Static electricity question on high voltage equipment?

Question

Why is it that on high voltage electrical equipment, the blobs of solder should be rounded and smooth??

Answer 1

The shape of conductors effects the electric field strength. If you have two metal spheres, one with a large diameter and the other with a small diameter but at the same voltage, the electric field at the surface of the small sphere will be greater than the electric field at the surface of the large sphere.

If you have solder with edge on it or points, those sharp radiuses of curvature will concentrate the electric field considerably. When the electric field increases high enough, about 30 kV/cm, you get ionization and a spark will occur.

If you are making a power supply, the last thing you want to happen is to have the high voltage leaking and causing sparks inside the power supply. Even if sparks do not occur, but you only get a relatively harmless glow discharge, the chemistry caused by the glow discharge is very reactive and will corrode metal parts. The chemistry will also deposit ammonia salts (due to the reaction of nitrogen and water) onto surfaces inside the power supply. These salts on insulating surfaces will cause increased leakage and will lead to damaging currents.

Answer 2

The previous answer about discharges from points is correct but the solder joints should always be smooth just as an indicator of proper soldering regardless of voltage.
J-STD001 and IPC-610 instructor. ( current most accepted industry soldering standards )