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September 2006

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Tue, 12 Sep 2006 11:03:30 +0300
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The electrons pile up on the inside of the corner, just like Schumacher
and Alonso.

Brian

Wayne Thayer wrote:
> I have heard and read about a phenomenon which sounds kind of scientific
> but which I have never seen.  This is that if you have an acute angle in
> an etched circuit trace it will "trap" etchant and thus over-etch.  This
> is actually mentioned in Joseph Fjelstad's flex circuit book people have
> been talking about.
>
> I've done lots of etching and haven't seen this effect at all.
> Actually, my experience has been that inside corners under-etch, not
> over-etch, which I presume to be the result of the same hydrodynamic
> phenomenon quoted by the proponents of the over-etch theory:  Surface
> tension causes the etchant to stick in the corners.  This "stuck"
> etchant quickly becomes saturated with copper, and the etching process
> stalls because not as much hot, high pressure etchant can get to the
> affected area.
>
> Not that I intentionally design circuits with acute angles in the
> traces--I think they are non-optimal for other reasons, but I want to
> make sure I'm doing the right thing for the right reason.
>
> Wayne Thayer
>
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