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I' m following this guide; concretelly 3 and 4 chapters for High Voltage (HV) PCB design:

https://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf

The fact is that I have read interesting ways to avoid arcs and coronas between to high voltage conductors.

I have found here some of them as for example:

  1. Field gradient rings
  2. Routed Slots
  3. Inert Insulators
  4. Cover Coats for solder mask with Kapton
  5. Dielectric strength sheets material
  6. Rounded copper shapes

I must to design a board with some HV relays, 8 points x 2 relays. Every relay will connect some of these points to a source positive terminal. This High voltage will arrive to the every relay by a wire from an industrial HV source.

HV source is an external device that brings energy to the board relays towards H and L terminals:

enter image description here

Although the board or relays will handle a max of 10KV the application only will need a few mA from the HV source.

Board will only have relays, connectors and not too much elements apart of these; maybe some diode, decoupling C if needed or even some R (depends on relay specs). Relays coils will be fed by low voltage (12V or 24V).

My question here are:

  • Will I really have arc and coronas problems to avoid with this little current consumption: few mA (5, 10, etc)?
  • Will I really need to use those techniques: upper dielectric strength material for the sheet, routed slots to prevent carbonation of board, Kapton Cover Coats for increasing the dielectric strength of the board, etc.. or can I still using low voltage PCB design materials and techniques?
  • At page 14 autor says that "corona and leakage current from the field must be calculated o experimented with" when designing pcb. How can I calculate corona and current leakage effects? So in case I get them, how must I use them?
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    \$\begingroup\$ 1) Yes from surface creepage 2) yes ( if you want to extinguish arc, air gap is better) no to LV methods due to surface ionic contaminants \$\endgroup\$
    – Tony Stewart EE75
    May 15, 2019 at 13:40
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    \$\begingroup\$ Conformal coatings can also help. \$\endgroup\$
    – DKNguyen
    May 15, 2019 at 15:00
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    \$\begingroup\$ Coronas and/or arcing are caused by the high voltage; the current in the conductors is not relevant. \$\endgroup\$
    – JimmyB
    May 21, 2019 at 10:21
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    \$\begingroup\$ @Sunnyskyguy EE75 I have just found HV relays with "flying lead connection". I think that using them I could let HV signals out of LV signal printed circuit. I will bring the wires directly to the HV+- signals board. Main PCB will only be a distribution board based on relays that multiplexes few points to high potential and the rest of points to low level (GND). So only coil terminals will be soldered to the printed circuit. I see this way as a physically separation between HV and LV circuits. It could save some work and money. But I' m not sure whether my idea has sense or not. \$\endgroup\$
    – Suvi_Eu
    May 21, 2019 at 13:05
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    \$\begingroup\$ Yes that would create an air gap between HV conductors and reduce the exit surface area for leakage and work better. \$\endgroup\$
    – Tony Stewart EE75
    May 21, 2019 at 13:15

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I'd also take a look at the IPC 2221[edit: Electrical Clearances] standards before going any further with the PCB design. For a high voltage PCB, the one thing that matters the most is the material selected for the core/prepreg. Depending on the availability and budget, you can go with extra overcoats and better alternatives/versions of FR4. Also, consider a Kapton Overcoat if possible.

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  • \$\begingroup\$ Thanks @Kartikeya Veeramraju our pcb manufacturer said us that they work with a kind of modified FR4 "High Tg Multifunctional Epoxy Resin, Phenolic-Cured, Laminate & Prepreg" instead of BT epoxy and Polyamide for sheet materials. I don' t kow too much things about board manufacturing. Do you think it would be a good option? \$\endgroup\$
    – Suvi_Eu
    Jun 5, 2019 at 7:22
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    \$\begingroup\$ @Eugenia Suarez, As far as I know, ISOLA HR series is a very good prepreg/core material for the application range. Ask them if they do Kapton overcoats and also ask them to use this(Kapton) instead of their traditional solder mask. Normally, the solder masks they use are useful in the low voltage ranges. For high voltage, there's no guarantee that it'll hold up its dielectric strength, whereas Kapton does. If they dont do Kapton, I'd suggest you to use a conformal overcoat above the finally soldered pcb to give the board the necessary dielectric strength. \$\endgroup\$
    – darthMaul
    Jun 12, 2019 at 19:28
  • \$\begingroup\$ Yes, I have asked this just a few days ago. I'm waiting for their answer. I didn't know if kapton could be done by the manufacturer or if it was a postmanufacturing work. Because I have seen videos about people making manually kapton covers. I also asked them for conformal coats. They told me that this must be done after soldering process. So, they don' t work with conformal coat. \$\endgroup\$
    – Suvi_Eu
    Jun 13, 2019 at 6:31
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    \$\begingroup\$ Yes. The PCB fab house does not normally work with a conformal coat. You could use the spray on types and heat cure your final PCB for that end. \$\endgroup\$
    – darthMaul
    Jun 14, 2019 at 7:39
  • \$\begingroup\$ Yes, I have understood this after talking with them. \$\endgroup\$
    – Suvi_Eu
    Jun 14, 2019 at 8:02

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