Doug, It was a looong time ago, but I did take a fourth year course in photochemistry. Fluorescence can be "quenched" in a variety of ways. For instance quinine fluorescence can be quenched by chloride. See the Wikipedia link. http://en.wikipedia.org/wiki/Quenching_(fluorescence) Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls Sent: Wednesday, October 27, 2010 8:30 AM To: [log in to unmask] Subject: [TN] Disappearing Fluorescence Good morning all, I posted a picture to the IPC Technet gallery. http://ipc-technet.groupsite.com/gallery/16251 This is taken from a failure analysis effort I am working on. Its amazing what happens to electronics when you spill coffee into them. One of the assemblies I have been looking at has a very odd visual effect that I have never seen before. The conformal coating has a fluorescing dye to it that glows blue under black light, which is common. Notice how the fluoresence has disappeared from the areas over one set of traces. I have seen fluorescence disappear before, but it usually heat releated and over a large area, nothing highly localized like this. My first thought was that there had been a jumper wire installed in these locations, but that is not the case. I showed this to my good friend Phil Kinner at Humiseal, who is no stranger to the wierd and wacky world of conformal coating oddities, and he has not seen anything like this either. Anyone else seen this? Doug Pauls Maybe this could be one of Inge's Friday quiz items............ ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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 -----------------------------------------------------