The basic principles of printed circuit board design

- Aug 17, 2016-

   1, a printed circuit board design, from determining the size of the board, the size of the printed circuit board due to the chassis shell size restrictions to just ANN into the shell is appropriate; secondly, we should consider the printing circuit board and external components (mainly potentiometer, Jack or another printed circuit board) connection. The printed circuit board and the external element are generally connected through a plastic wire or a metal isolation line. But sometimes it is designed as a socket. That is: install a plug-in printed circuit board Jack yaoliuchu as the contact position in the equipment. For larger components installed on the printed circuit board, the metal attachment is fixed to improve the vibration resistance and impact resistance.

   2, wiring design method firstly need to fully understand the selected components and various socket specifications, size and area; all the parts of the position arrangement reasonable, careful consideration, mainly from the angle of electromagnetic compatibility, anti-interference and walk the line short, cross, power supply, the path and decoupling considering. Each component position is set, that is, the parts of the connection, in accordance with the circuit diagram to connect the pin, complete the method of a variety of printed circuit design with computer aided design and manual design method two.

The most primitive is the manual arrangement of cloth map. This relatively cumbersome, often repeated several times. Then finally completed, in the absence of other graphics equipment can be, the manual arrangement layout method is also helpful for the PCB designer just learning. Computer aided drawing, now has a variety of graphics software, different functions, but overall speaking, drawing, editing more convenient and can saved to disk storage and printing.

Then determine the required printed circuit board size and according to principle diagram, the position of each component is tentatively identified, then through continuous adjustment of the layout more reasonable, printed circuit board wiring between components in the arrangement is as follows:

   (1) the printed circuit is not allowed to have a cross circuit, for the possible intersection of the line, you can use the "drill", "around" two ways to solve. Namely, let a lead from other resistance, a capacitance, a triode tube at the foot of the void at the "drill" in the past, or from may cross at one end of a wire "around" in the past, in special circumstances how very complicated circuit, in order to simplify the design also allows with a wire jumper, resolve cross circuit problem.

   (2) resistance, diode, tubular capacitors and other components are "vertical", "horizontal" two installation methods. Vertical component perpendicular to the circuit board installation, welding, the utility model has the advantages of is space saving, referring to the horizontal is element parallel and close is arranged on the circuit board and welding, the utility model has the advantages of is component installation has good mechanical strength. These two kinds of different installation components, printed circuit board components on the hole distance is not the same.

   (3) the same level circuit grounding should as close as possible, and the circuit of the power supply filter capacitor should also be in the class to access locations. Especially level at the base of the transistor, the emission pole pick location cannot be too far away, otherwise because of two ground points of the copper foil is too long will cause interference with the self, using such a grounding method of circuit, work is stable, not easy to self.

   (4) total wire must be strictly according to the high frequency and middle frequency and low-frequency level level by weak to ferroelectric order arrangement principle, must not casually toss and turn in the chaos after, rather than between stages can be long connection point, must comply with this provision. In particular, the frequency of the head, the head of the regeneration, the frequency of the ground wire arrangement is more stringent requirements, such as improper will generate a self excitation that can not work. The high frequency circuit of the frequency modulation is often used in the large area of the ground wire, so as to ensure a good shielding effect.

   (5) strong current lead wire (common ground wire, power amplifier, power supply, etc.) should be as wide as possible to reduce the wiring resistance and voltage drop, can reduce the parasitic coupling and the self excitation.

   (6) the high impedance of the line as short as possible, low impedance of the line can be long, because the high impedance of the line is easy to send the signal and the absorption of the signal, causing circuit instability. Power line, ground wire, and no feedback components to the base walk the line, the emission electrode lead, all of which belong to low impedance line, the emitter follower is the base of the wire, wire recorder two channel must be separated each way, until the end of efficacy and close it, such as two ground even to even go, easily produce crosstalk, the separation degree decreased.

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