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CPWG trace widths and spaces

The Hittite document "Layout Guidelines For MMIC Components" is a great help but they only provide a single dielectric thickness, trace width, trace space and trace thickness combination that gives a 50ohm trace. It would be great to have a list of other combinations that work well with the various Rogers 4350 standard thicknesses. I noticed that many of the Hittite evaluation boards have trace widths and spaces that differ from the recommendations in the document but unfortunately the dielectric thickness and copper/plating thickness isn't mentioned so it is not so easy to duplicate.

Specifically I am looking for something that works well for a trace width of 15 to 20 mils (similar to what the HMC424 or HMC525 evaluation boards use).

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  • Hi Peter,

    To elaborate on Kagan's response.  The HMC525 eval board uses Rogers 4350 on the top layer (Er ~ 3.7)  The RF trace width is 16mils and the ground spacing is 13mils. We use 1/2 oz. copper on the top layer, when plating is complete the finished metal is 2.0 oz. or approximately 2.8 mils.  If you enter these into a grounded CPW calculator you will get approximately 55Ω.  The parasitic effects of the SMA connector drop the impedance to 50Ω.

    Regards,

    Mark


Reply
  • Hi Peter,

    To elaborate on Kagan's response.  The HMC525 eval board uses Rogers 4350 on the top layer (Er ~ 3.7)  The RF trace width is 16mils and the ground spacing is 13mils. We use 1/2 oz. copper on the top layer, when plating is complete the finished metal is 2.0 oz. or approximately 2.8 mils.  If you enter these into a grounded CPW calculator you will get approximately 55Ω.  The parasitic effects of the SMA connector drop the impedance to 50Ω.

    Regards,

    Mark


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