Resin composition and hardened film

Abstract

The purpose of this invention is to provide a resin composition capable of forming a hardened film with a low coefficient of linear expansion. This invention is a resin composition comprising epoxy resin, alumina particles, and flux, wherein the product X of the number of surface hydroxyl groups (number / nm²) of the alumina particles and the water solubility of the flux: logS is 8.0 (number / nm²) or higher. Preferably, the alumina particles have a volumetric D50 of 3.0 μm or less in their cumulative particle size distribution; and the alumina particles have an alpha radiation content of 0.006 cph / cm² or less.