Graham Sprague, about 1975, issued a statement about elcos and solvents. They had researched the effects and concluded that a) a few micrograms of all halogenated solvents entering an elco would cause failure within 0 to 6 months; b) aqueous and alcohol cleaning was safe and c) that only the Sprague series xxx was safe as this range was epoxy-sealed and was obligatory for mission-critical apps; all other elcos would allow solvent vapours to enter. However, this does sound more like attack of the rubber seal, where the aluminium case is swaged over it. I suggest you contact the supplier(s) and ask for epoxy sealed types. Brian Graham Naisbitt wrote: > Good evening Techies > > We have a customer who has discovered a "black deposit" underneath an > electrolytic capacitor that has caused a circuit failure. They conformally > coat the assembly using a classic AR coating and claim that the coating > softens the seal on the capacitor. We are awaiting the results of a surface > analysis they are running to determine what the "black deposit" might be. > > We believe that the solvents in the coating might be attacking the capacitor > seal causing the leakage, but cannot understand why this should happen on > components from a reputable supplier. The customer has changed the component > supplier, but the problem seems even more severe. > > The end product is safety critical Class 3 - folks may die if the product > fails. > > Can you good folks maybe shed some light on what might be done to overcome > the problem? > > Change the seal on the capacitor and if so, what type of seal should be > used? > > Anyone with similar experience? > > -- > Regards Graham Naisbitt > > [log in to unmask] > > Cell: 079 6858 2121 > Office: +44 (0)1252 813706 > > Concoat Limited - Engineering Reliability in Electronics > > Web: www.concoat.co.uk and www.concoatsystems.com > > --------------------------------------------------- > 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 -----------------------------------------------------