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Standard 4- and 6-Layer PCB Stackups

Posted by in on 4-17-13

Requirements for every PCB are unique, so it’s a bit of a misnomer to call the stackups presented below “standard.”  If for instance, you have a requirement that the PCB must pass FCC compliance testing while operating outside a shielded enclosure, perhaps these stackups aren’t for you.  With that said, these stackups are a great starting point and as-is, will suit most designer’s needs.

 

4 Layer Stackup

The classic 4-layer PCB stackup includes two routing layers and two internal planes, one for ground and the other for power.

 

Standard 4 Layer PCB Stackup

Classic 4 Layer PCB Stackup

 

Adhering to this stackup, including the core and prepreg heights shown, while utilizing FR-4 PCB material and 1 oz copper, the properties of 50 Ohm traces on the routing layers are provided in the table below.

 

Layer50 Ohm Trace Width
Top Layer0.017"
Bottom Layer0.017"

 

6 Layer Stackup

The 6-layer PCB classic stackup includes four routing layers (two outer and two internal) and two internal planes (one for ground and the other for power).

 

Standard 6 Layer PCB Stackup

Classic 6 Layer PCB Stackup

 

Again, adhering to this stackup while utilizing FR-4 PCB material and 1 oz copper, the properties of 50 Ohm traces are provided in the table below.

 

Layer50 Ohm Trace Width
Top Layer0.0170"
Internal Routing Layers0.0065"
Bottom Layer0.0170"

 

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Wrap-up

Remember, these stackups aren’t for every design.  For example, high speed designs will typically always keep power and ground planes on adjacent layers for decoupling and designs that require low electromagnetic emissions may need to utilize additional ground planes for shielding.  One final practicality to consider, always route traces perpendicular on adjacent routing layers, e.g., on the 6-layer stackup, side to side on Internal Routing Layer 1 and top to bottom on Internal Routing Layer 2.  This technique increases routing efficiency and also minimizes crosstalk.

 

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