Steve, I believe that is referring to the Minimum Standard Fabrication Allowance for Interconnection Lands, as defined in Table 9-1 in IPC-2221. "To meet the annular ring requirments, the minimum land surrounding a hole shall be determined by the following. The worst-case land-to-hole relationship is established by the equation: Land size, minimum = a + 2b + c where: a= maximum diameter of the finished hole b= minimum annular ring requirements c= a standard fabrication allowance (table 9-1) that considers production master tooling and process variations required to fabricate boards. Table 9-1 Producibility Level A - 0.4 mm Level B - 0.25 mm Level C - 0.2 mm" There are some additional notes on the table. But you've got the gist. Lisa Williams IPC 2215 Sanders Road Northbrook, IL 60062 URL: www.ipc.org >>> Steve Hawn <[log in to unmask]> 07/20/98 09:47AM >>> Hello, I'll try sending this one out again since I didn't see any responses last week. On all of our PCB fab drawings there is a specification which reads: Land/Hole fabrication allowance shall be 0.012 in. What does this spec mean? Our PCB designer and two board houses I've spoken to do not know what this spec is referring to. Our PCB designer states that this wording can be found in IPC-D-325A, Documentation Requirements for Printed Boards, in an example fab drawing. Steve Hawn Precision Digital Images ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################