SWRA672 May   2020 AWR6843AOP , IWR6843AOP

 

  1.   Thermal Design Guide for Antenna on Package mmWave Sensor
    1.     Trademarks
    2. 1 Introduction
    3. 2 mmWave AoP package
      1. 2.1 Thermal Characteristics of the Package
    4. 3 Salient features of AoP EVM
      1. 3.1 Thermal Challenges in Dissipating the Heat
    5. 4 Techniques for Mitigating the Heat Dissipation
      1. 4.1 Reduce the System Level Thermal Resistance
      2. 4.2 Board Size Scaling
      3. 4.3 Heatsink Options
        1. 4.3.1 Sheet Metal Heat Sink
        2. 4.3.2 Heat Sink Details
        3. 4.3.3 Mounting Options
        4. 4.3.4 Thermal Characteristics With the Sheet-Metal Heatsink
      4. 4.4 Heatsink with fins
        1. 4.4.1 Thermal Characteristics With the Heatsink
    6. 5 PCB based thermal improvements
      1. 5.1 Thermal via array
    7. 6 Application and Demos
    8. 7 Summary
    9. 8 Acknowledgment
    10. 9 References

3.1 Thermal Challenges in Dissipating the Heat

The size of the Antenna on package based mmWave sensor could be very small, for example, AoP EVM mission area where the entire radar system is packed under 15 mm x 36 mm, which poses further challenge to the heat dissipation problem for high performance and higher duty-cycled condition. Since the radar sensor has to be enclosed in a sealed box, there are limited options to dissipate the heat.

TI’s Antenna-on-Package (AoP) Radar chip dissipates about 2W of power in a use-case (with 50% duty cycle: Use Case: 3.2 MSPS, 25-ms frame time, 256 chirps, 128 samples/chirp, 8-µs inter-chirp time DSP active). Other essential components of the Radar system such as PMIC and passives and QSPI Flash will dissipate another 0.5W-1.0W causing a total of 2.5W-3W of power dissipation.

The top side of the AoP device is an electromagnetic radiating surface, heat-sink on the top side is not an option. The bottom-side heat-sink is an option, but the size of the heat-sink has to be small due to cost/weight/other reasons.

Larger board size of the PCB is another option without using heat sink or other thermal mitigation techniques. For those use-cases targeted for small form-factor applications with severe size constraints, increasing the board size is not an option, then heat-sink from the bottom side of the PCB need to be explored.