Hi Ioan, With the LEDs flush-mounted, it is likely that some of the PTHs are only partially solder filled [or not at all], and either the PTH barrel fractured due to the interface stress concentration or the solder joint due to the thermal expansion mismatch between the LED lead and the PCB. Only cross-sections can tell what you really have. The fillet on the other side is not where you are making contact when pressing on the LED, but likely somewhere inside the PTH. Werner Future workshops: Reliability Issues with Lead-Free Soldering Processes, June 17, London Interconnect Failures and Design for Reliability for PCB PTHs, June 17, London Pb-Free Soldering Processes—Survival, Quality, Reliability, August 18, Orlando Reliability Issues with Lead-Free Soldering Processes, September 22, Schaumburg Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture, ENIG), September 22, Schaumburg ************** Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food. (http://food.aol.com/tyler-florence?video=4?& NCID=aolfod00030000000002) --------------------------------------------------- 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 -----------------------------------------------------