If you go back and read the original 1972 work by the Navy on the development of MIL-P-XXXXX, which became MIL-P-28809, the original reason for PWA cleanliness testing was to make sure the assembly was clean prior to the application of conformal coating. The services were also concerned since MIL-RA fluxes were coming into use at about that time; these had significantly higher activator levels compared with the traditional RMA formulations. Before just concluding that since you don't conformally coat assemblies there is no need to do cleanliness testing, remember that component density, solder joint spacing etc. were crude compared to today's complex, high density multilayer assemblies. So cleanliness testing will provide a safety net that protects the PWA maker as the industry packs more and more with higher reliability requirements into a fraction of the space allowed in the early 1970's While on the topic of the changes in complexity and density since the '70's, let us not forget that the 'no clean' fluxes came into use (primarily in customer premise telephone circuitry) in the late '80's-- think how much has changed since then. [It always helps to consider things in context!] Bill Kenyon Global Centre Consulting 3336 Birmingham Drive Fort Collins, CO 80526 Tel: 970.207.9586 Cell: 970.980.6373 **************Start the year off right. Easy ways to stay in shape. http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------