[SI-LIST] Re: Surface roughness of PCB tracks at track/substrate interface ?
- From: "Zabinski, Patrick J." <zabinski.patrick@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 11 Jun 2001 06:15:33 -0500
Steve,
When speaking to PCB vendors, they typically refer to
surface roughness as "toothing profile", and most PCB
manufacturers are able to select a particular toothing
profile from their material vendor(s).
From cross sections of actual boards, peak-to-peak surface
roughness is in the range of 7 to 18 microns for common
PCBs.
If you're interested in reading bit more on surface roughness,
I suggest obtaining/reading a copy of:
TITLE Effect of Surface Roughness on Eddy Current Losses
at Microwave Frequencies
AUTHOR Samuel P. Morgan, Jr.
SOURCE Journal of Applied Physics
VOLUME 20
DATE April, 1949
PAGES 352-362
The paper takes an analytical approach to determining the
loss in a conductor due to surface roughness with different
profiles (e.g., sawtooth, square, etc.) and shows that
surface roughness can sometimes double the loss when compared
to a smooth conductor.
Pat
> Hello all,
>
> I am trying to find out value for the roughness of PCB traces on the
> substrate side of the track.
> As I understand it, a level of roughness is essential in
> order that the
> metal bonds mechanically with the substrate material. However
> I do wonder
> how much this rougness effects the Resistance of the trace at high
> frequencies. Some recent experiments I have carried out
> suggest that it may
> be quite significant. The skin depth is half the solution (I
> think), but I
> need some idea of how 'rough' typical surfaces are in order
> to get some idea
> of losses?
>
> All suggestions on this one are welcome
>
> Many thanks in advance
>
> Steve Rogers
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