Detected Layer-to-Layer Polygons that overlap

Hi Craig,

Your post should not have been blocked - I didn't stop it! Did you remember to zip the file?  I usually forget.

Dave (Moderator)

OK,

I just found and released several messages. I don't understand why they needed moderation. Sorry about that.

Dave

maxwellj said:

 Mike-

We're using some 1-ply material on our board due to the number of layers and a limited board thickness for mechanical reasons.  Our design coucil demands 2-ply at a minimum, but we can't do it because of physical size constraints.  They demand we provide all the poylgons (power) that cross so if there is a void in the material, they can assign probabilities to the chances of the board smoking. Yeah, I'm giggling here, too. :)   Truth is stranger than fiction.  This council has no technical knowledge, so our effort will be doubled to get it approved.

 joe

I feel your pain...  we should compare war stories.  I just spent 3 weeks with 4 engineers who all disagreed on an area that was in reality 100 mils by 300 mils.  Not one person considered the material weave effects but 0.1 mil adjustments were made by each person contrary to the other.  When the gerber was finally produced at 1:1, I could hear the deafening silence as everyone realized what filled my workstation screen was a microdot in real life. :)  Did we simulate this circuit? No.  We don't want to pay for a license.  Why do science when "feel good" engineering works? :)   Sigh...

You can use a script in OrCAD/Allegro Skill (SKILL) to detect overlapping polygons layer by layer. The general approach is:

1. Iterate through all layers and extract voltage polygons.
2. Compare each polygon with others on the same layer using dbGetOverlap or similar functions.
3. Calculate the percentage of overlap using area formulas.
4. Output a report listing overlapping polygons and their percentage of overlap.
   Here is the Script
   

   procedure(checkPolygonOverlap()
   let((layers polys layerPairs overlapResults)
   
   ;; Get all layers in the design
   layers = axlDBGetStackupLayers()
   layerPairs = nil
   
   ;; Create layer pairs (1-2, 2-3, etc.)
   for(i 1 (length(layers) - 1)
   layerPairs = cons(list(nth(i layers) nth(i+1 layers)) layerPairs)
   )
   
   overlapResults = nil
   
   ;; Loop through each layer pair
   foreach(layerPair layerPairs
   let((layer1 layer2 poly1 poly2 overlapArea poly1Area poly2Area overlapPercentage)
   layer1 = car(layerPair)
   layer2 = cadr(layerPair)
   
   ;; Get all polygons from both layers
   polys = axlDBGetShapesByLayer(list(layer1 layer2) 'dynamic_shape)
   
   foreach(poly1 polys
   foreach(poly2 polys
   if(poly1 != poly2 && axlDBOverlap(poly1 poly2)
   overlapArea = axlDBGetOverlap(poly1 poly2)
   poly1Area = axlDBGetArea(poly1)
   poly2Area = axlDBGetArea(poly2)
   
   overlapPercentage = 100.0 * overlapArea / max(poly1Area poly2Area)
   
   overlapResults = cons(
   list("Layer:" layer1 "&" layer2 "Overlap:" overlapPercentage "%")
   overlapResults
   )
   )
   )
   )
   )
   )
   
   ;; Print results
   foreach(result overlapResults
   printf("%s\n" result)
   )
   )
   )

   checkPolygonOverlap()