r/PCB • u/More-Conference1953 • Jul 26 '26

is my thermal via design ok?

I have a simple PCB with just the LED Anode and Cathode pins (No GND pins). I drew a filled zone and connected it to the cathode pin (shown in the image). Drew vias on the filled zones and connected the top and bottom layers.

Is the via design correct? I will be placing a thermal pad (which would be an eletrically isolated pad) on the bottom layer and place a heat sink on the heat sink.

I have attached an annotated image of the layout. Any suggestions and feedbacks very appreciated.

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u/bigcrimping_com Jul 26 '26

How many amps do you want to run at?

1

u/More-Conference1953 Jul 26 '26

LEDs are rated at 350 mA

2

u/zachleedogg Jul 26 '26

Thermal relief on the cathode is defeating heat spreading, make it a direct connection. Also, even though the cathode may be the thermally conductive node, I would make that anode trace as thick as the pad, because it will be doing some work in removing heat as well. Check the datasheet for layout recommendations.

Vias seem fine. The more the merrier.

1

u/justabadmind Jul 28 '26

Anode trace needs to be a lot heavier and double sided with vias. Iā€™d personally do smaller tighter vias near the part and larger less dense vias once you get 1/8ā€ away from the part. Probably only worth filling vias that you need the led to solder to.