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January 1998

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Subject:
From:
Paul Gould <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Sun, 4 Jan 1998 14:06:46 +0000
Content-Type:
text/plain
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text/plain (64 lines)
We implemented no clean flux about 4 years ago so this is a bit
anecdotal. Firstly, we opted for spray application using a retrofit
system for our flow solder machine supplied by Blundell in the UK who
were very helpful. You can't use normal fluxes in a spray system as the
solids content is too high and clogs the nozzles. With a low solids no-
clean flux, the spray system enables rapid changeover to different types
of flux for evaluation.

We used the standard MIL spec for ionic cleanliness (can't remember the
exact value) and tested sample boards with an Ionograph. Watch the
interpretation of the results from this test as different machines give
different values which have to be corrected to compare with the MIL
spec. I believe this is quoted in the spec.

Once we found a flux which worked well for us, we found ATE testing to
be no problem as the soldered joints did not have any residue, only the
solder mask surface. Cosmetics were good although high gloss solder mask
shows more marking then semi-matt solder mask.

Not only have we eliminated cleaning and use of solvents, but the amount
of flux and thinners has gone down from maybe 8 litres per day to around
a 5 litres a week, a big plus for the environment. Of course, no-clean
solder paste is an easier option and much of our throughput is now
surface mount.

Happy New Year and good luck.

Dhawan, Ashok wrote:-
>We are currently using water soluble flux soldering and considering
>seriously to change process to no-clean flux soldering. we do not do
>conformal coating.That way we need same info waht Alan has asked for.
>Can we also have access to experts.
>
>> ----------
>> From:         Alan Kreplick[SMTP:[log in to unmask]]
>> Sent:         December 30, 1997 12:51 PM
>> To:   [log in to unmask]
>> Subject:      [TN] Flux Evaluation
>>
>> Any Technetters out there willing to share information on their
>> evaluation
>> and implementation of no-clean flux at the wave solder process (on
>> boards
>> that are not conformally coated but are in-circuit tested).
>>
>> What criteria did you use: ionics, ICI testability, solderability
>> performance, cost, ???
Paul Gould
Teknacron Circuits Ltd
[log in to unmask]
Isle of Wight,UK

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