Ukuthetha Ibhodi PCB, 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.

Ibhodi PCB lungohlulwa lube ibhodi maleko olunye, ibhodi maleko kabini kunye nebhodi maleko multi. Izinto zombane zidityaniswe kwi-PCB. Kwisiseko sePCB yomaleko omnye, izinto zigxile kwelinye icala kwaye iingcingo zigxile kwelinye. Ke kufuneka senze imingxunya ebhodini ukuze izikhonkwane zingene ebhodini ziye kwelinye icala, ke izikhonkwane zamalungu zi-welding kwelinye icala. 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. Ngamanye amaxesha kuye kufuneke ukuba uqhagamshele ucingo olunye ukusuka kwelinye icala ukuya kwelinye icala lebhodi ngomngxunya wesikhokelo (nge). Imingxunya yesikhokelo yimingxunya emincinci kwi-PCB ezaliswe okanye egalelwe isinyithi enokuqhagamshelwa kwiingcingo kumacala omabini. Ngoku uninzi lwee-motherboards zekhompyuter zisebenzisa ii-4 okanye ii-6 zeebhodi zebhodi ye-PCB, ngelixa amakhadi emizobo ngokubanzi esebenzisa iileya ezi-6 zebhodi yePCB. Amakhadi emizobo aphezulu aphezulu njenge-nVIDIAGeForce4Ti uthotho lusebenzisa ii-8 zeebhodi zePCB, ebizwa ngokuba yibhodi yePCB emininzi. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Ngenxa yokuba i-PCB enemigangatho emininzi, ngamanye amaxesha imingxunya yesikhokelo ayifuni ukungena kwi-PCB iphela. Imingxunya yesikhokelo enjalo ibizwa ngokuba yiBuriedvias kunye neBlindvias kuba zingena kuphela kwizingqengqelo ezimbalwa. Imingxunya engaboniyo idibanisa ii-PCBS zangaphakathi kumphezulu wePCBS ngaphandle kokungena kuyo yonke ibhodi. Imingxunya yokungcwatywa ixhunyiwe kuphela kwi-PCB yangaphakathi, ke ukukhanya akubonakali ngaphezulu. Kwi-PCB ye-multilayer, wonke umaleko uqhagamshelwe ngqo kwicingo lomhlaba kunye nonikezelo lwamandla. Ke sihlela iileya njengoMqondiso, aMandla okanye oMhlaba. Ukuba iinxalenye kwi-PCB zifuna ezahlukeneyo unikezelo lwamandla, badla ngokuba amandla ngaphezu kwamabini kunye maleko ngocingo. 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 ephambili ikakhulu maleko 4. Xa kusenziwa imveliso, izaleko ezibini eziphakathi ziyaqengqeleka, zisikwe, zagxunyekwa, zaxutywa kunye neelectroplated ngokwahlukeneyo. Amacwecwe amane angumphezulu wecandelo, amandla ombane, umtya kunye ne-solder lamination ngokwahlukeneyo. Amacwecwe amane emva koko acinezelwe kunye ukwenza i-PCB yebhodi ephambili. Then the holes were punched and made. Emva kokucoca, iileya ezimbini zangaphandle zomgca ziyashicilelwa, ubhedu, ukutsala, ukuvavanya, umaleko wokumelana ne-welding, ukuprinta kwescreen. Okokugqibela, yonke i-PCB (kubandakanya neebhodi zee-mama ezininzi) ifakwe istampu kwi-PCB yebhodi nganye yomama, emva koko ipakishwe nge-vacuum yenziwa emva kokuphumelela uvavanyo. 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. Ubuqhetseba kukusasaza umaleko omncinci wobhedu wobhedu ngaphezulu kobuso bonke kwaye ususe nakuphi na ukugqitha. Ukufaka isicelo sokudlulisa yenye indlela engasetyenziswanga kangako, eyokufaka ucingo lobhedu kuphela apho lufuneka khona, kodwa asizukuthetha ngalo apha.

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 yitemplate yokwenza ulwahlulo lwe-PCB. I-hood egubungela i-photoresist kwi-PCB ithintela ezinye iindawo ze-photoresist ekuvezweni de ifotoresist ivezwe kukukhanya kwe-UV. These areas, which are covered with photoresist, will become wiring. Amanye amalungu obhedu angenanto aza kudweliswa emva kophuhliso lwefotoresist. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Ngokubanzi kusetyenziswa isinyibilikisi sokulinganisa, After etching, remove the remaining photoresist.

1. Ububanzi bengcingo kunye nolwangoku

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).

Xa ubukhulu befoyile yobhedu bumalunga ne-50um, ububanzi bocingo yi-1 ~ 1.5mm (60mil) = 2A

Umhlaba oqhelekileyo ngokubanzi ungama-80mil, ngakumbi kwizicelo ezinee-microprocessors.

2. Lingakanani isantya sokuphindaphindwa kwebhodi yesantya esiphezulu?

Xa ukunyuka / ukuhla kwexesha lesiginali “amaxesha ama-3 ~ ama-6 ixesha lokuhambisa umqondiso, ithathwa njengesantya esiphezulu.

Kwiisekethe zedijithali, isitshixo kukujonga ukujija komda wesiginali, ixesha elithathayo ukunyuka 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! – – – – – – ezizezi! 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 ingqokelela kunye nokubekwa

The four – layer plate has the following stacking sequence. Izinto eziluncedo nezingeloncedo zokulaminetha okuhlukeneyo zichaziwe apha ngezantsi:

Ityala lokuqala liya kuba lelona lihlelekileyo kwezi zahlulo zine. 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. Nangona kunjalo, ityala lokuqala alinakusetyenziswa xa uxinano lwebhodi luphezulu kakhulu. Kuba emva koko, ingqibelelo yomaleko wokuqala ayiqinisekiswanga, kwaye isimboli yesibini yomqondiso sibi kakhulu. Ukongeza, olu lwakhiwo alunakusetyenziswa kwimeko yokusetyenziswa kwamandla amakhulu kuyo yonke ibhodi.

The second case is the one we usually use the most. Ukusuka kubume bebhodi, ayilungelanga uyilo lweesekethe ezihamba ngesantya esiphezulu. Kunzima ukugcina impedance yamandla asezantsi kolu lwakhiwo. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Ke umaleko wesiginali kunye nombindi woyilo yi-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. S2. Ukukhusela i-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

Ubungakanani besiginali yombane obonakalisiweyo umiselwe ngumlinganiso ombonisa umlinganiso ρ S kunye nomlinganiso wokuboniswa komthwalo ρL

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

Kule nxaki ingentla, ukuba i-RL = Z0, umlinganiso wokuboniswa komthwalo ρL = 0. Ukuba i-RS = Z0 yomthombo wokuphela kokubonisa ukungalingani ρS = 0.

Ngenxa yokuba i-impedance yokuhambisa umgca oqhelekileyo i-Z0 ihlala ihlangabezana neemfuno ze-50 ω 50 ω, kwaye i-impedance yomthwalo ihlala ikumawaka ee-ohms ukuya kumashumi amawaka ee-ohms. Ke ngoko, kunzima ukuqonda ukungqinelana kwe-impedance kwicala lomthwalo. Nangona kunjalo, ngenxa yokuba umthombo wesiginali (ukuphuma) impedance ihlala incinci, phantse kumashumi ee-ohms. Kulula kakhulu ukuphumeza ukungqinelana kwe-impedance kumthombo. Ukuba isixhobo sokuxhathisa siqhagamshelwe esiphelweni somthwalo, isichaso siyakuthatha inxenye yesiginali kwingozi yosasazo (ukuqonda kwam). Xa kukhethwe i-TTL / CMOS esemgangathweni ye-24mA drive yangoku, isiphumo sayo sokuphuma simalunga ne-13 ω. Ukuba umgca wokuhambisa u-Z0 = 50 ed, kufuneka ke kongezwe isiphelo somthombo sokugqibela esingu-33. I-13 ω +33 ω = 46 ω (malunga ne-50 ω, ukuthoba ubuthathaka obuthathaka kunceda ixesha lokuseta uphawu)

Xa kukhethwa eminye imigangatho yokuhambisa kunye nokuqhutywa kwemisinga, ukungqinelana okungafaniyo kunokuba ngokwahlukileyo. Kwisantya esiphezulu sokuma kunye nokuyilwa kwesekethe, kweminye imiqondiso ephambili, enje ngewotshi, imiqondiso yolawulo, sicebisa ukuba isitshixo sokudibanisa umthombo masongezwe.

Ngale ndlela, isiginali edityanisiweyo iya kubonakala ngasemva kwicala lomthwalo, kuba umthombo wempazamo yomthombo, umqondiso obonisiweyo awuzukuboniswa umva.