Prentað hringrás borð (PCB) er að finna í næstum alls konar rafeindatækjum. 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. A standard PCB looks something like this. 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. Á grunn PCB eru hlutarnir einbeittir á annarri hliðinni og vírarnir einbeittir á hina. 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.

Ef það eru hlutar á PCB sem hægt er að fjarlægja eða setja aftur á eftir framleiðslu, verður Socket notað til að setja hlutina upp. 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. Gullfingurinn inniheldur fjölda berra koparpúða sem eru í raun hluti af PCB raflögnum. Venjulega, til að tengja, setjum við gullfingur á annarri PCB í viðeigandi rauf (venjulega kallaður stækkunar rauf) á hinum PCB. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Græni eða brúni liturinn á PCB er liturinn á lóðmálmgrímunni. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Annar silki skjár verður prentaður á lóðmálmsþolið lag. 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

Þjóðsaga).

Einhliða stjórnir

Eins og við nefndum, á grunn PCB, eru hlutarnir einbeittir á annarri hliðinni og vírarnir einbeittir á hina. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Vegna þess að einar spjöld höfðu margar strangar takmarkanir á hönnun hringrásarinnar (vegna þess að það var aðeins ein hlið, raflögnin gátu ekki farið yfir og þurftu að fara sérstaka leið), aðeins snemma hringrás notaði slíkar stjórnir.

Tvíhliða stjórnir

Hringrásin er með raflögn á báðum hliðum. But in order to use both wires, there must be proper electrical connections between the two sides. Þessi „brú“ milli hringrása er kölluð leiðargat (VIA). Leiðargöt eru lítil göt í PCB fyllt eða húðuð með málmi sem hægt er að tengja við vír á báðum hliðum. 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

Til að auka flatarmál sem hægt er að tengja eru fleiri ein- eða tvíhliða raflagnir notaðir. Fjöllaga borðið notar nokkrar tvöfaldar spjöld og lag af einangrun er sett á milli hvers spjalds og límt (pressað). 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. Flestar stórtölvur nota allnokkur lög af móðurborðum en þau hafa fallið úr notkun þar sem hægt er að skipta þeim fyrir þyrpingar af venjulegum tölvum. 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.

Hluti umbúðatækni

Í gegnum holatækni

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. Þannig að liðirnir þeirra taka í raun pláss á báðum hliðum og lóðmálmur er tiltölulega stór. Á hinn bóginn eru THT hlutar betur tengdir PCB en Surface Mounted Technology (SMT) hlutar, sem við munum tala um síðar. 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.

Yfirborðslímhlutar geta jafnvel verið soðnir á báðum hliðum.

SMT hefur einnig minni hluta en 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

Í PCB hönnun eru í raun mjög löng skref að fara í gegnum formlegar raflagnir. Eftirfarandi er aðalhönnunarferlið:

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

Næsta skref er að búa til hagnýtt blokkarmynd af kerfinu. Tengslin milli ferninganna verða einnig að vera merkt.

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.

Ákveðið umbúðaaðferðina sem á að nota og stærð hvers 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. Einnig skal taka tillit til gæða og hraða hringrásarmyndarinnar þegar tæknin er valin.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. PCB í öllum kerfum verður að lýsa og flest þeirra nota CAD (Computer Aided Design) um þessar mundir. Here is an example of a CircuitMakerTM design.

Skýringarmynd af PCB hringrás

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. Þeir verða að tengjast brautinni á sem hagkvæmastan hátt. 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

Sum tölvuhugbúnaður í dag getur athugað hvort hægt sé að tengja staðsetningu hvers íhlutar rétt eða athuga hvort hann geti virkað rétt á miklum hraða. Þetta skref er kallað að raða hlutum, en við munum ekki fara of langt í þetta. Ef vandamál eru með hönnun hringrásarinnar er einnig hægt að endurraða hlutum áður en hringrásin er flutt út á sviði.

Útflutningsrás á PCB

The connections in the sketch will now look like wiring in the field. Þetta skref er venjulega fullkomlega sjálfvirkt, þó að venjulega sé þörf á handvirkum breytingum. Below is the wire template for 2 laminates. Rauðu og bláu línurnar tákna PCB hlutarlagið og suðu lagið í sömu röð. The white text and squares represent the markings on the screen printing surface. Rauðu punktarnir og hringirnir tákna boranir og leiðarholur. Lengst til hægri sjáum við gullfingur á suðuyfirborði PCB. 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. Þessar forskriftir eru mismunandi eftir hraða hringrásarinnar, styrk merkisins sem á að senda, næmi hringrásarinnar fyrir orkunotkun og hávaða og gæði efnisins og framleiðslutækisins. 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. Ef þörf er á fleiri en 2 lögum, er raflagið og jarðlagið venjulega notað til að koma í veg fyrir að sendimerki á merkislaginu hafi áhrif á það og hægt er að nota það sem skjöld merkislagsins.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Þessi próf leitar einnig að röngum tengingum og allar tengingar fylgja skýringarmyndinni.

Stofna og skrá

Vegna þess að nú eru mörg CAD verkfæri til að hanna PCBS verða framleiðendur að hafa snið sem uppfyllir staðlana áður en þeir geta framleitt spjöld. 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

Rafeindabúnaður sem ekki er hannaður samkvæmt EMC forskriftum mun líklega gefa frá sér rafsegulorku og trufla nálæg tæki. EMC setur hámarksmörk fyrir rafsegultruflanir (EMI), rafsegulsvið (EMF) og útvarpsbylgjutruflanir (RFI). This regulation can ensure the normal operation of the appliance and other nearby appliances. EMC setur strangar takmarkanir á magn orku sem hægt er að dreifa eða senda frá einu tæki til annars og er hannað til að draga úr næmi fyrir utanaðkomandi EMF, EMI, RFI osfrv. 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. Innra EMI, svo sem straumtap milli leiðara, eykst þegar tíðnin hækkar. Ef núverandi munur á þessu tvennu er of mikill, vertu viss um að lengja fjarlægðina á milli þeirra. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Töf á raflögn er einnig mikilvæg, þannig að því styttri lengd, því betra. Þannig að lítill PCB með góðum raflögnum mun virka betur á miklum hraða en stór PCB.