Hi, Regarding design of pads for internal and extrenal layers, I think the best will be to have them in the same size, this to better see misalignment on finish board. However for manufacturing of PCB the internal pads should be something like 0.1mm larger than extrenal pads this due to misaligment during lamination of internal layers. One PCB company has the following criteria: that the internal pads shall be 0.35mm larger than drilled hole and extrenal layer 0.25mm larger than drilled hole. For finish board the criteria, will be a larger distance between the pad edge and the hole edge on extrenal layers, this to be able to have good soldering (for example 0.15mm). For internal layers it is enough with for example 0.05mm. If the manufacturing tolerance is 0.1mm larger for the internal layer but the criteria for the internal layer is 0.1mm less, so will the result be that it will be possible to use the same size of pads. Best Regards Peter Dahlén Saab Ericsson Space [log in to unmask] At 07:26 1997-08-04 -0400, you wrote: > John.. > I'm still surprised! We have been designing 12-14 layer (standard) > smt designs for about a zillion years, maybe not quite a zillion, but > a looonnng time and no vendor has ever requested that the inner layer > pads be larger. In fact, unless I am looking at the formula/chart in > the Mil and IPC specs incorrectly, the minimum annular ring requirement > for internal is .001/.002 mils vs .002/.004 mils for external layers. > Therefore, by definition, your external pads should be larger. What > am I missing??? > Regards, > Bob >