Thermal pad construction on pcb

barry said:

If you don’t have the vias, how will the pad connect to ground?

You could also have a single solid pad with vias in the pad, but this is a little harder to solder.

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BigBoss said:

Surround the square pads with 12 small vias and pour them with a copper.
Sounds good ?

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Rajinder1268 said:

Hi
Could I create a larger copper pad and then have small tracks with vias on the periphery connected to GND.
In the data sheet it mentions the copper pad does not need to be soldered.
Do I need to connect each via to one of the 9 pads using a small track?

--- Updated Jun 26, 2022 ---

If the Copper Pad does not need to be soldered, simply place a copper pour with many thru vias. Of course you should open solder resist mask to make IC less warm.

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Rajinder1268 said:

Hi
Could I create a larger copper pad and then have small tracks with vias on the periphery connected to GND.
In the data sheet it mentions the copper pad does not need to be soldered.
Do I need to connect each via to one of the 9 pads using a small track?

--- Updated Jun 26, 2022 ---

Not sure what you mean.
Do I connect the vias with small tracks to the 9 pads, the vias making the connection to GND?

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barry said:

the data sheet says the pad doesn’t HAVE to be connected, but you’ll get better performance if it is. If you’re going for better performance, then solder the pad. Going to the trouble of creating a land pattern with a bunch of copper and vias, and then not soldering it is a waste of time.

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barry said:

unless you've got the world's worst PCB house, there should be no problem putting the vias right in the pad. Check with your vendor.

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Rajinder1268 said:

I will but from past experience they do not have the knowledge on how to do this. Hence my recommendation for the vias to GND and then run short tracks to the 9 pads, that should work I think.

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barry said:

I think the point of the ground pad in this case is for thermal, not electrical, purposes. So, a thin trace to a via is not going to work well.

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KlausST said:

Hi,

You don't need a "GND" plane, you just need copper to spread the heat.
The electrical connection is not important for this.

While you don't need a GND plane, you still can use it, if you have.
A xxx-plane is copper ... and copper spreads the heat.
The vias (copper) are used to spread the heat from one copper layer to the other. So if you want the heat to go from TOP layer to BOTTOM layer you need copper. The more coper the better the thermal conductivity. Use multiple vias, use big vias (as long as it does not create other problems)
But if the heat now is at the bottom side ... you still ned a big copper area there to spread this heat.

Klaus

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Rajinder1268 said:

Hi
my confusion is in the understanding. I have 9 small copper pads and in between them vias. How do I connect/track this up? My second layer is GND on a 4 layer PCB. Do I need to connect only the vias to the GND plane? What about the 9 pads of copper that I have?

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barry said:

Posts 12, 10, 8, etc. keep telling you what to do. You keep ignoring the advice.

1) you need copper to dissipate the heat.
2) it doesn’t HAVE to be connected to ground plane
3) the vias don’t dissipate heat. they need to be, somehow, connected to the pad of the device. that‘s what the copper pads are for.

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