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What is the required creepage (e.g. trace-to-trace) distance for PCBs handling 240VAC rms? What about 120VAC?

This is for UL and CE certification.


The standards for PCB Creepage (e.g. the distance across the surface of a PCB between high-voltage connections) are locked up in proprietary, pay-only IEC standards (specifically, IEC Report 664/664A ).

This is troubling, as following these standards is a good way to ensure safety, even if you never intend to actually get your project UL or CE certified.

Can we get a nice summary of what trace-trace spacing should be maintained for common voltages (e.g. 120V, 240V), with common materials (e.g. FR4, etc...)?

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  • \$\begingroup\$ what is a pollution degree in layout? \$\endgroup\$ – user30651 Oct 19 '13 at 11:56
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Brings back memories. not all good ones.
Herewith potpourri / hodgepodge - some value.


Useful online calculator covering subset of question.

They say

  • Insulation Calculator

    This program is based on Table 2G and Figure 2F of IEC 60950. Select the circuits that bridge the insulation to be determined by using the drop down lists. For example, a Primary Circuit to a Primary Circuit requires Functional Insulation. The Insulation Calculator will automatically determine the insulation. Notes are also provided as called out in Table 2G. Acknowledgement

  • The author thanks the International Electrotechnical Commission (IEC) for permission to reproduce Section 2.9 "Insulation", Section 2.10 "Clearances, creepage distance and distances through insulation", and Section 5.2 "Electric Strength" from its International Standard IEC 60950. All such extracts are copyright of IEC, Geneva, Switzerland. All rights reserved. Consult with IEC 60950 for all final design decisions.


Useful summary page

Includes

From DIN EN 60664-1 (VDE 0110-1), creepage.

enter image description here

From DIN EN 60664-1 (VDE 0110-1), clearance

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Insulation Material groups:

In the table "material groups" are mentioned. Materials are grouped according to their CTI (Comparative Tracking Index).
CTI is a measure of the material's resistance to the formation of conductive tracks which lead to material breakdown when exposed to a standard CTI test. From here

Insulation Material Groups (in accordance with EN 60664-1:2007 and VDE 0110-1)

For the purposes of the above mentioned standards, materials are classified into four groups according to their CTI values. These values are determined in accordance with IEC 60112 using solution A. The groups are as follows:

Insulation materials group I 600 ≤ CTI
Insulation materials group II 400 ≤ CTI < 600
Insulation materials group IIIa 175 ≤ CTI < 400
Insulation materials group IIIb 100 ≤ CTI < 175.

The proof tracking index (PTI) is used to verify the tracking characteristics of materials. A material may be included in one of these four groups on the basis that the PTI is not less than the lower value specified for the group.

The means of assessing CTI is described here
and this video [1m 38s] is both impressive and informative. Arcs sparks smoke and flames happen :-).

CTI testing - stand clear:

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And again from here not much else useful on this exact topic but MANY OTHER SIMILAR pages with links to portions of relevant standards.

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Small but useful extract from (Extract DIN VDE 0110-04.97*)
They say:

  • This standard is a technical adaptation of IEC Report 664/664A and specifies, in general, the minimum insulation distances for equipment. It can be used by committees to protect persons and property in the best possible way from the effects of electrical voltages or currents (e.g. fire hazard) or from functional failure of the equipment by providing adequate dimensioning of clearances and creepage distances in equipment.)

Useful subset


Interesting comment from here:

  • IEC 60601-1 Third Edition: Creepage Distance and Clearance Requirements July 04, 2011

    It's simple: Engineers must be aware of the design for each medical device. The awareness of what is most critical is important. But why? The isolation required between parts with different operating voltages, to prevent against unacceptable risk, is the primary reason for the importance of creepage and clearance distances.
    Specifically, creepage is the shortest distance between the path of two conductive parts of a medical device and is measures along the surface of insulation. The clearance is similar, but very different. It [clearance] is the shortest distance between two conductive parts, measured through air. In IEC 60601-1 Third Edition, there are requirements for creepage distance and clearance, which follows the IEC "Modern Standard" approach. This approach though requires the use of six different tables for spacings and the introduction of five additional requirements to be included as part of the evaluation. But what if your company has already begun to address these requirements established by Second Edition? "If your product meets Second Edition's creepage and clearance, then the medical product will be in compliance with the requirements for Third Edition," said Todd Konieczny, North American Medical Technical Leader. "The Third Edition requirements for creepage and clearance require less stringent parameters for operator protection – which, ultimately, allows companies to build a smaller product."

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  • 3
    \$\begingroup\$ A lot of this is fairly easy to find. While it is useful, it is couched in pretty obscure terminology (really, IEC? "Board Pollution Level"?). What would be much more useful is a couple of examples, say 120V and 240V, with a break down of what creepage distance you want, and what the contributing factors r.e. IEC codes are that result in the desired creepage distance. \$\endgroup\$ – Connor Wolf Nov 27 '11 at 12:08
  • \$\begingroup\$ Be my guest :-) \$\endgroup\$ – Russell McMahon Nov 27 '11 at 12:43
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    \$\begingroup\$ I would if I had any of the actual IEC documents. I asked the question to supplement my knowledge with experience from someone who actually has access to the real IEC codes. Basically, I want to idiot-check my own work. \$\endgroup\$ – Connor Wolf Nov 27 '11 at 12:48
  • \$\begingroup\$ What means "material group" in the table? \$\endgroup\$ – Roman Matveev Sep 20 '19 at 9:28
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    \$\begingroup\$ @RomanMatveev I have added a section on material groups. You can find the same information by web searching using the search string : material group EN 60664-1 \$\endgroup\$ – Russell McMahon Sep 21 '19 at 13:23
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As a first pass, I try to keep line voltage isolated circuitry separated by 5 mm. That will do. If that's too much, then you have to consult the details in the spec.

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Pollution degree 2 applies to the vast majority of ITE (information technology equipment) - degree 3 is for stuff that is subjected to significant external contamination.

www.creepage.com has handy calculation tools. (I hate that viewing this site on an iOS device doesn't show the usual editing links...)

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The 60950 standard is available as AS/NZ or International (IEC) and costs around $239 in pdf form or $266 in hardcopy from saiglobal.com SAI Global 60950

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  • 3
    \$\begingroup\$ Welcome to Electrical Engineering! While your link may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. Also, while SAI Global may sell the spec, the question author specified that they weren't looking for the spec. If you are affiliated with either site, please declare so in your answers. Thanks! \$\endgroup\$ – Kevin Vermeer Nov 28 '11 at 1:24

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