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From: Klaus Vestergaard Kragelund <klauskvik@hotmail.com>
Newsgroups: sci.electronics.design
Subject: Re: Minimum clearance for 230V AC.
Date: Fri, 4 Oct 2024 00:22:03 +0200
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On 03-10-2024 20:03, john larkin wrote:
> On Thu, 3 Oct 2024 22:05:37 +1000, Chris Jones
> <lugnut808@spam.yahoo.com> wrote:
> 
>> On 3/10/2024 8:11 pm, Pimpom wrote:
>>> What's the minimum surface clearance you consider adequate for 230VAC,
>>> on FR4 without slots or added creepage? Forget about IPC-2221 unless you
>>> base your layout strictly on it.
>>>
>>> Personally, I try to maintain 3mm edge-to-edge between tracks and pads,
>>> more if space permits. What do you think?
>>
>> The distance along a surface is called creepage in the standards.
>>
>> The required distance depends on whether the insulation is supposed to
>> be single insulation (functional, basic or supplementary) or double
>> insulation (reinforced insulation).
>>
>> Basically, if the insulation failing ought not to kill someone because
>> the part that would become live is either protectively earthed or
>> separated by supplementary insulation from the user, then a smaller
>> creepage is allowable.
>>
>> If the insulation failing could immediately give someone a shock because
>> there is no protective earthing or supplementary insulation, then a
>> larger creepage distance is required.
>>
>> The exact distances required in different standards tend to be
>> different, though I think a lot of different products that used to be
>> subject to different standards have recently been grouped into one set
>> of standards, IEC62368-1.
>>
>> There are some tables here:
>> https://www.powerctc.com/en/node/4757
>>
>> I think you are going to come up with something like 2.5mm for basic
>> insulation and 5mm for reinforced, but you should check carefully what
>> the standards say, and for some classes of equipment it can be much
>> more, like 6mm or 8mm.
>>
> 
> 
> What about voltage clearances for inner-layer traces on a multilayer
> board? Same layer and between layers?
> 
> 
> 
Typical inner layers in x-y direction is 1.2mm for reinforced. If you do 
impulse voltage testing, you may get that down to 0.5mm

In the z direction, it's 0.4mm IIRC