creepage

Creepage distance, often referred to simply as creepage, is the shortest path along the surface of an insulating material between two conductive parts. It differs from clearance, which is the shortest distance through air. Creepage is a key factor in determining how well a given insulation system can withstand high voltage without surface arcing or tracking along the surface.

Creepage is influenced by several factors, including the applied voltage, the insulating material’s electrical strength or material group, the presence of surface contaminants, humidity, and surface moisture. Standards define minimum creepage distances for equipment, taking into account pollution degree and material grouping. In practice, creepage increases with higher voltage, harsher pollution conditions, and lower material quality. Methods to increase creepage include selecting higher-grade insulation, applying conformal coatings, using barriers or potting compounds, and increasing the distance along the surface.

In design practice, creepage values are specified alongside clearance to assess insulation coordination and safety margins in electrical equipment and consumer devices. For printed circuit boards, creepage is considered along the board surface between conductors and is often addressed by coatings or routing changes to maintain adequate distances between high-voltage nets. Standards such as IEC 60664-1 and IPC-2221 provide guidelines for creepage and clearance in equipment and PCB design, helping engineers ensure adequate insulation under varying environmental conditions.