US Patent 7208062 Method of producing multilayer printed wiring board

Adhesive films which are useful for preparing laminated circuit boards may be produced by laminating a resin composition layer made of a layer A and layer B on a support base film, in whichlayer A is a layer of a thermosetting resin composition that has an inorganic filler content of from 0 to less than 40% by weight, has a cured surface which after roughening, allows forming a conductor layer by plating, and is solid at ambient temperature,layer B is a layer of a thermosetting resin composition that has an inorganic filler content of 40% by weight or more, and is solid at ambient temperature,layer A is laminated adjacent to the support base film, andlayer B layer has a fluidity that allows the filling of a resin into a through hole and/or a via hole.