Sorry for delay Guy: First thank you for your interesting description. We use 3 min preheating, 1 min to soak and 1min in reflow. It s to no clean solder paste. Thanks.. saul >>> "Guy Ramsey" <[log in to unmask]> 3/11/2005 10:37:46 AM >>> I once watched a real time x-ray video, produced by Phoenix X-ray. The video was a 9 minute reflow of a BGA package. In the sequence one could observe the initial wetting and second drop of the BGA package (reminiscent of the Ersa real time view from a side mounted camera). Immediately after the second drop the solder fillets were nearly perfect with negligible voids. During the following few minutes voids began to form within the balls. They began small and grew larger, quite large. Subsequently, they voids broke up forming many small voids. The package spent about 5 minutes ramping to reflow and about 4 minutes in reflow. Everything looked perfect until about 150 seconds into reflow. I really don't know mechanisms behind the phenomena. But, wonder if you aren't seeing something related to an extended it. -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Saul MorenoRodriguez Sent: Wednesday, March 09, 2005 10:15 PM To: [log in to unmask] Subject: [TN] Voids Hello Technetters: In a recently running we had a problem with voids in Micro BGA's. We resolved succesfully only increasing the preheat and the soak time, this to dry the humidity correctly in the devices. But my doubt is here: The Micro BGA's are placed on first side and in first reflow we didn't have problems, all was ok, but voids showed up in the second reflow . We detected them in 5DX. Could you tell me why this happened ? Thanks in advance.. Saul Moreno R. Process Engineer _____________________________________________________________________________ Scanned by Sanmina-SCI eShield _____________________________________________________________________________ --------------------------------------------------- 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 -----------------------------------------------------