This invention relates to methods and apparatuses for manufacturing resin-impregnated sheet materials and, more specifically, to such method and apparatus that gas present in voids within a fibrous sheet material is expelled from the sheet in a vacuum space and the gas-expelled sheet is then uniformly impregnated with a resin varnish to manufacture a resin-impregnated sheet material.
A resin-impregnated sheet material prepared in the manner referred to can be of high quality without any voids by sufficiently deaerating the sheet material and then impregnating the deaerated sheet with the resin varnish, to be effectively utilizable as laminating material for a high quality printed wiring board or the like.