Is anyone out there investigating or using a conductive Polymer Thick Film layer on the outside of the board to reduce EMI. Using this PTF allows you to possibly go from a 4 layer board with internal ground planes to a 2 layer board. CHEAPER!!!!!!!! [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Re: Internal and external ground planes Author: Non-HP-dwalker ([log in to unmask]) at HP-Vancouver,shargw2 Date: 10/23/96 8:38 AM I believe you should tie the external ground plane at one point only. The return current path often completes a loop antenna - a highly directional radiation source - and if, by connecting the components to the outer shield, you make the outer plane a part of the current return path you have turned your shield into a radiation source. Don Walker [log in to unmask] > We design high speed line scan cameras and use internal and > external ground planes (external for shielding) on our PCB's. > My question is this- > > Should the internal and external planes be tied throughout the board (at > vias, etc.) or should the external planes be tied back only at a single > soure (power connector) and leave the internal plane(s) for all component > connections? I am wondering if there are advantages of one over the other. > > VIP Lab > University of Arkansas *************************************************************************** * TechNet 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. * *************************************************************************** *************************************************************************** * TechNet 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. * ***************************************************************************