Seen worse.........8-( I have encountered this on a number of occasions and have come to a few thoughts on the subject. In my experience it is generally found on the smaller components (such as 0201) and often only on the ceramic parts. The conclusion that I came to with this is that the flux itself is running out of steam as the smaller components are experiencing overheating in the ramp up phase of the reflow profile compared to the larger devices. They have a smaller amount of solder paste and hence flux, and they are exposed to the full effect of the reflow profile often in less densely populated areas. Ceramic also has a very good thermal transfer co-efficient and heat capacity compared to the other packaging materials such as BAG and other plastic bodied parts. The reason that I came to this conclusion is that often you will see this effect on a small ceramic part but not at all on a QFP or a BGA. Inevitably in the speed required to "fix" things I instructed our CEM to back off on the ramp profile and the problem went away. And yes some soldering materials are less "robust" in this respect. Sad to say, but I have never seen this condition with leaded solder...........8-) John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of stephen gregory Sent: Wednesday, January 13, 2010 12:24 PM To: [log in to unmask] Subject: [TN] Return of the "Snotballs" Maybe some of you remember a post I made a couple of years ago when I was in Tulsa and I had a reflow problem with a SAC solderpaste. It was then I learned of a new term called "Snotballs". Here was the picture I posted back then: http://stevezeva.homestead.com/files/Snotballs.jpg Well guess who decided to follow me out to Pennsylvania? Check out: http://stevezeva.homestead.com/Type_4.JPG Same vendor, same alloy. All I can say is make sure you know where your powder is coming from. Steve Gregory --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------