Patent ID: 7336499

Claim:
A flexible printed wiring board comprising an insulating layer; a wiring pattern formed of a plurality of juxtaposed wirings, which wiring pattern is formed through patterning a conductor layer stacked on at least one surface of the insulating layer and on which wiring pattern a semiconductor chip is to be mounted; and grid-like dummy patterns formed in a blank area where the wiring pattern is not provided, wherein the dummy patterns are formed in a width direction generally symmetrically with respect to the longitudinal direction of the flexible printed wiring board, which is configured such that a device hole is provided in an area where the semiconductor chip is to be mounted, the area corresponding to longitudinal mid portions of the wirings of the wiring pattern, and that a flexural slit is provided for imparting appropriate bending to the board, the flexural slit including a plurality of component slits that are aligned so as to form a row running in a direction of juxtaposition of the juxtaposed wirings, and the flexural slit being provided on at least one of two opposing areas divided by the device hole along the longitudinal direction of the flexible printed wiring board, wherein adjacent component slits are separated from each other by a strut portion therebetween, and the strut portion is disposed away, in the width direction of the flexible printed wiring board, from the position of each end of the device hole with respect to a direction of juxtaposition of the juxtaposed wirings.