Best 6-Layer PCB Stackups for Signal Integrity & Impedance Control

Why Impedance Control Matters in 6-Layer PCB Design

Forget theory – impedance control in your 6-layer PCB stackup directly determines if your high-speed signals actually work. Get it wrong with a common 1.6mm board thickness and 1oz copper thickness, and reflections trash your signal integrity. Think jitter, data errors, and failed compliance tests. It’s why experienced designers constantly wrestle with the core question: "How do I arrange this 6-layer stackup for precise impedance?"

The problem? Squeezing planes and signals into that fixed 1.6mm height while hitting targets like 50Ω/90Ω. Random layer ordering makes controlled impedance nearly impossible using practical trace widths. A bad stack guarantees tuning nightmares or a dead board. This guide cuts through that – showing you an optimized layer arrangement that makes impedance predictable, ensuring your design performs reliably, not just on paper.

Optimized 6-Layer PCB Stackup for 50Ω/90Ω Impedance (1.6mm, 1oz)

6-layer board, 1.6mm board thickness, 1oz copper thickness, how to arrange the stackup to achieve the best impedance effect?

The laminate structure recommended to customers:Board Thickness = 1.6mm

Why is this arrangement the best for impedance?

1. Double GND planes symmetrically clamp signals

• Inner1 and Inner4 are both GND planes, clamped on both sides, effectively shielding signal crosstalk and improving signal integrity.
• The internal signal layers (L2, L3) have reference planes on the top and bottom to ensure impedance stability and excellent EMI performance.

2. The signal layer is close to the reference plane for easy impedance control

• Top Layer is close to Inner1 (GND)
• Bottom Layer is close to Inner4 (GND)
• Inner2 is close to Inner1 (GND)
• Inner3 is close to Inner4 (GND)
• The distance from the signal layer to the reference plane is moderate (0.13~0.18mm), which is convenient for 50Ω single-ended and 90Ω differential impedance control, and the line width is also easy to achieve.

3. Reasonable distribution of PWR layer to reduce power noise

The PWR layer is placed in the middle, forming a plane pair with the upper and lower GND Planes, which plays a distributed decoupling role and reduces power noise and electromagnetic radiation.

4. Symmetrical upper and lower stacking to prevent board warping and deformation

The copper content, dielectric thickness, and reference surface distribution of the upper and lower signal layers are symmetrical to ensure processing and assembly stability.

Impedance Target Recommendations: 50Ω Single-Ended & 90Ω Differential

Want to learn more? We have a dedicated article on PCB impedance. Also have practical tutorial regarding How to Achieve 50 Ohm Impedance Requirements for PCB Routing without extra charges. If your design has other impedance control requirements, feel free to reach out to our tech team anytime for support.