FLEXIBLE CIRCUIT BOARD AND STRUCTURE OF BEND SECTION OF FLEXIBLE CIRCUIT BOARD

摘要

Disclosed is a flexible circuit board which has a bend section subjected to repeated bending and straightening with a small radius of curvature under severe conditions and which yet has durability and excellent flexibility. Specifically, the flexible circuit board is provided with a resin layer and wiring formed of metal foil and has a bend section in at least one portion of the wiring, wherein the metal foil is made of a metal having a face-centered cubic structure, wherein the preferred orientation region, in which the fundamental crystal axis <100> of each unit lattice of the face-centered cubic structure is within 10° of perpendicular to the thickness direction of the metal foil and to a direction along the surface of the foil, occupies an area of 50% or more of the area of the board, and wherein the breaking elongation of the metal foil in a direction tangent to a cross-section (P) of the wiring taken along a plane extending from the ridge line of the bend section in the thickness direction of the metal foil is 3.5% or more and 20% or less.