I have a 5-10% void on a bottom side BGA that grows to a 20-40% void when the top side is assembled and reflowed. Paste lead free OM338, profile is peak temp is 246 for 60 seconds. Immersion tin board finish. Why would the void expand on a second reflow? There are 22 BGA's on this assembly. Only a few are growing voids, most voids seen are in the 5-10% or less range. Two parts are in the process of cross sectioning, to verify where the void really is. Only have in line x-ray capablility, no angled views. --------------------------------------------------- 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 -----------------------------------------------------