No, if you quit and become a consultant, you become richer—the up-side. The down-—you are on the job 24/7/365.
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]; [log in to unmask]
Sent: Wed, 27 May 2009 1:45 pm
Subject: Re: [TN] humidity test failure
So, if I quit, you become richer, can we share your
extras?
Inge
----- Original Message -----
From:
[log in to unmask]
To: [log in to unmask] ; [log in to unmask]
Sent: Wednesday, May 27, 2009 7:08
PM
Subject: Re: [TN] humidity test
failure
Hi Inge,
"Why do we repeat all failures that have
been known for decades?"
Easy, most companies get rid of their experienced
people. And the new hires simply do not have the time to learn about anything
that happened previously.
——sure keeps consultants busy,
though.
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To:
[log in to unmask]
Sent: Wed, 27 May 2009
1:02 pm
Subject: Re: [TN] humidity test failure
We
had an awful lot of environmental test chambers, and we followed MIL-STD like
a blind klinging to his stick. With time, we have realized the questionable
relationship between those tests and the unpredictable mother Nature. The
exact repetition of temperature up, temp down, dwell, temp down=2
0etc does not
always correspond to the erratic reality with endless variations and
combinations of condensation and vibration, heat and salt, power switching and
deep freeze, sun irradiation and sand blast , very short exposure followed by
extremly long one etc etc. I listened to a guy who was a successful design
manager, whose motto was 'skip all testing, do the right design or process
from the beginnin g' . Easy said, but still interesting topic. Am brought up
with MIL-STD, so I'm little ambivalent, but I try to think like him. And, in
fact, with all billion hours of testing everything on this planet, should we
not have background enough for avoiding all disasters..like corroded ceramic
caps, for instance. Why do we repeat
all failures that have been known for
decades?
Inge
----- Original
Message ----- From: "Chris Mahanna" <[log in to unmask]>
To:
<[log in to unmask]>
Sent:
Wednesday, May 27, 2009 6:34 PM
Subject: Re: [TN] humidity test
failure
Hi Wayne,
Agreed. The DUT
probably slipped close to, or below dew. Close can be just as bad. And, surely
there is trapped ionics. But, I suspect a correlation ranking might show those
non-wetted solderable surfaces as your real
culprit.
Ability to control the chamber and DUT is highly
dependent on absolute humidity. 85/85 is very tough. Anything higher is crazy.
=2
0 The common 25-65C, 90% is quite difficult without good multi loop control. If
you're cycling a heavy assembly you will probably want to use the surface temp
as an input to your controller.
IPC-9201A is a good source of info.
NPL has several papers.
Fully processed comb patterns can
'survive' 85/85 or 25-65/90 SIR/ECM tests for 1000 hours without cc, but it's
not
easy.
Chris
-----Original
Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of
Thayer, Wayne
Sent: Tuesday, May 26, 2009 10:01 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 n eed 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 a
t: 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 fiel d): 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 o
f 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
-----------------------------------------------------
|
