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I'm using the RFM98PW-433S2 1W(+30dBm) 433MHz RF module. After a couple of minutes of working the module gets to above 70°C temperature. Probably reaches 90°C and above after couple more minutes. I have placed 2 Raspberry Pi passive heatsinks on the module to help it cool a little bit. My circuit will need to operate for 2 hours at max. Should I be concerned about the heat?

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My PCB also has IMUs and a GPS module as well as pressure sensors. The operating temperature is between -40 to 85°C degrees for the sensors but I'm still concerned.

What should I do to decrease the heating of this RF module?

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  • \$\begingroup\$ This sounds like you might also have a lack of proper board design to dissipate the power produced by that module. If you have thermal vias going through your board you also could try putting a heat sink on the back or just mount it onto an aluminum frame etc \$\endgroup\$
    – MadHatter
    Commented Jul 22, 2021 at 1:14
  • \$\begingroup\$ I would check the allowable duty cycle for transmit. At 20dBm, you may be limited to 1%, so the Power Amplifier dissipation does not cause overheating. \$\endgroup\$
    – elchambro
    Commented Jul 22, 2021 at 3:44
  • \$\begingroup\$ At 1W you probably need to ensure the antenna is correctly matched and tuned, so that it isn't reflecting most of the power back into the transmitter. Where in the world are you, that you can transmit 1W on this band legally? en.wikipedia.org/wiki/LPD433 \$\endgroup\$
    – user16324
    Commented Jul 22, 2021 at 12:22
  • \$\begingroup\$ @user_1818839 I will use this in a rocketry competition away from civilization so I don't think I should be concerned about legal issues. You are probably right about the antenna but the datasheet says that it can withstand 10W of power. Link to datasheet: rcscomponents.kiev.ua/datasheets/hp-433-3800n-datasheet.pdf Can you explain the tuning part further? \$\endgroup\$
    – Exclose
    Commented Jul 22, 2021 at 12:29
  • \$\begingroup\$ I'll note it says you can use up to 400 watts if you're using the frequency for ham radio purposes in the UK. For all we know, Exclose could be a licensed ham. But then he'd know more about antenna tuning. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Jul 22, 2021 at 13:24

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Adding just the heatsink will help a little bit, anodizing the heat sink will improve radiation effectiveness which helps a little bit, but blowing air over the area works wonders. You don't need much air, perhaps a 15 to 30 cfm fan. You want the air stream hitting the heat sink as well as the area around the module on the PCB. The PCB is also pulling heat away from the module. With moving air, you might not need the heat sink.

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