Wouter van Ooijen wrote: > No, i have never dealt with a PCB of that complexity, but I answered > someone who was alarmed at the idea of a PCB without part numbers. If > finding the part numbers on a multi-color (probably magnified) printout > is difficult I don't think part numbers on the silkscreen will make > things easier! I think component designators (part numbers actually means something else) are a good idea on the silkscreen where possible. They make debugging easier and make it just a little less likely that someone will screw up during manufacturing. They may be technically redundant, but redundancy can be a good thing when trying to reduce human error. Unfortunately with the newer smaller components and more tightly packed boards, it's not always possible to put all component designators on the silkscreen. I have developed several ways to deal with this using Eagle. I have gone back to all my library parts and added component designators in a small font in the tDocu layer, then also put component designators intended for the silkscreen in the tNames layer. The smallest I use for silkscreen is size .05 with ratio 16, which comes out to .008 line width. That's the smallest I trust silkscreen to reproduce without explicit specs to the contrary. This scheme works with my GRID_BRD ULP. This automates the creation of gray scale drawings of the top and bottom sides of the board. The appropriate Docu layers are shown in full black to stand out easily, with the silkscreen, copper, and other layers in various shades of gray to provide a good visual match between the drawing and the board. GRID_BRD also draws a 1" grid in light gray with labeled coordinates so that it is easy to find a particular X,Y coordinate on the board. Then my INDEX ULP creates a part finder index that gives schematic page, coordinate within page, and board X,Y coordinate for each part. The assembly house gets the BOM, the board drawings, and the part locator index. I've had assemblers comment to me that they really liked the parts locator and wished everybody else would provide one too. I put an example board drawing at http://www.embedinc.com/temp/eusb2_top.gif and the corresponding locator index at http://www.embedinc.com/temp/eusb2_index.txt. The small black component designators only show up on the drawing, not on the board. Another important step that all too often gets skipped is to clean up the silkscreen after you're done routing. Parts will have been placed in orientations that make sense for the layout, and the resulting tNames text can end up in awkward places. Neatness counts, both for reducing human error and towards the impression others get when looking at the board. Yes it's tedious, but I go thru and move around the text for each part to make it right side up when possible, make sure it's not on top of any vias (which will put a hole in the silkscreen), clearly labeling the associated part and not some other, not colliding with other text, etc. Sometimes it's not possible to fit everything. For example look at C45 and R15 near the lower left corner of the board. In such cases it is better to leave the labels off than to try to cram them where they will make a mess and cause more confusion than they might eliminate. I couldn't put the label below C45 because of there were 3 vias there. Not having a label on C45 would have made a label below R15 ambiguous whether it was referring to the part above or below it, so I left that off too. I probably spent two hours just on the silkscreen after getting the final route. This included adding other text beyond just adjusting the component designators, like the labels for each pin of P8 near the top right corner. Oh, yeah, to get back to the original subject, see the lower right corner of the board. The "EUSB2" is in copper, and is how I designate that particular version of that particular board. All my Eagle files are called EUSB2 and are in a EUSB2 subdirectory. This is really an internal name and not relevant to a user. Just above the board part number is a filled silkscreen rectangle for the serial number. I plan on serial numbers being written by hand with a sharpie marker. There are better ways for high volumes, but for low volumes that works fine in my experience. You can try all this yourself easily. All the Eagle tools I've mentioned are available in my Eagle Tools download at http://www.embedinc.com/pic/dload.htm. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist