Clóbhuailte ciorcad Faightear (PCB) i mbeagnach gach cineál feiste leictreonach. 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. Ar PCB bunúsach, tá na codanna dírithe ar thaobh amháin agus tá na sreanga dírithe ar an taobh eile. 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.

Má tá páirteanna ar an PCB is féidir a bhaint nó a chur ar ais tar éis a monaraithe, úsáidfear Soicéad chun na codanna a shuiteáil. 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. Tá roinnt ceap lom copair sa mhéar óir atá mar chuid den sreangú PCB i ndáiríre. De ghnáth, chun nasc a dhéanamh, cuirimid an mhéar óir ar PCB amháin isteach sa Sliotán cuí (ar a dtugtar Sliotán leathnúcháin de ghnáth) ar an PCB eile. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Is é an dath glas nó donn ar an PCB dath an masc solder. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Déanfar scáileán síoda eile a phriontáil ar an gciseal friotaíochta solder. 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

Finscéal).

Boird Aon-Thaobh

Mar a luadh muid, ar PCB bunúsach, tá na codanna comhchruinnithe ar thaobh amháin agus tá na sreanga dírithe ar an taobh eile. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Toisc go raibh go leor srianta dochta ar phainéil aonair ar dhearadh an chiorcaid (toisc nach raibh ann ach taobh amháin, ní fhéadfadh an sreangú trasnú agus b’éigean dóibh cosán ar leithligh a thógáil), níor úsáid ach ciorcaid luatha cláir den sórt sin.

Boird dhá thaobh

Tá sreangú ag an mbord ciorcad ar an dá thaobh. But in order to use both wires, there must be proper electrical connections between the two sides. Tugtar poll treorach (VIA) ar an “droichead” seo idir ciorcaid. Is poill bheaga iad poill treorach sa PCB atá líonta nó brataithe le miotail is féidir a nascadh le sreanga ar an dá thaobh. 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

D’fhonn an limistéar is féidir a shreangú a mhéadú, úsáidtear níos mó clár sreangaithe aon-thaobh nó dhá thaobh. Úsáideann an bord multilayer roinnt painéal dúbailte, agus cuirtear sraith inslithe idir gach painéal agus greamaithe (brúite). 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. Baineann an chuid is mó de na sár-ríomhairí móra úsáid as cúpla sraith de mháthairchláir, ach tá siad as úsáid mar is féidir braislí de ghnáth ríomhairí a chur ina n-áit. 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.

Teicneolaíocht phacáistithe páirteach

Trí Theicneolaíocht Poll

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. Mar sin glacann a gcuid hailt spás ar an dá thaobh i ndáiríre, agus tá na hailt solder réasúnta mór. Ar an láimh eile, is fearr páirteanna THT a nascadh le PCB ná páirteanna Teicneolaíochta Dromchla (SMT), a mbeimid ag caint fúthu níos déanaí. 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.

Is féidir páirteanna greamaitheacha dromchla a tháthú fiú ar an dá thaobh.

Tá codanna níos lú ag SMT ná THT freisin. 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

I ndearadh PCB, tá céimeanna an-fhada le dul i ndáiríre sula ndéantar sreangú foirmiúil. Seo a leanas an príomhphróiseas dearaidh:

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

Is é an chéad chéim eile blocléaráid fheidhmiúil den chóras a chruthú. Caithfear an gaol idir na cearnóga a mharcáil freisin.

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.

Faigh amach an modh pacáistithe atá le húsáid agus méid gach 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. Ba cheart cáilíocht agus luas an léaráid chiorcaid a chur san áireamh agus an teicneolaíocht á roghnú.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. Caithfear cur síos a dhéanamh ar PCB i ngach córas, agus úsáideann an chuid is mó díobh CAD (Dearadh Ríomhchuidithe) faoi láthair. Here is an example of a CircuitMakerTM design.

Léaráid scéimeach de chiorcad PCB

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. Caithfidh siad a bheith ceangailte leis an gcosán ar an mbealach is éifeachtaí. 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

Is féidir le cuid de bhogearraí ríomhaireachta an lae inniu seiceáil an féidir socrúchán gach comhpháirte a nascadh i gceart, nó seiceáil an féidir leis oibriú i gceart ar luas ard. Tugtar páirteanna eagraithe ar an gcéim seo, ach ní rachaimid rófhada isteach ina leith seo. Má tá fadhb ann le dearadh an chiorcaid, is féidir páirteanna a atheagrú freisin sula ndéantar an ciorcad a onnmhairiú sa réimse.

Ciorcad easpórtála ar PCB

The connections in the sketch will now look like wiring in the field. This step is usually fully automated, although manual changes are usually required. Below is the wire template for 2 laminates. Léiríonn na línte dearga agus gorma ciseal páirteanna PCB agus an ciseal táthúcháin faoi seach. The white text and squares represent the markings on the screen printing surface. Léiríonn na poncanna dearga agus na ciorcail poill druileála agus treorach. Ar thaobh na láimhe deise is féidir linn an mhéar óir a fheiceáil ar dhromchla táthúcháin an 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. Athraíonn na sonraíochtaí seo de réir luas an chiorcaid, neart na comhartha atá le tarchur, íogaireacht an chiorcaid maidir le tomhaltas cumhachta agus torann, agus cáilíocht an ábhair agus an trealaimh déantúsaíochta. 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. Má theastaíonn níos mó ná 2 shraith, is gnách go n-úsáidtear an ciseal cumhachta agus an ciseal talún chun an comhartha tarchuir ar an gciseal comhartha a sheachaint, agus is féidir é a úsáid mar sciath den chiseal comhartha.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Seiceálann an tástáil seo naisc mhícheart freisin, agus leanann gach nasc an léaráid scéimeach.

Bunaigh agus comhdaigh

Because there are currently many CAD tools for designing PCBS, manufacturers must have a profile that meets the standards before they can manufacture boards. 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

Is dóigh go n-astaíonn feistí leictreonacha nach bhfuil deartha de réir shonraíochtaí EMC fuinneamh leictreamaighnéadach agus go gcuirfidh siad isteach ar fhearais in aice láimhe. Cuireann EMC uasteorainneacha ar chur isteach leictreamaighnéadach (EMI), réimse leictreamaighnéadach (EMF) agus cur isteach minicíochta raidió (RFI). This regulation can ensure the normal operation of the appliance and other nearby appliances. Cuireann EMC teorainneacha dochta ar an méid fuinnimh is féidir a scaipeadh nó a tharchur ó ghaireas amháin go gléas eile, agus tá sé deartha chun an so-ghabháltacht i leith EMF seachtrach, EMI, RFI, agus mar sin de, a laghdú. 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. Méadaíonn IEA inmheánach, amhail an caillteanas reatha idir seoltóirí, de réir mar a ardaíonn an mhinicíocht. If the current difference between the two is too large, make sure to lengthen the distance between them. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Tá an ráta moille ar shreangú tábhachtach freisin, mar sin is giorra an fad, is amhlaidh is fearr. Mar sin oibreoidh PCB beag le sreangú maith níos fearr ar luas ard ná PCB mór.