1 2 First Previous 16 Replies Latest reply on Oct 22, 2012 8:08 AM by Pete

    Thermal Relief Issues



           I have been trying to find a way to add thermal relief to certain surface mount pads in my PADS layout design to make solder rework slightly easier. The problem is that that I only want to do this for specified components as I have certain components operating at high current levels and want to flood over those. Is there any easy way to do this? I have tried unchecking/checking the Plane Thermal option in the Pin Properties but it is locked for every component.


      Thanks for your time.

        • 1. Re: Thermal Relief Issues

          Try turning your design rule checking off (modeless DRO) and then changing the pin properties again.  Just remember to turn your design rule checking back on when you are done.


          Do you want to add copper to pads for thermal relief; that's copper association.


          Or are you trying to add spokes to the pad?  I sometimes have to define circular pads to have spokes and oval pads to flood over and then redifine the pins on the parts that I want to flood.  This does get tricky if you have multiple parts on the board and you want some flooded and some not.  You'll need to define two decals for the part, one with circular pads and one with oval pads.  You can select the decal in Layout.  Just be careful with this technique, because the ECO process can reset the decal selection; if you don't notice in the Gerber generation you might not get what you expected.

          • 2. Re: Thermal Relief Issues

            Even with design rule checking off the plane thermal option is still locked.


            Yes, I am looking to add relief with spokes. I did the oval/circle trick for my through hole components/vias but for the surface mounts I have rectangular and sqaure pads so I can't set one as flooded and the other as relief. It looks like I may have to modify the pad shapes so that I can assign them appropriately but this doesn't seem like an ideal solution.

            • 3. Re: Thermal Relief Issues


                   Try this solution:

              1. RMB on a component-->Edit Decal;

              2. Go to Edit Padstack and change settings for thermals (you can set this pin to be flooded (Flood over)). Please, keep in mind, that flooding is only permited on wave side (usually Bottom). For inner layers and wave oposite side put thermals;

              3. Close Edit decal edittor and a message will appear: "Change selected component" or "Change all components". Put a check in "Keep atributes" and select what you want.


              This will help!


              Kind regards,


              • 4. Re: Thermal Relief Issues
                David Ricketts

                There is no easy way out of the box, but once you've set it up, it's pretty easy to use. I'm describing a way to make this part of your library, but you can do this edit/padstacks with for each part if you prefer, making it a solution just for the one design you're working on.


                First, you must make the layer a split/mixed plane, otherwise you only have the basic thermal options to work with, and as you've noticed, those are very limited.


                Then you need to create decals specific to the type of thermal you want, and assign them to the part. Start with the original decal, use edit/padstacks to get the thermal spokes you want, and save that decal with a different name. I'd append something like <decalname>-spokes. Modify another one in the same way, only instead of a thermal gap, make the outer width the same as the inner width. This will cause the pin to flood over in a plane connect. Name it something like <decalname>-flood. This gives you three decals with different pin thermal properties: none, spokes, and flood over. If you want one of the new ones as your default, you can reduce it to two. Assign them all to the part(s) you need.


                Update your part(s) from the library. Now, you can select each part, and change it to use the decal with the thermal you need. If you have decal checking turned on with Compare/ECO tools, don't forget to back annotate your schematic when you're done.

                • 5. Re: Thermal Relief Issues

                  Thanks for the help David, it is much appreciated.

                  • 6. Re: Thermal Relief Issues

                    What does "use edit/padstacks to get the thermal spokes you want," mean? I don't see anything in the padstack editor that refers to thermals.

                    I am also fighting with the issue of copper pours NOT generating thermals to pads that have associated copper.


                    Thank you


                    • 7. Re: Thermal Relief Issues
                      David Ricketts

                      On the Padstack editing menu, click on the "Pad style:" drop-down box, and select Thermal. There's plenty of options, as long as the pad is square or round.


                      For associated copper, I can't get thermal spokes to generate either. You can flood over the pad by setting the thermal outer size to be the same as the inner size, using the above procedure. But no thermals get generated if you set up thermal spokes, and that seems to be a missing feature, perhaps an outright bug.

                      • 8. Re: Thermal Relief Issues

                        I don't know what I am missing, but clcking on Thermal doesn't change anything. When I flood pours, I still get no thermals to that pad.

                        It seems to only be pads that have associated copper around them.

                        • 9. Re: Thermal Relief Issues
                          David Ricketts

                          You seem to have two separate issues. You asked how to create custom thermals. I described that. You also asked about thermals for a pad with associated copper. I wrote that they don't seem to work, but I don't know if that's by design or an oversight.

                          • 10. Re: Thermal Relief Issues

                            Yes, sorry I guess I misunderstood your answer(s).


                            Editing the thermal settings for even a standard pad (no associated copper) seems to have absolutely no effect on the thermals when I re-flood copper. I have tried different settings for the spokes, and I have tried “flood”. When I re-pour, I get the thermals that are specified by the global settings only.


                            Is this a bug or am I missing something?




                            • 11. Re: Thermal Relief Issues
                              David Ricketts

                              You need to be using a split/mixed plane for custom thermals to work.

                              • 12. Re: Thermal Relief Issues

                                Thanks –


                                If I change an outer (component) layer to Split/Mixed, the CAM output is incorrect. How do I make an outer layer generate the copper correctly if it’s split/mixed?



                                • 13. Re: Thermal Relief Issues

                                  Thanks – I found the settings for flooding the split/mixed plane layer, looks perfect. I have never used planes before, I always used copper pours…



                                  • 14. Re: Thermal Relief Issues

                                    Well, it was looking good, but it seems that using split/mixed planes on external layers may not work either. The “plane” areas (areas that were copper pours) are difficult (or impossible?) to edit. I haven’t been able to change the shape of one of these planes (on the split/mixed layer).


                                    And I saw this in the HELP file:


                                    Limit the assignment of split/mixed to internal, embedded plane layers. Assigning external routing layers as split/mixed layers may produce unexpected results.




                                    So using copper pours has issues with thermals. Using split/mixed planes (on component layers) isn’t recommended.


                                    Do you have any comments on this? Should I give the split/mixed planes some effort, or go back to using copper pours on outside layers (and live the poor thermals)?







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