Werner,
1) So if the IPC spec is wrong, why did we leave it as such in the last
round of discussions?
2) I agree crazy data would be measured with condensation on the boards.
However, wasn't the whole idea of the 96 hour latent period put in there
because that was the time found that it would take to lose any condensation
that might form during an uncontrolled ramp-up, where both temperature and
humidity controls were turned on at the same time?
3) I agree that the spacing and method of attachment of test wires is
important.  I never said otherwise.
4) I have never had the failure of an external reservoir on a humidity
chamber - once I made sure the floats were able to freely go up and down
because the float arms were no longer bent!  :)
5) I am only 46 and have only been in the industry for 10 years, so the 80's
are ancient to me.   :)

regards,
Bev
Nortel Networks

> -----Original Message-----
> From: Werner Engelmaier [SMTP:[log in to unmask]]
> Sent: Sunday, November 28, 1999 8:20 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] SIR
>
> Hi Bev,
> Brian is correct on all points, and just because people (that is who write
> Nortel or Telecordia or Bellcore or IPC specs, after all) established
> definitions does not make it a "fait accompli"; only sloppy use of
> language
> and a perfect source for miscommunication.
> Also, please do not misquote 'almost' ancient (I was part of it) work by
> Bell
> Labs; there indeed was a significant difference how one ramped up--the
> temperature increase had to precede the humidity increase and conversely,
> the
> humidity had to be decreased before the temperature was reduced. Crazy
> data
> resulted when condensation occurred.
> In both SIR and ECM it is very important, that only the areas to be
> measured
> contribute to the reduction in resistance. It thus becomes very important
> how
> the test leads are attached to the test vehicles and how much distance
> there
> is between attachment points.
> We have found, that for boards for which CAF paths are created PTH-to-PTH
> during T/RH/V exposure, such path are also created even if no bias is
> applied
> during the T/RH exposure; this path turn quickly into CAF upon application
> of
> the sensing voltage.
> One other thing we found was, that unless we supplied water to the
> internal
> wet-bulb reservoir via a peristaltic pump rather than an external refill
> reservoir, the internal reservoir can run dry.
> All in all, this is a rather complex subject matter.
>
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL  32174  USA
> Phone: 904-437-8747, Fax: 904-437-8737
> E-mail: [log in to unmask], Website: www.engelmaier.com
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> information.
> If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
> 847-509-9700 ext.5365
> ##############################################################