HI, Mark, I agree exactly with Carrie, with the slight addition that their paste may also be 'old' and the volatiles that provide the wetting action have disappeared. Or the paste could just contain a flux that isn't sufficiently active (this should not be very likely, though. Peter "Morse, Carrie" <[log in to unmask]> 03/09/2002 08:17 PM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to "Morse, Carrie" To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: Re: [TN] poor wetting- pcb or assy problem? My first guess would have been high tin content on the HASL, but, if the HASL's OK, then my next best guess is the reflow profile. Has the CM run a board through the oven with a Mole to measure the actual board temps at the sites not reflowing? If it's not the profile, my next guess is the paste ... maybe it's lead free and has a higher melting point than they expect. -----Original Message----- From: Mark Hargreaves [mailto:[log in to unmask]] Sent: Friday, August 30, 2002 2:59 PM To: [log in to unmask] Subject: [TN] poor wetting- pcb or assy problem? Hi All, We shipped 52 bare boards to our customer, who hand assembled 2, and then sent 50 to a contract manufacturer for assembly. The assembly house soldered the surface mount caps (paste & oven) and stopped because the solder was not "wetting". (there were apparently no problems with the hand assembled boards). I saw 4 of the partially assembled boards- they look ugly. The HASL solder covers the entire pad (no copper showing), but the paste solder doesn't flow to the pad edges. It looks like the two solders don't want to combine. The bare board HASL finish (vertical HASL) looks typical, the HASL solder content was analyzed (ok) the previous week, and the solder pot was skimmed that morning. So, we sent a spare bare board from the same lot to a test house for J-std 3, test A (dip test), which it passed. The assembly house says the bare boards are at fault, and that the dip test is less demanding than the paste/ I/R oven process used on these boards. Any ideas as to the root cause? Is there a straight forward way to verify this? It's been a year since we received our last solderability complaint. That ended in inconclusive discussion regarding "intermetallics". I'm hoping to resolve this one more logically. Thanks, Mark Hargreaves --------------------------------------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- [This e-mail is confidential and may also be privileged. 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