Printed mzunguko wa bodi (PCB) hupatikana karibu kila aina ya kifaa cha elektroniki. Ikiwa kuna vifaa vya elektroniki kwenye kipande cha vifaa, vimewekwa pia kwa saizi anuwai za PCB. Mbali na kurekebisha sehemu ndogo ndogo, kazi kuu ya PCB ni kutoa unganisho la umeme kati ya vifaa. 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 ya kawaida inaonekana kama hii. 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. Nyenzo ndogo ya laini ambayo inaweza kuonekana juu ya uso ni karatasi ya shaba. Hapo awali, karatasi ya shaba imefunikwa kwenye ubao mzima, na sehemu ya kati imewekwa katika mchakato wa utengenezaji, na sehemu iliyobaki inakuwa mtandao wa laini ndogo. Mistari hii inaitwa makondakta au makondakta na hutumiwa kutoa unganisho la umeme kwa sehemu kwenye PCB.

To secure parts to the PCB, we solder their pins directly to the wiring. Kwenye PCB ya msingi, sehemu hizo zinajilimbikizia upande mmoja na waya zinajilimbikizia upande mwingine. 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.

Ikiwa kuna sehemu kwenye PCB ambazo zinaweza kuondolewa au kuwekwa tena baada ya utengenezaji, Tundu litatumika kusanikisha sehemu hizo. 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. Lever iliyo karibu na tundu inaweza kushikilia sehemu hizo baada ya kuziingiza.

To connect two PCBS to each other, an edge connector is commonly used. Kidole cha dhahabu kina idadi ya pedi za wazi za shaba ambazo kwa kweli ni sehemu ya wiring ya PCB. Kwa kawaida, kuungana, tunaingiza kidole cha dhahabu kwenye PCB moja kwenye Slot inayofaa (kawaida huitwa Slot ya upanuzi) kwenye PCB nyingine. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Rangi ya kijani au hudhurungi kwenye PCB ni rangi ya kinyago cha solder. Safu hii ni ngao ya kuhami ambayo inalinda waya wa shaba na inazuia sehemu kutoka svetsade kwenda mahali pabaya. Skrini nyingine ya hariri itachapishwa kwenye safu ya upinzani ya solder. Kawaida huchapishwa na maneno na alama (zaidi nyeupe) kuonyesha msimamo wa sehemu kwenye ubao. Screen printing surface is also known as icon surface

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Bodi za upande mmoja

Kama tulivyosema, kwenye PCB ya msingi, sehemu hizo zinajilimbikizia upande mmoja na waya zinajilimbikizia upande mwingine. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Kwa sababu paneli moja zilikuwa na vizuizi vikali juu ya muundo wa mzunguko (kwa sababu kulikuwa na upande mmoja tu, wiring haikuweza kuvuka na ilibidi ichukue njia tofauti), nyaya tu za mapema zilitumia bodi kama hizo.

Bodi zenye pande mbili

Bodi ya mzunguko ina wiring pande zote mbili. Lakini ili kutumia waya zote mbili, lazima kuwe na unganisho sahihi la umeme kati ya pande hizo mbili. “Daraja” hili kati ya mizunguko huitwa shimo mwongozo (VIA). Mashimo ya mwongozo ni mashimo madogo kwenye PCB iliyojazwa au kufunikwa na chuma ambayo inaweza kushikamana na waya pande zote mbili. 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

Ili kuongeza eneo ambalo linaweza kuwa na waya, bodi za wiring zaidi au mbili-upande hutumiwa. Bodi ya multilayer hutumia paneli kadhaa mara mbili, na safu ya insulation imewekwa kati ya kila jopo na glued (taabu). Idadi ya matabaka ya bodi inawakilisha safu kadhaa za wiring huru, kawaida idadi hata ya tabaka, pamoja na tabaka mbili za nje. Most motherboards are built with four to eight layers, but it is technically possible to build up to 100 layers of PCBS. Watumiaji wengi wa kompyuta kubwa hutumia matabaka machache ya bodi za mama, lakini zimetoweka kutumika kwani zinaweza kubadilishwa na nguzo za kompyuta za kawaida. 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.

Shimo la mwongozo (VIA) ambalo tumetaja tu, ikiwa linatumiwa kwa jopo mara mbili, lazima liwe kupitia bodi nzima

Lakini katika safu nyingi, ikiwa unataka tu kuunganisha mistari, mashimo ya mwongozo yanaweza kupoteza nafasi ya mstari kwenye safu zingine. 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. Mashimo ya kuzikwa yameunganishwa tu na PCB ya ndani, kwa hivyo mwanga hauonekani kutoka juu.

In a multilayer PCB, the entire layer is directly connected to the ground wire and the power supply. Kwa hivyo tunaainisha tabaka kama Signal, Power au Ground. If the parts on the PCB require different power supplies, they usually have more than two power and wire layers.

Teknolojia ya ufungaji wa sehemu

Kupitia Teknolojia ya Shimo

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. Sehemu hii inachukua nafasi nyingi na shimo moja linachimbwa kwa kila pini. Kwa hivyo viungo vyao huchukua nafasi pande zote mbili, na viungo vya solder ni kubwa sana. Kwa upande mwingine, sehemu za THT zimeunganishwa vizuri na PCB kuliko sehemu za Teknolojia ya Juu (SMT), ambayo tutazungumza baadaye. Sockets like wired sockets and similar interfaces need to be pressure-tolerant, so they are usually THT packages.

Teknolojia ya Uso uliowekwa

Kwa sehemu za Teknolojia ya Juu (SMT), pini imeunganishwa upande huo na sehemu. This technique does not drill holes in the PCB for each pin.

Sehemu za wambiso wa uso zinaweza hata kuunganishwa pande zote mbili.

SMT pia ina sehemu ndogo kuliko 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

Katika muundo wa PCB, kwa kweli kuna hatua ndefu sana za kupita kabla ya wiring rasmi. Ifuatayo ni mchakato kuu wa kubuni:

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

Hatua inayofuata ni kuunda mchoro wa kuzuia mfumo. Uhusiano kati ya mraba lazima pia uweke alama.

Divide the system into several PCBS

Kugawanya mfumo kuwa PCBS kadhaa sio tu inapunguza saizi, lakini pia huipa mfumo uwezo wa kuboresha na kubadilisha sehemu. 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.

Tambua njia ya ufungaji itakayotumika na saizi ya kila 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. Ubora na kasi ya mchoro wa mzunguko inapaswa pia kuzingatiwa wakati wa kuchagua teknolojia.

Chora michoro za mzunguko wa PCB zote

Maelezo ya unganisho kati ya sehemu inapaswa kuonyeshwa kwenye mchoro. PCB katika mifumo yote lazima ielezwe, na wengi wao hutumia CAD (Ubunifu wa Kompyuta) kwa sasa. Here is an example of a CircuitMakerTM design.

Mchoro wa kimkakati wa mzunguko wa PCB

Preliminary design of simulation operation

To ensure that the designed circuit diagram works, it must first be simulated using computer software. Programu kama hiyo inaweza kusoma michoro na kuonyesha jinsi mzunguko unafanya kazi kwa njia nyingi. This is much more efficient than actually making a sample PCB and then measuring it manually.

Place the parts on the PCB

Njia ambazo sehemu zinawekwa hutegemea jinsi zinavyounganishwa kwa kila mmoja. Lazima ziunganishwe na njia kwa njia bora zaidi. 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

Baadhi ya programu za kompyuta za leo zinaweza kuangalia ikiwa uwekaji wa kila sehemu unaweza kushikamana kwa usahihi, au angalia ikiwa inaweza kufanya kazi kwa usahihi kwa kasi kubwa. Hatua hii inaitwa kupanga sehemu, lakini hatutaenda mbali sana katika hii. Ikiwa kuna shida na muundo wa mzunguko, sehemu zinaweza pia kupangwa upya kabla ya mzunguko kusafirishwa uwanjani.

Export mzunguko juu ya PCB

The connections in the sketch will now look like wiring in the field. Hatua hii kawaida huwa otomatiki, ingawa kawaida mabadiliko ya mwongozo huhitajika. Below is the wire template for 2 laminates. Mistari nyekundu na bluu inawakilisha safu ya sehemu za PCB na safu ya kulehemu mtawaliwa. Nakala nyeupe na mraba zinawakilisha alama kwenye uso wa kuchapisha skrini. Dots nyekundu na miduara inawakilisha mashimo ya kuchimba visima na kuongoza. Kulia kabisa tunaweza kuona kidole cha dhahabu kwenye uso wa kulehemu wa 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. Uainishaji huu hutofautiana kulingana na kasi ya mzunguko, nguvu ya ishara inayoweza kupitishwa, unyeti wa mzunguko kwa matumizi ya nguvu na kelele, na ubora wa vifaa na vifaa vya utengenezaji. 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. Ikiwa zaidi ya tabaka 2 zinahitajika, safu ya nguvu na safu ya ardhi kawaida hutumiwa kuzuia ishara ya usambazaji kwenye safu ya ishara imeathiriwa, na inaweza kutumika kama ngao ya safu ya ishara.

Waya baada ya mtihani wa mzunguko

Ili kuhakikisha kuwa laini inafanya kazi vizuri nyuma ya waya, lazima ipitishe mtihani wa mwisho. Jaribio hili pia linaangalia muunganisho usio sahihi, na maunganisho yote yanafuata mchoro wa skimu.

Anzisha na uweke faili

Kwa sababu kwa sasa kuna zana nyingi za CAD za kuunda PCBS, wazalishaji lazima wawe na wasifu ambao unakidhi viwango kabla ya kutengeneza bodi. Kuna vipimo kadhaa vya kawaida, lakini kawaida ni vipimo vya Faili za Gerber. Seti ya faili za Gerber ni pamoja na mpango wa kila ishara, nguvu na safu ya ardhi, mpango wa safu ya upinzani ya solder na uso wa kuchapisha skrini, na faili maalum za kuchimba visima na kuhamisha makazi.

Electromagnetic compatibility problem

Vifaa vya elektroniki ambavyo havijatengenezwa kwa uainishaji wa EMC vinaweza kutoa nishati ya umeme na kuingiliana na vifaa vya karibu. EMC inaweka mipaka ya kiwango cha juu kwa kuingiliwa kwa umeme (EMI), uwanja wa umeme (EMF) na kuingiliwa kwa masafa ya redio (RFI). Kanuni hii inaweza kuhakikisha utendaji wa kawaida wa kifaa na vifaa vingine vya karibu. EMC inaweka mipaka madhubuti juu ya kiwango cha nishati inayoweza kutawanyika au kupitishwa kutoka kifaa kimoja hadi kingine, na imeundwa ili kupunguza uwezekano wa EMF ya nje, EMI, RFI, na kadhalika. 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. EMI ya ndani, kama vile upotezaji wa sasa kati ya makondakta, huongezeka kadiri mzunguko unavyoongezeka. Ikiwa tofauti ya sasa kati ya hizi ni kubwa sana, hakikisha kuongeza urefu kati yao. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Kiwango cha kuchelewa kwa wiring pia ni muhimu, kwa hivyo urefu mfupi ni bora. Kwa hivyo PCB ndogo na wiring nzuri itafanya kazi vizuri kwa kasi kubwa kuliko PCB kubwa.