I've never heard of soldermask causing HV breakdown issues. If you have a blank board, you can try measuring leakage with a HV supply, and a sensitive current meter. For example, if you have a 200V (higher would be even better...) supply and a 50uA meter, you can easily see 1uA of leakage, which equates to 200Megohms. Note that using an ohmmeter wont necessarily give you the whole story, because the ohmmeter wont be testing at higher voltages where creepage effects kick-in.
I've done several boards with voltages ranging from 200V up to 2000V, and never had or suspected a creepage problem. My biggest fears about HV wiring on PCBs are around the AC mains input (120 VAC in the US), especially the wiring leading up to the fuses on the PCB because shorts between those areas are not fuse-protected. Destructive energy requires voltage and current, so until one or both are limited, there is elevated risk. Since I use a power-entry module (IEC connector + switch + fuse) in my projects, it's a manageable risk because everything is sized to handle much more current than the fuse in the power-entry module. After I get the power thru a transformer, or a resistor, where the current is forced to be lower, I ease-up on the over-conservatism. For added protection, I use 2 fuses (1 for hot, 1 for neutral), a varistor to absorb surges, and a 0.01uF to absorb super-fast spikes that are too quick for the varistor. On Saturday, September 17, 2022 at 9:00:01 AM UTC-7 Paolo Cravero wrote: > Hello. > > 2. Spacing for higher voltages. Again, look for online calculators/table >> for creepage and clearance. There are various factors that affect spacing >> including pollution levels. I always pick the most conservative rules I can >> find. Spacing for 500V or less is pretty small, around 2mm. >> > > @gregebert Have you noticed, or is it documented in some standard, an > effect on the spacing with respect to the silkscreen color? I use each > project to refine my board design skills by imposing new challenges to > myself and I have little experience with PCBs at >150V levels. So far I > have been lucky and never had to go for a second round of the same design, > also considering that I usually build a couple of each circuit but get 5 > PCBs from the fabhouse... > > Anyway, on a Nixie design I had the feeling that the black silkscreen was > "leaky" and the 180V on one line was pulling the one nearby. Is that > possible, or I didn't respect the minimum spacing? I think I don't have > that old KiCAD project anymore. > > TIA > Paolo > > > > > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/3ed14f1d-c6c5-425a-9651-9bf951743038n%40googlegroups.com.
