Dry Heat Test
In most areas, the average temperature is around 0℃~40℃, and during the summers, the temperature is around -30℃~49℃, with an average of 43℃ (environmental/ air temperature). However, thermal radiation will bring a 17℃~33℃ temperature rise. The effect will vary depending on the color of the product's surface coating and the reflection from the surface. Outdoor products can reduce radiation by choosing carefully the color of the outer coating if being used outdoors for a long period of time.
The environmental setting of consumer electronics are usually between 35℃~45℃; telecommunication products and industrial product, due to life expectation, usually are between 45℃~55℃. If the products are in outdoor environments for an extended time, the recommended temperature should be around above 70℃ for better reliability. For automotive electronics, it would depend on the installation process.
In order to accurately inspect and verify the product under high thermal conditions without the influence of humidity, International Electrotechnical Commission (IEC) requires the chamber's absolute humidity to be less than 20g/m3 for the Dry Heat Test and has specified standards for preconditioning, post testing conditioning, temperature rising speed, constant temperature definition, temperature load condition, unit under testing and chamber volume ratio and so on.
Heat Test Application:
Generally, test applications are divided into High Temperature Storage Test and High Temperature Operating Test. It is recommended to use ambient temperature and high temperature cycling for High Temperature Storage Test and a stabilized temperature for High Temperature Operating Test. The application in the MIL standard suggests:
Simulatation of the real life environmental conditions
Environmental testing should start with Dry Heat Test
Continuous test order: Vibration, Shock, High Temperature, High Altitude (often used during product designing stage)
Often seen effects:
Difference in coefficient of expansion causing material to fail or wedge
Improper cooling causing components to overheat and lose electric powers
Belts loosening, accelerated aging, discoloration or turn yellow
Plastic softening, decrease in performance, change in characteristics, oxidation, etc.