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I have a pcb that needs an isolation gap where no components, pads, taces, or copper must be placed. But due to board space limitation, a cetain area of the isolation gap must have pads in them. This would compromise the isolation.

To get back the isolation specification, I was thinking of placing a slit in that area as a substitute. Because i would assume that air has better insulation than the PCB FR4 material.

In the image below the hight of the gap is 10mm. So i am thinking of placing an air gap of aroun 1-2mm thickness and make sure that the shortest route between pad-pad around that slit is more than 10mm

enter image description here

Am i doing think correctly?

Jake quin
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  • placing slots for insulation is typcially common practice, especially when dealing with high voltage (>60V). Have you done clearance and creepage calculations? What is the voltage you are dealing with and what is the insulation requirement between pads? – F. Heisenberg Jun 20 '20 at 15:04
  • A cut in the PCB can help you meet "creepage" requirements, but it does not do anything for "clearance" requirements. – Dave Tweed Jun 20 '20 at 15:05
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    Does this answer your question? [Air gap on isolation space](https://electronics.stackexchange.com/questions/173575/air-gap-on-isolation-space/173577#173577) – Andy aka Jun 20 '20 at 15:09
  • @F.Heisenberg actually im dealing with very low voltage 3volts only, BUT upon a failure im dealing with mains voltage. So components have to first fail. the isolation IC im using is rated for upto 10kV surge and recommended a gap about that thick. – Jake quin Jun 20 '20 at 15:16
  • You should add the datasheet link for the isolation IC to get better advice. – DSI Jun 20 '20 at 15:18
  • @DaveTweed Unfortunatley there is nothing more i can do with clearances. Does clearance requirements tend to be smaller than creepage requirements?? ( since PCB is a better conuctor than air?) – Jake quin Jun 20 '20 at 15:23
  • How can you design anything if you don't know what your actual requirements are? Look it up! – Dave Tweed Jun 20 '20 at 15:46
  • Your min creepage distance will always be equal or larger than your clearance distance. For isolation transformers I would strongly suggest you to stick to the given clearance requirements and not go lower. Yes, please add a link to datasheet. – F. Heisenberg Jun 21 '20 at 15:54

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