PCB Electrical Clearance & Creepage Calculator

IPC-2221 is a generic PCB design standard that defines the minimum spacing required between internal, external, and coated conductors at different voltages. IPC-9592B is a standard specifically for power conversion devices and requires larger spacing for safety.

IPC-2221B Spacing Table

Voltage range (V)	External conductor spacing (mm)	Internal conductor spacing (mm)	Coated conductor spacing (mm)
0-30	0.1	0.1	0.1
31-50	0.6	0.1	0.1
51-100	0.6	0.1	0.1
101-150	0.6	0.6	0.6
151-300	1.25	0.6	0.6
301-500	2.5	1.25	1.25
>500	additional 0.005 mm per volt	additional 0.0025 mm per volt	additional 0.0025 mm per volt

IPC-9592B Spacing Table

Voltage range (V)	Minimum spacing (mm)
0-14	0.13
15-29	0.25
30-99	0.1 + (0.01 × voltage)
≥100	0.6 + (0.005 × voltage)

Insufficient electrical spacing on PCBs can lead to several metal migration failure modes, the most common being dendrite growth:

• Dendrite growth: With sufficient voltage between two conductors in a humid environment, electrochemical migration may occur, forming dendritic metal structures that eventually short the circuit. This is common when ionic contamination is present.
• Corona discharge: At high voltages, when the electric field exceeds the breakdown strength of air, corona discharge occurs, producing visible bluish light and causing long-term insulation aging.
• Arc discharge: With even higher field strength, arc discharge can occur, which immediately damages the PCB.

High-Voltage PCB Design Recommendations

To avoid these issues, follow these principles in high-voltage PCB design:

• Strictly follow electrical spacing requirements from relevant IPC standards
• Use appropriate coatings such as conformal coating
• Plan routing to avoid long parallel high-voltage traces
• Use cutouts in high-voltage regions to increase creepage distance
• Consider environment: altitude, pollution degree, humidity
• Select components with sufficient lead spacing

Note: IPC standards are voluntary. For products covered by mandatory safety standards (e.g., building/electrical codes), creepage and clearance requirements from UL or IEC standards may be compulsory. For example, IEC 62368-1 (which replaced IEC 60950-1) provides safety requirements for IT and telecom equipment powered by AC or batteries.