From what I've learned from the TechNet experts, no-clean flux can, with the combination of heat, time, moisture and voltage cause leakage. So why use no-clean? That is something to be wrestled with. If I may quote Doug Pauls... "It depends". IMHO no-clean works fine on large pitch or through hole, but where real fine pitch is used or you need high reliability I'd build with a washable flux and wash the board. Best regards, Phil -----Original Message----- From: James Verrette [mailto:[log in to unmask]] Sent: Friday, September 19, 2008 5:18 PM To: Phil Nutting; TechNet E-Mail Forum Subject: RE: Can desoldering and soldering fix a leaky MLCC The board passed ICT testing and final assembled product test. It is believed that something is happening at some point during a 24hour heat soak in a 55 deg C oven. -Jim -----Original Message----- From: Phil Nutting [mailto:[log in to unmask]] Sent: Friday, September 19, 2008 4:44 PM To: TechNet E-Mail Forum; James Verrette Subject: RE: Can desoldering and soldering fix a leaky MLCC Jim, I would suspect resistance from flux or some other foreign matter. We had a board that had all sorts of instabilities. It was an R&D board that had many hand reworks. After many long late hours the engineer was telling me his tail of woe and I suggested we wash the board. Board washed, problem solved. I converted another non-believer that removing flux was a good thing. Phil -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of James Verrette Sent: Friday, September 19, 2008 4:23 PM To: [log in to unmask] Subject: [TN] Can desoldering and soldering fix a leaky MLCC I had a case where I was measuring about 100k accross two nets on a PCB Assembly with an Ohm meter. I removed a .1uF X7R MLCC SMT 0402 size from the board and the 100k short went away. I measured the cap and the ohm meter and the resistance was OL. I put the capacitor back on the board and remeasured the resistance and there was no short. I looked for obvious damage on the cap under a microscope, but didn't see anything. Is it possible that desoldering and resoldering by hand could cause a leaky MLCC to stop leaking? I am trying to find an explaination for what made the 100k short circuit go away. The only other expaination is that there was something under the part that caused leakaget. The boards are assembled with no-clean flux, SnPb solder paste. Based on what I have read flex cracks could cause the leakage we saw before the modification, but could desoldering and soldering cause it to go away? Jim Verrette Senior Electrical Engineer --------------------------------------------------- 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 ----------------------------------------------------- Note: All the information contained in this e-mail and its attachments is proprietary to Kaiser Systems, Inc. and it may not be reproduced without the prior written permission of sender. If you have received this email in error, please immediately return it to sender and delete the copy you received. Note: All the information contained in this e-mail and its attachments is proprietary to Kaiser Systems, Inc. and it may not be reproduced without the prior written permission of sender. If you have received this email in error, please immediately return it to sender and delete the copy you received. --------------------------------------------------- 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 -----------------------------------------------------