Basic Principles and Points for Attention in Printed Circuit Board Design (2)

Second, the following points should be noted in the design of printing plate

1. Wiring direction: From the soldering surface, the alignment of the components is kept consistent with the schematic diagram as much as possible, and the wiring direction is preferably the same as the wiring direction of the circuit diagram. As the production process usually requires testing of various parameters at the soldering surface, This facilitates inspections, commissioning, and inspections during production (Note: This refers to the premise of satisfying circuit performance and overall machine installation and panel layout requirements).

2. The arrangement of the components should be reasonable and uniform in order to be neat, beautiful and structurally rigorous.

3. Resistance, diode placement: divided into two kinds of flat and vertical:

(1) Placement: When the number of circuit components is small, and the circuit board size is large, it is generally better to use a flat place; for a place where the resistance is less than 1/4W, the distance between two lands is generally small. Take 4/10 inch, 1/2W resistance when laid flat, the distance between the two pads is generally 5/10 inch; diode flat, 1N400X series rectifier, generally take 3/10 inch; 1N540X series rectifier, generally Take 4 to 5/10 inches.

(2) Vertical placement: When the number of circuit components is large, and the size of the circuit board is not large, vertical placement is generally adopted. When the vertical placement is performed, the distance between two pads is generally taken as 1 to 2/10 inches.

4. Potentiometer: Placement principle of IC holder

(1) Potentiometer: used to adjust the output voltage in the regulator, so the design potentiometer should be full clockwise adjustment when the output voltage increases, anti-clock regulator output voltage decreases at the festival; in the adjustable constant current charger The medium potentiometer is used to adjust the charge current fold size. When the potentiometer is designed to adjust clockwise in full clock, the current increases.

Potentiometer mounting position Xuan should be full of the structure of the whole machine installation and panel layout requirements, so should put Xuan on the edge of the board, rotating handle outward.

(2) IC Holder: When designing a printed board drawing, when using an IC Holder, be sure to pay special attention to whether the orientation of the positioning groove on the IC Holder is correct, and pay attention to whether each IC pin is correct. For example, pin 1 can only be Located in the lower right corner or upper left corner of the IC seat, and close to the positioning slot (see from the welding surface).

5. Access terminal layout

(1) The associated two lead terminals should not be too far away, generally about 2 to 3/10 inches.

(2) Inlet and outlet ends should be concentrated on one or two sides as much as possible. Do not be too discrete.

6. When designing the wiring diagram, pay attention to the order of the pins, and the distance between the components should be reasonable.

7. Under the premise of guaranteeing the circuit performance requirements, the design should be based on the principle of seeking reasonable cabling, using less external crossover wires, and routing the cabling according to certain requirements, and strive to be intuitive, easy to install, and maintain and maintain.

8. When designing the wiring diagram, the wiring should be as small as possible, and the lines should be simple and straightforward.

9. The width of the wiring strip and the spacing between the lines must be moderate, and the distance between the two pads of the capacitor should be as close as possible to the pitch of the capacitor lead.

10. The design should be carried out in a certain order, for example from left to right and from top to bottom.