Graham, sorry I wasn't quicker on the trigger. The alcohol/water dishwasher system that we use before conformal coat was marketed by Electronic Controls Design as the Model 7300 Meg-A-Rinse SMD. This system purges the wash chamber with nitrogen before the alcohol/water wash. It's a good design, with explosion-proof this and that, sensors, interlocks, and fail safes - we've never had a door blow off, and I'm not worried about it. The 75% IPA/25% DI water mix does a decent job of ensuring final ionic cleanliness and removing fingerprints and dust. Much better than the degreaser and manual alcohol/water spray process that it replaced. We verified this with Omega Meter testing and 10-day humidity on conformal coated samples (virtually no mealing). The neat thing about this system is that we get a final clean and cleanliness test with one operation, because the system monitors resistivity of the mix in the wash sump. As long as we have 1000 square inches of board surface being cleaned, resistivity of 2 megohm-cm. is consistent with 14 micrograms NaCl/sq.in. equivalent in the Omega Meter. Of course, we typically get much better than 2 megohms. We still maintain an Omega Meter 600SMD for lots smaller than 1000 square inches, but it's rarely used. We continue to use an official acceptance limit of 14, but we would be surprised to see anything higher than 2 or so. By the way, we currently use RMA in all operations, so we're not too concerned about sealing in anything nasty. We're beginning a project to implement water soluble flux, and will be developing a contamination tester from CSL to assess localized areas of contamination on board surfaces. Too bad that ECD discontinued the 7300 before they sold their dishwasher business to AAT. We have two machines, and they've worked very well for about 10 years, but it's getting difficult to find parts. And nobody offers anything comparable, believe me I've looked. Joe Kane BAE SYSTEMS Platform Solutions Johnson City, NY -----Original Message----- From: Graham Naisbitt [mailto:[log in to unmask]] Sent: Tuesday, April 22, 2003 9:55 AM To: [log in to unmask] Subject: Re: [TN] Cleaning Question - Rinse water resistivity? Bill For some peculiar reason, the message posted by Joseph Kane has been re-routed as though it is from me!? Jack - have you got your Technet ears on? My question is actually shown at the bottom of this lot.....and I agree with you, but that was going to be my next question! BTW, I am aware of a couple of IPA cleaners, but only 1 of the batch type described - that blew its door across the factory one day, long ago! > 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 >> >> --------------------------------------------------- >> 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 >> ----------------------------------------------------- > -- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------