What are creepage and clearance?

[@carstenfuchs7020]

Thank you for this video. In IEC standards such as 60664 and 60950 for voltages below 1000V and a pollution degree 1 or 2, PCBs benefit from reduced creepage dimensions. I wonder if those reduced dimensions only applie to the PCB itself or to the components like TI isolators as well? Besides I was not able to find an explanation why on PCBs one can apply shorter creepage distances...

[@seshansesha7645]

Great series...

[@hatimbv5896]

Can someone please explain why do we need higher creepage/clearance distances with lower pressure (higher altitude)? I understand lower pressure, lower atoms density, hard to arc through ... Thank you

[@TexasInstruments]

That’s a great question, Hatim! As Flexcope Inc. has noted, altitude effects the conductivity of air because as the altitude increases, the air becomes thinner and therefore less resistant. The reduction in resistance means that the conductivity will increase, and so will the risk of arcing.

[@hatimbv5896]

@@TexasInstruments Yes. But I think that vacuum has even a lower resistance if not infinite, right? Less air, more vacuum, higher resistance.

[@ikbendusan]

okay it is because of lower pressure, but it's a relationship between the distance between atoms and how easily they become ionised because of some velocity/momentum or whatever

[@jamesmellow1630]

The answer to this is the pashen law. Yes, the vacuum will have mich higher insulation. But there is a transition Phase where air ressure and distance (pd-product) lead to less resistance.

[@seshansesha7645]

To keep it simple : higher the air density more the energy required to break the air dielectric, lower the air density we need less energy to break the air dielectric....same insulation test voltage potential at lower and higher altitude will not give same results...that means breaking the air gap at higher altitude with same voltage potential is easy than breaking the air gap at lower altitude....hence we should have more clearance to avoid the isolation breakdown...you can imaging congested road with traffic jam as lower altitude air gap and road with normal traffic as higher altitude air gap....which is easy to cross ?

[@fleXcope]

Air is an insulting medium. At high altitude you have less air or lower air density

[@hatimbv5896]

Vacuum is an insulating medium too, isn't it? It's even a better insulator So having less air (more vacuum) should be harder to arc through