Steve,
forgot to tell you that with very high frequencies and high voltages, it's
sometimes meaningless to use concoat (except for Parylene C). Acrylics don't
stop water. If water diffuses in the acrylic, any violent issue can start
and in these circuits, the end is usually a big POFFFF! That's why the RF
guys want them naked. The boards.
Inge
----- Original Message -----
From: "Steve Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 27, 2009 4:22 PM
Subject: Re: [TN] humidity test failure
Inge has sent some examples. As usual, Inge's photos are quite
remarkable, and look just like Wayne's photo.
Check out: http://stevezeva.homestead.com/files/For_TN.doc
Steve
-----Original Message-----
From: Hernefjord Ingemar [mailto:[log in to unmask]]
Sent: Wednesday, May 27, 2009 8:17 AM
To: Steve Gregory
Subject: RE: [TN] humidity test failure
Steve & Wayne,
looks like what I dealt with a couple of years ago: high electrical RF
fields and contaminated water droplets equal to Tin and Silver migration
and finally catastrophic failures. DC not the master driver of this
mechanism.
I'll send a bunch of pics to Steve.
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: onsdag 27 maj 2009 14:00
To: [log in to unmask]
Subject: Re: [TN] humidity test failure
Good Morning!
Half the week down already. That's another nice thing about 3-day
weekends; you also get a 4-day work week either prior to, or after the
weekend.
I have Wayne's picture posted now. It's at:
http://stevezeva.homestead.com/files/C23_Humidity_failure.JPG
Definitely some kinda' junk there!
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne
Sent: Tuesday, May 26, 2009 9:01 PM
To: [log in to unmask]
Subject: [TN] humidity test failure
Hi Technet Gurus!
I have attached a picture of a part responsible for excess current draw
during an extended humidity/temperature cycling test. (I copied Steve so
he can hopefully post!)
The board was carefully solvent cleaned, but no SIR test validating the
process strips all ionic contamination. The board is in an enclosure
where plenty of ionic contaminants are available.
Humidity was supposed to not exceed 90% and was to be non-condensing
during cycling. There were a handful of components which displayed
similar deposits on the same circuit board. These were the only parts
biased during the humidity test. I believe the evidence suggests at
least some condensation occurred. To me the deposits look like salts.
But what do "the experts" think?
Is there any rule of thumb as to humidity levels where we are nuts to
try to survive without conformal coating? Part of the adjacent
circuitry contains RF devices and those guys get panic-stricken when
told we probably need to conformal coat!
Wayne Thayer
This e-mail and any files transmitted with it may be proprietary and are
intended solely for the use of the individual or entity to whom they are
addressed. If you have received this e-mail in error please notify the
sender.
Please note that any views or opinions presented in this e-mail are
solely those of the author and do not necessarily represent those of ITT
Corporation. The recipient should check this e-mail and any attachments
for the presence of viruses. ITT accepts no liability for any damage
caused by any virus transmitted by this e-mail.
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please
visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please
visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
