PCB News - The basic principle requirements of PCB board drawing design

The size of the printed circuit board starts from the determined size. Because the size of the printed circuit board is limited by the size of the housing, it is appropriate to use the active safety blue power supply. Secondly, the size of the printed circuit board and independent components (mainly Is the way of components, interfaces or additional printed circuit boards). The printed circuit board and the connection components are generally connected by plastic wires or metal isolation wires. But sometimes it is also designed into a formed form. That is: install one inside the device. The plug-in printed circuit board should be installed with metal socket contacts in a performance manner.

The basic method of design drawing design

First of all, we need to have a complete understanding of the antenna components and various features, dimensions, contours, etc.; reasonable and careful consideration of the various positions is to approach some lines from the perspective of electromagnetic fields and anti-interference. Short lines, less crossovers, and power supplies, Ground and decoupling considerations. There are two methods: computer-aided design and manual design.

The most manual method of arranging the layout is like it takes the original time to complete at the end. It can also be done without drawing equipment. This kind of manual layout is just learning the design instructions of the printed board. It is also very helpful. Computer-aided drawing, now there are many kinds of drawing software, different, but it can always be said that drawing and modification are convenient, and it can save and visit and print functions.

Dissemination, determined the required size of the printed circuit board, and determined the appearance of each position according to the schematic diagram, and then adjusted the layout to make the layout more reasonable. The wiring method of each component in the printed circuit board is as follows:

(1) There is no cross circuit in the circuit in the printed circuit. For solutions that may have problems, "two drilling methods" can be used. That is, a certain virtual line that may be "drilled or crossed" from other places, capacitors, and triode pins is allowed to pass from the "past". Under certain circumstances, the circuit is very complicated. To simplify the design, a winding wire can also be used. Connect to solve the problem of circuit crossing.

(2) Finger-joining another way, tubular structure and other components have two installation methods, "vertical" and "horizontal". The vertical type is the installation and welding perpendicular to the circuit board, which has the advantage of saving space. The horizontal type is that the component body is parallel and close to the circuit board installation, and the welding has the advantage that the mechanical strength of the component installation is very good. For these two different mounting components, the component hole pitch on the printed circuit board is not the same.

(3) The grounding point of the circuit of the same level should be close, and the power supply voltage capacitor of the circuit of this level should also be connected to the grounding point of this level. Otherwise, because the copper foil between the two grounding points is too long, it will cause interference and self-excitation. The circuit using this "one-point grounding method" will work more stable and not easy to self-excite.

(4) The total ground wire must be arranged in strict accordance with the principle of high frequency-intermediate frequency-low-level ground in the order of weak current to strong current, and must not be overturned and connected randomly. Long points can be drawn between levels and must be strictly regulated. Especially the grounding wire layout requirements of the frequency conversion head, regeneration head and frequency modulation head are more intense, and it is not easy to produce spontaneous work.

High-frequency circuits such as FM heads often use large outdoor external ground wires to ensure good shielding effects.

(5) The fresh evening spring (public ground wire, discharge power source, etc.) should appropriately reduce the excitation and voltage drop, which can spread the self-strength caused by the halo.

(6) The traces that love high are short, and the traces that are delicate and low can be longer, because the high traces are easy to detect and absorb signals and cause instability. The power cord, the ground wire, the basic wiring of the non-feedback component, the emitter, etc. are equally low and low. The emitter must be wired, and the ground wire of the radio recorder must be separate, each in the same way, until the new wiring is combined again If two ground wires are connected back and forth, it is easy to produce crosstalk and reduce the degree of separation.

Matters needing attention in PCB design

1. Detection direction: From the welding surface, the arrangement theme of the components should be consistent with the schematic diagram. The selection should be consistent with the wiring direction of the circuit diagram. Because the production process usually requires various parameters on the welding surface, it means that the damage is convenient for production. The inspection, debugging and realization (Note: under the premise of meeting the circuit performance and the requirements of the whole machine installation and panel equipment).

2. The arrangement of each component must be distributed and evenly distributed, and strive for overall beauty, beautiful structure, and process requirements.

3. Optoelectronics and photoelectric placement methods: There are two types:

(1) Flat laying: When the number of circuit components is small and the size of the circuit board is large, it is generally better to lay flat; for resistors below 1/4W, the distance between the two pads is general. Take 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 placement: When the number of circuit components is large, it is generally placed vertically. When placed vertically, the exaggerated one is generally taken as 1 to 2/1 inch 0.

4. Principle device: placement of IC holder

(1) Auxiliary device: The output voltage in the regulator, so the design of the makeup device should be fully declared, the output voltage rise is adjusted in reverse, and the output voltage is adjusted counterclockwise to reduce the voltage; the device has a constant and constant current output voltage; Sinochem auxiliary charging The energy is folded, and the current can be adjusted when the auxiliary device is designed.

The alloying seat should be installed in the structure of the whole machine and the requirements of the panel assembly, so it should be initially placed on the board boundary with the rotating handle facing outward.

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

5. In and out of the terminal

(1) The distance between the two ends of the linkage is related, generally about 2 to 3/10 is more appropriate.

(2) There are only 1 to 2 incoming and outgoing wire ends, without the last section.

6. Pay attention to the pin arrangement sequence when designing the drawing, and the component pins should be reasonable.

7. Under the premise of ensuring the performance requirements of the circuit, and the design requires reasonable wiring, less use of jumpers, wiring according to compliance requirements, and strive for introduction, convenience, installation height and support.

8. When designing the diagram, there are fewer turns in the routing, and the diagram is simple and clear.

9. The width and movement of the bar should be moderate, and the two shakes should have characteristics and specific characteristics of the fingers;

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