IPC-2221B 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 A are new criteria for surface plating, internal and external foil thicknesses, component placement and hole tolerances. Expanded coverage is provided for material properties, dimensioning and tolerancing rules, and via structures as well as updated coupon designs for quality assurance. 112 pages. .