At 09:44 AM 11/9/01 -0700, Bob Fearon wrote: >Abdul-Rahman > Yes I have seen an inner plane layer come all the way out to an edge. > The design was supposed to be "better for RF", but made no difference > in board performance. The two outside layers were plated aound the edge > and shorted ( on purpose ) to the inner layer. This was a nightmare to > build and cost "extra". > The same performance was achieved by placing a row of vias 100 mils > from the edge on a "regular" board, at a much lower cost.
This is not an example of what I asked for. Instead, this was a board deliberately fabricated without edge clearance. Yes, it was not a great idea from the start, as anyone who knows HF design would have anticipated, unless -- maybe -- one was trying to squeeze the last percent out of noise emissions *and* board space was very limited. I could see doing this with very small PCBs, where the via ring would take up an appreciable percentage of the board space. It should not have been much more expensive. In fact, as I recall, depending on the process, panel edges plate if you don't do something to prevent it! (The same electroless copper used to plate the inside of holes also plates the panel edge, I'd think, I don't remember actually seeing this; however, that edge is normally routed away when all the processing is done, leaving the unplated edges that we normally see. So to accomplish this relatively inexpensively, one would route the boards as one routes a breakaway board *before* going to the electroless copper; this would leave some unplated tabs but one might hide the unplated tabs behind mounting holes....) Edge effect with regard to radiated noise is a controversial subject, but actually plating the board edge I have never before seen suggested. [EMAIL PROTECTED] Abdulrahman Lomax Easthampton, Massachusetts USA * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
