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Conductor Clearance & Creepage

PCB & Copper

Minimum conductor spacing for your working voltage and construction.

Inputs

V

Results

1 passed · 1 to check
Required minimum spacing 

15.7 mil

0.4mm
Pass

Checked: drawn spacing ≥ 0.4 mm, IPC-2221 for B4, External, permanent polymer coating (any elevation) at 240 V

Margin
0.1mm
Highest voltage for your spacing
All results (1)
You have drawn
0.5mm

Accuracy

Source
  • IPC-2221

IPC-2221, Generic Standard on Printed Board Design a published table

Valid range
  • Voltage between conductors (DC or AC peak) at most 500 V

Voltage between conductors (DC or AC peak) The table runs to 500 V. Above that the standard gives a per-volt rule instead, which is applied here. IPC-2221

Precision
A table lookup, exact for the construction selected.

It does not cover pollution degree, altitude beyond its single 3050 m step, or product safety standards: IEC 60664 and IEC 62368 set their own distances, often larger.

IPC-2221

This is a design aid. The engineer remains responsible for the design and for checking the standard itself.

Parameter sweep

Vary one input over a range and see the answer and verdict at each step, as a table and a curve.Pro

Worst-case corners

Put a tolerance on each input and get the worst-case band around the answer.Pro

Cross-section

The principle

Conductors at different potentials can break down through the air (clearance) or track along the surface (creepage). IPC-2221 sets the minimum spacing by peak voltage, internal or external layer, coating and, for bare external conductors, altitude.

Above 500 V
d=d500+(V−500)⋅ad = d_{500} + (V - 500)\cdot a
a is the per-volt adder for the selected construction, from IPC-2221.
Paschen minimum (air, DC)
Vbd≈327  V at p d≈7.5  μm⋅barV_{bd} \approx 327\;\t{V at } p\,d \approx 7.5\;\t{μm·bar}
Air does not break down below about 330 V at any gap, so the low-voltage spacings are set by manufacturing and contamination.
  • VVpeak voltage between the two conductors, DC or AC peak
  • ddminimum permitted spacing
  • aaper-volt adder above 500 V for that category
More detail

Choosing the construction

  • B1: internal layers, protected from contamination, so the smallest spacings.
  • B2 / B3: external conductors with no permanent coating. B3 applies above 3050 m.
  • B4: external conductors under a permanent polymer coating, which can be a solder resist. The lands and leads it leaves bare for soldering follow A6.
  • A5 / A6 / A7: coated assemblies, and component leads and terminations.
Not a safety standard. Safety isolation depends on pollution degree, laminate CTI, overvoltage category and insulation class. IEC 60664-1 and the product standard set those, and often require 6.4 mm or more where IPC-2221 allows 2.5 mm.

Under IEC 60664-1, a slot milled between isolated regions lengthens the creepage path when it is wide enough to count. Keep the barrier free of vias, test points and silkscreen.

References: IPC-2221. For safety-critical work, consult IEC 60664-1 and the product standard (IEC 62368-1, IEC 61010-1, IEC 60601-1, UL 840). Check against the published standard before release.

Engine version ⁨1.26.4⁩