Temperature and Humidity Testing (Damp Heat Test)
In any natural environment, temperature and humidity are essential environmental conditions. The temperature and humidity condition variations change as the geographical locations and the climatical settings change. For example, Taiwan is a typical island climate with year-long high humidity; however, continental climates face drastic day-and-night temperature changes.
According to IEC60721, there are four conditions: High Temp./Low Humidity, High Temp./High Humidity, Low Temp./High Humidity, and Low Temp./Low Humidity. In IEC60721 and ETSI 300 019, European Telecommunications Standards, there is a clear chart on recommended temperature and humidity.
To avoid confusion and obscurity of the true reason for failure, each international company will conduct dry heat test, cold test, constant temperature/ humidity test, humidity cycle test seperately.
For plastic, PCB, PCBA multi-hole materials or products, each material will have a different effect to temperature and humidity. Temperature effects are usually plastic deformation, product overheat, poor cold start, etc. For multi-hole material and products, the breathing effect in a humid environment will cause surface moisture absorption, permeation, and condensation; in a low temperature environment, accumulation of static will cause failure.
Therefore, different temperature and humidity will cause different failure modes. In the past experience, temperature and humidity testing can discover much of the product or material’s potential defects, especially for finding PCB or PCBA Dendrite Effect after switching to lead-free production.
Only outdoor products are obligated to conduct condensation test. Due to the fact that condensation can easily cause shorts and fail, indoor products are often prevented from condensation during humidity testing.
Often humidity effects include loss of physical strength, chemical change, deterioration of insulation, short circuit, oxidation on metal surface, loss of flexibility, accelerated chemical change, component deterioration, etc.