Subject: | |
From: | |
Date: | Thu, 24 Apr 97 08:08:00 PDT |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
----------
From: D'Auteuil, Gerry
Sent: Wednesday, April 23, 1997 9:20 AM
To: TechNet-request
Subject: RE: Controlled Impedance Backplane
To the person at Lockheed Martin in Canada if you contact Robert Beland
at 1-508-933-1924 he has an answer on manufacturing this board to the
required impedance.
----------
From: TechNet-request[SMTP:[log in to unmask]]
Sent: Friday, April 18, 1997 3:26 PM
To: Technet
Subject: DES: Controlled Impedance Backplane
I am trying to specify the stackup for a controlled impedance
psudo-VME backplane. This backplane has controlled impedance traces
of
100 Ohms and 50 Ohms. The current finished board thickness is 0.093"
and consists of ten layers, 4 of which are controlled impedance
layers.
In discussion with a local fab shop I am finding that in order to
create 100 Ohm traces, the width of the dielectric (for FR-4) is
prohibitive.
The only alternatives are to cut back on the number of layers or
substantially increase the PWB thickness (which causes a large
headache in finding components with sufficient lead length).
I have two questions concerning this and I hope someone out there
can
help:
a.) Are there any major drawbacks to producing a backplane with,
say,
4 layers only? i.e. Is there a limitation on the minimum number of
layers for a backplane PWB that I don't know about?
b.) How are standard 0.093" OTS VME backplanes produced? They seem
to
me to have a fair number of layers without resorting to thick PWBs
or
superfine traces.
I hope that someone out there has had experience with this kind of
PWB
and can help me.
Thanks in advance,
--
Max.P.Harris
Hardware Design Engineer
Lockheed Martin Canada, Inc.
'Nil illegitime carborundum'
**************************************************************************
*
* TechNet mail list is provided as a service by IPC using SmartList v3.05
*
**************************************************************************
*
* To subscribe/unsubscribe send a message <to: [log in to unmask]>
*
* with <subject: subscribe/unsubscribe> and no text in the body.
*
**************************************************************************
*
* If you are having a problem with the IPC TechNet forum please contact
*
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]
*
**************************************************************************
*
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]> *
* with <subject: subscribe/unsubscribe> and no text in the body. *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] *
***************************************************************************
|
|
|