6.2 Hardware Recommendations

The following list presents the recommendations and measures that can be taken to minimize the junction-to-air thermal resistance of the device mounted in a specific application. These have a first order impact on the permissible ambient temperature at which a system can operate. Some are easy to implement at no cost, while others may generate a small cost adder in the application.

• Maximize the thermal inertia and thermal conduction of the PCB. When no heatsink is attached to the top of the device case, more than 70% of the heat generated by the processor is conducted to the PCB.
  • When possible, use larger PCBs and maximize the copper mass of the PCB. This can be done by pouring layout voids with copper shapes connected to ground and/or adding ground layers to the PCB stack.
• Pay attention to surrounding components that would conduct their heat to the processor. When possible, keep power dissipating devices to a reasonable distance from the processor.
• Add a heatsink or heat spreader over the processor case.
  • Some very cheap parts can bring a great improvement even when no air flow is present in the system.
  • In some cases, it may also be possible to thermally connect the device to the system enclosure when this enclosure is thermally conductive.
  • Create an airflow in the system with a fan. When a heatsink is mounted on the device top, forcing an airflow is a very effective way to decrease the device thermal resistance.
  • In Linux, a fan can be declared as a cooling device for a thermal zone and therefore be activated when temperature trip points are crossed.
• When possible, choose a SiP device that brings improved thermal performance over a standalone device.