Ukukhuluma PCB ibhodi, many friends will think that it can be seen everywhere around us, from all household appliances, all kinds of accessories in the computer, to all kinds of digital products, as long as electronic products almost all use PCB board, so what is PCB board? A PCB is a PrintedCircuitBlock, which is a printed circuit board for electronic components to be inserted. A copperplated base plate is printed and etched out of the etching circuit.

PCB ibhodi ingahlukaniswa ungqimba olulodwa ibhodi, ungqimba kabili ibhodi futhi multi ungqimba ibhodi. Izingxenye ze-elekthronikhi zihlanganiswe ne-PCB. Ku-PCB eyisisekelo engqimba eyodwa, izingxenye zigxilwe ngakolunye uhlangothi nezintambo zigxilwe kolunye. Ngakho-ke sidinga ukwenza izimbobo ebhodini ukuze izikhonkwane zikwazi ukudlula ebhodini ziye kolunye uhlangothi, ngakho-ke izikhonkwane zezingxenye zishiselwe kolunye uhlangothi. Because of this, the positive and negative sides of such PCB are respectively called ComponentSide and SolderSide.

A double-layer board can be seen as two single-layer boards glued together, with electronic components and wiring on both sides of the board. Kwesinye isikhathi kuyadingeka ukuxhuma ucingo olulodwa ukusuka kolunye uhlangothi kuye kolunye uhlangothi lwebhodi ngomgodi wokuqondisa (nge). Izimbobo zomhlahlandlela izimbobo ezincane ku-PCB ezigcwele noma ezifakwe insimbi ezingaxhunywa ezintanjeni ezinhlangothini zombili. Manje amabhodi we-computer amaningi asebenzisa izingqimba ezi-4 noma ezi-6 zebhodi le-PCB, kanti amakhadi emidwebo ngokuvamile asebenzisa izingqimba ezi-6 zebhodi le-PCB. Amakhadi wehluzo amaningi asezingeni eliphezulu afana nVIDIAGeForce4Ti chungechunge asebenzisa izingqimba eziyi-8 zebhodi le-PCB, elibizwa ngebhodi le-multi-layer PCB. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Ngoba iyi-PCB enezingqimba eziningi, kwesinye isikhathi izimbobo zomhlahlandlela azidingi ukungena kulo lonke i-PCB. Izimbobo ezinjalo zomhlahlandlela zibizwa ngokuthi iBuriedvias neBlindvias ngoba zingena kuphela ezingqimbeni ezimbalwa. Izimbobo eziyimpumputhe zixhuma izingqimba eziningana ze-PCBS zangaphakathi kuma-PCBS angaphandle kokungena kulo lonke ibhodi. Izimbobo ezingcwatshwe zixhunywe kwi-PCB yangaphakathi kuphela, ngakho ukukhanya akubonakali ebusweni. Ku-PCB e-multilayer, ungqimba wonke uxhunywe ngqo ocingweni lomhlaba nokunikezwa kwamandla. Ngakho-ke sihlukanisa izingqimba njengeSiginali, Amandla noma iGround. Uma izingxenye ku-PCB zidinga amandla kagesi ahlukile, imvamisa zinezingqimba zamandla nezintambo ezingaphezu kwezimbili. The more layers you use, the higher the cost. Of course, the use of more layers of PCB board to provide signal stability is very helpful.

The process of making a professional PCB board is quite complicated. Take a 4-layer PCB board for example. I-PCB yebhodi eliyinhloko ikakhulukazi izingqimba ezi-4. Lapho kwenziwa, izingqimba ezimbili eziphakathi ziyasongwa, zisikwe, ziqoshwe, zifakwe i-oxidized futhi zikhethwe ngokulandelana. Izendlalelo ezine zingaphezulu kwengxenye, ungqimba lwamandla, umucu kanye ne-solder lamination ngokulandelana. Izendlalelo ezine bese zicindezelwa ndawonye ukwenza i-PCB yebhodi elikhulu. Then the holes were punched and made. Ngemuva kokuhlanza, izingqimba ezimbili zangaphandle zomugqa ziphrintiwe, ithusi, ukuthwebula, ukuhlolwa, ungqimba lokumelana nokushisela, ukuphrinta kwesikrini. Ekugcineni, yonke i-PCB (kufaka phakathi amabhodi womama amaningi) igxivizwa ibe yi-PCB yebhodi lomama ngalinye, bese kuthi ukupakisha komshini kwenziwe ngemuva kokudlula esivivinyweni. If the copper skin is not well coated in THE process of PCB production, there will be poor adhesion phenomenon, easy to imply short circuit or capacitance effect (easy to cause interference). The holes on PCB must also be taken care of. If the hole is punched not in the middle, but on one side, it will result in uneven matching or easy contact with the power supply layer or formation in the middle, resulting in potential short-circuiting or bad grounding factors.

Copper wiring process

The first step in fabrication is to establish an online wiring between parts. We use negative transfer to express the working negative on a metal conductor. Ubuqili ukusabalalisa ungqimba oluncane lwefoyile yethusi phezu kobuso bonke bese ususa noma ikuphi okweqile. Ukufaka isicelo sokudlulisa kungenye indlela engasetshenziswanga kangako, okungukufaka ucingo lwethusi kuphela lapho kudingeka khona, kepha ngeke sikhulume ngakho lapha.

Positive photoresists are made from photosensitizers that dissolve under illumination. There are many ways to treat photoresist on copper, but the most common way is to heat it and roll it over a surface containing photoresist. It can also be sprayed in liquid form, but the dry film provides higher resolution and allows for thinner wires. I-hood iyisifanekiso nje sokwenza izingqimba ze-PCB. Isigqoko esimboza i-photoresist ku-PCB sivimbela izindawo ezithile ze-photoresist ukuthi zivezwe kuze kube yilapho i-photoresist ivezwa ukukhanya kwe-UV. These areas, which are covered with photoresist, will become wiring. Ezinye izingxenye zethusi ezingenalutho ezizofakwa ngemuva kokuthuthuka kwe-photoresist. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Isetshenziswa ngokujwayelekile njenge-solching solvent isebenzisa i-ferric chloride njll. After etching, remove the remaining photoresist.

1.Wiring ububanzi futhi zamanje

General width should not be less than 0.2mm (8mil)

On high density and high precision PCBS, pitch and line width are generally 0.3mm (12mil).

Lapho ukushuba kocwecwe lwethusi kumayelana no-50um, ububanzi bocingo bungu-1 ~ 1.5mm (60mil) = 2A

Umhlabathi ovamile ngokuvamile yi-80mil, ikakhulukazi kuzinhlelo zokusebenza ezine-microprocessors.

2.Iphakama kangakanani imvamisa yebhodi elinejubane elikhulu?

Lapho ukukhuphuka / ukuwa kwesikhathi sesiginali “izikhathi ezi-3 ~ 6 isikhathi sokudluliswa kwesiginali, kubhekwa njengesiginali yesivinini esikhulu.

Kumasekethe edijithali, ukhiye ukubuka ukuqina kwesiginali, isikhathi esithathayo ukuphakama nokuwa,

According to a very classic book “High Speed Digtal Design” theory, the signal from 10% to 90% of the time is less than 6 times the wire delay, is high-speed signal! – – – – – – okungukuthi! Even 8KHz square wave signals, as long as the edges are steep enough, are still high-speed signals, and transmission line theory needs to be used in wiring

3.PCB ukustaka nokubeka

The four – layer plate has the following stacking sequence. Ubuhle nobubi be-lamination ehlukile buchazwe ngezansi:

Icala lokuqala kufanele libe lihamba phambili kulezi zingqimba ezine. Because the outer layer is the stratum, it has a shielding effect on EMI. Meanwhile, the power supply layer is reliable and close to the stratum, which makes the internal resistance of the power supply smaller and achieves the best suburbs. Kodwa-ke, icala lokuqala alinakusetshenziswa lapho ukuminyana kwebhodi kuphakeme kakhulu. Ngoba-ke, ubuqotho besendlalelo sokuqala abuqinisekisiwe, futhi isignali yesendlalelo yesibili yimbi kakhulu. Ngaphezu kwalokho, lesi sakhiwo asinakusetshenziswa esimweni sokusetshenziswa kwamandla amakhulu kwebhodi lonke.

The second case is the one we usually use the most. Kusukela ekwakhiweni kwebhodi, ayifanele ukuklanywa kwesifunda esinejubane eliphezulu. Kunzima ukugcina impedance yamandla aphansi kulesi sakhiwo. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Ngakho-ke ungqimba lwesiginali kanye nendawo yokwakheka kungu-0.14mm. The formation and power layer are 1.58mm. This greatly increases the internal resistance of the power supply. In this kind of structure, because the radiation is to the space, shielding plate is needed to reduce EMI.

In the third case, the signal line on layer S1 has the best quality. I-S2. Ukuvikelwa kwe-EMI. But the power supply impedance is large. This board can be used when the power consumption of the whole board is high and the board is an interference source or adjacent to the interference source.

4. Impedance matching

Ubukhulu besiginali yamandla wevolthi ebonakalisiwe bunqunywa ngumlingani wokukhombisa umthombo ρ S kanye nomlinganiso wokukhombisa umthwalo ρL

ρL = (RL-z0)/(RL + Z0) and ρS = (rS-z0)/(RS + Z0)

Ku-equation engenhla, uma i-RL = Z0, inani lokulinganisa lomthwalo ρL = 0. Uma i-RS = Z0 coefficient reflection reflection ρS = 0.

Ngoba i-impedance ejwayelekile yokuhambisa umugqa i-Z0 kufanele ihlangabezane nezidingo ze-50 ω 50 ω, futhi i-impedance yokulayisha ivame ukuba sezinkulungwaneni zama-ohms kuya kumashumi ezinkulungwane zama-ohms. Ngakho-ke, kunzima ukubona ukufana kwe-impedance ohlangothini lomthwalo. Kodwa-ke, ngoba impedance yomthombo wesiginali (okukhiphayo) imvamisa incane kakhulu, cishe emashumini ama-ohms. Ngakho-ke kulula kakhulu ukusebenzisa ukufana kwe-impedance emthonjeni. Uma i-resistor ixhunywe ekugcineni komthwalo, i-resistor izomunca ingxenye yesiginali ukulimaza ukudluliswa (ukuqonda kwami). Lapho kukhethwa i-TTL / CMOS standard 24mA drive yamanje, impedance yayo yokukhipha icishe ibe ngu-13 ω. Uma i-impedance yolayini wokudlulisa i-Z0 = 50 ω, khona-ke kufanele kungezwe i-resistor yomthombo wokugcina ongu-33.. I-13 ω +33 ω = 46 ω (cishe ama-50 ω, ukwehlisa amandla okubuthakathaka kusiza isikhathi sokusetha isiginali)

Lapho kukhethwa amanye amazinga wokudlulisa nemisinga yokushayela, impedance efanayo ingahluka. Ngomqondo wejubane eliphezulu nokwakhiwa kwesifunda, kwamanye amasiginali asemqoka, njengewashi, amasiginali wokulawula, sincoma ukuthi imishini yokuphikisana nomthombo kufanele ingezwe.

Ngale ndlela, isignali exhunyiwe izokhonjiswa emuva ohlangothini lomthwalo, ngoba umthombo we-impedance womthombo, isignali ekhonjisiwe ngeke iphinde iboniswe emuva.