# Minimum distance between two connectors in a high voltage PCB design

My application will have low current (mA) but high voltage lines. High voltage will arriving from external source using banana jacks on the case.

I am looking for an example in which someone uses PCB connectors (i.e., terminal blocks) that carry high voltage (e.g., 5KV). But I'm not having success.

I have not found any connector with more than 2.5kV dielectric strength. But I must put external 5kV signal at one connector and 0V to the other one, if it's possible in the same PCB.

I would like to know how can be calculated the distance between two (separated) connectors that have a 2.5KV breakdown voltage but they need to support a bigger voltage difference between connector 1 and connector 2: 5kV.

• Connector 1: VCC+ (5KV)
• Connector 2: VSS- (0V)

With BV = 2.5KV for me it's clear that bringing the two connectors so close to each other the material will break. Maybe I'm wrong.

I know the creepage and clearance techniques, but if I understood well it's referred to the sheet material and the copper over it, that has its own breakdown voltage/mil. But what about connector material? I thought that E field will be constant between two connectors, but voltage will be decreasing equipotential lines.

1. So, could I find a distance between both connectors in which the VCC+ connector and VSS- connector will be safe from breakdown?

2. Whereas trace and pad spacing literature suggests for certain kind of material to divide nKV/30cm to obtain safety distance between pads or traces with high voltage differences, what can be applied to the gap of connectors? How to get the minimum distance between two connectors with higher voltage level than its breakdown voltage? I need to be sure of minimum distance in which I could solder them in a board without damage.

Take into account that I'm not talking about connector (copper) pads to another printed pad/trace distance. I know how to calculate the minimum clearance and creepage.

I try to say that I will use 2 separated connectors, one for V+ and other one for V-, as far as they can from each other. But how to relate the manufacturer parameter limitation (1kV) with the distance needed for 5kV (or whatever) between them? That's the point of the question. If connector dielectric parameter is negligible, please let me now.

So, could I find a distance between both connectors in which the VCC+ connector and VSS- connector will be safe from breakdown?

Yes, but it's already been done for you in the IPC specs the table below shows this. It might be best to use two separate 1 conductor connectors, instead of finding one that has both (although the connector wouldn't be keyed for polarity). Here is a breakdown of how to calculate spacing between PCB traces:

• Hi @laptop2d thanks for the information. I'm not asking for the distance between traces on board conductors. I knew this table. I'm asking for using connectors with less breakdown voltage (maybe 1kV) than they must carry (5kV). Are you saying that a pcb connector could be considered a coated conductor? It could be fine, but I'm not sure this table is having into account that every kind of connector could have different dielectric strengh. Maybe.. is this manufacturer parameter negligible? Commented Jun 6, 2019 at 16:56
• The table also covers external connectors, If you had bare copper, this would be an uncoated connector. A PCB connector with insulation would be a coated connector, (which you should be using HV insulation). Those are the minimum spacing's required for regulatory. I would probably add a little more if your not space constrained. The table covers bare conductors, connectors and PCB's Commented Jun 6, 2019 at 16:58
• so it doesn' t matter the connector dielectric strength? Commented Jun 6, 2019 at 17:02
• @EugeniaSuarez That also matters because if the dielectric strength is not high enough, then your connector material also becomes conductive. One thing that I forgot to mention is pollution degree. If the connectors are in a dirty or humid environment, it can also cause arcing Commented Jun 6, 2019 at 17:13
• how do you apply this 1kV strength of the connector to your previous table? if PCB will has one connector with 0V and the other one at 5KV. I try to find the separation between 0V and 5Kv connectors knowing that connector has a strength = 1KV. I have read the link but I can' t see how is calculated the external conductor coated values. I can' t see how connector strength is involved there. Commented Jun 11, 2019 at 9:18

If you understand creepage is the ionic breakdown of a good insulator due to the accumulation of dust and humidity, then you will understand why an air gap is good. You may need 2 connectors.

Clean air is about 5kV/mm between smooth parallel surfaces. Plastic can be >10kV/mm.

The highest level of indoor contamination of residential humid dust on the best dielectric reduces to about 0.3kV/mm so 0.2kV/mm became the standard.

There exist various levels of dust& RH vs withstanding voltage in between. Thin Polymer coating such as soldermask only improves a bit. (50%) Thick protection improves a lot, such as conformal coating or potting.

• So, if manufacturer says "1kV", what does it actually mean with this value? is not dielectric resistance between connector and other point with different voltage? Commented Jun 6, 2019 at 17:20
• If 1kV is the withstanding voltage, I expect the surface gap between conductors and solder pads limits this voltage for a specified contamination level. Commented Jun 6, 2019 at 17:23
• Hi, thanks @Sunnyskyguy EE75 what about having wire connectors on a PCB metal case side and having some conductors, as copper tracks or more connectors, on the PCB surface? How to know what distance is needed between two metal case connectors (at V+ vs 0V)? and between metal case connector and PCB connector or track knowing that conformal coating and kapton will be applied over the board? Commented Jul 29, 2019 at 7:00