Joe, Several considerations... You don't want to put your ground and power planes as the external layers. It would cause you to have to cut huge holes in your plane and create, in effect many slot antennas. If you placed the planes at any other position you will have to pick and choose what traces to route inside the planes and what outside. Traces which you had not considered critical or high freq (fast switching) may carry the noise to an outer layer if they run both inside the planes and out. This means that you may not get the results you were expecting. You will lose the benefit of distributed capacitance (small though it may be) you get from having the planes close together. One other thing, any disturbance in the conductive path may, under certain signal conditions, become a source of radiation. Most of the time square corners make no difference -- if, however, that corner happens to be at length matched to the propagation delay of the waveform it becomes a disturbance point, the signal reflects back on itself and the current level at that point increases, thus increasing the radiation. You want to keep the current distribution as even as possible. At very high frequencies even 45 degree angles can cause problems. You want to keep current distributions as even as possible, high freq signals as short as possible, noise away from signals which connect to I/O, and concentrate your efforts on the most electrically noisy area -- keep it isolated -- shrink it -- move it away from the edges -- shield it. L8R, DonW... Don Walker Sr. CAD Designer [log in to unmask] **************************************************************************** * The mail list is provided as a service by IPC using SmartList v3.05 * **************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ****************************************************************************