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It is time to choose the proper enclosure for a high voltage PCB. We will need to do holes for LV external connectors and external connectors for high voltage wires. I was looking for standard boxes from different providers' catalog and the most are offered in metallic (aluminium) material. I know that this material is often used due its conductivity. But I'm wondering how it may to have influence on isolation between conductors if I have some case surface connectors (bananas) at HV and the other ones at LV (or 0V). They will connect external wires with board components through internal wires soldered to the bananas copper connector (internal side). In other words, I would like to apply clearance and creepage distances between connectors at case surface, but they depends on kind of surface material, normally air gap or PCB sheets material. I don't know what happen when surface material has high conductivity like aluminium.

I have seen high voltage source (few kV), that has metallic cases and red banana plug is about 3 cm separated from black banana jack datasheet here

  1. So if this is commonly done it would has a coherent explanation for not to use/offer another isolation material, as for example plastic since aluminium conductivity is "similar" to the copper, how can people deal with this? How can it be used for these applications?

  2. If yes, what clearance and creepage distances will we need?

  3. If these boxes were not correct for a portable device like this (V < 7 kV), how does developers get the correct enclosure for a high voltage PCB?

Notes:

  • PCB will be covered by conformal coat
  • A kind of silicone paste for coating the banana copper-wire junctions.
  • Kapton mask instead of solder mask.
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    \$\begingroup\$ 2. Normally this is given by UL/EN/IEC 60950. Go to www.creepage.com for an online calculator. For creepage and clearance there is no difference between copper and aluminum. Is your box grounded? \$\endgroup\$ – winny Jul 30 at 10:48
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    \$\begingroup\$ Banana plugs and sockets are definitely not rated to be safe at anything other than low voltages and 7 kV sounds like a disaster waiting to happen. Read this. \$\endgroup\$ – Andy aka Jul 30 at 10:48
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    \$\begingroup\$ Such connectors better fit the HV job. The creepage is dealt with inside the connector, as well as maximum aperture. I recall LEMO is one of the top manufacturers, but you also pay a top price for it. \$\endgroup\$ – Huisman Jul 30 at 11:00
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    \$\begingroup\$ Did you also consider protection in case someone opens the enclosure? There may be components still having HV even when the device is turned off. \$\endgroup\$ – Huisman Jul 30 at 11:02
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    \$\begingroup\$ I very much doubt the 60950 is applicable here! For sure, the IEC60950 is not. "It is applicable to mains-powered or battery-powered information technology equipment, including electrical business equipment and associated equipment, with a RATED VOLTAGE not exceeding 600 V." source \$\endgroup\$ – Huisman Jul 30 at 11:31

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