Fickian Diffusion Kinetics and Desorption Times for Molded Packages
Fickian desorption calculations use temperature-dependent diffusivity to determine exact package bake times, preventing reflow popcorning and structural delamination.
Dynamic Vapor Sorption
Gravimetric Measurement
Analytical instrumentation using controlled gas flows to continuously weigh a specimen under varying relative humidity provides precise measurement of moisture uptake and loss. Utilizing dynamic vapor sorption allows researchers to generate moisture absorption isotherms for solder mask materials and polymer substrates. This method replaces traditional static desiccator testing by providing real-time weight changes as humidity is stepped.
Isotherm Profile
Automated microbalances within the measurement chamber record weight changes as small as a fraction of a microgram. During dynamic vapor sorption testing, the system maintains a constant temperature while the relative humidity is stepped through a pre-programmed sequence. The balance waits for the specimen’s mass to stabilize at each step before moving to the next level, resulting in highly accurate moisture absorption and desorption curves.
This continuous tracking eliminates the measurement errors associated with manually removing samples from humidity chambers for weighing.
Sorption Analysis
Moisture diffusion coefficients calculated from these step-response mass curves are used to predict the shelf life of plastic-encapsulated microcircuits. By exposing the test sample to dynamic vapor sorption, engineers can quickly identify the saturation limits and diffusion rates of newly developed packaging polymers. These material constants are then fed into finite element simulations to model the moisture behavior during storage and assembly.