0°C is typically the minimum recommended operating temperature for commercial grade silicon. You’ll find this specified on pretty much any hardware that is commercial grade (the commercial temperature range is usually 0°C to 70°C).
This is in contrast to industrial grade (-45°C to 85°C) and military grade (-55°C to 125°C).
What you’re asking however, is how concerned should you be about keeping GigaBlox Nano below 0°C. The answer is nuanced.
In nearly all cases, it is more important to stay below the upper temperature value than staying above the lower temperature value. As devices get hot, you can end up with increased power dissipation in the chip (resistive heating), which further increases heat, increasing power, leading to a thermal runaway.
At the colder side of things, this doesn’t happen, and in fact most electronics run better when cooler, however there is a limit to that. It should also be mentioned that the chip itself will dissipate power and keep itself warmer than ambient. In other words, even at 0°C, the temperature of the chip’s internal die is going to be a few degrees warmer.
We have existing customers using GigaBlox Nano down to -10°C without issue, and we’ve verified that the board down to -20°C. However it is a question of risk. At below 0°C, we are outside recommended operating conditions. Usually this means a reduced MTBF and an increased risk of random failure. The estimated MTBF of GigaBlox Nano is 200,000 hours (approximately 20 years), so even a conservative halving of the MTBF is still 10 years of operation.
For some of our customers, this risk is simply not acceptable. As an example, if you’re putting GigaBlox Nano in a chamber that goes to the sea floor, and costs $$$ to retrieve for maintenance, you’re better off using something like UbiSwitch, which is rated for operation to -45°C. However if your application is easy to maintain and is not mission critical, then running GigaBlox Nano at down to -20°C is often an acceptable risk vs cost tradeoff.
A final point to mention is temperature gradient. Running electronics at a steady temperature below 0°C is a lot less demanding that having a temperature that changes quickly. Quick changes in temperature can cause microfractures on the chip and board, leading to mechanical failure, along with inducing other internal stresses.
In the end, whether you should use GigaBlox Nano for your application will depend on what the application is, and whether the reduced cost is worth the slightly elevated risk of failure. Feel free to share more information here and we can advise.