Circuit design skills PCB design prosess

Generell PCB grunnleggende designprosess er som følger: foreløpig forberedelse ->; PCB structure design -& GT; PCB -oppsett – & gt; Kabling – & gt; Rutingoptimalisering og skjermutskrift -> 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. Kravene til PCB -komponentbibliotek er høye, det påvirker brettinstallasjonen direkte; 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. Så er den skjematiske designen, klar til å gjøre PCB -design.

For det andre: PCB -konstruksjon. I dette trinnet, i henhold til kretskortets størrelse og mekaniske posisjonering, tegnes PCB -plateoverflaten i PCB -designmiljøet, og kontakter, knapper/brytere, skruehull, monteringshull og så videre plasseres i henhold til posisjoneringskrav. 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).

Tredje: PCB -layout. 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), og importer deretter nettverkstabellen på PCB-diagrammet (design-gt; LoadNets). Se enhetshubb av hele bunken opp, mellom pinnene og flylinje -ledetilkoblingen. Du kan deretter legge ut enheten. Den generelle utformingen utføres i henhold til følgende prinsipper:

(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; Varmeelementet bør skilles fra det temperaturfølsomme elementet, og om nødvendig bør termiske konveksjonstiltak vurderes;

(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); En tantalkondensator kan også plasseres rundt flere integrerte kretser når plass på kretskortet er trangt.

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

I dag. 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.

Fjerde: ledninger. Kabling er den viktigste prosessen i PCB -design. Dette vil direkte påvirke ytelsen til kretskortet. 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. Dette er standarden for å måle om et kretskort er kvalifisert. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Så er det estetikk. 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. Ledninger skal være ryddig og ensartet, ikke kryss og tvers uten regler. Alt dette bør oppnås i sammenheng med å sikre elektrisk ytelse og oppfylle andre individuelle krav, ellers er det å forlate essensen. Kabling bør utføres i henhold til følgende prinsipper:

(1). Generelt bør strømkabelen og jordkabelen føres først for å sikre den elektriske ytelsen til kretskortet. I omfang som tilstanden tillater, bredere bredde på strømforsyningen, jordledning så langt som mulig, er det best at jordledningen er bredere enn kraftledningen, deres forhold er: jordledning> kraftledning> signallinje, vanligvis er signallinjebredden : 0.2 ~ 0.3 mm, den tynneste bredden kan nå 0.05 ~ 0.07 mm, kraftledningen er 1.2 ~ 2.5 mm generelt. Kretskortet til en digital krets kan brukes i en krets med brede jordledere, det vil si et jordnett. (Analog bakken kan ikke brukes på denne måten.)

(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; Signallinje gjennom hullet skal være så liten som mulig;

6. The key line should be short and thick, with protection on both sides.

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

I dag. 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). linje

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

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)

Når tettheten er høy:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: ≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Femte: ledningsoptimalisering og skjermutskrift. “There is no best, only better”! Uansett hvor mye krefter du legger ned i designet, kan du se på det igjen når du er ferdig, og du vil fortsatt føle at du kan endre mye. En generell tommelfingerregel er at optimal ledning tar dobbelt så lang tid som den første ledningen. Når du føler at ingenting trenger å fikses, kan du plassere kobber. PolygonPlane). Legging av kobber legger vanligvis jordkabel (vær oppmerksom på separasjonen av analog og digital jord), kan flerlagsbrett også trenge å legge strøm. For screen printing, we should pay attention to not be blocked by the device or removed by the hole and pad. På samme tid, design for å vende mot komponentoverflaten, bør bunnen av ordet være speilbehandling, for ikke å forvirre nivået.

Sjette: nettverks- og DRC -sjekk og strukturkontroll. For det første, med forutsetningen om at den skjematiske designen er riktig, er de genererte PCB -nettverksfilene og de skjematiske nettverksfilene NETCHECK for fysisk tilkoblingsforhold, og designet endres i tide i henhold til utdatafilresultatene for å sikre korrektheten i kabelforbindelsesforholdet; Etter at nettverkskontrollen er bestått korrekt, vil DRC -sjekk bli utført på PCB -designet, og designet vil bli endret i henhold til utdatafilresultatene i tide for å sikre den elektriske ytelsen til PCB -ledninger. Til slutt bør den mekaniske installasjonsstrukturen til PCB sjekkes og bekreftes ytterligere.

Syvende: tallerkenlaging. It is best to have a review process before doing so.

PCB -design er en test av tankene på arbeidet, som er nær sinnet, høy erfaring, design av brettet er bra. Så designen bør være ekstremt forsiktig, fullt ut vurdere faktorene til alle aspekter (for eksempel forenkle vedlikehold og inspeksjon av dette mange mennesker ikke anser), fortreffelighet, vil være i stand til å designe et godt brett.