Hi Terry, Design Metrics are directly tied to your fabricator's capabilities, and that's where I'd recommend you start. Factors such as product type, volume, and margin are definetely to be considered. There are fabricators who produce 3 mil trace 4 mil space (and lower) controlled impedance HDI designs in high volumes cost effectively. At lower volumes, there's no way you could use such rules unless you receive large margins on your products. Be sure to verify with the fabricator what the standard production (no cost added) capabilities are. For general information, search on "Walt Custer" - he releases a quarterly update on the Electronics industry which includes a fair deal of information on leading Fabricators and CMs. Hth, Dave --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 -----------------------------------------------------