What are design rules in PCB design?
PCB layout best practices recommend that you always place short, direct traces between components when possible, although this may not always be practical in larger boards. If your component placement forces horizontal trace routing on one side of the board, then always route traces vertically on the opposite side.
Which standards are followed in PCB design?
IPC-2221 is the standard guideline for the process of designing PCBs. Within the 2220 series, there is also an IPC standard for flex PCBs, as well as standards for rigid and MCM-L PCBs.