Let's use IPC-2221 and 2222. 2222 places the conductive feature locations in paragraph 9.1.5 for board dimensions with x-y dimensions less than 300 mm: Preferred tolerance 0.3mm; Standard tolerance 0.2mm and reduced yield at 0.10mm. 2221 places the hole location tolerance in table 9-3 Preferred tolerance 0.25mm; Standard tolerance 0.2mm and reduced yield at 0.15mm. Caution: Your question seems simple but it is not. Dimensioning systems can alter the meaning of tolerances. Figure 5-4 of 2221 and the associated text discuss the problem. Tolerances can accumulate, the hole location tolerance above is for the center of the hole, but the hole size has a tolerance as well. > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of Eric Christison > Sent: Thursday, May 02, 2002 8:19 AM > To: [log in to unmask] > Subject: [TN] Some Advice on PCB tols required > > > I wonder if some experts could refresh my memory on some PCB > tolerances assuming materials and processes > suitable for very high volume commercial quality PCB's. > > Imagine I have a rectangular board about 50 X 100 mm (2"X4") with > four fixing holes - one in each corner > and a set of pads somewhere in the middle of the board. Here's > the features I'd like tols on: > > The tolerance on the fixing hole diameter. > > The tolerance on the position of the pad pattern to the fixing hole. > > The tolerance between individual pads in the pattern - assume > each pad is 1mm wide by 2mm long. > > > Thanks, > > > -- > Eric Christison > Mechanical Engineer > STMicroelectronics > 33 Pinkhill > Edinburgh > EH12 7BF > > Tel: (0)131 336 6165 > Fax: (0)131 336 6001 > > ------------------------------------------------------------------ > --------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > 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 delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL > 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 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------