Degradation Mechanism
Environmental stress tests evaluate the long term reliability of components by exposing them to high heat without electrical bias. Undergoing elevated temperature storage accelerates the chemical and physical degradation processes that occur over years of normal use. This procedure identifies weaknesses in material interfaces and the stability of plastic encapsulants.
Qualification Standard
Testing follows specific protocols such as JESD22 which define durations ranging from one hundred to one thousand hours. The temperature is typically set at 125 or 150 degrees Celsius depending on the grade of the device. Parts are measured before and after the soak to check for shifts in electrical parameters.
Failure Analysis
Post test inspection reveals the extent of structural damage and electrical drift. Sensors might show a change in sensitivity or an increase in noise due to the aging of the sensing element. This data helps engineers predict the useful life of the product in harsh environments.
Atomic Diffusion
Movement within the semiconductor lattice and at the wire bond interfaces increases at higher temperatures. These movements can lead to the formation of voiding or the growth of brittle intermetallic compounds. Sustained heat also drives out volatile organic compounds from adhesives and coatings.
The test duration is calibrated to simulate twenty years of field service.
