Why Upgrade to 6 Layers?

When a 4-layer PCB no longer suffices, it’s time to consider a 6-layer board. The additional layers offer several benefits:

1. More signal routing space
2. An extra plane pair
3. Flexibility in conductor arrangement

The key to success lies in the PCB stackup arrangement and routing strategy.

Reasons to Choose a 6-Layer Board

1. More surface space: Moving power and signal layers inside frees up room for components on the surface.
2. Mixed-signal boards: Dedicate a surface layer to analog interfaces and use an internal layer for slower digital routing.
3. High-speed, high I/O count boards: Separate signals into different layers for better organization.

Typical 6-Layer PCB Stackup

A common 6-layer stackup arrangement:

1. Signal (Top)
2. Ground
3. Power
4. Signal
5. Ground
6. Signal (Bottom)

Signal Routing Guidelines

• Use top and bottom layers for impedance-controlled signals.
• Thin dielectrics (≤10 mil) are preferable for these outer layers.
• For digital interfaces with differential pairs, reduced trace width allows routing to fine-pitch components.

Power Routing Strategies

• Dedicate an internal layer to power distribution.
• Break up the power plane into rails for multiple voltages if needed.
• You can still route power on signal layers using copper pour or thick traces when necessary.

High Current Considerations

For high current applications:

• Use two internal power layers interleaved with ground.
• Consider using the back layer as an additional power plane for increased current handling.

3-Core vs. 2-Core Stackup

A 3-core (or 1 thick central core with thin outer layers) arrangement is often superior:

1. Increases PDN plane capacitance
2. Reduces spreading inductance
3. Minimizes radiated emissions from PCB edge
4. Provides more consistent impedance for signals on L4

Best Practices

1. Get your stackup approved by a fabrication house before layout and routing.
2. Apply EMC strategies used in 4-layer and 8-layer boards.
3. Consider DFM (Design for Manufacturing) guidelines throughout the process.

Remember, the stackup arrangement significantly impacts EMC and signal integrity, so choose wisely based on your specific application needs.

6 Layer PCB stackup reference for different thickness:

• Read more about: 4 Layer PCB Stackup

If you need stackup suggestion for your 6 layer PCB design, welcome to contact us.