Hi Wayne,



Not that often, but once in a while I have a customer with a similar problem. In cases like that we mechanically remove the component(s) of interest (so, no additional heat would be applied) and then run FTIR and SEM/EDS tests on the residue. Guessing is good, but data - much better :-)



Regards,



Vladimir

SENTEC





SENTEC

11 Canadian Road, Unit 7.

Scarborough, ON M1R 5G1

Tel: (416) 899-1882

Fax: (905) 882-8812

www.sentec.ca





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

From: Steve Gregory <[log in to unmask]>



Date:         Wed, 27 May 2009 06:59:42 

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



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