Abstract: A rigid-flexible circuit board is fabricated by providing a core having a dielectric substrate and conductive layer thereon. A sub-composite comprising a polyimide and rigid dielectric substrate adjacent the conductive layer and in both the rigid and flexible segments of the board is provided. A release layer corresponding to the flexible segment of the board is provided. A rigid bonding layer is provided at rigid segments of the board but not at the flexible segments. A composite is formed by providing a second conductive layer adjacent the rigid bonding layer. The composite is laminated. Portions of the second conductive layer corresponding to the flexible segment and release layer are removed.

Abstract: A composite for providing a rigid-flexible circuit board includes at least one core that contains a dielectric substrate and at least one conductive layer thereon; at least one sub-composite that includes a polyimide and a rigid dielectric substrate; a release layer; at least one rigid bonding layer and a second conductive layer. The composite is used in the fabrication of a rigid-flexible circuit board.

Abstract: A dicyandiamide crosslinked epoxy prepreg substantially free from dicyandiamide crystals is obtained by subjecting an epoxy composition containing dicyandiamide to elevated temperature to thereby form a substantially prereacted product, adding solvents if desired, desolvating, and then thermally advancing the prereacted product to the desired state of crosslinking to thereby form the prepreg.

Abstract: Woven glass cloth and method of its manufacture suitable for use as a resin-impregnated substrate for printed circuits in which the major dimension or transverse axis of the elliptical warp yarns exceeds a predetermined fraction of that dimension of the fill yarns of the woven cloth. Multi-filament warp yarns are typically subjected to tensile stress during weaving and firing such that the yarn compaction prevents the thorough impregnation by a resin. The result is that voids are maintained along the innermost filaments of the yarn. These voids, when filled with materials other than resin, such as plating solution, ultimately produce circuit failures.