> Also I believe there is an extra process step involved when you have > pad area on a NPT hole.
I've talked to a couple of vendors about the implications of PTH/NPTH holes. Their requirements are essentially that they want copper of the minimum annular ring outside of the hole for PTH and that amount of clearance inside the hole for NPTH due to drilling tolerance. That assumes a hole that is small enough to be masked by the etch resist and those holes will be drilled prior to plating (no cost penalty). The allowable size of the hole seems to vary quite a bit and isn't usually published (that I've noticed). If the hole is bigger than that threshold, it will be done on the routing machine near the end of the process. Probing a bit further with one vendor, I found out that although the NPTH drill and the outline routing run on the same machine, they are two separate programs so the boards go through it twice. (This particular place was rather 'low-end' so I don't know how applicable that it to other fab shops). In the case of the vanishing fiducials, the board house was getting so many boards with pads the same size as the holes for NPTH holes, they have got into the habit of removing all pads from NPTH drill sites. That's quite reasonable except that the CAM operator decided to select based on pad size and that caused my fiducials to fall off. Regards, Steve. ====================================================== Steve Baldwin Electronic Product Design TLA Microsystems Ltd Microcontroller Specialists PO Box 15-680, New Lynn http://www.tla.co.nz Auckland, New Zealand ph +64 9 820-2221 email: [EMAIL PROTECTED] fax +64 9 820-1929 ====================================================== * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
