IPC-2221C is the foundation design standard for all documents in the IPC-2220 series. It establishes the generic requirements for the design of printed boards and other forms of component mounting or interconnecting structures, whether single-sided, double-sided or multilayer. Among the many updates to Revision C are new guidance and requirements on material and copper foil selection, palletization of printed boards, edge board plating, minimum electrical clearance (e.g., dielectric withstanding voltage, corona effect and creepage), impedance tolerances, clearance areas in planes, feature location tolerances, compliant pins (press-fit) and back-drilling. Appendix A provides updated test coupon designs used for lot acceptance and quality conformance testing in corresponding IPC-6010 series performance specifications. For use with one or more of the applicable sectional standards (i.e., IPC-2222, IPC-2223, IPC-2226 and/or IPC-2228). Supersedes IPC-2221B.