Author Topic: Heat sink Vias on FR4 Vs Aluminum core PCB  (Read 1421 times)

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Offline alderbaran748159Topic starter

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Heat sink Vias on FR4 Vs Aluminum core PCB
« on: May 31, 2021, 03:34:35 am »
Hi everyone,

I would like sink the heat from mosfets on a PCB and I am curious about using aluminum core PCB instead of using regular FR4 and add lot of vias to sink the heat from the top to the bottom.

I was wondering if it's actually more effective to use an aluminum core, if we compare a FR4 with lot of vias, the top and the bottom are directly connected using copper with a low thermal resistance.
Now if we take an alu PCB, there is the dielectric between the copper and the aluminum that might also be low thermal resistance but not as better as copper?!

I did not find a lot of info about the comparaison, let me know if you have any experience with alu PCB

Thanks
 

Offline T3sl4co1l

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Re: Heat sink Vias on FR4 Vs Aluminum core PCB
« Reply #1 on: May 31, 2021, 02:35:55 pm »
Which process would this be, one-side build (layups on one side of core only) or two (layups on both sides, insulated thru vias)?  Obviously the latter will work better but be careful that it is what you are getting!

Tim
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Offline alderbaran748159Topic starter

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Re: Heat sink Vias on FR4 Vs Aluminum core PCB
« Reply #2 on: May 31, 2021, 05:07:59 pm »
I was thinking of this:


Regular 2 layer FR4 with vias vs one layer aluminum core
 

Offline T3sl4co1l

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Re: Heat sink Vias on FR4 Vs Aluminum core PCB
« Reply #3 on: May 31, 2021, 05:21:19 pm »
But that doesn't have vias...

OH, you meant a comma there, the FR4 with vias, versus plain aluminum core?  I see!

You can run the numbers, take typical footprint dimensions and combine with the specs of the adhesive layer to find thermal resistance.

The thermal spreading of aluminum is obviously far higher than FR4.  You can apply the same steps (take typical via dimensions, copper plating thickness, copper conductivity, etc.) and derive the values for FR4.  It's rather unimpressive, which is why we use metal core for things that need it, like lamps.

Additional routing layers tend to be difficult to fab (expensive) so metal core PCBs aren't used so much for power electronics; a single routing layer isn't enough to realize most designs.  But it's more than adequate for simple designs like chains of LEDs.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
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Offline Sal Ammoniac

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Re: Heat sink Vias on FR4 Vs Aluminum core PCB
« Reply #4 on: May 31, 2021, 05:42:02 pm »
I was wondering if it's actually more effective to use an aluminum core, if we compare a FR4 with lot of vias, the top and the bottom are directly connected using copper with a low thermal resistance.

Yes, it's far more effective to use an aluminum core board versus an FR4 board with vias to another copper layer on the other side of the board.
"That's not even wrong" -- Wolfgang Pauli
 


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