An effective method of characterizing moisture desorption of polymeric materials at high temperature

Moisture diffusion characterization at high temperatures in polymeric packaging materials is important since moisture adsorption of polymeric packaging materials plays a determining role in "popcom cracking" of IC packages during the solder reflow process. Karl Fischer Titration is proposed as an effective method for characterizing moisture desorption of polymeric packaging materials in this paper. Samples of molding compound, underfill and die attach materials were preconditioned at 85C/%85RH till saturation. The rate of moisture diffusion was then measured at 5 different temperatures using both Karl Fischer Titration and Thermo-gravimetric Analysis (TGA) methods and compared. The differences at high temperatures was attributed to the outgassing of polymeric materials at high temperatures. This was confirmed using Gas Chromatography/Mass Spectrometry (GC/MS). This questioned the use of TGA or any other conventional gravimetric methods for measuring moisture desorption properties at high temperatures. The differences at lower temperatures was attributed to the low sensitivity of Karl Fischer Titration at relatively lower temperatures.