Environmental Temperature Guidelines for Libre Computer Boards

We engineer our products for reliability and a big component of that is operating temperature. We have both low power low performance and high power high performance parts so we want to put out some information on how temperature affects our products and how our software interacts with our boards.

Board components are held in place by ROHS solder. Solder joints are subject to corrosion and cracking due to environmental factors. Temperature plays a big role in these two issues. Thermal cycling is the repeated heating and cooling of an area. Due to different coefficients of expansion of materials and components, repeated thermal cycling creates stress fractures that can lead to cracking. All electronic components will eventually fail from thermal cycling. Higher temperatures also lead to higher rates of corrosion that will degrade the solder joints over time and make them more sensitive to crack formation.

There are hundreds of millions to billions of transistors on the components powering a board. They are subject to transistor aging that is accelerated by higher temperatures. This is not typically an issue for a device that is expected to operate for less than a decade unless the temperatures approaches the transistor junction temperature limits.

Flash based data storage like eMMC, MicroSD cards, NVME drives lose charge over time and eventually lead to complete data loss. Flash medium is limited as a long term storage medium unless the data is actively refreshed and the cells recharged to the appropriate level to keep the data intact. The higher the temperature, the faster the flash cells lose charge and lead to data corruption and loss. We highly recommend that flash storage media be kept at lower temperature during long term operation or storage.

Our software work together with our board hardware to keep the device running within temperature limits and reliably. We have set the following temperature thresholds:

  • 65C - Performance limited to reduce power and heat
  • 70C - Performance is reduced to the minimum
  • 80C - Software initiates shutdown sequence