Patent ID: 8119924

Claim:
A flexible wiring board wherein a plurality of insulation layers and wiring layers are piled up alternately and the wiring layers are via-connected each other, comprising: a reinforced area being reinforced against an external stress; a bending area bending easier than the reinforced area by the external stress; and a stress relaxation area that is provided in an area between the reinforced area and the bending area, bends easier than the reinforced area by the external stress and not easier than the bending area by the external stress, and relaxes the stress carried from the bending area to the reinforced area, wherein a degree of crystallization of at least one insulation layer of the stress relaxation area is smaller than a degree of crystallization of at least one insulation layer of the reinforced area and is larger than a degree of crystallization of at least one insulation layer of the bending area, and wherein the degree of crystallization of the stress relaxation area changes continuously from a high value correspondent with a side near to the reinforced area to a low value correspondent with a side near to the bending area.