How to Transfer Heat from one side to the other

Thread Starter

KlingonTarg

Joined Jan 10, 2022
3
I'm attaching a PCB to a device that generates a decent amount of heat. This will be on the top side. My heat sink is attached to the bottom side.

What is the best way to transfer heat from the top to the bottom? Is there an optimal size via? Should I place polygons a certain way? I don't know if there have been any studies on this. I did a quick search and didn't see any.

Thanks for your thoughts.
 

stasbala

Joined May 24, 2021
8
Also did a quick search, and Cadence makes a claim about the "optimal" thermal via sizing and spacings:
Thermal Vias for Circuit Board Heat Management: Techniques and Tips | Advanced PCB Design Blog (cadence.com)
As far as whether this will be sufficient or not is up to how much a decent amount of heat actually is quantified.
Notably the claim does not present any substantiating Data.

Do you have any ability for removing heat on the top side of the board in the event the thermal via dissipation isn't enough?

If it is a serious amount of heat, and you have the resources at your disposal, I believe modern CAD tools are capable of doing some form of basic thermal simulations to get you in the ballpark.
 

Thread Starter

KlingonTarg

Joined Jan 10, 2022
3
Nice find! Thank you. I'll check that out.

Do you have any ability for removing heat on the top side of the board in the event the thermal via dissipation isn't enough?
Unfortunately, no. The top side of the board is flush against a camera. A cooling fan on the heat sink is also out due to vibration issues.

We have mechanical designers that have done a thermal analysis, but having a PCB in between is a bit of an unknown. Hopefully, this will be enough.

Thanks again.
 

drjohsmith

Joined Dec 13, 2021
376
The more the better

A few more links

https://www.ti.com/lit/pdf/snva183

https://www.edn.com/pcb-design-a-close-look-at-facts-and-myths-about-thermal-vias/

The other thing to keep in mind, is manufacturability
You need the vias to have a nice plane on the bottom

This means that a lot of heat is needed in the top to get the part to solder,
Great for vapour phase, not so good for hand soldering,

I would also check the parts thermal data
different chips put different percentage of their heat up or down,
depends how the silicon is mounted,

you might find the thermal path to the base of the chip is not very good,
 

BobaMosfet

Joined Jul 1, 2009
1,942
I'm attaching a PCB to a device that generates a decent amount of heat. This will be on the top side. My heat sink is attached to the bottom side.

What is the best way to transfer heat from the top to the bottom? Is there an optimal size via? Should I place polygons a certain way? I don't know if there have been any studies on this. I did a quick search and didn't see any.

Thanks for your thoughts.
The best you can do is create a large copper section on the bottom and top of the board, with a number of interconnecting vias, and attach your heatsink on the bottom to the bottom copper layer. Just don't connect those 2 layers to anything else. They exist solely to transfer heat.
 

panic mode

Joined Oct 10, 2011
2,110
i do not see attachment or reference to product used.
the best is to make heatsink reach the heat producing device. if need perhaps consider having cutout on the PCB
 
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