Printplaat (PCB) word in byna elke soort elektroniese toestel aangetref. If there are electronic components in a piece of equipment, they are also embedded in various sizes of PCB. In addition to fixing various small parts, the main function of the PCB is to provide electrical connections between the components. As electronic equipment becomes more and more complex, more and more parts are needed, and the wiring and parts on the PCB become more and more dense. ‘N Standaard PCB lyk so. Bare Board (without parts on it) is also often referred to as “Printed Wiring Board (PWB).

The substrate of the board itself is made of a material that is insulated and resistant to bending. The small line material that can be seen on the surface is copper foil. Originally, the copper foil is covered on the whole board, and the middle part is etched away in the manufacturing process, and the remaining part becomes a network of small lines. These lines are called conductors or conductors and are used to provide electrical connections to parts on the PCB.

To secure parts to the PCB, we solder their pins directly to the wiring. Op ‘n basiese PCB is die dele aan die een kant gekonsentreer en die drade aan die ander kant. So we need to make holes in the board so that the pins can go through the board to the other side, so the pins of the parts are welded to the other side. Because of this, the front and back sides of a PCB are called Component Side and Solder Side respectively.

As daar dele op die PCB is wat verwyder kan word of weer aangesit kan word na vervaardiging, sal Socket gebruik word om die dele te installeer. Because the socket is directly welded to the board, the parts can be arbitrarily disassembled. A ZIF (Zero InserTIon Force) plug allows parts to be inserted and removed easily. The lever next to the socket can hold the parts in place after you insert them.

To connect two PCBS to each other, an edge connector is commonly used. Die goue vinger bevat ‘n aantal koperblokkies wat eintlik deel uitmaak van die PCB -bedrading. Normaalweg steek ons ​​die goue vinger op die een PCB in die toepaslike gleuf (gewoonlik uitbreidingsgleuf) op die ander PCB om aan te sluit. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Die groen of bruin kleur op die PCB is die kleur van die soldeermasker. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. ‘N Ander syskerm word op die soldeerweerstandlaag gedruk. It is usually printed with words and symbols (mostly white) to indicate the position of the parts on the board. Screen printing surface is also known as icon surface

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Enkelkantige planke

Soos ons genoem het, is die dele op ‘n basiese PCB aan die een kant gekonsentreer en die drade aan die ander kant. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Omdat enkelpanele baie streng beperkings op die ontwerp van die stroombaan gehad het (omdat daar slegs een kant was, kon die bedrading nie kruis nie en moes ‘n aparte pad loop), het slegs vroeë stroombane sulke borde gebruik.

Dubbelkantige planke

Die printplaat het bedrading aan beide kante. But in order to use both wires, there must be proper electrical connections between the two sides. Hierdie ‘brug’ tussen stroombane word ‘n geleidingsgat (VIA) genoem. Gidingsgate is klein gaatjies in die PCB gevul of bedek met metaal wat aan beide kante met drade verbind kan word. Because a dual panel has twice the area of a single panel, and because the wiring can be interlaced (it can be wound around to the other side), it is better for more complex circuits than a single panel.

Multi-layer Boards

Om die bedrade oppervlakte te vergroot, word meer enkel- of dubbelzijdige bedradingplanke gebruik. Die meerlaagse bord gebruik verskeie dubbele panele, en ‘n laag isolasie word tussen elke paneel geplaas en vasgeplak (vasgedruk). The number of layers of the board represents several independent wiring layers, usually an even number of layers, including the outermost two layers. Most motherboards are built with four to eight layers, but it is technically possible to build up to 100 layers of PCBS. Die meeste groot superrekenaars gebruik ‘n hele paar lae moederborde, maar dit is buite gebruik omdat dit deur groepe gewone rekenaars vervang kan word. Because the layers in a PCB are so tightly integrated, it’s not always easy to see the actual number, but if you look closely at the motherboard, you might be able to.

The guide hole (VIA) we just mentioned, if applied to a double panel, must be through the entire board

But in a multilayer, if you only want to connect some of the lines, the guide holes may waste some of the line space in the other layers. Buried vias and Blind vias avoid this problem because they only penetrate a few layers. Blind holes connect several layers of internal PCBS to surface PCBS without penetrating the entire board. Buried holes are only connected to the internal PCB, so light is not visible from the surface.

In a multilayer PCB, the entire layer is directly connected to the ground wire and the power supply. So we classify the layers as Signal, Power or Ground. If the parts on the PCB require different power supplies, they usually have more than two power and wire layers.

Gedeeltelike verpakkingstegnologie

Deur gattegnologie

The technique of placing parts on one side of the board and welding the pins to the other side is called “Through Hole Technology (THT)” encapsulation. This part takes up a lot of space and one hole is drilled for each pin. Die gewrigte neem dus aan beide kante ruimte in beslag, en die soldeerverbindings is relatief groot. Aan die ander kant is THT -dele beter verbind met PCB as Surface Mounted Technology (SMT) -onderdele, waaroor ons later sal praat. Sockets like wired sockets and similar interfaces need to be pressure-tolerant, so they are usually THT packages.

Surface Mounted Technology

For Surface Mounted Technology (SMT) parts, the pin is welded on the same side with the parts. This technique does not drill holes in the PCB for each pin.

Gomonderdele kan selfs aan beide kante gelas word.

SMT het ook kleiner dele as THT. Compared to PCB with THT parts, PCB with SMT technology is much denser. SMT package parts are also less expensive than THT’s. So it’s no surprise that most of today’s PCBS are SMT.

Because the solder joints and pins of parts are very small, it is very difficult to weld them manually. However, given that current assembly is fully automated, this problem will only occur when repairing parts.

The design process

In PCB -ontwerp is daar eintlik baie lang stappe om te doen voordat formele bedrading plaasvind. Die volgende is die belangrikste ontwerpproses:

The system specifications

First of all, the system specifications of the electronic equipment should be planned. It covers system functionality, cost constraints, size, operation and so on.

System function block diagram

Die volgende stap is om ‘n funksionele blokdiagram van die stelsel op te stel. Die verhouding tussen die vierkante moet ook gemerk word.

Divide the system into several PCBS

Dividing the system into several PCBS not only reduces the size, but also gives the system the ability to upgrade and swap parts. The system function block diagram provides the basis for our segmentation. Computers, for example, can be divided into motherboards, display cards, sound cards, floppy disk drives, power supplies, and so on.

Bepaal die verpakkingsmetode wat gebruik moet word en die grootte van elke PCB

Once the technology and the number of circuits used for each PCB has been determined, the next step is to determine the size of the board. If the design is too large, then packaging technology will have to change, or re-split the action. Die kwaliteit en spoed van die kringdiagram moet ook in ag geneem word by die keuse van die tegnologie.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. PCB in alle stelsels moet beskryf word, en die meeste van hulle gebruik tans CAD (Computer Aided Design). Here is an example of a CircuitMakerTM design.

Skematiese diagram van PCB -stroombaan

Preliminary design of simulation operation

To ensure that the designed circuit diagram works, it must first be simulated using computer software. Such software can read blueprints and show how the circuit works in many ways. This is much more efficient than actually making a sample PCB and then measuring it manually.

Place the parts on the PCB

The way parts are placed depends on how they are connected to each other. Hulle moet op die doeltreffendste manier met die pad verbind word. Efficient wiring means the shortest possible wiring and fewer layers (which also reduces the number of guide holes), but we’ll come back to this in actual wiring. Here is what the bus looks like on a PCB. Placement is important in order for each part to have perfect wiring.

Test wiring possibilities with correct operation at high speed

Sommige van die huidige rekenaarprogrammatuur kan kyk of die plasing van elke komponent korrek gekoppel kan word, of kyk of dit teen hoë spoed korrek kan werk. Hierdie stap word die rangskikking van dele genoem, maar ons gaan nie te ver hierop in nie. As daar ‘n probleem met die kringontwerp is, kan onderdele ook herrangskik word voordat die kring in die veld uitgevoer word.

Uitvoerbaan op PCB

The connections in the sketch will now look like wiring in the field. Hierdie stap is gewoonlik volledig outomaties, hoewel handmatige veranderinge gewoonlik nodig is. Below is the wire template for 2 laminates. Die rooi en blou lyne verteenwoordig die PCB -onderdele en die laslaag onderskeidelik. The white text and squares represent the markings on the screen printing surface. Die rooi kolletjies en sirkels verteenwoordig boor- en leidingsgate. Heel regs kan ons die goue vinger op die lasoppervlak van die PCB sien. The final composition of this PCB is often referred to as the working Artwork.

Each design must conform to a set of rules, such as minimum reserved gaps between lines, minimum line widths, and other similar practical limitations. Hierdie spesifikasies wissel na gelang van die snelheid van die kring, die sterkte van die sein wat oorgedra moet word, die sensitiwiteit van die stroombaan vir kragverbruik en geraas, en die kwaliteit van die materiaal en vervaardigingstoerusting. If the strength of the current increases, the thickness of the wire must also increase. In order to reduce PCB costs, while reducing the number of layers, it is also necessary to pay attention to whether these regulations are still met. As meer as 2 lae nodig is, word die kraglaag en grondlaag gewoonlik gebruik om te voorkom dat die oordragsein op die seinlaag aangetas word, en kan dit as ‘n skild van die seinlaag gebruik word.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Hierdie toets kyk ook na verkeerde verbindings, en alle verbindings volg die skematiese diagram.

Vestig en lêer

Omdat daar tans baie CAD -gereedskap is vir die ontwerp van PCBS, moet vervaardigers ‘n profiel hê wat aan die standaarde voldoen voordat hulle borde kan vervaardig. There are several standard specifications, but the most common is the Gerber Files specification. A set of Gerber files includes a plan of each signal, power and ground layer, a plan of the solder resistance layer and the screen printing surface, and specified files of drilling and displacing.

Electromagnetic compatibility problem

Elektroniese toestelle wat nie volgens EMC -spesifikasies ontwerp is nie, sal waarskynlik elektromagnetiese energie afgee en toestelle in die omgewing belemmer. EMC stel maksimum perke op elektromagnetiese interferensie (EMI), elektromagnetiese veld (EMF) en radiofrekwensie -interferensie (RFI). Hierdie regulasie kan die normale werking van die toestel en ander nabygeleë toestelle verseker. EMC stel streng beperkings op die hoeveelheid energie wat van een toestel na ‘n ander versprei of oorgedra kan word, en is ontwerp om die vatbaarheid vir eksterne EMF, EMI, RFI, ensovoorts te verminder. In other words, the purpose of this regulation is to prevent electromagnetic energy from entering or emanating from the device. This is a very difficult problem to solve, and is usually solved by using power and grounding layers, or putting PCBS into metal boxes. The power and ground layers protect the signal layer from interference, and the metal box works equally well. We won’t go too far into these issues.

The maximum speed of the circuit depends on EMC compliance. Interne EMI, soos stroomverlies tussen geleiers, neem toe namate die frekwensie styg. As die huidige verskil tussen die twee te groot is, moet u die afstand tussen hulle langer maak. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Die vertragingsgraad in die bedrading is ook belangrik, dus hoe korter die lengte, hoe beter. ‘N Klein PCB met goeie bedrading werk dus teen hoë snelhede beter as ‘n groot PCB.