Application Note B-TA1054
Introduction
Polyimide resins are widely used in fields such as the aerospace industry, automotive applications, electronic components, and semiconductors due to their excellent heat resistance, mechanical properties, electrical insulation, and chemical resistance. On the other hand, they are known to exhibit dimensional and property changes when they absorb water or moisture.
This application presents the results of measuring the expansion and shrinkage of polyimide films under varying relative humidity conditions.
Measurement and results
As a sample, a polyimide film (thickness: 12 μm) was cut into strips of 5 mm width and 15 mm length. Equipped with a tensile load attachment, expansion and shrinkage were measured under a load of 50 mN while varying the controlled humidity atmosphere in 20% increments from dry conditions at 25°C to 80% relative humidity. The holding time at each relative humidity level was set to 40 minutes.
Figure 1 :Expansion and shrinkage associated with changes in humidity
During the process of stepwise increasing relative humidity, a nearly linear expansion in the range of 0.023% to 0.028% was observed for each 20% increase in relative humidity, while during the process of decreasing relative humidity, a shrinkage in the range of 0.020% to 0.026% was observed for each 20% decrease.
Since this measurement successfully captured expansion and shrinkage caused by changes in humidity, this method is considered effective for evaluating deformation and dimensional stability resulting from changes in the controlled humidity atmosphere.
