Abstract: A varnish includes an epoxy resin, a curing agent, an accelerator agent and fillers. The fillers include sericite powders. The sericite powders have composition of SiO2 in weight ratio of 55±3%. Furthermore, the Mohs' scale of hardness of the sericite powder is between 2 to 3. Glass fabric cloth is dipped into the varnish so as to form a prepreg with better machined-work capability.

Abstract: The present invention discloses a thermosetting resin for expediting a thermosetting process. The thermosetting resin is composed of 100 parts of primary resin formed by mixing a brominized epoxy resin, a tetrafunctional epoxy resin and an epoxy resin with a high bromine content, and other materials including 35 parts of phenolic resin curing agent, 30 parts of tetrabromobisphenol A curing agent, 0.1 part of 2-ethyl-4-methylimidazole, 0.8 part Lewis acid, and 50˜70 parts of solvent, calculated based on every 100 parts of the primary resin by weight. The invention can expedite a thermosetting process and enhance the Tg of prepregs and clad laminates.