12 Replies Latest reply on Mar 6, 2012 9:26 PM by sabitha.jamal

    Query regarding the CAD short

    sabitha.jamal

      Hello

       

      We have Vsure with Fab and Assembly modules,One of our DFM board having some issue like cad short ,Vcc shorted to net ground,

       

      But this not recogonized while doing DFM,I mean not reported through CAD short

       

       

      Please reply

       

      Thanks and Regards

      sabitha

       

        • 1. Re: Query regarding the CAD short
          max_clark

          Sabitha,

           

          If you are indicating that the DFM analysis, specifically Signal Layer analysis, is not locating this short that would be because two copper features on the signal layers having these two net names come in contact with one another.  That is good because the issue should not be from a signal layer.  Therefore the problem is most likely directly on the power and ground planes.

           

          If you are indicating that the Netlist analysis is not locating this issue, then I would open a service request for this item as it should find it if the problem really exists.  We would need a bit more information than the design simply fails once manufactured because the issue might be manufacturing induced and we would not be able to come to that conclusion without this information.  We would need to know the location where the net short occurred and then work backwards.

           

          In either case, if you open a service request an engineer will be more than happy to provide assistance.

           

          Regards,

          Max Clark

          1 of 1 people found this helpful
          • 2. Re: Query regarding the CAD short
            sabitha.jamal

            We don't have the netlist analyser module. Is it work only in Netlist Analyser module?

             

             

            Thanks and Regards

            sabitha

            • 3. Re: Query regarding the CAD short
              max_clark

              Sabitha,

               

              Yes, you will need the Netlist Analyzer to find that a design has an issue like this or any other netlist related issues that occurs between layers.  Verifying net copper names on an individual signal layer basis is only a very basic form of netlist analysis.  It is by far from what is required for really verifying that the intended copper provides the nets as expected.

               

              The Netlist Analyzer will indicate that there is a power and ground problem, then try to locate the source.  These types of electrical issues could be a challenge to locate since the magnitude of the problem may consume a large portion of the design.  There are some techniques that can be used to locate more challenging problems.

               

              I hope this information you found helpful.

               

              Regards,

              Max

              1 of 1 people found this helpful
              • 4. Re: Query regarding the CAD short
                sabitha.jamal

                Hi Max,

                 

                 

                     Thanks for the information ,We bought the netlist Analyzer module from Mentro Graphics seperately. We have been getting no net name short in netlist analyzer module in running jobs ,by considering the less criticality we will not be shared this to customer ,I tried many times to locate the real short point in earlier issue odb file with VCC and GND short.But unfortunately not get the output..Most of the time our station is engaged with Graphic station for DFM jobs ,so I could n't get the chance to work out in netlist Analyzer module ,My query is, whether we can open the netlist analyzer seperately in second station? Means I would like to open the netlist analyzer seperately from my PC while working the other person in Graphic station.If it is possible it will be very useful for us.

                 

                Thanks and Regards

                sabitha

                • 5. Re: Query regarding the CAD short
                  yu.yanfeng

                  Hi sabitha,

                   

                  Valor's netlist analyzer is trustable. By using this tool, We always catched all short issue before sending to fab. If you foudn your real pcb vcc/gnd got shorted but Valor reports no CAD short there, the prolem may be in CAM data.  I mean your CAD data is ok, but CAM data not.  Did you run netlist check to CAM data?

                   

                  Based on my experience, most to such short is caused by ill Gerber 274x data(self-interection-polygons). As Max told it's difficult to position which location happened sometimes. To your question, I suggest you run drill check for power-ground short and find the short location.

                   

                  Netlist analyzer is an option, you may need minium license feature of Ggraphics station and netlist analyzer.

                   

                  Yanfeng

                  • 6. Re: Query regarding the CAD short
                    yu.yanfeng

                    BTW,

                     

                    Most of time, "no name" net shorts with other nets be common due to CAD library where librarian put multiple pin objects and spread copper pour in cell  but only one pin get electrical connection in schematics, for example, ground  mouting holes etc. You can walk through to see whether there are such type of cells on your design.

                     

                    Yanfeng 

                    • 7. Re: Query regarding the CAD short
                      max_clark

                      Sabitha,

                       

                      I suggest that you contact your local sales or support organization to provide you guidance for this level of support.  The base use model requires the available of the Graphic Station to obtain access to supporting modules, including the Netlist Analyzer.  Within the application, analysis is viewed as a result of being able to review the design content within the Graphic Station.  For a more detailed explanation, please contact your local Mentor Graphics representative.

                       

                      Thanks,

                      Max

                      • 8. Re: Query regarding the CAD short
                        sabitha.jamal

                        Hello Yu.Yanfeng,

                         

                         

                                 I am not fully understand the multiple pin objects during library creation ,Suppose we have 2 pin connector ,the multiple pin objects related to both pins or for particular pin of the connector having with multiple properties.? From your reply , I understand that the "no net name" short related to the difference of schematic netlist  and it may or may not be an error.

                         

                         

                        Thanks and Regards

                        sabitha

                        • 9. Re: Query regarding the CAD short
                          sabitha.jamal

                          Hi Yu

                           

                               The issue was in both gerber and odb files ,and because of vcc and gnd shorts many other short happened in board and it all displayed in Netlist Analyzer .The main cause was the padstack property of blind and buried vias,But when customer asked the origin of short our PCB fabricator gave the exact point after doing with netlist Analyzer ,but I couldn't locate the exact point in the same file after purchasing the netlist module that is the issue  being faced .This is not related to netlist analyzer but my lack of experience in Netlist module .

                           

                          Thanks for your comments

                           

                           

                          Best Regards

                          Sabitha Jamal

                          • 10. Re: Query regarding the CAD short
                            sabitha.jamal

                            Hello Max

                             

                             

                                 Thanks for your feedbacks will contact to local support to detect the exact issue .

                             

                             

                            Thanks and Regards

                            sabitha

                            • 11. Re: Query regarding the CAD short
                              yu.yanfeng

                              Take an example for a mount hole with annular ring , the librarian created the cell with 8 pins on the annular ring and created a schemtics symbol with one pin(this make schematics clear). If designer connects this pin of symbol to ground net, Valor will reports this type of short because other 7 pins be dummy nets(no name) but it short with ground due to annular copper convering the pin 1 with ground net name and other 7 pins with dummy nets(no name).

                               

                              Yanfeng

                              • 12. Re: Query regarding the CAD short
                                sabitha.jamal

                                Hi Yu

                                 

                                 

                                    Thanks for quick feedback ,now I understood the real scenario...

                                 

                                 

                                Best Regards

                                sabitha jamal