Hi Leif, you've just listened to His Master's Voice. You should take off your cap, when you speak to Richard Stadem. Impressive! I begin to feel that there are two exceptional stars at TN. Steve...we already knew Richard...a supernova Inge Gah...my example was not very clever...a supernova is bright just for a short time...hmmm...a red giant then? hmmm...or a white dwarf...hm...none of them very striking....hmm....shining like Betelgeuse...hmm.....maybe Master Whittaker can give a hand? ----- Original Message ----- From: "Stadem, Richard D." <[log in to unmask]> To: <[log in to unmask]> Sent: Wednesday, July 30, 2008 6:53 AM Subject: Re: [TN] Solder Paste with craters. Hi, Leif Send your pictures to [log in to unmask] Can you tell me what solder paste it is you are using? How was it qualified for use? Here are just some of the questions you need to ask yourself in order to determine why you have an issue with solder fines: Do you have a good documented solder paste handling procedure? How is the paste handled, from vendor or distributor to your factory? When was the last time you stopped in at the distributor to verify their stock is being rotated and is kept refrigerated immediately upon receipt from the factory? How often do they turn the packages upside down to prevent flux separation? Are they a certified distributor who will pass on to you a lot recall notice from your solder paste vendor if there is a known bad lot? How long is the paste allowed to sit out on the stencil and how many times can a line of paste on the stencil be sheared (printed back and forth) before it is removed and replenished with fresh paste? Are the operators allowed to scrape up the unused paste on the stencil and re-deposit it into a jar for re-use later? Is the jar or tube of solder paste, once removed from refrigeration, allowed to set for two to four hours (depending on paste vendor and paste type) to reach room temperature prior to printing? Once removed from the refrigerator, is unused solder paste allowed to be put back in the refrigerator? Are you using Type 4 paste or Type 3? How good is the printer setup, ie, the repeatability of the registration of the stencil to the PWB? Are you performing some type of aperture reduction on all pads in general and at least a 50% reduction on large belly pads to prevent solder fines from being printed onto the board? If a board is misprinted, does the operator know better than to simply wipe off the board (embedding the paste into every space between the edges of the pads and the soldermask, into every small via, into every through hole, etc.) but is there a documented procedure detailing how the misprinted board is to be cleaned to prevent this? How is the solder paste packaged, jar or tube? (Tubes prevent a much larger volume of paste from being exposed to air and humidity, and also help prevent re-use of solder paste that has been out for awhile). Do you perform a good solder paste print inspection using a 3d AOI or some other type of automated inspection, and do you use the data from this inspection process to detect (real-time) paste defect trends and react to them with corrective actions? Sorry to ask so many questions, but all of these can contribute to fines, and there are many more factors that can cause them. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leif Erik Laerum Sent: Wednesday, July 30, 2008 8:29 AM To: [log in to unmask] Subject: [TN] Solder Paste with craters. Technetters, We are having an issue with solder fines on our lead free boards. We are using SAC305 WS and no nitrogen. I noticed that our boards have craters in the paste on the pads after being printed. Not all pads are deposited this way, but maybe 25%. These craters have an air bubble in them. The bubbles usually burst before the boards goes into the P&P, but the crater stays. The screening process is exactly the same for leaded and unleaded paste. The leaded paste does not behave this way. Could these craters be a symptom of the cause of the solder fines? Anyone have any experience with this? How do I go about posting pictures to stevezeva.homestead.com?. -- Leif Erik Laerum Quality Assurance Manager Texas Memory Systems [log in to unmask] Tel: (713) 266-3200 x468 www.texmemsys.com --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------