Used in conjunction with IPC-2221, IPC-2223 establishes the specific requirements for the design of flexible printed boards and forms of component mounting and interconnecting structures. The flexible materials used in the structures are comprised of insulating films, reinforced and/or non-reinforced dielectric in combination with metallic materials. Revision D provides new design guidance and requirements for material selection and construction, selective (button) plating, minimum bending for flexible circuits with coverlay, impedance and capacitance control, unsupported edge conductors/fingers and copper filled vias/microvias.