnetic interference much better than a 2-layer board and provides solid reference planes for signals to return to, which is essential for smooth circuits.

In this article, I’ll explain common stackup configurations, highlight design challenges, and offer some general advice on working with PCB fabricators who specialize in multilayer boards.

What a 4-Layer Stackup Looks Like and Why It Matters

A four-layer printed circuit board consists of four layers of copper separated by insulating material. Usually, signal traces go on the top and bottom layers, while the two inner layers serve as power and ground planes. Imagine it like a sandwich: the bread slices are your signal layers, and the filling is your power and ground that help the board operate cleanly.

Two common layouts are:

Signal — Ground — Power — Signal
Ground — Signal — Signal — Ground The first layout is effective for reducing noise, placing ground next to the top signal layer. The second layout, with double grounding, works well in high-frequency or sensitive circuits by providing additional shielding.

Key Design Considerations

Several small details can determine how well your PCB performs. Layer thickness and materials affect signal travel and impedance, which should typically be kept around 50 ohms for high-speed signals.

Power and ground layers not only deliver voltage but also act as shields against interference. It’s best practice to route signals close to these reference planes. Vias connect ground planes across layers, enhancing signal stability and reducing noise.

Common Mistakes to Avoid

Here are some pitfalls I’ve seen and learned from:

Routing signals without a continuous ground plane underneath, causing noisy signals.
Layer arrangements that isolate ground and signal layers, breaking return paths.
Ignoring heat dissipation inside the board, which can cause problems in multilayers.
Using power layers for signals without proper filtering, adding noise to the system. Avoiding these issues leads to more robust designs.

Fabrication Tips

When preparing your design for production, using fabricators with established 4-layer stackup standards can simplify the process and improve consistency. Confirming their material specifications and layer details beforehand can save time and prevent surprises.

It’s beneficial to choose manufacturers experienced with multilayer PCBs like JLCPCB, who can guide you through design-for-manufacturing aspects and help ensure your design transitions smoothly from concept to production.

Conclusion

Stepping up to a 4-layer PCB stackup is a meaningful upgrade in electronic design, improving signal quality and reducing interference. Understanding stackup configurations, paying attention to design details, and collaborating closely with knowledgeable fabricators can help you get the results you need.

If you’re exploring multilayer boards, I encourage you to research and reach out to board houses that specialize in this area, they can be valuable partners in bringing your designs to life.