Fabrication And Properties Of Aluminum Oxide Filled Epoxy Encapsulates For Pulse Power Supplier

The encapsulate composite for pulsed piezoelectric power supplier was investigated in this paper, in which a bisphenol A liquid epoxy EP828/E51 was resin matrix and aluminum oxide was filler. The acoustic impedance, tensile strength, dielectric properties and pulsed dielectric breakdown were investigated. As the pulsed piezoelectric power supplier encapsulate, these properties must match for the piezoelectric material, besides protection function.The fabrication technique was an injection mold processing. Alumina was mixed into epoxy resin under 80℃, then curative was filled in mixture. The alumina/epoxy mixture was vacuum pumped under 0.5 Torr. Finally, the mixture was injected the mold and cured.There were three different types of aluminum oxides as filler, AF-2 random particle aluminum oxide, CA-15 tabular aluminum oxide, A-F-3 tabular aluminum oxide. It is suggested that the rate of aluminum oxide sedimentation in composites decrease with the content of aluminum oxide increase, but the composite density was increase. Therefore, the acoustic impedance was increase with the aluminum oxide, especially, for the CA-15 tabular aluminum oxide. CA-15 tabular alumina /epoxy composites show the best tensile strength. The dielectric constant of composites increased with increasing the content of alumina, but the dielectric loss decreased. The shape and the size of alumina had no effect on dielectric properties. When epoxy resins were loaded with alumina filler, the pulsed dielectric breakdown of the encapsulate composites decreased, however, the pulse dielectric breakdown of encapsulate composites are improved by changing electrodes, as well as choosing suitable matrixes, fillers, coupling agents and curative agents.In summary, the CA-15 tabular alumina/epoxy composite was chosen as the best candidate of encapsulate composites for the pulsed piezoelectric power supplier. The composites could be used to encapsulate for the pulsed piezoelectric power supplier, in which the contents of alumina were from 35% to 40%.