Has anyone experienced solder paste disappearing in a convection oven? We have experienced several "insufficient solder" (no solder) defects on smt gull wing leads (typically fine pitch but not always). The last controlled lot, produced 3 of 10 boards with defects. Defects: One lead on each of 2 boards, and 3 leads on the last board. Component types are QFP208, TSOP48 and QFP100 Additional information: 1) The paste (6 - 7mils thick) is verified on the pads just prior to entering the reflow oven. The paste is a SN63 RMA. 2) Solderablity of the component leads is acceptable 3) Solderability of the board is acceptable 4) There are vias attached to every pad but the solder is not going into the vias. 5) The defective joints exhibit a small fillet of flux around the leads with no solder. It appears as though solder was never printed on the pad. 6) The missing solder is not on the lead, pad or adjacent component leads or pads. It's just gone. 7) Defects found on 11 boards over 3 different lots (months apart). 8) Minute solder balls are evident on the board but may have been from paste print process. 9) The lead is in contact with the pad. Theories: 1) Paste outgassing?? 2) Gremlins in the oven stealing the paste?? --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------