Moisture Concentration Monitor for Epoxy/Composite Materials
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Monitoring of the moisture content of epoxy layers sandwiched between layers of metal foil in a circuit board composite is essential in resin development and process quality control. A method which permits an intermittent measurement of the moisture in epoxy layers works as follows. Small polar groups or molecules, such as water, respond to an applied electric field by reorienting so as to oppose the applied field. This behavior is the source of the relatively high dielectric constant of a polar material such as water (E = 80.3), compared to a non-polar material such as carbon tetrachloride (E = 2.2). At a sufficiently high frequency of the applied electric field, however, the polar groups of any molecule will be unable to respond to the applied field.