In zone properties what are the optimum minimum value that I can assign for clearance and minimum width in electrical properties section?
That will mainly depend on the capabilities of your PCB manufacturer . . .
So here what I will write. Can
I write zero for clearence?
If you set the clearance to 0, the actual clearance will be determined by the value(s) specified in your board setup.
Who is making the PCB for you ?
Zones are copper, like tracks. Use the same or larger than minimum track to track clearance and minimum track width. 0.025 width certainly isn’t safe even if KiCad allows it.
For zones I always use clearance 0.25 and Minimum width 0.2.
It has some historical reasons. When at whole PCB I use 0.2mm clearance than really only in few places clearance is 0.2 (for example track going near pad corner) but on the rest clearances are higher. But if you specify 0.2mm zone clearances than along all copper objects zone will be so close to them.
In 90s when I had long distances with 8 mils clearance it happened me to get PCB with shorts (our PCB manufacturer those time didn’t used electrical PCB check - they only used human ‘look through PCB’ and I am not surprised that some hair connecting adjacent paths can be missed.
Because of this I use little bigger clearance (0.25) for zones than for rest of PCB (0.2).
But it happened me also 3 years ago that few % of ordered PCBs had a shorts between adjacent coils. Electric check didn’t detect it (all copper at this very small PCB is one net) and I didn’t know that I should specify in order that they should be tested in ‘coil mode’. A person learns throughout his whole life.