Quantifying Parametric Drift and Test Uncertainty in Sourced Microelectronics
Quantifying test uncertainty and parametric drift through guardbanding and thermal acceleration equations prevents field returns and secures accurate component tolerances.
Pecks Model
Acceleration Formula
Empirical equations determine the acceleration of stress-induced wear when electronic packages are exposed to high temperatures and humidity. A widely used calculation method, known as pecks model, uses an activation energy alongside a humidity exponent to calculate the acceleration factor of moisture-induced failures. This calculation helps test engineers to relate laboratory test times to real-world operation in humid environments.
It is a standard tool in electronic packaging qualification.
Environmental Variable
High humidity coupled with elevated temperatures accelerates the penetration of moisture through plastic packaging. According to pecks model, the acceleration factor rises exponentially with relative humidity and follows an Arrhenius relationship for temperature. Testing processes like highly accelerated stress testing rely on these calculations to design test profiles that compress months of environmental exposure into hours.
This compression reduces the time to market for new products.
Fit Assessment
Calibration of the model coefficients is necessary for different package styles and moulding compounds. The activation energy in pecks model varies between different plastics, which requires experimental testing to extract the correct parameters for each material. This extraction ensures the calculated acceleration factors are accurate.
Reliability Limit
The accuracy of the model degrades if the temperature exceeds the glass transition temperature of the polymer. Under these conditions, the failure mechanisms change, rendering the calculated acceleration factors invalid.