> 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
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
