Hi all,

I'm designing a RF PCB and I was looking at some PCB design guide and a recommendation I found was to place a large number of vias (to the ground plane) under any integrated circuits as they provide good RF grounds and thermal conductivity. I was just wondering why having a large number of vias under an integrated circuit provides good thermal conductivity.

I guess as the temperature rises you have more atoms colliding with each other and knocking electrons off their constituent atoms. The vias would provide an easy path for these electrons. But I'm not sure how that keeps the atoms from knocking the sides of the chip and heating it up. Any ideas?

Not sure if this would be better suited in the physics section. Thanks for reading!

 

Vias are copper plated..
Copper conducts heat better than fr4 (or whatever) glass laminate.
Thermal vias are used to conduct heat from one side (or plane) of the board to the other.
Vias also increase the amount of surface area for dissipation/convection. Just like a heat sink with more surface area is better than one with less surface area.

 

Basically it's the fact that you have alot more surface area to spread the heat over. The vias are there to lead the heat to the other side.

I try not to think too much about electrons bouncing around, it makes my head spin.

-
Kolbjørn

 

The vias are just better than trying to get heat through the circuit board material because they are metal. Really doesn't have anything to do with electrons. It's whole atoms that vibrate because of heat.

 

Ah that makes more sense. You increase the thermal conductivity by increasing the amount of surface area present underneath the IC. I don't think my vias are copper plated. I just drill a hole through my FR4 board and then thread a wire through and solder it to the ground plane (bottom of the board). Guess I over-complicated things a bit.

 

Drill a fat hole and use a fat wire, like 10 or 12 gauge, not stranded.

 

Ah that makes more sense. You increase the thermal conductivity by increasing the amount of surface area present underneath the IC. I don't think my vias are copper plated. I just drill a hole through my FR4 board and then thread a wire through and solder it to the ground plane (bottom of the board). Guess I over-complicated things a bit.

You just have a DIY PCB.. In a true circuit board the via is copper plated.
In a DIY PCB its just a wire stub or even rivet. But its function is the same.

A "via" is simply a conductive hole connecting 1 layer to another in a PCB.

A "thermal via" is just a regular via but its whole purpose is to pass heat not electrical signals.