Multilayer flexible wiring boards

摘要

A multilayer flexible wiring board, suited for mounting semiconductor elements. The flexible wiring board is fabricated in the following manner. A flexible wiring board piece having a metal wiring, in which a metal coating is exposed on at least a part of surface of the metal wiring, is adhered to another flexible wiring board piece having a metal projection on which a metal coating is formed. One of or both of the metal coatings on the metal wiring and the metal projection is composed of a soft metal coating a surface of which has a Vickers' hardness of 80 kgf/mm<2 >or lower. The metal coating of the metal wiring contacts with the metal coating of said metal projection and ultrasonic wave is applied thereto to connect the metal wiring with the metal projection.