As I recollect from a former life in fab shops, if the location of the tooling holes that one pins to are is inaccurate or if the loction of the pins on the drill is not constant or the pins are worn (or the 0,0 location is not accurately known), the whole pattern will shift. Also, there is a bit of drill deflection that becomes worse as the drill bit penetrates further into the stack, especially on smaller diameter holes. Thers's about a milliion other factors that effect drill accuracy including material growth all of which made me happy to be involved in chemical things rather than mechanical. George -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Roger Stoops Sent: Thursday, May 05, 2005 10:33 AM To: [log in to unmask] Subject: Re: [TN] Through hole drill accuracy Thanks for the clarification. However, for a given pattern or grouping of plated holes on a board, pin tolerances would have little if any effect, would they? The only effect they would have is when moving a board stack from one machine to another, correct? If a particular press-fit connector required both plated and non-plated holes, the additional tolerances added by the use of pins could become a real concern. But those new-fangled drill machines with vision capability could help negate that, yes? Excellon has some purdy machines... Regards, Roger -----Original Message----- From: Jeffrey Bush [mailto:[log in to unmask]] Sent: Thursday, May 05, 2005 10:09 AM To: TechNet E-Mail Forum; Roger Stoops Subject: RE: [TN] Through hole drill accuracy What about other factors in drilling beyond machine accuracy - pin tolerance, pin to tooling tolerance, and pin to bed tolerance. These factors are also constituents in the overall drill accuracy beyond the machine tolerances native to the process. Jeffrey Bush Director, Quality Assurance and Technical Support VERMONT CIRCUITS INCORPORATED 76 Technology Drive - POB 1890 Brattleboro, Vermont 05302 Voice: 802.257.4571.21 Fax: 802.257.0011 http://www.vtcircuits.com -----Original Message----- From: Roger Stoops [mailto:[log in to unmask]] Sent: Thursday, May 05, 2005 9:30 AM To: [log in to unmask] Subject: Re: [TN] Through hole drill accuracy If the alignment is off by 2mils or more, sounds like your fab house needs to check their drilling machine, or else use a better, more accurate one than typically used. The issue is one of positional accuracy plus repeatability. If a machine has a drilling accuracy of +/-.001, positional accuracy of +/-.0005, and repeatability of +/-.0005, then the total accumulated tolerance can be as large as +/-.002. Sound like you need to specify a location tolerance (true position) of +/-.0015 (or better) for the holes in question. The wider the tolerance for hole diameter, the narrower the tolerance for location accuracy, and vice versa, for press-fit connectors. IPC-2221 9.2.2 says you can expect +/-.002 for fabs built to level B. Asking for Level C would give you +/-.0015 tolerance. (If I'm missing something, somebody *please* set me on the straight and narrow...) Use of GD&T (IPC-2615) would help in specifying what you really want, because tolerance zones with GD&T are round, not square as in the (unfortunately) typical drawing practice. All said and done: it's up to you to specify hole size, tolerance, *and* accuracy for your design. If you don't specify accuracy, the board vendor may provide you with what's easy for them to make, to the widest tolerances possible. Best Regards, Roger -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Scott Lefebvre Sent: Wednesday, May 04, 2005 6:10 PM To: [log in to unmask] Subject: [TN] Through hole drill accuracy I have looked profusely at IPC-6012 for a specification I could not find. I need to know if there is a specification for PTH drill accuracy and repeatability. We have a press-fit connector we are having problems with. The component manufacturer tested one of our boards and said the alignment is off 2 mils or more in some locations. I could not find what is the spec in IPC to reference to, could someone please point me to the correct document I should look at. Sincerely, SCOTT L --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- @ipc.org or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------