Rich:
You can find the base value in J-STD-001C para. 8.3, but
the limit of 1.56 micrograms per sq. cm. that is cited was
developed back in the dark ages for rosin based fluxes,
after cleaning with a vapor degreaser. The intent back then
was to ensure that RMA residues on unobstructed surfaces would
not affect adhesion of conformal coat.
There seems to be no established standards for what the
cleanliness limit should be for water soluble fluxes or
no-cleans. And if you ask what the number should be, the
first question back is - what is your application? Does
the service environment include condensing moisture? Are
you coating, and with what? What voltages are you running,
and what is the physical spacing?
How clean do you need to be? No easy answers.
By the way, the limit of 1.56 converts to 10 micrograms
per square inch, but the actual acceptance value will depend
on the test equipment. The equivalence limit of 14 that you
mention applies to the Omega Meter, and the only spec where I
know that's documented is in the long-cancelled MIL-P-29909A,
Table V.
-Joe
-----Original Message-----
From: Macko, Joe @ IEC [mailto:[log in to unmask]]
Sent: Thursday, August 19, 2004 1:20 PM
To: [log in to unmask]
Subject: Re: [TN] Cleanliness Specs
Rich,
Look at J-STD-001, section 8, Cleanliness requirements. Good luck.
joe
-----Original Message-----
From: Rich Lasko [mailto:[log in to unmask]]
Sent: Thursday, August 19, 2004 10:15 AM
To: [log in to unmask]
Subject: [TN] Cleanliness Specs
Good afternoon all,
I am trying to track down the specific cleanliness specs for electronic
assemblies prior to conformal coating. (ie < 14 micrograms/cm sq).
What document is this actual measurement listed in? (MIL-STD-28809)?
Hasn't that been cancelled and superseded by another document?
Please advise where I can get a copy of this cleanliness spec.
Thanks,
Rich
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