ICOM IC-7300 thermal dissipation of the FPGA chipset

I was curious about the rubber sheet on the FPGA chipset. Some people say that is good for thermal dissipation. Therefore, I put an infrared thermal camera at work and took some pictures of that chipset (Altera Cyclone IV FPGA with 55k logic units) .
When powered, the flexible rubber sheet shows that the temperature is almost at the room temperature.

Here is the board explained in the user manual of the radio.

You can see on the right side of the FPGA a small Al radiator. That is the ADC circuit, 14bit Linear Technology LTC2208-14, sampling at ~124 Msps. This chip is one of the the hottest chipset on the board at around 50 Celsius. The hottest is the 3V regulator, by the way!

A big surprise came when I ripped the rubber sheet and I found the FPGA at around 50 Celsius also! 

I also measured the resistance of that rubber sheet to see if there is some electrical properties but found that the Ohm-meter showed hundred of kOhms.

A quick conclusion: I am not sure about the purpose of that rubber adhesive sheet! Looks more like a thermal insulator than a radiator so I put it back!