[SI-LIST] : Bends in PCB Traces (renamed from MECL System Design Handbook)

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From: Scott McMorrow ([email protected])
Date: Tue May 22 2001 - 06:43:34 PDT


Gus Panella of Molex and I have collaborated on some test structures and
measurements of right angle bends which would be appropriate
to share with the list at this time.

We are prepared to share a report containing data, measurements and
observations with anyone willing to contact us directly via email.
The report is titled:

" Impedance Discontinuties of Right Angle Bends"

Gus and I included these structures on a board we co-designed
6 months ago for some advanced characterization work.
All of our trace bends were created with circular arcs, in order to
totally eliminate the loss at corners. "Just for fun" we placed other
test structures on the board to see what the difference might be.
Because of the recent discussions of bends on the si-list, Gus has
just gotten around to making some measurements of these structures.
We have both agreed that sharing this data makes good sense at this

To give you some background, the board was fabricated with
state-of-the-art traces, materials and manufacturing processes.
The traces measured are of asymmetric stripline construction for
precise impedance control to 50 ohms. They are 12.5 mils wide and
built on Rogers 4003 substrate material and designed to propagate
signals at bandwidths greater than 10 GHz with low loss.

Here is a summary of the results:

1) We can measure the effects of corners with a "slow" TDR.
2) We can correlate this data to the available microwave literature.
3) We can make recommendations on when corner effects are
important and when they are not.
4) We can quantify the effects of radius corners vs. square corners
vs. angled corners.
5) We can tell you where to best place corners in your designs.
6) We believe that these results are valid for all corners used
on 50 ohm traces.

Again, if you would like a copy of our preliminary report, please
contact Gus or myself. We will send it out later today.


Gus and Scott

Gus Panella
[email protected]

Scott McMorrow Principal Engineer SiQual, Signal Quality Engineering 18735 SW Boones Ferry Road Tualatin, OR 97062-3090 (503) 885-1231 http://www.siqual.com

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