B’ċirkwit stampat (PCB) jinsabu fi kważi kull tip ta ‘apparat elettroniku. 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. PCB standard jidher xi ħaġa bħal din. 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. Fuq PCB bażiku, il-partijiet huma kkonċentrati fuq naħa waħda u l-wajers huma kkonċentrati fuq in-naħa l-oħra. 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.

Jekk hemm partijiet fuq il-PCB li jistgħu jitneħħew jew jerġgħu jitpoġġew wara l-manifattura, Socket jintuża biex jiġu installati l-partijiet. 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. Is-saba ‘tad-deheb fih numru ta’ pads tar-ram mikxufin li fil-fatt huma parti mill-wajers tal-PCB. Normalment, biex tikkonnettja, daħħalna s-saba ‘tad-deheb fuq PCB wieħed fis-Slott xieraq (komunement imsejjaħ Slot ta’ espansjoni) fuq il-PCB l-ieħor. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Il-kulur aħdar jew kannella fuq il-PCB huwa l-kulur tal-maskra tal-istann. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Skrin ieħor tal-ħarir se jkun stampat fuq is-saff ta ‘reżistenza għall-istann. 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

Leġġenda).

Bordijiet fuq naħa waħda

Kif semmejna, fuq PCB bażiku, il-partijiet huma kkonċentrati fuq naħa waħda u l-wajers huma kkonċentrati fuq in-naħa l-oħra. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Minħabba li pannelli singoli kellhom ħafna restrizzjonijiet stretti fuq id-disinn taċ-ċirkwit (minħabba li kien hemm naħa waħda biss, il-wajers ma setgħux jaqsmu u kellhom jieħdu triq separata), ċirkwiti bikrija biss użaw bordijiet bħal dawn.

Bordijiet b’żewġ naħat

Iċ-ċirkwit għandu wajers fuq iż-żewġ naħat. But in order to use both wires, there must be proper electrical connections between the two sides. Dan il- “pont” bejn ċirkwiti jissejjaħ toqba ta ‘gwida (VIA). It-toqob tal-gwida huma toqob żgħar fil-PCB mimlija jew miksija b’metall li jistgħu jiġu mqabbda ma ‘wajers fuq iż-żewġ naħat. 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

Sabiex tiżdied iż-żona li tista ‘tkun bil-fili, jintużaw aktar bordijiet tal-wajers b’żewġ naħat jew b’żewġ naħat. Il-bord b’ħafna saffi juża bosta pannelli doppji, u saff ta ‘insulazzjoni jitqiegħed bejn kull pannell u inkollat ​​(ippressat). 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. Il-biċċa l-kbira tas-superkompjuters kbar jużaw pjuttost ftit saffi ta ‘motherboards, iżda ma baqgħux jintużaw peress li jistgħu jiġu sostitwiti minn raggruppamenti ta’ kompjuters ordinarji. 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.

Teknoloġija tal-ippakkjar tal-partijiet

Permezz tat-Teknoloġija Toqba

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. Allura l-ġonot tagħhom fil-fatt jieħdu spazju fuq iż-żewġ naħat, u l-ġonot tal-istann huma relattivament kbar. Min-naħa l-oħra, il-partijiet THT huma konnessi aħjar mal-PCB minn partijiet tal-Surface Mounted Technology (SMT), li dwarhom se nitkellmu aktar tard. 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.

Partijiet adeżivi tal-wiċċ jistgħu saħansitra jiġu wweldjati fuq iż-żewġ naħat.

SMT għandu wkoll partijiet iżgħar minn 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

Fid-disinn tal-PCB, fil-fatt hemm passi twal ħafna x’għandek tgħaddi qabel il-wajers formali. Dan li ġej huwa l-proċess tad-disinn ewlieni:

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

Il-pass li jmiss huwa li tinħoloq dijagramma blokka funzjonali tas-sistema. Ir-relazzjoni bejn il-kwadri trid tkun immarkata wkoll.

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.

Iddetermina l-metodu ta ‘ppakkjar li għandu jintuża u d-daqs ta’ kull 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. Il-kwalità u l-veloċità tad-dijagramma taċ-ċirkwit għandhom jiġu kkunsidrati wkoll meta tintgħażel it-teknoloġija.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. Il-PCB fis-sistemi kollha għandhom jiġu deskritti, u ħafna minnhom jużaw CAD (Computer Aided Design) fil-preżent. Here is an example of a CircuitMakerTM design.

Dijagramma skematika taċ-ċirkwit tal-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. Għandhom ikunu konnessi mat-triq bl-iktar mod effiċjenti. 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

Uħud mis-softwer tal-kompjuter tal-lum jistgħu jivverifikaw jekk it-tqegħid ta ‘kull komponent jistax ikun imqabbad b’mod korrett, jew jivverifika jekk jistax jaħdem sewwa b’veloċità għolja. Dan il-pass jissejjaħ jirranġa partijiet, imma aħna mhux se nidħlu ‘l bogħod wisq f’dan. Jekk hemm problema bid-disinn taċ-ċirkwit, il-partijiet jistgħu wkoll jiġu rranġati mill-ġdid qabel ma ċ-ċirkwit jiġi esportat fil-post.

Ċirkwit tal-esportazzjoni fuq il-PCB

The connections in the sketch will now look like wiring in the field. Dan il-pass huwa ġeneralment kompletament awtomatizzat, għalkemm bidliet manwali huma ġeneralment meħtieġa. Below is the wire template for 2 laminates. Il-linji ħomor u blu jirrappreżentaw is-saff tal-partijiet tal-PCB u s-saff tal-iwweldjar rispettivament. The white text and squares represent the markings on the screen printing surface. Il-tikek ħomor u ċ-ċrieki jirrappreżentaw toqob għat-tħaffir u l-gwida. Fuq il-lemin estrem nistgħu naraw is-saba ‘tad-deheb fuq il-wiċċ tal-iwweldjar tal-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. Dawn l-ispeċifikazzjonijiet ivarjaw skont il-veloċità taċ-ċirkwit, is-saħħa tas-sinjal li għandu jiġi trasmess, is-sensittività taċ-ċirkwit għall-konsum tal-enerġija u l-istorbju, u l-kwalità tal-materjal u t-tagħmir tal-manifattura. 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. Jekk huma meħtieġa aktar minn 2 saffi, is-saff ta ‘l-enerġija u s-saff ta’ l-art ġeneralment jintużaw biex jiġi evitat is-sinjal tat-trasmissjoni fuq is-saff tas-sinjal huwa affettwat, u jistgħu jintużaw bħala tarka tas-saff tas-sinjal.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Dan it-test jikkontrolla wkoll għal konnessjonijiet mhux korretti, u l-konnessjonijiet kollha jsegwu d-dijagramma skematika.

Stabbilixxi u ffajlja

Minħabba li bħalissa hemm ħafna għodod CAD għat-tfassil tal-PCBS, il-manifatturi għandu jkollhom profil li jissodisfa l-istandards qabel ma jkunu jistgħu jimmanifatturaw bordijiet. 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

Apparati elettroniċi li mhumiex iddisinjati għall-ispeċifikazzjonijiet EMC x’aktarx li jarmu enerġija elettromanjetika u jinterferixxu ma ‘apparat fil-qrib. L-EMC timponi limiti massimi fuq l-interferenza elettromanjetika (EMI), il-kamp elettromanjetiku (EMF) u l-interferenza tal-frekwenza tar-radju (RFI). Dan ir-regolament jista ‘jiżgura t-tħaddim normali tal-apparat u apparat ieħor fil-qrib. L-EMC timponi limiti stretti fuq l-ammont ta ‘enerġija li tista’ tkun imxerrda jew trasmessa minn apparat għal ieħor, u hija mfassla biex tnaqqas is-suxxettibilità għal EMF esterni, EMI, RFI, eċċ. 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. L-EMI intern, bħat-telf tal-kurrent bejn il-kondutturi, jiżdied hekk kif il-frekwenza togħla. Jekk id-differenza attwali bejn it-tnejn hija kbira wisq, kun żgur li ttawwal id-distanza bejniethom. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Ir-rata ta ‘dewmien fil-wajers hija wkoll importanti, allura iktar ma jkun iqsar it-tul, aħjar. Allura PCB żgħir b’wajering tajjeb jaħdem aħjar b’veloċitajiet għoljin minn PCB kbir.