Patent ID: 7701722

Claim:
A flexible printed wiring board comprising an insulating layer, which insulating film has, along longitudinal edges thereof, rows of sprocket holes at predetermined intervals; 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; a plurality of flexural slits provided in the longitudinal direction of the wiring board; and grid-like dummy patterns, each of which having a plurality of dummy wirings extending in a grid-like manner, formed only in a blank area where the wiring pattern is not provided, which blank area is present between the wiring pattern and the rows of sprocket holes, wherein the dummy patterns are formed in a width direction generally symmetrically with respect to the longitudinal direction of the flexible printed wiring board, and are separated by mediation of an area where the flexural slit has been provided.