[SI-LIST] Re: 90 degree bend
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "dgun@xxxxxxxxxx" <dgun@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Tue, 31 Aug 2004 10:10:00 -0700
Daniel,
In PCBs, the trace widths used to achieve 50 ohms are rarely wider than 8
mils and are often 5 mils. At these widths, the effects of right angle
bends are undetectable at edge speeds as fast as 18 pSec. (What's the
first harmonic of an 18 pSec edge? Higher than 10 GHz I think and that is
clearly multigigahertz) It is true that with trace widths of 50 mils plus,
the effect is visible.
Since the principal use of traces, at least by the subscribers of this
list, is for PCBs, the trace widths are likely to be less than 10 mils and
the statements about right angle bends being of no concern hold.
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: <dgun@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 8/31/2004 8:51:12 AM
> Subject: [SI-LIST] Re: 90 degree bend
>
> Lee,
>
> Which statement are you referring to? There are two below: etchant
causing
> break in trace and noticeable effects on multi-ghz boards.
>
> Scott,
>
> 10 and 25mil alumina is very common in microwave designs, giving a 50-ohm
> trace width of roughly 10 and 25mil, respectively. Sorry, couldn't help
> picking nits.
>
> --
> Daniel
>
> From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
> > This is another of those statements that are not true and should not be
> > repeated. Where did this one start?
> >
> > I use right angle bends in every signal, or rather, I allow them, even
2.4
> > GB/S.
> >
> > How long will it take to get the misinformation purged from our
profession?
> >
> > Lee W. Ritchey
> > Speeding Edge
> > P. O. Box 2194
> > Glen Ellen, CA 95442
> > Phone- 707-568-3983
> > FAX- 707-568-3504
> >
> > I just used the energy it took to be angry to write some blues.
> > Count Basie
> >
> >
> > > [Original Message]
> > > From: Andrew Ingraham <a.ingraham@xxxxxxxx>
> > > To: <si-list@xxxxxxxxxxxxx>
> > > Date: 8/30/2004 9:13:51 AM
> > > Subject: [SI-LIST] Re: 90 degree bend
> > >
> > > The other problem is that right-angle bends tend to concentrate
etchant
> > and
> > > may result in over-etching the trace a bit in the corner. Presumably
it
> > can
> > > lead to a break in the trace.
> > >
> > > For most of us, that's the reason why we don't use right-angle
corners.
> > The
> > > electrical effects become noticeable if you're doing multi-GHz boards.
> > >
> > > Regards,
> > > Andy
>
> --
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