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Conductor Clearance & Creepage

PCB & Copper

Minimum conductor spacing for your working voltage and construction.

Inputs

Fab profile

Fills Drawn spacing from your active fab profile.

V

Results

1 passed · 1 to check
Required minimum spacing

15.7 mil, B4, External, permanent polymer coating (any elevation)
0.4mm
Pass

Checked: drawn spacing ≥ 0.4 mm, IPC-2221B Table 6-1 for B4, External, permanent polymer coating (any elevation) at 240 V
Margin
0.1mm
All results (1)
You have drawn

19.7 mil
0.5mm
Drawn spacing 0.5 mm meets the 0.4 mm minimum for B4, External, permanent polymer coating (any elevation) at 240 V.
IPC-2221 is a design-practice standard, not a safety standard. For mains-connected or certified equipment, IEC 60664-1 and the product standard govern, and usually demand more than this.

Above about 60 V DC / 30 V AC most product standards treat this as hazardous voltage, with extra creepage, isolation and test requirements.

Accuracy

Source
  • IPC-2221B Table 6-1 (2012)

IPC-2221B, Generic Standard on Printed Board Design, Table 6-1 (2012) 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-2221B Table 6-1

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-2221B Table 6-1

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 Table 6-1 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-2221B Table 6-1.
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: bare external copper or solder mask only. Solder mask does not count as a permanent polymer coating. B3 applies above 3050 m.
  • B4: external conductors under a qualified permanent polymer coating.
  • 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.

To gain creepage, mill a slot between the isolated regions, and keep the barrier free of vias, test points and silkscreen.

References: IPC-2221B Table 6-1. 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 ⁨1.18.3⁩