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.
Gravimetric Analysis
Weight Determination
Quantitative analytical methods relying on the measurement of an object’s mass before and after a physical or chemical process determine the quantity of volatile substances lost or gained. In electronic assembly, gravimetric analysis is the primary method used to evaluate moisture absorption in polymer materials and printed circuit boards. The precision of these measurements is governed by the sensitivity of the balance used, which must resolve sub-milligram changes.
This method provides the foundational data needed to calibrate numerical moisture diffusion simulations for plastic-encapsulated microcircuits.
Sorption Modeling
Test specimens are placed in controlled humidity chambers to absorb moisture under specific environmental conditions. Periodic gravimetric analysis measurements of these specimens provide data points for plotting mass gain over time, allowing the calculation of diffusion coefficients. This process requires quick handling to prevent the sample from exchanging moisture with the ambient air during the weighing step itself.
Process Validation
Baking efficiency is commonly validated by measuring mass loss until a stable dry baseline is established. Implementing gravimetric analysis of sample coupons verifies that dry baking protocols successfully remove absorbed moisture from materials before reflow. This validation reduces the risk of internal vapor pressures causing package delamination during high-temperature soldering.