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I have very limited PCB design experience. I've been using this program called Fritzing (it... has its pros and cons). Something I noticed is that when I do a ground fill with this software, it leaves copperless borders around ground pins except for traces I manually draw.

For example, here is a rough draft of a power supply board I'm trying to make. The circuit, for reference, is:

enter image description here

It's just a linear regulator, some capacitors, and some terminals. Now, take a corresponding PCB layout. This is a rendering of the copper mask (light gray) on the ground layer:

enter image description here

I've drawn blue dotted lines around the ground pads.

As you can see, there are borders around the ground pins, with only one edge of each pin connected. Most notably there's very minimal copper between the regulators heat sink fin and the rest of the copper fill.

I suspect that this is not a good idea. My gut tells me there should be copper all around those pins, if only for heat management, e.g. something like:

enter image description here

So, my question is: Is my suspicion correct? Should those border areas around the pins also be filled with copper?


Note: The above PCB is my first draft of this design; I'm aware that it might need improvements; e.g. routing practices, via and trace sizes, capacitor selection and placement, etc. But, no spoilers please! 😁 I'm saving that for its own question after I do a little research. For this question, I'm just wondering about those ground fill pin borders in general.

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    \$\begingroup\$ If all is copper, then you have to heat a large copper area to solder components, which could damage pcb or component. \$\endgroup\$ yesterday
  • \$\begingroup\$ It sounds like "solderability" related. It is hard to solder on solid copper. \$\endgroup\$
    – jay
    yesterday
  • \$\begingroup\$ I'm not worried about solderability, I'm just going to have a third-party assemble it. But that is good to know for hand-assembled boards. \$\endgroup\$
    – Jason C
    yesterday
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    \$\begingroup\$ @JasonC , h h ... I like the solution! And, your third-party must be happy with you. \$\endgroup\$
    – jay
    yesterday
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    \$\begingroup\$ @jay Haha, yeah... customer laziness is the friend of every fabricator, 😂 \$\endgroup\$
    – Jason C
    yesterday
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This is called thermal relieving.

If pads are directly connected to a copper plane, it can be very difficult to hand solder the component, as all the heat from the soldering iron is transferred into the copper plane acting as a heat sink. To solve this, you use thermal relief.

All CAD suites I've ever used has settings for this, where you can select how many "spokes" the pad should have, at what angles and how wide they should be.

When it comes to SMD parts, if the boards are only reflow soldered, you can often get away without thermal reliefs. This has some advantages when it comes to heat transfer from power components, lower impedance etc. But it can be a pain to repair such boards. When it comes to thru-hole parts, especially on multi-layer boards, one has to use thermal relieving or you will never be able to properly solder these pins directly connected to copper planes.

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  • \$\begingroup\$ Make sense. I added a spoke to the other three edges of the regulator's sink, then, and I'm going to make a Fritzing feature request about adding spokes to thermal relief areas (because convincing it to place 3 other traces there was a little intense). Everything else I imagine is fine as is; can't see the other components dissipating much heat. \$\endgroup\$
    – Jason C
    yesterday
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It is common to have gaps between a ground pad and the ground plane - these are soemtimes called "thermal relief" or "thermal break".

If the pad was solidily connected to the plane as in your second picture, it would be very hard to heat the area enough for solder to flow as the plane would suck heat away from the pin and hole.

Other PC programs will often use four tracks rather than Fritzing's single connection.

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