8 Replies Latest reply on Jul 28, 2014 7:35 AM by kabaleeswaran.K.R

    What is mean by Body to Body clearance ??


      Hi everyone,


      Let me know what is mean by body to body clearance.is it represent clearance (spacing)between components assembly to assembly or Silkscreen to silkscreen ??

      while placing component ususally i set the grid 20 mil between component to component.if i set the body to body clearance is 15mil,which one software will be consider ??

      is it possible to increase the thermal relief for any one of through hole component ?? is it possible.


      please reply any one to clear my doubt

        • 1. Re: What is mean by Body to Body clearance ??

          It seems body to body clearance would work off the shape on the Assembly Drawing Top layer (27).  The 9.5 documentation talks about being able to define a 'nudge outline' on layer 20 that appears to take precedence.


          If you use the <View><Clearance> tool it shows the clearance from silkscreen to silkscreen.


          On a side note, it appears it you make an IDF Export by default it takes the shape from layer 19.  It appears this is very inconsistent.



          I believe in 2005 the only thermal control is global for all thru-hole pins.  You can set a different option for Oval and Circle but those are the only two variants.

          • 2. Re: What is mean by Body to Body clearance ??

            Layer 19 is used to output component outline data to 3D conversion programs (IDF)


            Layer 20 is used as the placement outline.  This might be a larger size than the Layer 19 outline, to add extra clearance for a particular part.


            Those outlines must be a single, closed polygon.


            Shapes on the Assembly drawing layers can be mul;tiple lines, open lines, anything you want to show on an assembly drawing. 


            Of course, if you are using Layer 19 shapes, you are probably doing assembly drawings in your 3D CAD program and don't need Assembly Drawing layers.

            • 3. Re: What is mean by Body to Body clearance ??

              Thanks for your reply,

              i could not understand what is the use of body to body clearance.Are you giving statement as clearance between assembly to assembly is body to body to clearance or mean it different ?? incase if you mean it, why should i need to keep pad to pad clearance.for example if i set body to body as 20 mil clearance,component to be place one by one as 20 mil spacing only, right?.so pad never overlapping with other right ??explain to me clearly.


              i have one more doubt,ususally i define the Mechanical layer (DXF),in layer 105,while import the DXF i choosen only  the available layer as DXF remaing layer i removed,in that case if i import the DXF it is not importing in that layer.instead of if i choose all layers in selected box it is importing again i need to change into DXF layer.it is double work for me.so please explain How to import the DXF (Mechanical drawing) in defined layer.Please clarify any one for this queries.

              • 4. Re: What is mean by Body to Body clearance ??

                There are many through-hole parts (such as an oscillator) where the body is larger than the pad spacing, so two oscillators would be concerned about the body to body placement.  It varies from part to part.


                If we don't get a defining answer from someone at Mentor for how the clearance rules are prioritized, you'll have to experiment around with it.


                I suspect it works like this but I haven't verified this:


                Check for clearance on layer 20 (placement outline)

                if no violations on layer 20

                     check for clearance on layer 26 (silkscreen top)

                     If no violations on layer 26

                          check for clearance on layer 27 (silkscreen top)



                • 5. Re: What is mean by Body to Body clearance ??

                  Body to Body clerance serves a completely different purpose than copper clearance.


                  Body clearance is a mechanical requirement.  It is the space that is required between compnenets for placement and inspection.  So you may set your body clearance to 20mils to allow the pick and place machine to place parts.


                  Copper clearance is an electrical requirement.  It is the space required to make sure your signals don't short (or crosstalk, etc.).  You might set this clearance to 10 mils.  Since through hole pads or surface mount lands often extend past the part outlines, you could place parts 25 mils apart, but if the pads extend 10 mils from the bodies, you would violate the copper clearance.


                  (copper clearance is also a fabrication requirement, but we don't need to get into that to answer this question)


                  As for PADS checking:


                  There is no checking hierarchy based on layers.  PADS Verify checks for violations on all diosplayed layers.  Except for body clearance. (As of v9.4) The Verify Design only checks part outlines on the top layer (or bottom, for bottom side parts).  If you have placement outlines defined on layer 1 and silkscreen on Layer 26, that's fine.  My library was defined back when the PADS structure was different, silkscreen is Layer 1, checking is useless.  BUT, because PADS recognizes Layer 20 as the placement outline layer, If I place parts with DRC on, I can not violate my body to body clearance without manually allowing the violation.



                  • 6. Re: What is mean by Body to Body clearance ??

                    Thanks for your reply.but if i keep body to body clerance 20mil after placing the component not placing perfectly,it is shown the clerance is 34mil.please clear second question as i posted previous

                    • 7. Re: What is mean by Body to Body clearance ??

                      Where are you seeing 34 mil?  Is it in 'View clearance' or a design rule report?  Can you post a picture or attach the report?


                      it sounds like PADS is checking something different than what you are expecting it to check.

                      • 8. Re: What is mean by Body to Body clearance ??

                        Hi thanks for your reply

                        i set body to body clearance is 20mil and design grid(placement grid) is 1mil,but while placing clearance is changing but incase if i set the design grid (placement grid ) is 25mil,i got clearance as 28 mil .so which one i have to consider.placement grid if i change the clearance will be changing how to solve this