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tStop Polygon Causes DRC Errors

rossw

I'm trying to create a heat sink under a 7806 voltage regulator by drawing

a polygon in the tStop layer around the metal tab (I'll use heat sink

grease and maybe a nut & bolt to make a good connection). I want to add

vias to transfer the heat from the top layer ground plane to the bottom

layer ground plane. The problem is that when I add a polygon in the tStop

layer (so there's no solder mask under the metal tab, just bare metal) it

then causes multiple DRC errors on layer 29. I can't get rid of those DRC

errors even if I remove the polygon (either by CTRL-Z or manually delete

it). What am I doing wrong?

 

 

 

(Ignore the red-dotted polygon around the device - that's not needed (I

don't think) since I already have a top/bottom ground plane.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

 

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  • You are probably getting tStop errors because your tStop polygon overlaps

    the silkscreen (tPlace). Just approve those errors. BTW, your tStop polygon

    should cover the entire metal portion of the regulator's body, not just the

    tab.

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • in reply to autodeskguest

    David Pollum wrote on Mon, 09 November 2015 20:18

    You are probably getting tStop errors because your tStop polygon

    overlaps the silkscreen (tPlace). Just approve those errors. BTW, your

    tStop polygon should cover the entire metal portion of the regulator's

    body, not just the tab.

     

    Thanks David. I also read that I should use vias to connect the top ground

    plane to the bottom for better heat transfer. If so, do I need to turn off

    the thermal mask on them? Anything else I should do to make this heat sink

    work?

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • in reply to rossw

    RossW wrote on Mon, 09 November 2015 22:05

    David Pollum wrote on Mon, 09 November 2015 20:18

    You are probably getting tStop errors because your tStop polygon

    overlaps the silkscreen (tPlace). Just approve those errors. BTW, your

    tStop polygon should cover the entire metal portion of the regulator's

    body, not just the tab.

     

    Thanks David. I also read that I should use vias to connect the top

    ground plane to the bottom for better heat transfer. If so, do I need to

    turn off the thermal mask on them? Anything else I should do to make this

    heat sink work?

     

    You don't want thermals on because you want maximum heat flow from top to

    bottom. You do want to have the vias' metal exposed, so you want tStop and

    bStop for the vias. BTW the Arduino Duemilanove uses 24mil vias around its

    5 volt SMD regulator to connect its top copper polygon to its bottom copper

    polygon.

     

     

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • in reply to autodeskguest

    Thanks David. I know I can turn the Thermals off on a via with the 'i'

    tool, but how do I change the tStop & bStop solder masks on a via? I was

    planning on drawing a polygon in both the tStop & bStop layers around the

    whole regulator - will that work?

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • in reply to rossw

    RossW wrote on Tue, 10 November 2015 20:16

    Thanks David. I know I can turn the Thermals off on a via with the 'i'

    tool, but how do I change the tStop & bStop solder masks on a via? I was

    planning on drawing a polygon in both the tStop & bStop layers around the

    whole regulator - will that work?

     

    In the board editor go to Design Rules, Masks and look at the "limit" box.

    This is normally set to 0. That means that all vias will have a tStop

    solder mask. So your idea will work.

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

Reply
  • in reply to rossw

    RossW wrote on Tue, 10 November 2015 20:16

    Thanks David. I know I can turn the Thermals off on a via with the 'i'

    tool, but how do I change the tStop & bStop solder masks on a via? I was

    planning on drawing a polygon in both the tStop & bStop layers around the

    whole regulator - will that work?

     

    In the board editor go to Design Rules, Masks and look at the "limit" box.

    This is normally set to 0. That means that all vias will have a tStop

    solder mask. So your idea will work.

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

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