I am working on a project which will be essentially a commercial product. Its an Li-Po 3.7V 5000mAH Battery Powered IoT Wireless Device consist of an ARM CPU Module and some other necessary circuits (Like Power Regulator, Battery charging, USB, LCD etc).
Now due to some Connector placement requirement I had to place the CPU Module at Bottom Side of the PCB and underneath it the Li-Po Battery will be there. So Basically the Parts stack will be like this inside the Plastic Enclosure.
I found the CPU Module generates heat when operating. I can not say what amount of heat it generates but if I slight touch the Processor Chip with finger tip ... its very very hot.
My ques is ... is it good idea to place the Parts like the picture above? Here I am afraid about the heat heat dissipation. Any idea in this regard? Please note I can not use too bulky Heat-Sink as my device need to be compact in size. May be I can allow 2mm gap between battery and CPU Module. Is there any kind of thin material which I can put between Battery and CPU which can help here? Also is there any risk if the Li-Po gets hot due to heat of CPU?
The heat in a box is the heat in a box .... it does not matter much how you arrange it.
But you need to avoid hot spots. You don't need a heat sink, you maybe need a heat spreader. A sheet of copper may be sufficient.
A gap inside a box is not what you need, it is no(t much) benefit.
If the temperature in the box is too high, then you need to tranport more heat to the outside. Metal box, holes, peltier...