I raised the issue in the open forum for a reason. (OBTW ... It's not my design) One, I may be able to locate someone else who has had this problem before and knew of a spec that would enlighten the folks involved in reviewing this. Two, I may find that there is no spec and we are at fault for not specifying SMOBC and that we have been enormously lucky all these years that the vendor we were using interpreted our preference for assemblies that don't short out under the soldermask after wave soldering.... I went to the IPC specs looking for guidance on this and found little that I could interpret to be related to this scenario. Here are the notes off the actual drawing... Maybe you guys can shed some light on the results we received... (it was a new vendor) NOTES: UNLESS OTHERWISE SPECIFIED 1. Material: .062 FR-4 C2/C2 Finished 2. Solder Plate exposed copper .0003 to .0005 3. Hole sizes are after plating, Min. wall .001 thk 4. Finished board to comply with IPC-A-600, Class II 5. Component side shown 6. Solder Mask Both Sides 7. Silkscreen component side with white epoxy ink 8. Tolerances: Front to Back: +/- .005 Hole location: +/- .003 Hole Diameter: +/- .003 That's all there was... I didn't create the notes, I have only been here 2 years, it was created before 1996 by another designer. So any speculation on why one vendor used SMOBC and another used SOS... ? - BB Bill Brooks -----Original Message----- From: Barmuta, Mike [mailto:[log in to unmask]] Sent: Tuesday, October 22, 2002 12:57 PM To: 'TechNet E-Mail Forum.'; 'Brooks,Bill' Cc: Barmuta, Mike Subject: RE: [TN] Solder UNDER Soldermask Accept/Reject Criteria? Bill: 1. Since this board has been made for over 10 years, did you change fabricators? If so the new fab shop obviously was not aware of your SMOBC desire. Although a good board supplier should have reviewed your drawing and questioned you as to what style of fab and final finish you wanted. Never assume what someone's default process is. 2. From your description this sounds like an electroplated fused Sn/Pb board with soldermask. At least I hope it's fused. If the fab shop is set up for this process it's cheaper to build than an SMOBC board. Did somebody try to get a lower cost on this board? 3. Soldermask over fused Sn/Pb is not necessarily a bad thing. If done properly it should have better solderability and shelf life than HASL. The issue of wrinkling mask in the wavesolder process could be a problem. However it depends on the board design. If you don't have large features or groundplanes on the bottom wavesolder side of the board you should not see much, if any loss of mask. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: Brooks,Bill [mailto:[log in to unmask]] Sent: Tuesday, October 22, 2002 12:20 PM To: [log in to unmask] Subject: Re: [TN] Solder UNDER Soldermask Accept/Reject Criteria? I guess I should clarify also that this is a board that has been made for years. Without the soldermask coming in over solder. The board has been around more than 10 years and this was a shock to the manufacturing folks when it happened... we just don't see this sort of thing happen anymore.... I think the last time I saw this was in 1985. We all learned to call out SMOBC to get the vendors to avoid making the boards with solder under the soldermask. In fact, it took some convincing of some engineers that the board would be fine without a solder coat over the entire copper surface, and that they only needed the solder where the component lead was... I'm sure there are some of you guys that are my age (46) that remember this stuff... its just so surprising to see it in this day and age... :) Bill Brooks -----Original Message----- From: Brooks,Bill [mailto:[log in to unmask]] Sent: Tuesday, October 22, 2002 12:08 PM To: [log in to unmask] Subject: Re: [TN] Solder UNDER Soldermask Accept/Reject Criteria? The Print did not specify SMOBC. But it also didn't specify SOS (Soldermask over solder) either! The implication is that the order of the notes IMPLIES that we want soldermask after the solder coating process. Don't all PCB vendors know that the solder under the soldermask will reflow, wrinkle and damage the soldermask in assembly? If we have soldermask on a thru hole technology board.... we are going to wave solder the board. Why would a vendor interpret the drawing in such a way as to compromise the performance of the board? I can't believe this is still happening in 2002. I thought we learned our lesson back in 1980.....the first time I ever saw anyone DO that... Doesn't IPC have a spec that tells us not to do it that way? Bill Brooks -----Original Message----- From: Steve Gregory [mailto:[log in to unmask]] Sent: Tuesday, October 22, 2002 11:44 AM To: [log in to unmask] Subject: Re: [TN] Solder UNDER Soldermask Accept/Reject Criteria? Hi Bill! Was that called out on the fab drawing? I've ran across a few boards here that still call that out on the drawing, and TRY and get that changed before the boards are fabbed...most of the time I've been lucky, but there's been a few that slipped by me. Bottomline, if it's called out on the drawing, you don't have much recourse... -Steve Gregory- Anyone aware of a spec that sets the accept/reject criteria for boards that come in with solder UNDER the soldermask? Is this actually done as a legitimate practice? WHY would a vendor make the boards this way? Shouldn't we be making all boards to be SMOBC when there is a soldermask? Bill Brooks --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------