Minimum distances between box case connectors and PCB surface conductors

Question

I am working on a few kV PCB design with external voltage connectors (HIGH and GND levels). So user interface connectors are thought to be bananas jacks (they support until 7kV but has soldering terminals).

Now I am searching commercial boxes for packaging the PCB. Providers, that I have consulted, they have boxes with fixed sizes, and they are not much long. Unfortunately I will have exigent area requirements, due components arrays with substantial volumes. So I must face box size limitation and PCB area needs.

The fact or question is that I have found one case that seems to be a solution in terms of long and width. Since we would like to fit bananas on the chasis as you can see at the picture:

I wondered for the minimal distances d1, d2 and d3. Having into account:

1. Kapton instead solder mask
2. Conformal coating after soldering
3. 6kV and 0V wires from PCB (from relays) to banana connectors must be soldered but we will use some suggested silicones for this kind of junction (solder).
4. I doesn't choose the kind of material of the case, but it seems to be available in aluminium or PVC.
5. Black banana has 0V and red one is i e 6kV (it can be smaller)

If banana will be into the case surface is the distance between:

• banana - banana: d2,
• banana - bare conductor: d3,
• banana - coated connector (terminal block with screws): d1

considered as the same distances on PCB board? in. ex: if clearance between a copper pad at 6 kV and other one at 0V -with a concrete CTI and pollution degree- must be 32mm, could I apply this distance between banana at 6kV - PCB conductor at 0V or banana at 6kV - banana 0V?

Answer 1

Just like on the PCB itself, you need to pay attention to clearance (arcing) and creepage (leakage through surface contamination).

If you use wire with insulation rated for 6 kV, then the only real issues are in the immediate areas around where the wires are terminated on the banana jacks and the PCB connections.