Basic Principles of Printed Circuit Board (1)

Basic Principles of Printed Circuit Board:

1. Wiring Direction

From the perspective of the soldering surface, the arrangement of the components should be as consistent as possible with the schematic diagram. The wiring direction is best to be consistent with the wiring direction of the circuit diagram. Because various parameters are usually tested on the soldering surface during the production process, it is convenient to do so. Inspection, debugging and maintenance during production (Note: It refers to the premise of meeting the requirements of circuit performance, installation and panel layout of the whole machine).

2. Arrangement of Components

The distribution should be reasonable and even, and strive to be neat, beautiful, and strict in structure.

3. The Placement of Resistors and Diodes

Divided into two types: horizontal placement and vertical placement:

(1) Horizontal placement: When the number of circuit components is small and the size of the circuit board is large, it is generally better to use horizontal placement. For resistors below 1/4W, the distance between the two pads is general 4/10 inches, when the 1/2W resistor is placed flat, the distance between the two pads is generally 5/10 inches. When the diode is placed flat, 1N400X series rectifier tubes, generally take 3/10 inches. 1N540X series rectifier tubes, generally Take 4 to 5/10 inches.

(2) Vertical installation: When there are a large number of circuit components and the size of the circuit board is small, the vertical installation is generally adopted, and the distance between the two pads is generally 1 to 2/10 inches in the vertical installation.

4. Potentiometer: the placement principle of the chip (IC) holder

(1) Potentiometer: It is used to adjust the output voltage in the regulator, so the design potentiometer should increase when the potentiometer is fully adjusted clockwise, and the output voltage of the counterclockwise regulator decreases when the output voltage is reduced. In the adjustable constant current charger the middle potentiometer is used to adjust the size of the charging current. When the potentiometer is designed, the current will increase when the potentiometer is fully adjusted clockwise.

The potentiometer should be placed in the position to meet the requirements of the whole machine structure installation and panel layout, so it should be placed on the edge of the board as much as possible, with the rotating handle facing outward.

(2) IC Holder: When designing the printed board diagram, when using the IC holder, be sure to pay special attention to whether the orientation of the positioning slot on the IC holder is correct, and pay attention to whether each IC pin is correct, for example, the first pin can only be used. Located at the lower right or upper left corner of the IC socket, and close to the positioning groove (viewed from the welding surface).