Circuit design skills PCB ûntwerpproses

Algemien PCB basis ûntwerpproses is as folget: foarriedige tarieding ->; PCB structure design -& GT; PCB -yndieling – & GT; Wiring – & GT; Routingoptimalisaasje en skermprintsje -> Network and DRC inspections and structural inspections – > Plate making.

First: preparation. This includes preparing component libraries and schematics. “To do good work, must first sharpen its device”, to make a good board, in addition to the principle of good design, but also draw well. Before PCB design, the component library of schematic SCH and the component library of PCB should be prepared first. Peotel libraries can be used, but in general it is difficult to find a suitable library, it is best to make your own library according to the standard size information of the selected device. In principle, make PCB component library first, and then SCH component library. PCB -komponintbibleteekeasken binne heech, it hat direkte ynfloed op de boerdynstallaasje; SCH’s component library requirements are relatively loose, as long as attention is paid to the definition of pin attributes and the corresponding relationship with PCB components. PS: Note the hidden pins in the standard library. Dan is it skematyske ûntwerp, klear om PCB -ûntwerp te dwaan.

Twad: PCB struktureel ûntwerp. Yn dizze stap, neffens de grutte fan ‘e printplaat en meganyske posysjonearring, wurdt PCB -boerdflak tekene yn’ e PCB -ûntwerpomjouwing, en ferbiningen, knoppen/skakelaars, skroefgatten, montagegaten ensafuorthinne wurde pleatst neffens posysjeasken. And fully consider and determine the wiring area and non-wiring area (such as how much of the screw hole around the non-wiring area).

Tredde: PCB -yndieling. Layout is basically putting devices on a board. At this point, if all the preparatory work mentioned above is done, the network table can be generated on the schematic diagram (Design- >; CreateNetlist), en ymportearje dan de netwurktabel op it PCB-diagram (design-gt; LoadNets). Sjoch de hubber fan it apparaat fan ‘e heule stapel, tusken de pinnen en fleanline -promptferbining. Jo kinne it apparaat dan útlizze. De algemiene yndieling wurdt útfierd neffens de folgjende prinsipes:

(1). According to the electrical performance reasonable partition, generally divided into: digital circuit area (that is, afraid of interference, and interference), analog circuit area

(fear of interference), power drive area (interference source);

(2). Complete the same function of the circuit, should be placed as close as possible, and adjust the components to ensure the most simple connection; At the same time, adjust the relative position between the functional blocks to make the connection between the functional blocks the most concise;

(3). Installation position and installation intensity should be considered for components with large mass; It ferwaarmingselemint moat wurde skieden fan it temperatuergefoelige elemint, en as it nedich is, moatte termyske konveksjemaatregelen wurde beskôge;

(4). I/O drive device as close as possible to the edge of the printing plate, close to the outlet connector;

(5). Clock generator (such as: crystal oscillator or clock oscillator) should be as close as possible to the device using the clock;

6. In each integrated circuit between the power input pin and the ground, need to add a decoupling capacitor (generally using high frequency good monolithic capacitor); In tantalkondensator kin ek wurde pleatst om ferskate yntegreare sirkels as de romte fan ‘e printplaat is krap.

Alle grûnbesitters. Relay coil to add discharge diode (1N4148 can be);

Hjoed. Layout requirements should be balanced, dense and orderly, not top-heavy or heavy

— Special attention should be paid to the actual size (area and height) of the components and the relative position of the components when placing the components to ensure the electrical performance of the circuit board and the feasibility and convenience of production and installation. At the same time, the above principles should be reflected

Under the premise, modify the placement of devices appropriately to make them neat and beautiful. For example, the same devices should be placed neatly and in the same direction, instead of being “strewn at random”. This step concerns the difficulty of board integral figure and next wiring degree, want to spend big effort to consider so. When layout, can make preliminary wiring first to not quite affirmative place, sufficient consideration.

Fjirde: wiring. Wiring is it wichtichste proses yn PCB -ûntwerp. Dit sil de prestaasjes fan PCB -boerd direkt beynfloedzje. In the process of PCB design, wiring generally has such three levels of division: the first is the distribution, which is the most basic requirement of PCB design. If the line is not cloth, get everywhere is flying line, it will be a unqualified board, can say that there is no entry. The second is the satisfaction of electrical performance. Dit is de standert om te mjitten oft in printplaat kwalifisearre is. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Dan is d’r estetyk. If your wiring cloth was connected, also do not have the place that what affects electric appliance performance, but look past desultorily, add colourful, brightly colored, that calculates how your electric appliance performance is good, still be rubbish in others eye. This brings great inconvenience to testing and maintenance. Bedrading moat kreas en unifoarm wêze, net kriskras sûnder regels. Al dizze moatte wurde berikt yn ‘e kontekst fan it garandearjen fan elektryske prestaasjes en it foldwaan oan oare yndividuele easken, oars is it de essinsje te ferlitten. Bedrading moat wurde útfierd neffens de folgjende prinsipes:

(1). Yn ‘t algemien moatte de stroomkabel en ierdkabel earst wurde routed om de elektryske prestaasjes fan it circuit board te garandearjen. Yn ‘t berik dat dizze tastân, breder breedte fan stroomfoarsjenning, grûndraad sa fier mooglik makket, is it it bêste dat grûndraad breder is dan machtline, har relaasje is: grûndraad> stroomline> sinjaalline, meastal is sinjaalline breedte : 0.2 ~ 0.3mm, de tinste breedte kin 0.05 ~ 0.07mm berikke, machtline is 1.2 ~ 2.5mm algemien. De PCB fan in digitaal circuit kin wurde brûkt yn in circuit mei brede grûnlieders, dat is in grûnnetwurk. (Analoge grûn kin op dizze manier net wurde brûkt.)

(2). In advance, wire strict requirements (such as high frequency line) for wiring, input and output side line should avoid adjacent parallel, so as not to produce reflection interference. When necessary, ground wire should be added to isolate, and the wiring of two adjacent layers should be perpendicular to each other, which is easy to produce parasitic coupling in parallel.

(3). The oscillator housing should be grounded, and the clock line should be as short as possible, and not spread all over the place. Below the clock oscillation circuit, the special high-speed logic circuit should increase the area of the ground, and should not go to other signal lines, so that the surrounding electric field tends to zero;

(4). In order to reduce the radiation of high frequency signal, 45O broken line should be used as far as possible, instead of 90O broken line. (High requirements of the line also use double arc)

(5). Any signal line should not form a loop, if unavoidable, loop should be as small as possible; Sinjaalline troch it gat moat sa min mooglik wêze;

6. De toetsline moat koart en dik wêze, mei beskerming oan beide kanten.

Alle grûnbesitters. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Hjoed. Test points should be reserved for key signals to facilitate production and maintenance testing

Pet-name ruby. After schematic diagram wiring is completed, wiring should be optimized; At the same time, after the preliminary network check and DRC check is correct, the ground wire is filled in the area without wiring, and a large area of copper layer is used as ground wire, and the unused places are connected with the ground as ground wire on the printed board. Or make it multi-layer board, power supply, grounding line each occupy a layer.

— PCB wiring process requirements

(1). rigel

Generally, the signal line width is 0.3mm(12mil), and the power line width is 0.77mm(30mil) or 1.27mm(50mil). Line mei

The distance between lines and between lines and pads should be greater than or equal to 0.33mm(13mil). In practical application, it should be considered to increase the distance when conditions permit; When the cabling density is high, it is advisable (but not recommended) to use two cables between IC pins. The width of the cables is 0.254mm(10mil), and the distance between the cables is not less than 0.254mm(10mil).

Under special circumstances, when the pin of the device is dense and the width is narrow, the line width and line spacing can be appropriately reduced.

(2). PAD (PAD)

The basic requirements of PAD and transition hole (VIA) are: the diameter of PAD is greater than 0.6mm than the diameter of hole; For example, universal pin type resistors, capacitors and integrated circuits, using disk/hole size 1.6mm/0.8mm (63mil/32mil), socket, pin and diode 1N4007, using 1.8mm/1.0mm (71mil/39mil). In practical application, it should be determined according to the size of the actual components. If conditions are available, the size of the pad can be appropriately increased. The installation aperture of the components designed on the PCB board should be about 0.2 ~ 0.4mm larger than the actual size of the pins.

(3). Through hole (VIA)

Generally 1.27mm/0.7mm(50mil/28mil);

When the wiring density is high, the hole size can be appropriately reduced, but not too small, can consider 1.0mm/0.6mm(40mil/24mil).

(4). Spacing requirements for pads, wires and through-holes

PADandVIA: ≥0.3mm (12mil)

PADandPAD: ≥0.3mm (12mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

As tichtheid heech is:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: ≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Fyfde: bedradingoptimalisaasje en skermprintsje. “There is no best, only better”! Gjin saak hoefolle muoite jo hawwe ynset foar it ûntwerp, as jo klear binne, besjoch it opnij, en jo sille noch fiele dat jo in protte kinne feroarje. In algemiene ûntwerpregel is dat optimale bedrading twa kear sa lang duorret as earste bedrading. As jo ​​ienris fiele dat neat repareare hoecht, kinne jo koper pleatse. PolygonPlane). Koper lizze oer it algemien lizzen fan grûndraad (oandachtje foar de skieding fan analoge en digitale grûn), mearlaachplank kin ek macht moatte lizze. For screen printing, we should pay attention to not be blocked by the device or removed by the hole and pad. Tagelyk, ûntwerp foar it komponintoerflak, de boaiem fan it wurd moat spegelferwurking wêze, om it nivo net te ferwarjen.

Seisde: netwurk- en DRC -kontrôle en struktuerkontrôle. Yn it foarste plak, op it útgongspunt dat it skematyske ûntwerp korrekt is, binne de oanmakke PCB -netwurktriemmen en skematyske netwurkbestannen NETCHECK foar fysike ferbiningsferhâlding, en it ûntwerp wurdt tydlik oanpast neffens de útfierbestânresultaten om de juste te garandearjen fan ferbiningferbining; Neidat de netwurkkontrôle goed is trochjûn, sil DRC -kontrôle wurde útfierd op it PCB -ûntwerp, en it ûntwerp sil op ‘e tiid wurde oanpast neffens de útfierbestânresultaten om de elektryske prestaasjes fan PCB -bedrading te garandearjen. Uteinlik moat de meganyske ynstallaasjestruktuer fan PCB fierder wurde kontroleare en befêstige.

Sânde: plaat meitsje. It is best to have a review process before doing so.

PCB -ûntwerp is in test fan ‘e geast fan it wurk, dy’t tichtby de geast is, hege ûnderfining, it ûntwerp fan it boerd is goed. Dat it ûntwerp moat heul foarsichtich wêze, folslein beskôgje de faktoaren fan alle aspekten (lykas it fasilitearjen fan ûnderhâld en ynspeksje hjirfan dy’t in protte minsken net beskôgje), treflikens, sil in goed boerd kinne ûntwerpe.