Everyone who has commented is basically right based on their varying perspectives. Providing a tolerance on a via is not necessary for accept or reject, so long as it has the copper needed/requested but it is important to know what is happening on internal layers and therein lies the rub. It is very helpful for the designer to know something about the manufacturing process and manufacturing tolerances to avoid painting themselves into a corner (which happens more often than should be) and wasting time with after the fact clarifications. Time spent with a manufacture learning about the process before designing is time well spent. Joe In a message dated 7/9/2008 7:33:47 A.M. Pacific Daylight Time, [log in to unmask] writes: I tend to recommend keeping the fab print to reflect the "finished" PCB requirements. That way the inspectors have a "black and white" document to inspect the PCBs too throughout the fab process. If the process attributes were specified they might change depending on which factory and where they are made. Those could be written up in a Customer Specification document that is separate than the fab print but chances are there would be a series of waivers/deviation requests between the fabricator and OEM. Cheers, Groovy (aka, Dave Hoover) ----- Original Message ----- From: "Barton, Ken" <[log in to unmask]> To: <[log in to unmask]> Sent: Wednesday, July 09, 2008 7:19 AM Subject: Re: [TN] Flex specifications - tolerance on hole size If we started dialing in the drill sizes for actual drill size before plate as opposed to finished (plated) size, it would surely confuse the heck out of our fab houses. Ken Barton -----Original Message----- From: John Burke [mailto:[log in to unmask]] Sent: Tuesday, July 08, 2008 4:28 PM To: [log in to unmask] Subject: Re: [TN] Flex specifications - tolerance on hole size The hole size MUST be the drilled size. If it is NOT the drilled size you have no control whatsoever over the design in terms of drill to copper clearances. If you must call out a finished hole size do it separately on the drawing for the holes concerned. John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins Sent: Tuesday, July 08, 2008 8:45 AM To: [log in to unmask] Subject: Re: [TN] Flex specifications - tolerance on hole size Hey guys. Thanks for all the opinions and info. I'm stuck in the middle, on one side is a designer saying that it means pre-finishing size, on the other I've got a fabricator saying it means finished hole size. The drawing is ambiguous on this point. I just want parts to build things with!!! I do agree with Werner that it does not matter as they are only vias, but once someone had inspected and measured something it became a debate. regards, - Graham -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ken Bloomquist Sent: Monday, July 07, 2008 7:57 PM To: [log in to unmask] Subject: Re: [TN] Flex specifications - tolerance on hole size Hi Werner, I like your thinking but... I'm not in the quality department, no offense to those of you who are, but I wouldn't want to be ;-) But thinking like an inspector, how would you verify that you got the right size holes if you don't call out a finished hole size? I guess you could do a cross section but a pin gage is a lot simpler. Just thinking out loud, KennyB -----Original Message----- From: Werner Engelmaier /* [mailto:[log in to unmask]] Sent: Monday, July 07, 2008 3:36 PM To: [log in to unmask] Subject: Re: [TN] Flex specifications - tolerance on hole size Hi Graham, Why do you care what the finished hole size is? Do you put component leads into 0.028"/+- 0.003" holes, that is 25 mils minimum? The finished hole size specifications are an anachronism harking back to the THT-days-today they only should be specified for componet lead holes. For vias the drilled hole diameter should be specified-it is much more important. Werner Future workshops: Pb-Free Soldering Processes-Survival, Quality, Reliability, July 17/18, Thal, Switzerland Pb-Free Soldering Processes-Survival, Quality, Reliability, July 21/22, Bad Segeberg, Germany Pb-Free Soldering Processes-Survival, Quality, Reliability, August 18, Orlando Reliability Issues with Lead-Free Soldering Processes, September 22, Schaumburg Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture, ENIG), September 22, Schaumburg Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia Solder Joint Reliability: Parts 1 & 4, Oct. 17, Timisoara, Rumania Solder Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- **************Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com! 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