For what purpose? If you are generating voltages high enough to create a spark then you are also generating a lot of heat in the path of the spark. This heat will almost certainly burn the bare fibreglass of the PCB substrate. That will obviously damage the board and will also create a low resistance path which will effectively short out the voltage source that you are using to initiate the spark after the first few strikes. Another problem is that the copper track used to form the gap is thin and will be eroded by the current flow through the arc created after the initial spark. To make a spark gap you need some sort of soldered on wires. If all you want is to form a high voltage breakdown protection path to ground then just buy a dedicated spark gap protection device.

would like to... even if it is useless ;) i have seen these in some commercial PCB's https://i.ytimg.com/vi/vfP_65gSSBU/maxresdefault.jpg

As in the photo, you need to have one or more gaps made by forming two pointed tracks with the pointed tips opposite each other. Note that you can see the beginnings of burning in the PCB fibreglass at the tips in the right hand gap. Air breaks down at about 3kV/mm (3V/um). In other words if you were to form a gap of 0.5mm between the tips then the gap would spark across at approximately 1500V. That is about the same voltage as is developed at the output of CFL backlight inverters found in older style laptops etc. **Beware**: if you are building spark gaps of gaps wider than about 18um you are dealing with voltages above the SELV limit of 48V. ### Voltages capable of causing breakdown in air of gaps of wider than about 18um are therefore considered to be lethal. ###