OSH Park 4 layer stackup and impedance data

Note: If you want to use this data for designing your own PCBs, please ensure that my stackup data matches what OSH Park is currently using.

Here’s some data on the OSH Park 4 layer stackup:

osh park 4 layer stackup data from website

If you want a 50 ohm trace on the top layer and the second layer is ground (as it should be) then you want the trace width to be 14.47 thousands of an inch:

osh_park_4lyr_microstrip_top

I used Agilent LineCalc this time. It performs an actual e-mag simulation to synthesize the correct line width. I am quite confident that this is the correct value given the inputs.

 

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6 Comments

  1. Nice write up.
    I am just getting into differential pairs and was wondering why you have the Z0e set to 100 instead of the Z0.
    Furthermore, what values might you recommend for USB 90 ohm differential pairs using the OSH Park 4-Layer Stackup.

    Thank You.

    1. I think you caught a mistake on my part. Thank you for notifying me.
      As you’ve figured out, I’m not an expert on trace impedance.
      Putting the numbers into Wcalc, I come up with the following for a 90 ohm differential coupled microstrip:
      Wcalc screenshot

    1. Are you sure? I’ve calculated your traces using kicad and TXLine. Both of them show about 70 Ohms impedance for your traces.

      1. I’ve lost the images from my website as you can see. I will update this post and hopefully you will agree with my new calculations. Thank you for commenting.

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