Jerry: You are correct in saying that most board houses don't do a "true" net list test based on your supplied netlist; rather a test fixture is created from the Gerber in most cases. At least this is the case at HADCO. HADCO takes the Gerber data provided and "pre-netlists" it before any modifications. These modifications (teardropping, adjusting pad & line widths, thieving, etc.) are then performed and a "post-netlist" is generated. We then do a pre/post netlist compare to ensure that we did not chnage the intent of the design in any way. We have embraced IPC-D-356 netlist formatting as the vehicle for those of our customers who prefer to supply us with a netlist from which to build the fixture. We viewed -356 as the most universally accepted format out there. Unfortunately, there are usually discrepancies between supplied netlist and Gerber (on one job there were over 700 discrepancies!). For this reason, we have chosen to use a certification program with our customers who desire us to use their -356 data. Three successive designs must be sent in with no discrepancies to become certified. It's a great learning curve for both HADCO and our customer. At present, I believe we only have two "certified" customers out of a customer base of over 500. Let me share with you some of the common problems encountered: - Non-plated holes called out as a net - Ground areas which are physically disconnected but part of the same net, which are not listed in the same net - Naming convention errors (ex: "Signal A" later listed as "Sig A" and then not tied together) - Manual changes to Gerber not reflected in CAE data (ex: split power/ground) - CAE netlist not in IPC-D-356 format. Much of the data that we receive seems to have a personal touch mixed in with the IPC format. We need data that has been built under the guidelines of IPC-D-356 from the first column to the last (70th). We will gladly work with any customer who wants us to generate fixtures from their supplied IPC-D-356 netlist data. We need the name, telephone #, and fax # of a person designated to work resolutions on the CAD vs. Gerber conflicts. In summary, IPC-D-356 testing is a computer-generated file in a specific format which describes which points are interconnected, or part of a common net. Gerber-extract testing is taking customer Gerber image files, processing this information on a CAM workstation, and then computer-generating a netlist program for electrical test. Regards, Tom Coyle Field Services Engineer HADCO Corporation [log in to unmask]