Inge, Inge, Inge......
There is no such thing as a salary for a consultant.
You take what comes in [very often very late], pay your bills, and if anything is left over, it is yours.
And Inge, very tricky using a double-negative: "you get money without doing nothing"—gotcha!
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 27 May 2009 2:46 pm
Subject: Re: [TN] humidity test failure
Better you quit, and I take your job and get your salary, I become rich = 10
times what I have now. It's so much , that I can be generous and give you
one half back= you get money without doing nothing.
Inge
----- Original Message -----
From: "Werner Engelmaier /*" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 27, 2009 7:59 PM
Subject: Re: [TN] humidity test failure
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 Message20-----
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=C
2
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=2
0you 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=C
2
"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
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