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PCB board design diagram and detailed analysis points
Date:2014-2-28 11:46:13

The basic principle requires PCB board design.
A printed circuit board design , the size determined from the start board , the printed circuit board size due to the size limitations of the chassis housing to the housing can be placed just An appropriate next to consider the external components and the printed circuit board ( mainly potentiometers, sockets or another printed circuit board ) connection. Printed circuit board and external components typically connected via a plastic or metal wire isolated lines . But sometimes also designed to form the socket . Namely: the installation of a plug- in printed circuit board acts as the contact position within the apparatus to set aside the socket . For larger components mounted on the printed circuit board to be fixed with metal attachments to improve resistance to vibration and impact resistance .
2, the basic method of the wiring pattern design
You first need to have a complete understanding of the components and a variety of socket specifications , dimensions and area of choice ; arrangement of the components of the position to make a reasonable , careful consideration , mainly from electromagnetic compatibility , interference point of view, to go lines are short , cross- less , power, ground and decoupling path and other considerations . After the location of the components set is the online components , in accordance with the relevant circuit diagram connecting pins , there are several ways to complete printed circuit diagram design and computer-aided design manual design two ways .
The original arrangement is hand layout . This relatively cumbersome, often repeated several times in order to finalize , which can also be used when no other plot device , this hand- arranged layout method just learning FOOTPRINT designers also helpful. Computer Aided Drafting , there are now a variety of graphics software , different functions , but in general , to draw , modify more convenient and can save storage and printing.
Next, determine the size of the printed circuit board required , press schematics, initially identified the location of the various components down, and then through constant adjustments to make more rational layout , wiring arrangement between the components of the printed circuit board as follows :
( 1 ) are not allowed in the printed circuit cross circuit , may cross the line , you can use the " drill" , "around " two kinds of solutions . That is , let a lead from the gap at the other resistors, capacitors , transistors at the foot of the "drill " in the past , or from one end of a cross section may lead "around" in the past , how the circuit is very complicated , in exceptional circumstances , in order to simplify the design allows the jumper wire , cross- circuit problem solving .
( 2 ) resistors, diodes, capacitors and other components are tubular , " vertical ", " horizontal " two installation methods . Vertical refers to the component perpendicular to a circuit board mounting , solder , the advantage of saving space, the horizontal refers to the component parallel to and close to the body of the circuit board mounting , solder , the advantage of better mechanical strength of the components installed . These two different installation components , printed circuit board assembly pitch is not the same .
( 3 ) the same level circuits should be as close to the ground , and power supply filter capacitor circuits at this level should also be connected on the level ground. In particular, the level of the transistor base and emitter of the ground is not too far away , otherwise it would be too long because of the copper foil between the two ground causing interference with the self-excited , the use of such a " point ground method " circuit , working over the stability, not the self-excited .
( 4 ) The total ground must be strictly in accordance with the high-frequency - IF - low frequency level by level to weak to strong electric order principle , must not just repetitious random access , inter-stage and grade can be rather long connection point, to comply with this requirement. In particular frequency head , the playback head , the head of the grounding wire FM arrangements more stringent requirements , if any, will arise from improper excited that does not work .
Prime FM frequency circuit is often used large wraparound ground , in order to ensure a good shielding effect.
( 5 ) a strong current lead ( common ground , amplifier power lead , etc. ) should be as wide as those to reduce wiring resistance and voltage drop can be reduced parasitic coupling arising from shock .
( 6 ) high impedance traces short , low impedance traces can be longer because of the high impedance traces prone flute and absorption signals , causing circuit instability. Power lines, ground , no feedback component base alignment, the emitter lead , etc. are low-impedance traces emitter follower base alignment, ground recorders of both channels must be separated into their own way until the end of efficacy together again , even if the two -way to connect the ground wire to easily generate crosstalk , the separation decreased. PCB design should pay attention to the following points
1 , the wiring direction : from the welding face side , the arrangement orientation of the components as possible consistent with maintaining schematic circuit diagram of the best alignment direction of the wiring direction is consistent due to the production process often requires the welding surface for detecting various parameters , so doing facilitate the production of inspection , testing and maintenance ( Note : refers to satisfy the premise of the whole circuit performance and installation and panel layout requirements ) .
2 , the components are arranged to be reasonable and uniform distribution , and strive neat, attractive , well-structured process requirements.
3 , resistors, diodes placement: flat and upright divided into two categories:
( 1 ) flat : When the circuit components in small quantities, and the next board size is large, typically using flat better ; For less resistance when 1/4W flat, the distance between the two pads general take 4/ 10 inches , when 1/2W resistor flat, two- pad spacing generally take 5/ 10 in. ; diode flat , 1N400X series rectifier , generally take 3/ 10 inches , 1N540X series rectifier , general take 4 to 5/ 10 inches .
( 2 ) heel : when the number of components in the circuit more, but not the size of the circuit board , the heel is generally used when the distance between the two heel pads generally take 1 to 2/10 inches.
4 , potentiometers : IC Block placement guidelines
( 1 ) Potentiometer : The regulator used to regulate the output voltage , so the design should be full potentiometer clockwise increases the output voltage regulation , anti-clockwise section of the output voltage is reduced when the regulator ; adjustable constant current charger the potentiometer is used to adjust the charge current fold size , the design should be full clockwise potentiometer adjustment , the current increases .
Potentiometer placed in position over the whole structure should Xuan installation and panel layout requirements, so the edge of the plate should be placed Xuan possible , rotate the handle facing out.
(2) IC Block : printed circuit board design diagram, in the case of using the IC socket , IC must pay special attention to the orientation of the seat positioning groove positioned correctly , and note each IC pin is correct, for example, only 1 foot located in the lower right corner of Block IC line or the upper left corner , and close to the positioning groove ( from the welding face) .
5 , and out of the terminal layout
( 1 ) associated with both ends not lead distance is too large , typically 2 to 3 /10 inch or so suitable.
( 2 ) as far as possible into the outlet end of the focus on 1-2 side , not too discrete .
6 , should pay attention to when designing wiring diagram pin arrangement order , component pin spacing to be reasonable.
7 , under the premise of guaranteed circuit performance requirements , the design should strive to walk a reasonable line, less external across the line , and then filling certain requirements along the alignment , and strive intuitive, easy to install , height and maintenance.
8 , traces the design to minimize the wiring diagram turn, sought to simple lines .
9 , wiring strip width and line spacing should be moderate, two- pad spacing distance between the capacitor capacitance should be as consistent with the lead foot ;
10 , the direction of the design should be in a certain order , for example, can be carried out by order of left to right and top to bottom .

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