Bev/Ingemar, Is the wetting balance test still feasible, based on your comments that the wetting balance test results will not be statistically significant for small DPMO? In other words, can running a daily test on a small batch of components detect enough lots of non-solderable components and prevent them from reaching the production floor often enough to justify the cost of performing the testing? Are there more "escapes" of bad lots to the production floor than there are "detections"? I would assume that it is only useful in high-volume production scenarios where a bad lot of components with poor solderability could create a real nightmare in terms of rework cost, scrap, etc. Does a real-time solder process DPMO rate detection make more sense? I understand that in some cases a certain amount of part preparation has already taken place by the time the solder defects are discovered, especially with leaded through-hole parts (cut and form ops). With current improvements in component solderability, I personally seldom see a lot of solder defects caused by component solderability issues anymore. This is why I question whether performing WB testing is still a value-added activity. Just asking. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian Sent: Tuesday, May 31, 2005 8:15 AM To: [log in to unmask] Subject: Re: [TN] Wetting balance Ingemar, I am somewhat surprised by your abandonment of your wetting balance. Although I am "married" to it, here it is usually run by a continuing rotation of co-op students, changing every four months. Are you sure the variation is not in the components rather than the operators? If there is one downfall of a wetting balance, or for that matter ANY solderability test, short of building actual product, it is THEY WILL NEVER BE STATISTICALLY SIGNIFICANT FOR SMALL DPMO. Do the math, the number of parts you would have to test is horrendous. So I am not surprised by Luigi talking about pass wetting balance/fail on line. It is NOT a function of the relatively conservative wetting balance test, but the statistics of where you took the parts out of the reel. We use the wetting balance to get a snapshot. Sometimes we are lucky. And if the whole reel is indeed crummy then we have the evidence to bludgeon the supplier. And you are 100% right about needing a person who knows about soldering and the book you mention is THE BEST. Regards, Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord (KC/EMW) Sent: May 31, 2005 3:38 AM To: [log in to unmask] Subject: Re: [TN] Wetting balance Bon giorno, My response is late, been in Rome for some days, 35 Centigrades and polluted city air, could study the wetting of sweat very well. If it were not for the watching police, I had jumped into Fontana di Trevi. Very interesting to see the answers on solder wetting. We have a Multicore WB, but it's abandoned, been placed in a corner and never asked for. The reason is that we could not find a person that got enough in love and married the machine and who promised to be a good husband for decades. With different operators we got too much variations of parameters. If inspecting just a few items per day, I think Bev's recipe is working, but if you have hundreds and hundreds of samples to test, I ask myself if not WB is necessary to use. At least if you have a WB enthusiast and someone who can use statistics. We have found that better than a machine or any dip pots or whatever, is a person who KNOWS about soldering. Even if samples are WB tested from a lot of 100,000 chip caps, and that sample looks nice, we know that there can still be soldering trouble. When you get soldering problems in the line, the root cause must be found in hours. A person who KNOWS about soldering use to have that ability. Usually, those guys are greyhaired gentlemen with shit under the nails despite a PhD grade, and with no take-overs. Two of the guys at our company left big holes when they withdraw. There are a few left, don't see how we will manage the time they too leave. Knowing a lot about soldering is not on the hit list..... For those who are interested in KNOWING about soldering and wetting, I recommend this book: "The Mechanisms of Solder Alloy Wetting and Spreading" written by Frederick G. Yost, F.Michael Hosking and Darrel R. Frear. Sandia Lab guys. ISBN-0-442-01752-9 Van Nostrand Reinhold, 115 Fifth Avenue, New York, NY 10003. 300 pages about wetting and only wetting! Ingemar Hernefjord Ericsson Microwave Systems -----Original Message----- From: Luigi Cantagallo [mailto:[log in to unmask]] Sent: Wednesday, May 25, 2005 2:00 AM To: [log in to unmask]<mailto:[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 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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