Luigi You didn't say what flux you were using. I assume it's the flux called out in the spec. My experience at AT&T (and resulting contributions to the IPC wetting balance test) are that if you use ANY flux but water white rosin (WWR) the results you get in production will NOT equal the results of the wetting test. The test will always look better. I and my co-workers published this as a reliability study at the SMI conference in San Jose, CA in 1995. I have heard the arguments that wetting balance is inherently too noisy to provide good repeatable data from site to site if one uses WWR. Yup! A little activation in the flux definitely improves the repeatability: It makes everything good. And when that happens, from an assembly standpoint, you're the loser. I suggest a simpler alternative: use the "dip and look" test with WWR and the wetting balance to control immersion depth and speed. But only accept the parts if the area wetted exceeds the area dipped. Why? Simple! In production you want the solder to wet "up" the part/wet "over" the lead. When you put the part in the solder with WWR and the solder climbs up the lead you know it's good! If all the solder does is wet the immersed area . . . well, on my desk I have some carbon fiber bundles that exhibit good "wetting" per the current test. They're well covered with SnPb over the area immersed. But I defy anyone to actually make good connections in production with leads like that. (Years ago John Devore, if I remember correctly, would show people a solder surface that was well wetted. Then he'd hand it to them. It was a wood toothpick with solder adhered to part of the wood. Sure looked it'd solder per the spec!) So, per my opinion, WWR and demonstrated active wetting of the parts are the only way to go in solderability testing. Greg Munie -----Original Message----- From: Luigi Cantagallo [mailto:[log in to unmask]] Sent: Wednesday, May 25, 2005 2:00 AM To: [log in to unmask] Subject: [TN] Wetting balance Hello Technetters, I have questions about wetting balance. We intend to use a wetting balance not to accept/reject supplied SMD's (Our SMD's are 1 to 5 years old) but to minimize the risk of solderability defects in production (Low volume, SnPb technology). So we don't apply J-STD-002D criterium but we try to find them to corroborate wetting balance and production results. On some tests (Wetting balance calibrated and in order, same type of flux, same alloy) on same component lots, we have not a perfect correspondence between wetting balance and visual inspections results in production (Vapor phase soldering). One of the case is "Good at the solderability test/Defect in production" and this one is the most risky. Somebody have experience with that kind of problem? What actions have you made ? Thanks for answers. Best regards, CANTAGALLO Luigi --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------