First, PCB design requires different grid settings at different stages.
A large grid point can be used for component layout in the layout stage。
For IC, non-locating connectors and other large components, you can use the grid point accuracy 50-100mil for the PCB layout, and for resistors and capacitors and inductors and other passive small components,you can use 25mil grid for layout. Precision of large grid point contributes to the alignment of components and the beauty of layout.
PCB layout rules:
1, under normal circumstances,all the elements should be arranged on the same side of the PCB board.Only the top element is too close , some of the highly limited and small heat device, such as chip resistors, chip capacitors, stickers chip IC, etc. can be arranged on the lower level.
2, on the premise of ensuring the electrical performance, the element should be placed on the grid and arranged parallel or perpendicular to each other, in order to clean, beautiful, In general,overlapping elements is not allowed.Elements are arranged to be compact.The element should be uniform distribution and consistent density on the entire plate.
3,The minimum spacing between adjacent land pattern of different components on the circuit board should be more than 1mm.
4, The distance from the edge of the PCB board is generally not less than 2mm. Best board shape is rectangular .Aspect ratio is 3: 2 or 4: 3 .When the size of the printed circuit board is greater than 200MM by 150MM,we should consider the board can sustain mechanical strength.
Second, in the PCB design layout, we should analyze the circuit board unit, according to the function to layout design.
The layout of all the components of the printed circuit board should comply with the following principles:
1, according to the process of the circuit ,arrange the position of the respective functional circuit elements which enable the layout is easy to the signal flow and make the signal a consistent direction as far as possible.
2, centering on the core components of each functional unit ,around which to layout.Components shoulde have uniform ,integral,and compact arrangement on the PCB.we should minimize and shorten the lead and the connection between the various components as far as possible.