Bare external conductors require significantly more spacing than conductors protected by a solder mask or conformal coating. Summary of Minimum Electrical Clearance (IPC-2221) Voltage (DC or Peak AC) Bare Conductors (Internal Layers) Bare Conductors (External, 0 - 15V 0.05 mm (2 mils) 0.1 mm (4 mils) 0.05 mm (2 mils) 16 - 30V 0.05 mm (2 mils) 0.1 mm (4 mils) 0.05 mm (2 mils) 31 - 50V 0.1 mm (4 mils) 0.6 mm (24 mils) 0.13 mm (5 mils) 51 - 100V 0.1 mm (4 mils) 0.6 mm (24 mils) 0.13 mm (5 mils) 101 - 150V 0.2 mm (8 mils) 0.6 mm (24 mils) 0.4 mm (16 mils) 151 - 170V 0.2 mm (8 mils) 1.25 mm (50 mils) 0.4 mm (16 mils) 171 - 250V 0.2 mm (8 mils) 1.25 mm (50 mils) 0.4 mm (16 mils) 251 - 500V 0.25 mm (10 mils) 2.5 mm (100 mils) 0.8 mm (32 mils)
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While many summaries exist, the complete, official IPC-2221 standard is a copyrighted document. You can purchase the most current IPC-2221C PDF from the . Ipc-2221 Pcb Design Pdf
Materials and finishes
: More precise clearance requirements for aerospace and high-altitude environments. If you share with third parties, their policies apply
Sectional Design Standard for Flexible/Rigid-Flex Printed Boards.
Electrical Clearance, Creepage, and Voltage-Related Rules While many summaries exist, the complete, official IPC-2221
The is widely recognized as the foundational document for the electronics design industry. Officially titled the "Generic Standard on Printed Board Design," it establishes the baseline requirements for nearly every aspect of printed circuit board (PCB) layout and assembly.
Electrical isolation is vital to prevent arcing and short circuits between adjacent conductors. IPC-2221 specifies minimum electrical clearance based on: The potential difference between two conductors.
IPC-2221 is the "Bible" of PCB design. It is not a tutorial; it is a specification. If you are designing boards for professional, industrial, or high-reliability applications, this is the foundational document you must follow.