Don't forget the etchback either. That removes a little bit of dielectric from underneath the pad next to the drilled hole and adds to the problem. Andy K. Sychip Inc Office (972) 202 8852 -----Original Message----- From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Gary Ferrari Sent: Wednesday, December 10, 2003 11:25 AM To: [log in to unmask] Subject: Re: [DC] Manufacture adjusting Gerber's Stan, I believe that Andy Kowalewski described the reasoning very well. However, the laminate material shrinks back into a drilled hole resulting in a smaller diameter that required. If one were to plate the hole, the finished size would be smaller than desired. Therefore, the fabricator overdrills the hole so that when the laminate material shrinks, it shrinks to a level that will still produce the minimum desired hole size. If the designer does not allow for this overdrill in his land pattern size, it is very possible that the drill will completely remove all the copper in the land resulting in no land at all. Typically fabricators adjust line widths to compensate for etch factors. They rarely compensate lands unless they discover a serious problem and only after notifying the designer of how they propose to fix the problem. By compensating land sizes they are subject to the risk of creating a greater number of spacing violations. This results in far too many fixes on the fabricators part unless they elect to charge for the service. Regards, Gary ------------------------------------------------------------------------ --------- 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 ---------------------------------------------------------------------------------