When drawing a PCB layout, it is very important to provide suitable clearance between traces and provide enough space between the components, especially in high voltage applications, in order to avoid any electrical arcing and breakdowns.
Before designing the circuit, the designer should become familiar with the following technical terminology:
Functional insulation -- the insulation only required for circuit operation. It does not imply safety protection.
The grade of insulation, PCB type, environment and altitude will affect the clearance and creepage
The PCB designer should follow safety standards such as UL60950-1(USA) or CSA 22.3 (Canada)