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Tue, 11 Mar 2003 11:57:24 -0500 |
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Hi Tom
The only flaw in your premise is the second part of number 2 - how are you sure you have removed all washable flux residue? No flux residue under low clearance components? None stuck under connectors? Magic!
It comes down to:
- how clean is clean enough (end use environment, reliability requirements)
- what do you have when you mix no-clean with a bit of residue from an OA or other type of flux?
It is easier to sleep nights if you don't mix flux. You may not have a problem with cleaning and then using no-clean, but it's easier to be sure if you can use no-clean for everything.
regards,
Graham Collins
Process Engineer,
Northrop Grumman Canada Corporation
Halifax
(902) 873-2000 ext 6215
>>> [log in to unmask] 03/11/03 12:39PM >>>
I've read the recent questions and information concerning mixing of
fluxes. I agree - do not mix flux types when soldering. However,
here's one for you that can be looked at from a couple of angles....
1. I build a board - wave solder using washable flux. Flux is
activated, does it's thing, and board is soldered.
2. Water Wash and Dry the board. All washable flux residue is gone.
3. Add a couple of more components that CANNOT be washed (water will
enter the component and ruin it), using NO-CLEAN.
4. Board is done.
Technically, I have used 2 types of fluxes on one assembly....
Another scenario:
1. Board (described above) is finished. But, fails test - I find a bad
component...
2. I have to use NO CLEAN to replace the component because I cannot
water wash the board (remember the other components that cannot be
subjected to water wash..)
3. Board is done. Passes test - finished.
Again - Technically, I have mixed fluxes on the same assembly.
In the above description, I do not see a problem - or am I missing
something?
Thanks,
Tom
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