Alan, In this case I can use 5 and 12 split mixed plane. One of my main reason I do signals in middle layers is to protect circuit agents reverse engineering. Most engineers give up when they see no traces on top or bottom of the board. Andre -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Alan B. Pearce Sent: Monday, November 24, 2008 10:03 AM To: Microcontroller discussion list - Public. Subject: Re: PCB power plane question Personally I would do it as follows: - Layer1: signal Layer2: 5v plane & 12V track as required. Layer3: ground Layer4: signal The area supplied by 12V will probably be only a small portion of the PCB, and I would have 12V to just that area, with the rest of that layer as a 5V plane. However without knowing precisely what you are setting out to do, it is difficult to advise you properly. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist IMPORTANT NOTICE: This notice constitutes Proprietary Rights identification of this email including all attachments, which is property that is intended only for the use of the individual or entity to which it is addressed. It also may contain proprietary data or information that is privileged, confidential, or otherwise protected from disclosure under applicable law. The recipient of this data agrees to abide by the United States Export Control of Technical Data and Equipment under the International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR). The recipient agrees to abide by these laws and their regulations not only for export and re-export, but for disclosure to non-U.S. citizens. This email does not grant or assign rights of ownership in the proprietary subject matter herein, nor shall it be construed as a joint venture, partnership, teaming agreement, or other formal business relationship. If the reader of this e-mail transmission! is not the intended recipient or the employee or agent responsible for delivering the transmission to the intended recipient, you are hereby notified that any dissemination, distribution, copying or use of this e-mail or its contents is strictly prohibited. Please notify the sender you received it in error by responding to the e-mail and then permanently delete it and all copies of the e-mail immediately, including any copies of it in your deleted email folder. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist