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 C provides new design guidance and requirements for bends, folds and creases, staggered flexible layer bands, and strain relief fillets. Also included is a new design tutorial providing guidance on material selection, size and shape of flexible circuits and fabrication allowances. IPC-2223C includes, as Appendix A, a new design tutorial with guidance on material selection, size and shape of flex circuits and fabrication allowances. 39 pages.