Moisture Analysis
An analytical technique determines the quantity of water absorbed by a material by measuring its increase in weight over time. This mass gain gravimetry is widely used to evaluate the hygroscopic behavior of plastic packaging materials. High precision balances track the weight changes in controlled temperature and humidity chambers.
The resulting absorption curve identifies when the material reaches moisture saturation.
Equipment Calibration
The balance must be calibrated with certified standard weights to ensure measurement accuracy. Temperature and humidity sensors in the test chamber are also calibrated to maintain stable environmental conditions during the test. Small variations in these conditions can affect the rate of moisture absorption.
Measurement Protocol
Test samples are first dried to a constant mass in an oven to establish a baseline dry weight. They are then placed in the environmental chamber and periodically removed for rapid weighing to minimize moisture loss during handling. The change in weight is recorded and plotted against the square root of time to analyze diffusion behavior.
This process continues until successive measurements show no further change in mass.
Diffusion Model
The gathered data is used to calculate the diffusion coefficient and the maximum moisture capacity of the material. These parameters are essential for predicting the shelf life and reflow performance of plastic encapsulated electronics. They allow designers to select materials with low moisture sensitivity.
