[vbezhenar]

We're using 2D schemes because we live in 3D world and we can move heat into third dimension. With 3D circuit you won't be able to transfer heat from the insides. I guess it could be possible with some integrated cooling nano pipes, but it's hard to imagine how that would work.

[FrostKiwi]

Many pieces of circuitry on different scales are already 3D. On the big side, PCBs are printed in multiple layers, going smaller we have 3D NAND flash, micro processors are very much printed in "layers" with components being connected "one story up" and those layers are again connected "two stories above". Finally you might argue on the atomic scale, individual transistors are very much 3D as well, with how source, gate and drain are constructed. But I get your point, you can't just stack those layers ad infinitum.

[Causality1]

Always been fascinating to me that we only bolt a heat sink onto one side of the board. Nobody's come up with a circuit board material that's electrically insulating but thermally conductive so we could sink an appreciable amount of heat out of the back side?

[CamperBob2]

Interestingly, thermal and electrical conductivity is highly correlated. You don't see a lot of materials that conduct heat well but behave as good electrical insulators, or vice versa. Both mechanisms benefit strongly from the availability of highly-mobile electrons, which is another way of saying "metal."

[michaelt]

> Nobody's come up with a circuit board material that's electrically insulating but thermally conductive so we could sink an appreciable amount of heat out of the back side?

In applications like high-power LED lights, you'll often get 'Insulated Metal Substrate' PCBs where the printed circuit is on an aluminium or copper board, separated by a very thin electrically insulating layer. [1]

However, this has a few downsides: The electrically insulating layers aren't perfectly thermally conductive, meaning a directly attached heatsink will usually perform better; if you make a complex board with 8+ layers of copper (like a modern motherboard) you end up with 8+ layers of insulation; and it's nigh-impossible to use through-hole components.

For LED lighting those are non-issues and, a top-mounted heatsink wasn't an option anyway.

[1] https://dm.henkel-dam.com/is/content/henkel/Bergquist%20Comp...

[kortex]

Oh, that is in fact an important heat path on all but the most intensive components. But with high power components, the heat flux is pretty insane. You can move a huge amount of heat with heat pipes, and it's just easier to move heat out the back.

[StillBored]

I put a fairly large/flat heatsink on the back metal of the heatsink support bracket on my intel (overclocked) desktop a few years back it pulled the temps down a couple degrees when a fan was blowing at it under moderate load.

I've been thinking about this for my ryzen lately too, since it appears keeping the top of the die cool is unusually challenging. A lot of mobile/etc parts use the PCB ground plane as a heatsink, so it makes sense that if you can attach a larger heatsink to the back of a normal PC board you should be able to pull heat out of both sides. Particularly in a water cooled system where the top of the heat spreader is remaining fairly cool but the surrounding board is heating up (like my ryzen).

[nanomonkey]

There are in fact thermal PCBs (a.k.a. MCPCB) used for LEDs and other electronics that need to dissipate heat. They have an aluminum or copper layer that supplies rigidity and a heat path out the backside or center of a PCB.

[moffkalast]

Yeah especially with something like the Pi, you could effectively double the core count by slapping another chip on the other side and add another heatsink.