I'm considering on creepage distances on my PCB. I have read UL840,there are two significant tables. 6.1 "Minimum acceptable creepage distances" and 6.2 "Minimum acceptable creepage distances on printed wiring boards". I have read post: Trace width and clearance calculations. I noticed that Dave Tweed recommends to use 6.2 table. But in table 6.1 there is a sentence: "Creepage distances for equipment subject to long-term stress". I'm considering what does it mean, and when i should use values from table 6.1?
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The difference between 6.1 and 6.2 is based on the continuous voltage differential between the traces.
For example: If you expect a continuous 1000V between two traces, it should be spaced according to 6.1.
If you only need to be able to withstand a 1000V surge infrequently and/or for brief periods of time, then the spacing can be according to 6.2.
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\$\begingroup\$ I was thinking the same, but now i have new consideration. I design 27V circuit and creepage valu for this voltge from 6.1 is 0,53 mm. But on my PCB i have INA138NA/250 in SOT-23. Pin gnd and pin Vin are next to each other and the spacing beetwen them is 0,45 mm. I should think about milling? \$\endgroup\$– M.KrukCommented Mar 21, 2018 at 10:22
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\$\begingroup\$ What pollution levels are you expecting? You may not need to include spacing for level 2 if you don't expect level 2. If you read note Z of table 1, it mentions that under 32V there isn't risk of tracking, simply corrosion. I wouldn't be too concerned with the spacing at 27V, its fairly low and the component is clearly designed for it. \$\endgroup\$– RedjaCommented Mar 22, 2018 at 18:58