Hi, according to IPC4101 the specified breakdown voltage of FR4 is 40kV/mm for laminates thicker than 0.5mm, according to IPC2221 the internal conductor distance for 500V DC is 0.25mm. Is there any specification which says high and low voltage traces are not allowed to cross between internal layers of an pcb? Or is it fine to use the FR4 as an isolation between areas where basic isolation is recommended? Thanks, Torsten ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------