4 Replies Latest reply on Jan 9, 2009 5:44 PM by yu.yanfeng

    Plane Scallops/Peninsulas Removal






      I would like to ask the community about plane scallops/peninsulas in order to get opinions on if they are needed, should be removed by default, and how these should behave when plane connections are needed.



      In the graphic below, figure 1, I have two situations; the bottom situation is the normal planes generation where the user will see these scallops/peninsulas generated between the pins. The top situation is where these scallops/peninsulas have been removed.


      Figure 1



      • Based on this example, which methodology is preferred and why?

      • Is there any reason a user would want to keep the scallops/peninsulas between the pins of is it more common these should be removed?

      • Based on the thermal tie to the plane on the top right, should the scallops/peninsulas be kept in order to get an optimal number of thermal ties?




      In figure 2, this is the same example but a case where the pins are not offset as in Figure 1 and the hatch width causes the scallops/peninsulas as seen in figure 3. In this case the scallops/peninsulas are removed since they do not fully go between the pins.


      Figure 2






      Figure 3



      Specific to thermal ties, I feel the scallops/peninsulas should be left and not removed in order to have a higher number of thermal ties generated.



      • Does the community agree that scallops should be left in order to complete tie connections as seen in Figure 1 and 2?

      • What about if the user defines only two ties, maybe scallops could be removed as seen in Figure 4?




      Figure 4


      • What are some general opinions on scallops/peninsulas?

      • Is this a corner case or a typical problem seen by many users requiring a automated solution?

      • If this is a typical problem, how are users solving this problem today?


      I would appricate any input from users on this subject so this problem can be clearly understood.






      Jerry Suiter

      Product Marketing Manager Expedition / Xtreme PCB

        • 1. Re: Plane Scallops/Peninsulas Removal



          my first thought was about signal integrity. Sometimes you wish to have the "usual" ground plane as far embracing the signal as you can. Probably increased noise immunity. What is your take on this?


          I assume that nowadays the  fabrication  of the pcb does not have issues (sliver, acid traps, etc...), so why do you want to remove them?





          • 2. Re: Plane Scallops/Peninsulas Removal


            I agree with Matija on shielding requirement.



            There are couple of factors need to be considered -


            1. Shielding area with respect to ground plane, in case of couple of pins it is must.

            2. Balancing copper for proper heat distribution during plating processes on padstacks

            3. Simply we cannot remove number of thermal ties its depend on Power characteristics of the pin - may reuqire more than 2


            Please let us know any other reason than above any thing else demands to keep Plane Scallops/Peninsulas.



            Both above cases based on nature of layout density, pin characteristic and board parameters.



            Hence users may want to keep or may want to remove Plane Scallops/Peninsulas based on specifications.



            Option to choose remove or keep is best solution.



            In addition to that in case of keep option if some parametric conditions like - min - max clearance is appreciable.



            Sanjay Jagtap



            • 3. Re: Plane Scallops/Peninsulas Removal





              Thanks for the information from Matija and Sanjay on this topic.  I totally agree that any removal of Plane Scallops/Peninsulas should be optional.  Also, I want to explain the two use cases I have heard on why this functionality is needed:



              High Voltage Pins - This is a situation when a High Voltage Pin is within plane metal it should have no Scallops/Peninsulas around the pin.  This is to reduce the possibility of arching between the scallop point and the pin.  So the idea is to keep the plane metal around the High Voltage Pin as smooth as possible.



              Manufacturing - I have been told that specific to manufacturing customers which to remove Scallops and Peninsulas.  Interesting enough I have not been provided details to the specific manufacturing problem that would be caused.  I suspect it's specific to solder bridging between exposed plane metal and neighboring pads where the scallop ends up exposed between pads.  I think this is a corner case specific to users who are not using soldermask pads and build soldermask opens as shapes around rows of closely place pads.  I really would like to hear what the community thinks about this use case.









              • 4. Re: Plane Scallops/Peninsulas Removal

                Hi Jerry,

                Removal of Scappops/Penisulas is welcomed. At present, much of SIPs(self-intersectiing polygon) be generated and it causes

                PCB fabs complains it when they read the gerber into thier CAM system.