Effect of UV curing on electrical properties of a UV-Curable co-Polyacrylate/Silica nanocomposite as a transparent encapsulation resin for device packaging

Abstract

Electrical properties of UV-curable co-polyacrylate/silica nanocomposite resins prepared via sol-gel process for device encapsulation were investigated. It was found that, by appropriate UV curing process and the formation of nanoscale silica particles finely dispersed in the resin matrix, the leakage current density of the nanocomposite resin films decreases from 235 to 1.3 nA (.) cm(-2) at the applied electrical field of 10 kV (.) cm(-1). The silica nanoparticles also restricted the motions of polar functional groups in organic matrix that the nanocomposite films with satisfactory dielectric properties [dielectric constant (epsilon) = 3.93 and tangent loss (tan delta = 0.0472) could be obtained. Chemical structure analyses revealed that excessive UV curing results in photooxidation and/or photodegradation in resin samples, leading to the polar groups and ionic/radical segments in organic matrix as well as the -Si-O-Si- structure in the vicinity of silica nanoparticles. These organic/inorganic functional groups generated more permeation paths for charge carrier migration and hence deteriorated the electrical properties of the nanocomposite samples. Though post-baking treatment at 80 degrees C for 1 h followed by UV curing improved the rigidity of the resin sample, it brought the polar functional groups closer to each other and similarly degraded electrical properties of the nanocomposite resins.