In PCB design, the following points need to be paid special attention:
1.Routing direction: Seen from the welding surface, components’ arrangement should be in line with the schematic graph as much as possible and the routing should be best line with that of the routing graph, because the welding surface often needs all kinds of parameter testing in the production process. This will be helpful to the inspection, adjusting and maintenance in the manufacturing process(Remark: It must be on condition that all the requirements in terms of performance, machine assembling, board laying out, should be met).
2.The arrangements of components should be reasonable and even in layout, neat and beautiful in appearance, rigid and precise in structure technique.
3.Placement of electric resistance and diode: flat and vertical.
1).Flat: When there are not so many electronic components and the size of the circuit board is big, they are generally placed in a flat way; For electric resistance below 1/4W and placed in flat, the distance between the two welding pads is generally 4/10 inches; For electric resistance below 1/2W and placed in flat, the distance between the two welding pads is generally 5/10 inches; when the diode is placed in flat, rectifying tube of 1N540X series with 3/10 inches is generally chosen.
2).Vertical: When there are many electronic components and the size of the circuit board is small, they are generally placed in a vertical way. The distance between the two welding pads is generally 1～2/10 inches.
4.Placement of potentiometer and IC socket
1).Potentiometer: it is used to adjust output voltage in voltage stabilizer. Therefore, potentiometer design should meet the demands: output voltage will rise when adjusted in clockwise while output voltage will drop when adjusted in anticlockwise. Potentiometer in the constant current charger can be adjusted to change the current. When designing potentiometer, it should follow the principle that current will increase when adjusting in a clockwise direction.
The placement of potentiometer should take the whole machine into consideration and meet the layout requirements of the board. Therefore, it should be put on the edge of the board with rotating handle pointing to the outside.
2).IC socket: In designing printing board graph with IC socket, special attention must be paid to the direction of locating slots to make sure whether they are all right and whether the IC foot position is all right. For example, the first foot should be located at the lower right corner or upper left corner of the IC socket and be close to the placing slot(seen from the welding surface).
5.Layout of the input and output connective ends:
1).The distance between the ends of the two connective leads shouldn’t be too long. Generally, around 2～3/10 inches will be proper.
2).The input and output wire ends should be concentrated on one or two sides, and not too loose.
6.Attention should also be given to the order of base pins when designing routing graphs and there should be a reasonable distance between them.
7.Provided that circuit performance is guaranteed, routing should be reasonable, few external over lines should be adopted and routing should be in particular order in designing to ensure they are clear, easy to assemble and maintain.
8.There should be few bending in routing when designing the routing graph. It is suggested that the routing should be simple and clear.
9.The wiring circuits should be moderate in size and the distance between lines should also be reasonable. The distance between welding pads of the electric capacitors should be in line with the distance between pins of the capacitance.
10.The design should be in a certain order, for example, it can follow an order of from left to right or from up to down.
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