Abstract: From the perspective of electromagnetic compatibility of electronic systems, the layout of components on the double-sided printed circuit board, the wiring principle of power supply lines and signal lines are described in detail; and the automatic wiring of double-sided printed boards is discussed.
A printed circuit board (referred to as a printed circuit board) is a high-level assembly of components, power lines, and signal lines in an electronic application system. The quality of the printed board has a great influence on the electromagnetic compatibility of the system. Therefore, the design of the printed board is not only the simple layout and arrangement of components and lines, as long as it is consciously enhanced with electromagnetic compatibility design. In order to enhance the anti-interference ability of the system and improve its stability.
For commonly used single-chip microcomputer systems, the clock frequency is generally 4 to 12 MHz, and the remaining integrated circuits are mostly 74HC and 74LS series. If a single-sided printed board is used, it is difficult to meet the needs, and the multi-layer is expensive. Therefore, mostly double-sided printed boards are used. When using a double-sided printed board, as long as the electromagnetic compatibility problem is fully considered, it can meet the application requirements.
Of course, the problems involved in the electromagnetic compatibility of the single-chip system are all aspects. In this paper, only the layout of the unit circuit (or components) on the double-sided printed board, the layout of the line, and other issues related to electromagnetic compatibility are briefly analyzed, and specific measures are given accordingly.
1 layout of the unit circuit on the printed board
The mutual position of various unit circuits on the double-sided printed board directly affects the electromagnetic compatibility of the system. Therefore, it is important to screen the unit circuit to be used. The group circuits are grouped according to the degree of sensitivity to electromagnetic compatibility in use. The purpose of grouping is to divide the printed board sections by group and put the same group of components together so as to ensure that the components between the groups do not interfere with each other in space. It is generally grouped according to the speed of the work or the level of the power supply voltage.
1.1 group layout according to the speed of work
The higher the operating frequency of the unit circuit, the faster the speed and the richer the spectrum of the signal; the larger the proportion of the high-frequency component, the stronger the external interference. According to the operating frequency of the unit circuit, it can be divided into high-speed circuits (such as microprocessors), medium-speed circuits (such as display processing), low-speed circuits (such as interfaces) and analog circuits (such as analog signal amplifiers). The layout of multiple speed circuits on a printed board is generally shown in Figure 1.
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FFC connector is a new type of data cable made of PET insulation material and extremely thin tin-plated flat copper wire, which is pressed by high-tech automation equipment production line. It is soft, bending and folding at will, thin in thickness, small in volume, easy to connect, easy to disassemble and easy to solve electromagnetic shielding (EMI).
FPC Flexible Printed Circuit is a form of Circuit produced on a Flexible surface, which may or may not have an overlay (usually used to protect FPC circuits). FPC is more and more widely used because it can bend, fold or repeat motion in a variety of ways and has the advantages of light, thin and flexible compared with ordinary hard board (PCB).
FPC composition materials
1. Insulating film
The insulating film forms the base layer of the circuit, and the adhesive attaches the copper foil to the insulating layer. In a multilayer design, it is then bonded to the inner layer.
They have also been used as a protective cover, in order to make circuit from dust and damp, and the ability to reduce stress during bending, copper foil to form the conductive layer. In some flexible circuits, adopted by the aluminum or stainless steel formed by the rigid member, they can provide the size stability, provides a physical support components and resettlement of the wire, as well as the release of stress.
2, the conductor
Copper foil is suitable for use in flexible circuits, it can use the electric deposition (Electrodeposited, ED.), or plating system.
3. Adhesive
In addition to being used for bonding insulating films to conductive materials, adhesives can also be used as cladding, protective coating, and cladding. The main difference between the two is in the application in which the covering layer is bonded to the covering insulating film in order to form a laminated structure of the circuit.
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