2 Replies Latest reply on Feb 20, 2015 3:37 AM by sajivnglnice

    Body to body clearances violations

    ampohms

      It seems body to body clearance violation errors occur whenever a part outline touches another part outline.  This would seem to jive with the intent of the rule, but it doesn't.

       

      The problem is that part outlines with a thickness violate the rule whenever any part of that thick outline touches another outline.  This is a problem.  To look at it from another perspective... When I create a part, I create it based on spacing/dimensions provided in the manufacturer specifications for the part.  So, if the manufacturer suggests a courtyard of 100mil x 100mil, I draw an outline of 100mil x 100mil.  As long as another part does not violate my 100mil box, I'm good.  But if I give that outline a thickness of, say, 10 mil, then any parts placed on 100 mil centers will violate.  This is not because the courtyard dimensions have been broken.  Its because the courtyard line thicknesses have been broken.

       

      This is a flaw.  No one designs part decals according to manufacturers recommendations... oh, and by the way, be sure to remember to take into account line thicknesses in PADS.  Every outline would now require a calculation to adjust for the thickness, which, in addition to the additional work to create each new part, also makes decal creation more prone to to calculation errors.

       

      There is no doubt that this is a defect, I'm just wondering if this was designed into the tool on purpose, or just an oversight.

       

       

      (Before anyone proposes this as a solution, I'll go ahead and nip it in the bud... Changing the line thickness of the library part is not a solution to this problem.   It's a work around, which does not truly resolve the issue...  Line thicknesses may play other important roles in a design, which, in my case, they do.)

        • 1. Re: Body to body clearances violations
          Pete

          Here's your answer:

           

          Change the line thickness!  ;-)

           

          Yes, I read your post asking that I don't say that.  But aside from my contrarian nature, I've got a good reason to say it.

           

          On Layer 1, build your silkscreen outline.  Use 8 mils, 10 mils, whatever you like, don't worry about part size, make it pretty.

           

          On Layer 19, build an actual size (maximum for all alternate parts) part outline.  Use a 1 mil line width.  This one is for assembly drawings, output to IDF.  It must be a single closed polygon.

           

          On Layer 20, copy the Layer 19 shape (1 mil), and if you need additional clearance around the part for pick and place or ICT considerations, add it here.

           

          Set the Body to Body clearance rule to whatever you need, run your Verify Design with all outline layers except Layer 20 turned off.  Now here's the trick: set up your Clearance Checking to check Placement Outline, not Body to Body (that's right, it doesn't really make sense).

           

          Setting a 20 mil clearance, placing parts with 1 mil outlines 20 mils apart will give you no violation.  Less than 20, you'll get a violation.  My tall parts are oversized by 60 mils around the perimeter, that gives me 80 mils clearance.

           

          Layer 20 is the key.  PADS understands that as the Placement Outline layer.  When placing with DRC on, PADS will use Layer 20 to determine legal Placement Clearance.

           

          I have renamed Layers 19 and 20 in my default settings as "3D Outlines" and "Placement Courtyard" respectively.

          • 2. Re: Body to body clearances violations
            sajivnglnice

            Hi ampohms,

             

            Can you show some images, it will help me to understand and clarify your problem.

             

            Regards,

            Sajiv