According to my notes from Lee Ritchey's class, the dielectric breakdown voltage, DBV, of standard FR-4 is 1100 Volts/mil. So, it seems to me that you need, at least, 1.4 mils copper-to-copper spacing on the inner layers. The outer layers dielectric strength would also be a function of the DBV of the soldermask. So, you probably need more. TJ Thomas L. Jackson, PE Staff System Engineer L1-50, Remote Sensing Systems Engineering Missiles and Space Operations Lockheed Martin Space Systems Company telephone: (408) 742-2013 facsimile: (408) 742-7701 location: B149/E2 -----Original Message----- From: Ibrahim Khan [mailto:ikhan@xxxxxxxxxxxxxxxxxxx] Sent: Friday, August 02, 2002 10:11 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] copper-to-copper separation Hello si Gurus, Anyone has a reliable data on what should be the copper-to-copper separation for outer layers and inner layers (FR4) to run a 1500V highpot test. Thanks Ibrahim Khan ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu