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I've run into several situations where closely spaced vias are useful. Via stitching, reducing inductance, thermal vias in a pad, etc.

However, when I place power vias close together in software, the auto-generated thermal reliefs make a mess on the power planes. For example, Solidworks PCB does this:

Thermal reliefs of closely spaced vias in Solidworks PCB

I know I can disable the thermal reliefs and just do a direct connection, but that will cause soldering difficulties right?

Solidworks PCB doesn't give a good way to manually edit the thermal reliefs. I could turn off 2 of 3 thermal reliefs, and then leave the 3rd on, and give it a very large radius that encloses all 3 vias. But my "I'm doing this the hard way" radar went off, so I wanted to see what you guys usually do in this situation.

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    \$\begingroup\$ Why do you need to care about soldering difficulties for vias? \$\endgroup\$
    – Oskar Skog
    Commented Oct 24, 2022 at 18:52
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    \$\begingroup\$ In most (I can't say all, not having seen all designs at our place) PCB designs, thermal vias are not connected to planes. Therefore being able to solder to those vias is not an issue. \$\endgroup\$
    – SteveSh
    Commented Oct 25, 2022 at 0:26
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    \$\begingroup\$ Perhaps you've discovered why Solidworks isn't usually used for doing PCB design? \$\endgroup\$
    – Hearth
    Commented Oct 25, 2022 at 5:14
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    \$\begingroup\$ If used as a thermal relieve I just use direct. If used as a direct contact to GND next to a small pitch component, bridging can happen to the next pad. I resolve it by placing the via little further away from the pad and use rounded square pads and solderpaste. In a reflow oven you don’t worry about the thermoflow: the board is heated evenly. Only in case of handsoldering and hot air soldering it’s an issue. \$\endgroup\$
    – RemyHx
    Commented Oct 26, 2022 at 4:44

2 Answers 2

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Thermal relief is used on plated through-hole solder pads, to aid in soldering.

For vias (that are not also solder pads) it's not needed.

If you're stitching planes together with vias, don't use thermal relief.

So heatsink vias are the only interesting case, you want them well connected to the planes and the pads, but thermal relief isn't needed on heatsink pads because they are in the middle of the part so uneven heating is not going to cause tombstoning. But that's going to make rework harder, up from difficult to near impossible. something about having and eating cake.

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I assume these vias are for thermal relief to some exposed pad on a surface mount PCB. If that is a correct assumption then I wouldn't be too worried about a direct connection, unless your board is gigantic or has a strange stackup with an aluminum core, or some wacky ceramics, most boards even in an assembly pallet should come up to temperature during a thermal soak and reflow properly. I am not intimately familiar with Solidworks PCB, but since I believe it is a derivative of Circuit Studio and therefore Altium Designer you should be able to edit the thermal relief configuration in the Design Rule Dialog (dont ask me how to get to it in Solidworks PCB, thats what the docs are for!

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