In surface mount only situations, I generally see results in the low single
digits  (mg/sq.cm.).  Through hole and mixed assemblies usually in the upper
single to lower double digits.  For line control, I currently run
unpopulated "standard" boards over our wave lines and compare data day to
day.  Two Seho wave solder lines provide cleanliness numbers of 5 or less
while two are generally almost twice as high.  I haven't found the reason
for the difference but all four lines are tested with the same profile
recipe although no two wave lines are exactly alike in design.

The results were obtained on an Omegameter 700 run at 100F with a 3 minute
immersion (data changes less than 5% in 30 seconds after 3 min.).  The unit
is standardized with NIST traceable NaCl solution and no fudge factors are
employed to massage the result.  I intend to start checking immersible
boards that have had some hand assembly.  Results will generate some data
regarding the use of flux core and any additional flux.  The biggest problem
with Omegameter testing of finished assemblies is that not all components
are sealed and some shouldn't be immersed in water alcohol.

Your point about clean components is important.  I'm not sure that we always
know the cleanliness of our components.  In our case, we specify cleanliness
of fab boards but I don't know that components are specified or controled
with regard to cleanliness.  (Bare Boards tend to read 3 or lower).

Regarding the reactivation of flux components - who knows? I check the
boards and the result is what it is.  I look for trends and sudden blips.
Some times it's interesting to check one recipe against another with the
same "standard" board.

George

-----Original Message-----
From: Morse, Carrie [mailto:[log in to unmask]]
Sent: Tuesday, April 22, 2003 6:00 PM
To: [log in to unmask]
Subject: [TN] Omega Testing AND No-Clean


This question goes out to all those with No-Clean Chemistry Experience --
Especially
those who manufacture No-Clean Paste, Flux, and Cored Wire.

Once a circuit card assembly has been assembled and soldered with No-Clean
products .... Assuming (I know I know...) that the fluxes have been fully
activated,
what type of results should I expect to see....Assuming....that the boards
and components were
"clean" prior to assembly.

More specifically, will Alcohol "reactivate" the no-clean flux or "free"
contaminants that will
register on the Omega Tester?

-Carrie

P.S.  And No smart remarks like "How clean is clean" and "You know what
happens when you assume".

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