Tuesday, February 9, 2010

Altium Designer Polygon Pours - Turning off Thermals

I started doing PCBs using Cadsoft's EAGLE program, which I think is a great mix of user-friendly and powerful (though I must admit, when I first started with EAGLE I remember wondering why it is not intuitively structured). Migrating to Altium, I'm inclined to think in EAGLE.

When you want to fill a section of your PCB with copper (i.e. to reduce the inductance on a signal, for increased thermal conduction, or to reduce the amount of copper you are going to have to etch away in an acid bath), you can use the command poly, or  to select the polygon tool.

EAGLE Polygon tool

In EAGLE, you can activate or deactivate 'thermals' on your polygons. To adjust thermal relief settings in Altium Designer, you just have to change a few settings. Details after the jump!

When thermals are ON, parts' pads that belong to the same net as the polygon will not be entirely enveloped by the copper pour, but instead will be connected to the polygon by conducting lines. This can be good, for instance, if you don't want a really solid thermal connection between the pad and the polygon (it can be hard to heat a pad up to soldering temperature if it is connected to a huge copper plane).

EAGLE Polygon with thermals ON

EAGLE Polygon with thermals OFF

In Altium Designer, I had trouble finding this feature. I tried pouring a polygon with this result:

 Altium Designer polygon with default settings - thermals are ON

To turn that polygon into one solid copper area, I modified 2 settings
  1. Change the PCB Rules and Constraints
     Design > Rules > Plane > Constraints > Direct Connect 

   2.   Change the properties of the polygon

   Properties... > Net Options > Pour Over All Same Net Objects 

And the result... thermals are off and you have a solid chunk of copper.

Altium Designer polygon with changed settings - thermals are OFF

As is generally the case, Altium has more options for polygon pours, which means there is more to figure out when you use it.

Note: If you want to set thermal relief settings for individual polygons, use the polygon manager.

Create polygon connect style rule with the Polygon Manager

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