Sorry I don't have any scientific data to back this up, but when I used to do a lot of diff pairs the rule was to keep other copper a distance of 3x the trace width. The strength of the field decreases by the square of the distance, so even adding a tiny bit of clearance can reduce crosstalk (or whatever) a LOT. good luck, Jack |---------+----------------------------> | | Ray Dwyer | | | <Ray.Dwyer@DALSEM| | | I.COM> | | | Sent by: | | | DesignerCouncil | | | <DesignerCouncil@| | | ipc.org> | | | | | | | | | 02/05/2004 11:57 | | | AM | | | Please respond to| | | "(Designers | | | Council Forum)"; | | | Please respond to| | | Ray Dwyer | | | | |---------+----------------------------> >------------------------------------------------------------------------------------------------------------------------------| | | | | | | | | |To: [log in to unmask] | |cc: | | | | | | | | Subject: [DC] copper pour stand-off | >------------------------------------------------------------------------------------------------------------------------------| Caterpillar: Confidential Green Retain Until: 03/06/2004 Retention Category: G90 - General Matters/Administration Greetings, I am concerned about rules for stand-off distance for copper pour on an outer layer to provide added isolation to a pair of sensitive low current traces. There are other traces on the top layer as well. The basic info is 50 ohm impedance, 10 mil wide microstrip, digital TTL signal current as low as in 10s of mili-amps, FR-4 material, 1 oz copper. Ray Dwyer 972-371-4046 Maxim 4401 Beltwood Parkway Dallas, Tx. 75244 --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 847-509-9700 ext.5315 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 847-509-9700 ext.5315 ---------------------------------------------------------------------------------