Filler volume fraction effects on the breakdown resistance of an epoxy microcomposite dielectric

Studies have been made on the development of micro-composite dielectrics with electrical breakdown resistance superior to the neat epoxy resin. Micron-sized aluminium trihydroxide particles were used as reinforcements to enhance the time to breakdown of an Araldite epoxy resin. Electrical tree growth tests have been performed in point-plane specimens in unfilled resin and resin-filled with aluminium trihydroxide in the 0-15 wt% range. Results are presented which show that the addition of filler particles in the epoxy resin can make considerable improvements in breakdown resistance by increasing the times to breakdown. In particular, the times to breakdown of microcomposite dielectrics increase with the increasing filler volume fraction. A model is proposed for electrical treeing breakdown-resistant composite dielectrics which accounts well for these experimental observations.