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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M.
Date:
Wed, 27 May 2009 14:55:32 -0400
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text/plain (421 lines)
Werner,

Ingemar's offer sounds too good to pass up. 




Werner,



Ingemar's offer sounds too good to pass up.  The real problem is what

would you do with all of the free time? 



Regards,

George

George M. Wenger

Andrew Solutions

Senior Principal FMA/Reliability Engineer

40 Technology Drive, Warren, NJ 07059

(908) 546-4531 (Office) (732) 309-8964 (cell)

[log in to unmask]

-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge

Sent: Wednesday, May 27, 2009 2:47 PM

To: [log in to unmask]

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 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



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