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In the image shown below, why is the distance marked with "??" not considered for clearance? Is there a slot under that barrier, or does the barrier pass through the PCB?

Image

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    \$\begingroup\$ ...Clearance, is there is slot under that barrier , or the barrier pass throughout the PCB. It is not very clear what you mean. Do you mean if there is a slot under... ? \$\endgroup\$ – Bimpelrekkie May 18 '16 at 9:30
  • \$\begingroup\$ I think the barrier must extend down through a slot in the PCB otherwise it will not improve anything. \$\endgroup\$ – Bimpelrekkie May 18 '16 at 9:31
  • \$\begingroup\$ I mean the barrier shown in image , does there is a slot under that barrier. Or barrier is attached on PCB or barrier pass through the PCB. \$\endgroup\$ – Bharav May 18 '16 at 9:33
  • \$\begingroup\$ It's all down to the details of definitions. Does 'clearance' mean the distance a flexible wire can bridge? That would fit with the red trajectory. I know that 'creepage' is surface tracking, and from the look of that diagram, it passes under the barrier, so I guess they assume that the barrier does not interrupt the board surface. \$\endgroup\$ – Neil_UK May 18 '16 at 10:34
  • \$\begingroup\$ Obviously the picture just seeks to show the difference between clearance distance and creepage distance, as the terms are sometimes used sloppily. Sometimes people say clearance when they actually mean creepage. \$\endgroup\$ – Lundin May 18 '16 at 10:53
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Clearance is the shortest distance through air between two non insulating conductors.

I am making some assumptions about the image.

  1. The image is not a full PCB, but rather a section of a PCB. The PCB probably extends furthur but was cut off.
  2. The darker green colored areas is copper covered with soldermask.

With those assumptions, then the clearance is over the barrier and not around it and more specifically it is from the legs of the IC (since soldermask is an insulator).

IF the traces did extend completely towards the edge of the board, then I would say that the clearance would be around the barrier, since that would be the shortest path through air.

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