Joining of printed wiring board to aluminum stiffener using adhesive

Abstract

Materials having diverse coefficients of thermal expansion are joined together by means of an adhesive film, electrically insulative mesh structure that cures at room temperature. An adhesive film bonding technique is employed to mount a printed wiring board, having a relatively low coefficient of thermal expansion, to a thermally and electrically conductive aluminum stiffener having a relatively high coefficient of thermal expansion, while maintaining the printed wiring board electrically insulated from the aluminum stiffener. A non-adhesive plastic `release` film is initially attached to a flat support substrate. A layer of electrically insulative mesh (glass cloth) is taped onto the plastic release film. The glass cloth is then impregnated with an electrically insulative adhesive that cures at room temperature. The aluminum stiffener is then placed on the adhesive-impregnated cloth layer, which is then cut to fit, using the aluminum stiffener as a template. The release polyester film and the flat support substrate are removed, exposing the opposite side of the adhesive-impregnated cloth layer for attachment to the printed wiring board. The resulting laminate assembly of the printed wiring board, the adhesive-impregnated glass cloth, and the aluminum stiffener plate is placed in a vacuum bag and allowed to cure at room temperature. Because the laminate cures at room temperature, the physical configuration of the assembly will not have changed at cure.