Well, I have been racking the old memory banks since I posted this problem.  As I
recollect, I saw this problem a few years back when we first looked at using
LPI.  At that time I determined this pneumonia occurred with any rosin flux we
used and did not occur with a low solids resin (read: no-clean).  Also, the rosin
flux had to see the temperature of the solder wave for the film to occur.  If a
pwb was processed with the solder pumps off, no residue could be detected.

I also remember doing some tests in the Ionograph that indicated no abnormal
ionic levels.  The flux manufacturer tested some pwbs and reported that the film
looked to be a surfactant used in the soaponifier.

We have been using this soaponifier for boup coup years.  Perhaps its time to
investigate new chemistry for the in-line cleaner.  Just what I needed - another
opportunity.  Anyway, thanks for the responses.

[log in to unmask] wrote:

> Guessing only, but a chemist's guess.
>
> Sounds like the residue is because the flux has reacted with the soldermask,
> and left a residue of solder mask behind.
>
> Your cleaner removes the flux, but not the mask, so you leave behind mask
> residue.
>
> Any suggestion for an improvement in cleaning stands a good shot at attacking
> the mask.
>
> If this idea is correct, you have one of three choices, maybe four.
>
> 1. Change mask
> 2. Change flux
> 3. Change cleaner
> 4. (the easiest, and least likely to work) Get the boards from flux
> application to cleaning as fast as possible.
>
> Good luck
>
> Rudy Sedlak
> RD Chemical Company

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