From IEC-62368 for signals below 30kHz the creepage distance for pollution degree 2 and material group IIIa,IIIb (FR-4 boards are IIIa) at 40V is specified to be 1.1mm. We have a connector that has many BGA pads, and the copper-to-copper distance is 0.635mm:

Putting a slit between is not an option, the only way I could see is to add coating after assembly that would allow to use values for pollution degree 1, which would be 0.16mm, quite a drastic reduction.

One of the engineers mentioned that leaving a pin floating in between also counts towards increasing creepage, but I am not sure about that. The definition of creepage that is used in standard:

Creepage is the shortest path between two conductive parts measured along the surface of a solid insulating material

It would imply that it does not matter if the pin in between is floating or not, but on the other hand, how would the voltage be defined if one of the pins is floating? The voltage could be anything between those two pins! In my mind the pin would have to be physically removed from the connector body for this to be valid, and the pad removed from PCB.

Can anyone comment on the validity of such interpretations of creepage? If you have experience with other standards please share it, IEC is just where I got the numbers from.

posted 3 months ago

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Elleanor Lopez‭

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