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Date: Wed, 04 Dec 1996 07:10:33 -0600
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From: Pat McGuine <[log in to unmask]>
Subject: GEN: Acceptable level of indor humidity?
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Status: RO

Hello All:

Could anyone please advise as to what the acceptable range of indoor
humidity for a electronics assembly facility is?

Also, what methods have been successful in boosting the humidity level
during the winter months - can you put me in touch w/ a contractor who 
has
installed humidity increasing equipment in your facility.


-Pat-

-------------
Patrick McGuine
Nicolet Instrument
[log in to unmask]
(608) 276-6334

Pat,

There are several factors one should consider regarding rH in your 
facility.

One factor worth mention is ESD. To the best of my recollection, 40%rH 
is the lower end one might desire to minimize inadvertent static 
generation.

On the other end of the spectrum, increased rH will accelerate 
solderable surface oxidation and substrate absorption, a reasonable 
upper limit might be  60%rH.

Therefore, 50% +- 10% would be a good starting point. I do not know of 
any formal studies done on this and the data above is strictly "bits 
and pieces" from various trade sessions, conferences and seminars.

Another issue is HVAC efficiency and creature comforts. This is pretty 
clearly discussed in the book :

"Industrial Ventilation"
by: Commitee of Industrial Ventilation
P.O. Box 16153
Lansing Michigan, 48901
(513) 661-7881

Library of Congress Catalog Card No. 62-12929

I would suggest that you contact your local HVAC service organization 
who has working knowledge of your facility heating and cooling systems. 
Most likely they can be helpful in choosing the best humidity control 
system for your building's specifics. 

A word of caution: as one attempts to "economize" by heating outside 
air and recirculating the warm inside air thereby reducing makeup, the 
differential barometric pressure of the building will tend to fall as 
you begin "starving" the exhaust systems in your 
soldering/cleaning/etc. equipment. Be sure to evaluate the proper make 
up air as you explore the solutions to this challenge.

Regards,

Edward J. Popielarski
QTA Machine
(714) 364-6614
[log in to unmask]






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