GLASS CLOTH BASE LAMINATE

PROBLEM TO BE SOLVED: To obtain the subject laminate improve in tracking resistance, suitable as a substrate for electrical insulation boards, esp. printed wiring boards, by using, as base material, a glass cloth comprising glass fiber and provided with an alumina layer on the surface. SOLUTION: This base material is obtained by providing the surface of a glass cloth comprising glass fiber with an alumina coating layer as a layer needing at least tracking resistance. In this case, the glass fiber may be nonalkaline glass commonly used for electrical insulation such as E-glass fiber or C-glass fiber. To provide the alumina coating layer on the surface of the glass fiber, it is preferable to thermally spray the glass cloth with alumina because of simplicity and enabling direct resin impregnation. The alumina coating layer is pref. 3-10μm in thickness. The thermosetting resin to be impregnated in the glass cloth is pref. an epoxy resin. The solvent to be used for preparing a varnish by dissolving the thermosetting resin therein is pref. e.g. ethylene glycol monomethyl ether.