Hey All, All good points Matt, but what really is at the root of it all is process capability and the stacking of tolerances. Good point about the V-score, but in addition to that 1 mil (for instance) you would also best check your drawing for what manufacturing tolerance you are allowing for score location. If the toleance given is ±0.005" then the spacing from the edge just allowing for score alone would be 0.006" (0.001" slope plus the manufacturing tolerance). Take a look at all the processes that could bring the ground plane in contact with the edge of the board, start stacking tolerances. That will give your best answer. ) 0.039" should be very doable. Bob Dube ES&D -----Original Message----- From: Matthew Lamkin <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Friday, December 10, 1999 11:59 AM Subject: Re: [TN] Edge Clearance for power & ground planes >Hi there Ken, > >Rather than just give a measurement I'll explain why I keep power & >ground planes away from the edge of the board. > >If the board goes into a panel that is scored, you will need to bear in >mind that the edge of the board will have >a slope on it, caused by the V-scoring machine. This is typically 0.5mm >between boards in a panel. >Therefor you will lose 0.25mm (0.01") of the laminate around the edges. > >If the board is routed, you will not lose this, but it is always good >practice to keep the same distance away no matter what >method of panelisation. > >Once that is done, then you have to think about the solder resist edges. >If you have copper and solder resist >edges at the same distance from the edge you can get nasty things >creeping under it and corroding the board. >You need to leave a gap for an area of solder resist before the start of >your copper areas. > >I dare say that this also applies to the bonding of multiple layers, in >order to provide good adhesion of laminates >between the layers. > >What this then boils down to is keeping copper about 1mm (0.039") away >from the edge of the board. >If the board is large & has plenty of room then obviously this can be >increased, but should never be decreased. > >I dare say that its mentioned in one of the IPC specs somewhere. (I'd >like to know which one?). > >There... That's my tuppence... > >Hope it helps & doesn't confuse.... TIA - Matt. > > >>-----Original Message----- >>From: Ken Patel [SMTP:[log in to unmask]] >>Sent: Thursday, December 09, 1999 9:13 PM >>To: [log in to unmask] >>Subject: [TN] Edge Clearance for power & ground planes >> >>Guys, >>How far my power & ground planes should be away from the egge of the board? >> >>re, >>ken patel >>______________________________________________________ >>Ken Patel Phone: (408) 490-6804 >>1708 McCarthy Blvd. Fax: (408) 490-6859 >>Milpitas, CA 95035 Beeper: (888) 769-1808 >> >>############################################################## >>TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c >>############################################################## >>To subscribe/unsubscribe, send a message to [log in to unmask] with following >>text in >>the body: >>To subscribe: SUBSCRIBE TECHNET <your full name> >>To unsubscribe: SIGNOFF TECHNET >>############################################################## >>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional >>information. >>If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or >>847-509-9700 ext.5365 >>############################################################## > >############################################################## >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c >############################################################## >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in >the body: >To subscribe: SUBSCRIBE TECHNET <your full name> >To unsubscribe: SIGNOFF TECHNET >############################################################## >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional >information. >If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or >847-509-9700 ext.5365 >############################################################## > ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################