Hello All, We have a customer designed PCB that we're trying to understand better. It is a mixed dielectric board with .030" of Taconics material attached to approx .050" of FR-4. Currently the vias in the board in question are drilled to .014" and then plated per Class III, .001" min Cu with a subsequent Au flash. We understand aspect ratios of 1 to 10 or less is okay for single medium PCB's. The question we have is in regard to the proper aspect ratio for vias when used in mixed mediums. Any information you can forward would be much appreciated. Regards, Helena Helena Pasquito Manufacturing Skills Instructor M/A-COM, Tyco Electronics 1011 Pawtucket Blvd., M/S 107 Lowell, MA 01853 978-442-5024 [log in to unmask] <mailto:[log in to unmask]> --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------