Definition

IPC-2221 is the foundational design standard for all PCB types, establishing generic requirements for component mounting and interconnection structures. It covers conductor spacing and clearance (including high-voltage requirements up to 500V), trace width for current capacity (the famous charts), material selection, thermal management, via structures, and test coupon requirements. When your CAD tool flags a spacing violation, it's likely checking against IPC-2221 rules. The standard is the master reference that all sectional design standards (IPC-2222 for rigid, IPC-2223 for flex, IPC-2226 for HDI) build upon.