Space charge observation of a filler free epoxy resin

Space charge behaviour in epoxy resin and its effect on electrical ageing have been investigated for several years. For example, copper ion migration in an epoxy resin of a printed circuit board was observed by using the pulsed electroacoustic (PEA) space charge measurement system. In this work, a type of filler-free resins (CY1301) was used as a specimen in order to investigate the temperature dependence of space charge behaviour in an epoxy resin of which the glass transition temperature was just below 40 degreesC. Space charge profiles were measured by the PEA method at 20 degreesC and 40 degreesC either under the electric field of 15 kV/mm or after the electrodes were short circuited. At 20 degreesC, injected charges appeared near the electrodes. At 40 degreesC, on the other hand, only surface charge on the electrode remained even though the electrodes were short-circuited. Although further investigation is required, it is clear that the space charge phenomena is strongly influenced by the temperature, and it could be related to the glass transition temperature of the resin.