As seen below I’m building a simple PS board that has to supply 2 amps. I could easily get away
with 4mm traces but I thought I’d try my hand at filled zones with thermal reliefs. I don’t know
how to calculate spoke width for thermal reliefs so I took a guess at 1.5mm.
Regards,
Dan
I don’t feel the picture scale or your spoke width is not 1.5mm.
You can find the minimum total track width required using the Kicad Calculator Tool.
See Calculator Tools > Track Width.
Adjust your Relief Gaps and Spoke Widths in the Pad Properties > Connections > Thermal Relief Overrides.
I’m familiar with the track width calculator. That’s easy. I’ve been adjusting spoke widths in the zone properties. My question is more geared towards best practices and how you calculate spoke width to match the equivalent ampacity of a track.
Thanks for the response.
Dan
You are correct. I thought it was adjusting the width but it wasn’t. I might have to look at ‘pad properties’ as Jmk suggested.
Regards,
Dan
I figured it out. I had to refill the zone to activate the new spoke widths.
Regards,
Dan
I use spoke width in some way proportional to pad size (I have it defined in all my footprints that are bigger than standard = I have it defined in terminal block, but not in 0603 footprint). In my case they don’t depend on current as I don’t use high current.
About track width calculator. I suppose it calculates current assuming infinite track length. If you have 0.2mm track length and then solid copper then heat dissipation is much better than in infinite track so calculations are in my opinion not valid.
I’m inclined to use simple math for spoke width. If a 4mm trace will work then four 1mm spokes should suffice.
Regards,
Dan
That simple math is a good start in my opinion. KiCad is already content if a pad is connected with only two spokes to the zone (configurable in the board setup). But because the spokes are so short and connected to more copper, they also receive more cooling, so each of the spokes therefore has a higher current rating.
But in general, it does not matter much unless you get into really high currents or really high frequency content of the signals.
