Kinetic Model
Mathematical models for chemical kinetics provide the foundation for estimating long term reliability in electronics assembly. The arrhenius rate equation calculates how the rate of a physical or chemical change increases with temperature. This calculation uses the universal gas constant and an activation energy value specific to the failure mechanism.
Reliability Forecasting
Thermal stress testing often relies on this formula to compress years of operational life into a few hundred hours of laboratory time. Engineers use the arrhenius rate equation to determine acceleration factors when boards undergo high temperature storage or biased humidity testing. This approach allows a manufacturer to quantify the risk of solder joint oxidation or intermetallic growth without waiting for field failures to occur.
Accurate results require a precise activation energy for the specific material system under review, as small errors in this constant lead to massive discrepancies in predicted life. Validation of these predictions occurs through physical testing and cross-sectional analysis of aged samples.
Thermal Boundary
Application of the formula assumes that the failure mechanism remains constant across the entire temperature range. If a material reaches a glass transition point or a melting phase, the arrhenius rate equation no longer provides a valid prediction.
