Mornin' Grant & All -

The argument that conformal coating can be applied satisfactorily over the
leavings of low residue flux, or any other residue, could only be considered
valid if the conformal coating had been retested and passed  the
qualification requirements of IPC-CC-830, MIL-I-46058, or whatever
specification is valid in the case of that material.

IMHO, any statements by the formulator of any of the materials which are not
supported by this data would have to be considered trivia.  I think we've
all seen the cases of vessication, where the water molecule has passed thru
the vapor permeable barrier of the coating and attached itself to a
contaminant on the surface of the board, creating a microscopic cluster of
bubbles.  That is just one example of what may take place.

Regards - Kelly


-----Original Message-----
From: Grant Emandien <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, March 20, 2000 3:29 AM
Subject: [TN] Coating of assemblies with no clean fluxes


>Hi all,
>
>The debate on cleaning of fluxes as well as the use no-clean fluxes seems
to
>hang around forever. We have been informed by our solder an flux supplier
>that assemblies with no clean fluxes can be conformally coated without the
>need to clean the boards.
>
>The argument is that the high temperatures of the reflow oven 'burns off'
>the active ingredients, leaving only inactive residues. These flux residues
>do not have to be cleaned and can supposedly be coated. The rep. believes
we
>are taking a backward step by possibly opting to use water-based flux. Is
>this pure sales talk?
>
>Is anyone able to offer any advice or insight, or been able to assess the
>environmental and electrical performance of such assemblies.
>
>Regards
>Grant
>
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