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In a previous iteration of a PCB layout, I added a ground plane fill as recommended by many tutorials online (eg Sparkfun). By default Eagle creates thermals to ease soldering to the ground plane, but in practice I still struggled to get good (timely) heating on all my ground-plane pads.

Thus I'm wondering, in the next iteration, either to avoid adding the ground plane (my design doesn't really need one, mostly very low speed signalling), or if I can increase the thermal spacing (or other settings?) in Eagle so I don't create another soldering headache.

(I'm hand soldering the PCBs, no fancy reflow or similar. A preheat of the boards did help ease the soldering issues but still a chore for every ground-plane pad. And my iron is decent enough, although not a premium one)

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For the clearence between the pad and the ground plane, go to Design Rules -> Supply -> Thermal Isolation.

To change the thickness of the connection between the pad and the plane, change the thickness of the polygon outline.

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  • \$\begingroup\$ Excellent, I was hoping this was configurable somewhere. \$\endgroup\$ – James Turner Nov 10 at 14:28
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If you have digital lines, they may be considered to be high speed regardless of their fundamental/clock frequency. Keep that in mind.

What you need for your design(s) is something called "Thermal Relief". These are connections to a plane, such as ground, with "spokes" that extend from the pad to the plane. When you heat the pad, the pad can actually get hot since there isn't a giant copper heat sink to suck away the heat since the the thinner spokes limit how fast heat leaves the pad.

This is an example of a pad with thermal relief. There are of course different designs, just google image search thermal relief and you'll see a few different ones.

enter image description here

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  • \$\begingroup\$ given each of the 4 connections is about one square of copper (maybe 1mm by 1mm), the thermal resistance is 70 degree Centigrade per watt, divided by the 4 paths from Via to the PLANE. Thus you have about 18 degree Centigrade per watt. How big is your tip? are you using a bit of clean solder on the tip, to ensure better heating? \$\endgroup\$ – analogsystemsrf Oct 6 at 23:06
  • \$\begingroup\$ Eagle is already inserting thermals, they're just not 'enough' for me. I want fewer spokes, or longer spokes, to decrease the thermal coupling to the ground plane \$\endgroup\$ – James Turner Oct 7 at 13:09

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