[MTCD Software Development] SkyBeam2048:
Basically any heatsink will do. The surface of such a heatsink is much larger than the flat surface of the heat spreader on top of the PX5 unit. It's by far sufficient. I don't believe a fan is required at all and since there are very limited vent holes in my unit I will not install one.

The heat sink I used was a salvage part from some northbridge on an old PC mainboard. Basically any north/southbridge cooler from any PC mainboard will improve heat dissipation. My one comes with a push spring which I just fixed down to a lace I created using a wire put through some existing heatspreader holes. Be aware not so short out anything using this method.

You can also use thermal compound to glue it down. Please do not use any super-glue or similar. Due to thermal stress normal glue will not whitstand the thermal and mechanical forces and your heatsink is at risk of creating damage inside the unit if it comes lose. Also some thermal compound is required to assure a good heat transfer between the heat spreader and the heatsink.

As said I don't believe there is any need for a fan. If you put a fan you should also drill some vent holes and install the fan in there to suck out the warm air from the unit. A fan just inside the unit circulating warm air will just delay the heatup of the air inside the unit for some minutes, but certainly not for long.

I believe that thermal capacity of the air inside and heat dissipation on the case itself is by far sufficient to cool it. I never ever faced any overhating issues.

Moreover if you put vent holes and a fan you will collect lots of dust inside the unit over time which also lowers cooling efficiency again. Let alone also the added noise and mechanical issues of small high-speed fans. Never ever put a fan where a passive heatsink is doing the job as well.

---------- Post added at 05:55 PM ---------- Previous post was at 05:40 PM ----------

Have a look at the SoM. You can see the location of the main Rockchip CPU. It's among the center of the SoM. However it's not required to center the heatsink precisely over the CPU. The whole cover of the PX5 board is a heat spreader. As the name says it's spreading the heat among the whole plate. So It does not matter where you put the heatsink. Sure if you place it at the edges this will lower efficiency slightly as heat will have to travel from the center of the heatspreader to the sink, but it will still work. The whole purpose of the heatsink is to increase the surface of the "heat up area" to have a larger surface to exchange heat with the surrounding air. There are heatsinks which are better for active cooling (mainly the ones with lots of very thin fins) and some which are better for passive cooling (such as the one on my picture). But we are not talking about passively-cooling a 250W GPU, we are talking about some low-power ARM SOC.

Well, I never measured any temperatures. What tool do you use to read the temps from internal sensors?

80°C is for sure uncritical. Most of those SOC can also handle > 100°C. I wouldn't be worried about this too much. But you would perhaps be surprised what a good (even passive) heatsink can do. I remember times where old VIA chipsets in PCs were running very hot. Vendors were used to put those terrible 40mm fans with 3000rpm+ on the mainboards with terrible noise. Those fan-driven heatsinks were just flat base-plates with a fan mounted on them. They had a hard time to cool the chipsets below 70°C. I was used then to attach some larger passive heatsinks like the one I mounted in my head unit and usually temps dropped to 45-55° without any fan.

But even if I read my temps, it depends where it's mounted in the car, how large the unit is (air temp capacity) and for how long you run it at high load. Passively cooled units like mine will remain cool until the air inside is heated up and then temps will start to rise. If I would have problems with that, then the only way to get more cooling is to attach a fain to the case and force some air exchange.

But still I don't believe this is required at all.