Alan: In most cases I would agree with you, but in our case, we have had some problems with thieving being added on the outer surface over critical analog traces on inner layers. This caused a major problem with signal fidelity in high gigahertz inputs. It is much easier to define a thieving keepout and do it our selves. As you can imagine, people don't want to pay $20K or more for a scope that won't display their signals correctly :) Mitch: We have increasingly been using boards where 10-14 layers are processed and plated up, then 2-3 layers are laminated to the whole stack using low Dk prepregs and the whole board run thru plating again. What this means is that the thieving has to be added to the original "core" board outer layers to minimize warpage, and the real outer layers then need it as well. You may not have noticed the results of not adding thieving because your boards are smaller, or because the manufacturer was scrapping boards for flatness issues before they were delivered. -- George Patrick Tektronix, Inc. Central Engineering, PCB Design Group P.O. Box 500, M/S 39-512 Beaverton, OR 97077-0001 Phone: 503-627-5272 Fax: 503-627-5587 http://www.tektronix.com http://www.pcb-designer.com It's my opinion, not Tektronix' -----Original Message----- From: Ritter, Alan [mailto:Alan.Ritter@xxxxxxxxxx] Sent: Wednesday, September 22, 2004 10:52 To: icu-pcb-forum@xxxxxxxxxxxxx Subject: [PCB_FORUM] Re: Copper balancing "thieving dots" In general, we leave the addition of thieving up to the board fab house. They know their process and what their requirements are to keep the trace widths consistent. Because we design medical equipment, we have some boards where electrical safety concerns prohibit copper in certain areas, and these are called out on the fab drawings. On a lot of our boards, the only thieving required is on the tooling bars...none on the active area of the board itself. When it's a board fab process issue, I prefer letting the fab house dictate what to do (within certain limits) rather than trying to second-guess them. We EEs (yes, I'm an EE in addition to resident layout guru) generally don't have a clue as to what is required, unless we have taken the time to visit and/or talk extensively with the fab house. Basically, we have a solid enough relationship with the fab house that I know I can trust them to follow instructions and make the "engineered" artwork files match both their process requirements and our electrical requirements. /s/jar (alan.ritter@xxxxxxxxxx) http://www.mtritter.org Bausch & Lomb 150 Years of Perfecting Vision, Enhancing Life (TM) EMAIL DISCLAIMER Please Note: The information contained in this message may be privileged and confidential, protected from disclosure, and/or intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, distribution, copying or other dissemination of this communication is strictly prohibited. If you received this communication in error, please immediately reply to the sender, delete the message and destroy all copies of it. Thank You ----------------------------------------------------------- To subscribe/unsubscribe: Send a message to icu-pcb-forum-request@xxxxxxxxxxxxx with a subject of subscribe or unsubscribe To view the archives of this list please login at http://www.freelists.org. Our list name is icu-pcb-forum or go to http://www.freelists.org/archives/icu-pcb-forum/ Problems or Questions: Send an email to icu-pcb-forum-admins@xxxxxxxxxxxxx Want to post a job listing ? DON'T DO IT HERE! Better yet, join our jobs listing forum. SUBSCRIBE: icu-jobs-forum-subscribe@xxxxxxxxxx POST: icu-jobs-forum@xxxxxxxxxx ----------------------------------------------------------- ----------------------------------------------------------- To subscribe/unsubscribe: Send a message to icu-pcb-forum-request@xxxxxxxxxxxxx with a subject of subscribe or unsubscribe To view the archives of this list please login at http://www.freelists.org. Our list name is icu-pcb-forum or go to http://www.freelists.org/archives/icu-pcb-forum/ Problems or Questions: Send an email to icu-pcb-forum-admins@xxxxxxxxxxxxx Want to post a job listing ? DON'T DO IT HERE! Better yet, join our jobs listing forum. SUBSCRIBE: icu-jobs-forum-subscribe@xxxxxxxxxx POST: icu-jobs-forum@xxxxxxxxxx -----------------------------------------------------------