Carrie, I will try to answer your questions, although requiring me to cease my smart-ass comments limits my writing flair..... Brian Ellis has already given a pretty good answer and I will give some of my viewpoints. Your question is basically what will low residue fluxes do to the numbers I get in my cleanliness tester, and what should I do in the ensuing panic? The answer is that the numbers will get higher. The panic comes when you try to attach historical numbers and meaning to that increase. As Brian indicated, the fluxes are not reactivated by contact with isopropanol. The heat of soldering causes some chemical changes that are not reversible. The flux residues do not really absorb isopropanol either. However, isopropanol may solubilize/dissolve the flux residue, which then makes the extract solution more conductive, which then registers on the machine. You get an increase in reported level, but it means nothing to reliability. Ionic cleanliness testers should not be used for acceptance of product. They should be used for process control only. Anyone who deals with ionic cleanliness testing should read through IPC-TR-583, An In-Depth Look at Ionic Cleanliness Testing. That study, done in the 94-95 time frame, showed the instruments to have a lack of repeatability and reproducibility, even on the same machine type. Equivalence factors are bogus. The only valid use is for process control. If, for a particular assembly, I had a value of 5 last week, 5 yesterday, and today it is 15, something changed and I better go figure out what it was. From my days as a consultant, in the early 90s, when many manufacturers were transitioning to low residue fluxes, I lost tract of the number of panic calls when people who were used to seeing 5 started seeing 50. I'll tell you what I told them, throw out the historical "good" and "bad" numbers and stop using the machines for product acceptance. Determine what your new number means with respect to reliability, do designed experiments to find out the process window around the new number, then use the new number for process control only. It was harder 10 years ago because the mil-spec ROSE method was in so many contracts, but most listened. It can be done. Your machine is giving you a signal. Consider it an FM signal where mil specs are AM stations. You have to understand your signal and what it means. Your last question related to the freeing of contaminants. I would say generally this is not a problem, but if you apply high levels of flux to your assemblies and the ROSE tester dissolves them, there is the possibility of the flux residues being re-deposited in areas you don't want them, such as DIPswitches or relays. If your tester has sprays or a reasonable method of solution agitation, I think the occurrance unlikely. To rule this out, you can take some DIP switches, run them together with a flux loaded board. Run surface reflectance FTIR on the contact surfaces and see if flux residue has been deposited. As you might guess, I have written several papers and articles on the topic over the years. If I recall, I bundled them into a ZIP file and gave them to Jack Crawford for IPC use. He gets calls from newbies in the area all the time and this is some reading he can give them to educate them on the issues, usually with the statement "contact Doug for more details". Maybe Jack can send you this file. Doug Pauls Rockwell Collins Still on my first Diet Dew of the Day "Morse, Carrie" <CMorse@CIRTRONIC To: [log in to unmask] S.COM> cc: Sent by: TechNet Subject: [TN] Omega Testing AND No-Clean <[log in to unmask]> 04/22/2003 04:59 PM Please respond to "TechNet E-Mail Forum."; Please respond to "Morse, Carrie" This question goes out to all those with No-Clean Chemistry Experience -- Especially those who manufacture No-Clean Paste, Flux, and Cored Wire. Once a circuit card assembly has been assembled and soldered with No-Clean products .... Assuming (I know I know...) that the fluxes have been fully activated, what type of results should I expect to see....Assuming....that the boards and components were "clean" prior to assembly. More specifically, will Alcohol "reactivate" the no-clean flux or "free" contaminants that will register on the Omega Tester? -Carrie P.S. And No smart remarks like "How clean is clean" and "You know what happens when you assume". --------------------------------------------------- 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 -----------------------------------------------------