Jim
Quite an interesting one this, with implications beyond the obvious.
Firstly, despite what Mike says, I think most of us would agree that a
properly cleaned board, even soldered with a reasonably aggressive flux,
is less likely to be unreliable than an uncleaned one, under some given
conditions. Experience has proved this.
Then there are some "no-clean" fluxes/pastes which are REALLY dangerous,
so it is easy to imagine that someone could have been bitten.
However, I strongly suspect, reading between the lines, that this notion
may apply to conformally-coated boards. Here, there is a distinct
problem with "no-cleans" unless the homework is VERY carefully done and
the process is constantly requalified, including checking the
contamination on every batch of incoming components. Personally, I would
never advise a client to use "no-clean" products if the products were to
be coated. It could be a time bomb waiting to go off under your feet
even years later (especially, no pun, with armament electronics which
may be stored for 15 years and then used for the first and only time
during a period of a few minutes).
Finally, a PCB design which is optimised for use with a mild "no-clean"
wave-soldering flux or paste would be better redrafted if it were to be
changed to a less mild flux and cleaned. Many such boards would be
totally unsuitable for cleaning and the result may be worse than ever,
in terms of reliability, if there were no re-design.
I would therefore want the rumour to be substantiated before any action
was to be taken.
Brian
Jim Jenkins wrote:
>
> Hi everybody,
>
> I was just approached by one of our engineers whose customer told her that
> the Air Force has issued a directive disallowing the use of no-clean fluxes
> on any of their hardware. The customer is flowing down that requirement to
> us. Do any of you know of this directive or what they could be referring to?
>
> Thanks,
>
> Jim
>
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