I prefer specified finished hole tolerances. Hypothetically, what your colleague said is true, but it's just stupid to think any company would actually do (drill 20, plate to 10) such a dumb thing. Keep in mind that the internal pads and clearances (pad-to-pad, pad-to-trace), board thickness, copper weight (starting and finished) all contribute to the drilled hole size requirement and many shops will make fabrication adjustments to any or all of these to ensure a quality product meeting your requirements is the final result. These of course are just my opinion... Franklin -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wilson Sent: Monday, January 16, 2006 5:06 PM To: [log in to unmask] Subject: [TN] Drill and plated hole callouts Hello, I am a designer (...wait! wait! Don't throw anything yet!...) and we are discussing hole and drill callouts in standard high Tg FR4 material on the design side and I'd like to hear from ya'll. I specify a hole of .020 and a tolerance of plus .003 and minus .003 (inches), along with a note stating ALL HOLE SIZES ARE FINISHED. Now I don't care how the hole is made: drill, laser, plasma, teeth. As long as the hole is as I specify, I figure the board house knows what their best method would be. And I request electrical test before I see the boards on my loading dock. A well-respected colleague says that he specifies the drill hole and tolerance before finish. He maintains the fab house could drill a via hole at up to .020 and plate it down to .010, and that it will punch out any traces as the hole is made. Further, he says that electrical test isn't enough and when the board is stuffed and under full load that the heat could cause further problems. Make sense? How do you prefer to see the holes called out? Regards, Bob Wilson Electro-Mechanical Designer SpectraSensors, Inc. 972 N. Amelia Ave. San Dimas, CA 91773 800-619-2831 x239 www.spectrasensors.com --------------------------------------------------- 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 -----------------------------------------------------