Graham,
I am familiar with the "dishwasher" machine that you have described. My
curiosity is about the dishwasher machine where you use 75% isopropyl
alcohol and 25% water. Was this dishwasher specially made for this solution?
The reason I ask is due to the explosive nature of IPA. Normally anything to
do with IPA requires explosion proof motors and accessories.
Could you please comment? (cud u pls com?, I couldn't resist)
Thanks,
Bill Kasprzak
Moog Inc. Manufacturing Engineering, Electronics
> -----Original Message-----
> From: Graham Naisbitt [SMTP:[log in to unmask]]
> Sent: Tuesday, April 22, 2003 6:47 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning Question - Rinse water resistivity?
>
> > We have set up our Emulsonators with wash time of 30 minutes and
> > rinse time of 15, but the rinse cycle will continue for up to 30
> > minutes if wash sump resistivity does not reach at least 1
> > megohm-centimeter. If this level is not met within 30 minutes, the
> > cycle will abort.
> >
> > FYI to the group, this is a batch "dishwasher" style machine, with
> > counter-rotating spray arms at top and bottom, and separate wash
> > and rinse tanks. The wash tank contains water with 5 or 10% of wash
> > chemistry, in our case Bioact EC-7R. Bioact is not miscible, and
> > separates, but pumping action creates an emulsion that is pretty
> > effective at removing RMA flux.
> >
> > After the wash cycle, the emulsion drains back into the wash tank,
> > the valves close, and DI water is pumped into the cleaning chamber
> > from a separate tank and recirculating loop. In this loop, rinse
> > water drains from the wash chamber into a decanter, where Bioact
> > floats to the top, and the water returns to the rinse tank. Rinse
> > tank water is pumped through a particle filter, carbon, and
> > mixed-bed before it flows into the wash chamber.
> >
> > Since water does not mix with Bioact, the rinse operation uses
> > water to mechanically remove the solvent, basically "pushing"
> > the Bioact residue off of the board surfaces. Any solvent left
> > on the board will include flux and ionic residues dissolved within.
> > In our process, boards come out with no visible flux residue, but
> > we use these systems for gross flux removal, not final ionic
> > cleanliness. Before conformal coat, we clean with a separate
> > dishwasher containing 75% IPA and 25% DI water.
> >
>
> Joseph
>
> So before you coat - and seal in anything nasty - how do you determine if
> the end product will be reliable?
>
> Do you do any ROSE / SEC testing? If so, what level do work to?
>
> --
> Regards Graham Naisbitt
>
> [log in to unmask]
>
> Cell: +44 79 6858 2121
>
> Concoat Limited - Engineering Reliability in Electronics
>
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