1. Setting different grid points at different stages is essential in designing a printed circuit board (PCB).

2. Large grid points are recommended for device layout during the layout stage. For instance, a grid point accuracy of 50~100mil is suitable for ICs and non-positioning connectors, while a 25mil grid point is used for passive small devices such as resistors, capacitors, and inductors.

3. The accuracy of large grid points facilitates device alignment and layout aesthetics.

PCB Layout Rules:

1. Components should be arranged on the same side of the circuit board under normal circumstances. Exceptions include densely-packed top components, where limited height and low heat generation devices like chip resistors, capacitors, and ICs can be placed on the lower layer.

2. Components should be placed on the grid and arranged in parallel or perpendicular to each other, ensuring neatness and electrical performance.

3. The minimum spacing between adjacent pad patterns of different components on the circuit board should exceed 1MM.

4. The distance from the edge of the circuit board should generally be not less than 2MM. Ideal board shape is a rectangle, with an aspect ratio of 3:2 or 4:3. The board should have mechanical strength if its size exceeds 200MM by 150MM.

Layout Design Principles:

1. Arrange the position of each functional circuit unit according to the circuit process to facilitate the signal circulation.

2. Center the layout around the core components of each functional unit, ensuring an even and compact arrangement on the PCB to minimize leads and component connections.

Analyzing the unit of the circuit board during the layout design, and carrying out the layout design according to the function, are essential for PCB design.