When you say "comps", you mean components, right? I'm assuming two SMT devices, correct? If it's not a via in a pad, the only reason I can think of is ground bounce from a high di/dt on one device interacting with the other. And, if the trace from the pad to the via is too short, it could intefere with soldering--but that'd be true if there was only 1 component feeding that via. In short, I'm not coming up with reasons myself. Shawn Upton, KB1CKT Test Engineer Allegro MicroSystems, Inc [log in to unmask] 603.626.2429/fax: 603.641.5336 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry Kozlyk Sent: Tuesday, March 13, 2007 7:10 AM To: [log in to unmask] Subject: [TN] Comps on opposite side of PCB sharing GND vias Yesterday a colleague of mine at work said 2 comps on opposite sides of the PCB could NOT share a GND via which was nailed down to a solid plane in between. After thinking about it for an hour or so, I came up with my own several reasons. Just wanted to hear anyone elses opinions about this practice. I do it mainly to economize on vias taking up less space. Of course, the via has to be close to each comps GND pad. The comps are literally placed coincident to each other, for the main purpose of sharing a GND via. TDK (Terry) --------------------------------------------------- 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 -----------------------------------------------------