A20 SOM heat - why are the headers on the same side as the A20?

[Chax]

I have a couple of A10-lime boards and when running at 1GHz they tend to get quite hot. We are now in the process of selecting a SOM for our next product. The A20 may be a good candidate but I find it strange that Olimex decided to place the A20 at the same side as the pin headers (sockets).

So when the SOM is mounted it cannot easily radiate the heat because it is not only facing down but ALSO facing the mother board on which the SOM is mounted.

For the A10 I use the heat sinks but I don't think they will fit or do any good on the A20 SOM.

Can anyone tell me about their 'heat experience' with this SOM? Or can Olimex clarify why they created the SOM (their SOMs) this way and not with the headers on to bottom of the module?

[progmetalbg]

I also wonder why Olimex chose this design for the SoM. One possible reason is that in order to materialize your idea they have to use more complicated (and also more exprensive) design with multiple layer PCB. But I'm really noob in electronics and PCB design and that is just my speculation. I don't want to think about Olimex next RK3188-SoM with same header placement as A20-SoM, it will possible burst into flames under heavier load 

[JohnS]

The AW chips can't radiate heat in most tablets.  What happens to them?  Why not measure?  It seems they are OK, so will the same not be true for the SOM etc?

John

[Chax]

That's not completely true. In tablets it is not uncommon to use casing to spread the heat. This also gives a reasonable conductive path to the outside world. In this SOM the A20 is in between two PCBs so the radiated heat cannot really go anywhere.

I just don't think it is such a good idea and because the A10 lime can run quite hot and Olimex has a heat sink for this, with this SOM design that just does not really makes sense.

In our case the PCB/SOM will probably be mounted underneath the device and it is uncertain how much air flow there will be, so I tend not to use the Olimex SOM but use one of the devices from Acme Systems (Arm 9 and Cortex A5 are a bit more power efficient as well).

Maybe I will order an A20 SOM/EVB just to check but I am interested to see what Olimex has to say about this.

[JohnS]

A lot of tablets have plastic or other non-conducting things and of course no fans.  As I say, why not measure?

Tablets are very cheap as are the SOMs so this is a very easy and cheap exercise.

Also, why cannot you mount the SOM another way?  A different motherboard/etc.

John

[Chax]

I can only measure when I buy one, but the single core A10 can already become quite hot and may need a heat sink. Of course you can construct the motherboard in another way, but the design does not make sense.

The question is quite simple: why is the A20 on the same side as the headers? Having the headers on the other side would just make a lot more sense to me. About every other SOM that you can find has all main components on top (and they stay on top when mounted). I guess there is a good reason for that.

[MBR]

I'm not sure about spacing between the SOM and EVB, but you can try a piece of copper plate (or a very thin flat heatpipe) to act as a "thermal bridge" between chips and a heatsink.