Isagoo ka hadlayay of Guddiga 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.

Guddiga PCB waxaa loo qaybin karaa loox hal lakab ah, loox laba -lakab ah iyo looxyo badan. Qaybaha elektarooniga ah ayaa lagu daray PCB. PCB-da hal-lakabka ah ee aasaasiga ah, qaybaha ayaa ku urursan hal dhinac iyo fiilooyinku waxay ku urursan yihiin dhinaca kale. Markaa waxaan u baahanahay inaan guddiyada ka samayno godad si ay biinanka guddigu uga sii gudbaan dhinaca kale, sidaa darteed biinanka qaybaha ayaa alxanka u leh dhinaca kale. 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. Mararka qaarkood waxaa lagama maarmaan ah in lagu xiro hal silig hal dhinac ilaa dhinaca kale ee looxaanta iyada oo loo marayo daloolka hagaha (via). Daloollada hagaha waa godad yaryar oo ku jira PCB -ga oo laga buuxiyey ama lagu daboolay biro lagu xiriirin karo fiilooyinka labada dhinacba. Hadda boodhadh badan oo kombiyuutar ayaa isticmaalaya 4 ama xitaa 6 lakab oo loox PCB ah, halka kaararka garaafyada guud ahaan ay isticmaalaan 6 lakab oo ah guddiga PCB. Qaar badan oo kaararka garaafyada sare ah sida taxanaha nVIDIAGeForce4Ti waxay isticmaalaan 8 lakab oo ah guddiga PCB, oo loo yaqaan guddiga PCB-lakabka badan. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Sababtoo ah waa PCB-lakab badan, mararka qaarkood godadka hagaha uma baahna inay dhex galaan PCB-ga oo dhan. Daloollada noocaas ah waxaa loogu yeeraa Buriedvias iyo Blindvias maxaa yeelay waxay galaan oo keliya dhowr lakab. Daloollada indhoolayaasha waxay ku xiraan dhowr lakab oo PCBS -da gudaha PCBS -ka dushiisa iyadoon la dhex gelin guddiga oo dhan. Godadka la aasay waxay ku xiran yihiin PCB -ga gudaha, sidaa darteed iftiinku kama muuqdo dusha sare. PCB -ga badan, lakabka oo dhan wuxuu si toos ah ugu xiran yahay siligga dhulka iyo korontada. Markaa waxaan u kala saarnaa lakabyada inay yihiin Signal, Awood ama Dhul. Haddii qaybaha PCB -ga ay u baahan yihiin sahayda korontada oo kala duwan, badiyaa waxay leeyihiin wax ka badan laba lakab oo koronto iyo silig ah. 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. PCB -ga guddiga ugu weyn wuxuu u badan yahay 4 lakab. Marka wax -soo -saarka, labada lakab ee dhexe ayaa la duuduubaa, la gooyaa, la qallajiyaa, oksaydh iyo electroplated siday u kala horreeyaan. Afarta lakab waa dusha sare, lakabka korontada, stratum iyo alxanka alxanka siday u kala horreeyaan. Afarta lakab ayaa markaa la isku riixayaa si ay PCB ugu sameeyaan guddiga weyn. Then the holes were punched and made. Nadiifinta ka dib, labada lakab ee sare ee xariiqda ayaa la daabacay, naxaas, dhejis, tijaabin, alxanka lakabka iska caabinta, daabacaadda shaashadda. Ugu dambayntii, PCB -ga oo dhan (oo ay ku jiraan boodhadh -hooyooyin badan) ayaa lagu shaabadeeyey PCB -ga motherboard kasta, ka dibna baakidhka faaruqinta ayaa la sameeyaa ka dib marka la gudbo imtixaanka. 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. Xeeladdu waa in lagu faafiyo lakab khafiif ah oo bireedka naxaas ah dusha oo dhan lagana saaro wixii xad -dhaaf ah. Ku -biirinta wareejinta waa hab kale oo aan aad loo isticmaalin, kaas oo ah in lagu dabaqo silig naxaas ah meesha loo baahan yahay oo keliya, laakiin halkaan kaga hadli mayno.

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. Daboolku waa uun shaxanka samaynta lakabyada PCB. Dabool daboolaya sawir -qaadaha sawir -qaadaha ee PCB -ga ayaa ka horjoogsanaya in aagagga sawir -qaadaha qaarkood la soo bandhigo illaa sawir -qaadaha uu ka soo gaadho iftiinka UV. These areas, which are covered with photoresist, will become wiring. Other bare copper parts to be etched after photoresist development. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Guud ahaan waxaa loo isticmaalaa dareeraha qashin -qubka iyadoo la isticmaalayo chloride ferric iwm. After etching, remove the remaining photoresist.

1. Ballaca fiilooyinka iyo hadda

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).

Marka dhumucda bireedka naxaasku ay qiyaastii tahay 50um, ballaca siliggu waa 1 ~ 1.5mm (60mil) = 2A

Dhulka guud waa 80mil, gaar ahaan codsiyada microprocessors -ka.

2. Intee ayay le’eg tahay inta jeer ee loox-xawaaraha sare leh?

Marka kororka/dhicitaanka waqtiga signalada “3 ~ 6 jeer waqtiga gudbinta signalada, waxaa loo tixgeliyaa inay tahay signal xawaare sare leh.

Wareegyada dhijitaalka ah, furaha ayaa ah in la fiiriyo cidhifka cirifka ee signalada, waqtiga ay qaadanayso kor u kaca iyo dhicitaanka,

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! – – – – – – – yacni! 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.Baabilidda iyo lakabinta PCB

The four – layer plate has the following stacking sequence. Faa’iidooyinka iyo waxyeellooyinka dahaarka kala duwan ayaa hoos lagu sharxay:

Kiiska koowaad waa inuu ahaadaa kan ugu fiican afarta lakab. 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. Si kastaba ha ahaatee, kiiska koowaad lama isticmaali karo marka cufnaanta guddigu ay aad u sarreyso. Sababtoo ah markaa, daacadnimada lakabka koowaad lama dammaanad qaadayo, iyo calaamadda lakabka labaad ayaa ka sii daran. In addition, this structure can not be used in the case of large power consumption of the whole board.

The second case is the one we usually use the most. Laga soo bilaabo qaab-dhismeedka guddiga, kuma habboona naqshadeynta wareegga dhijitaalka ee xawaaraha sare leh. Way adag tahay in la joogteeyo carqaladeynta awoodda hoose ee qaab -dhismeedkan. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Marka lakabka signalada iyo dhexda samaysku waa 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. Difaaca 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

Baaxadda signalada korantada ee ka tarjumeysa waxaa go’aamiya isuduwaha milicsiga isha ρ S iyo isugeynta milicsiga culeyska ρL

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

Isla’egta kor ku xusan, haddii RL = Z0, isugeynta milicsiga culeyska ρL = 0. Haddii RS = Z0 is-beddelka milicsiga il-dhamaadka ρS = 0.

Sababtoo ah khadadka gudbinta caadiga ah ee xannibaadda Z0 waa inay sida caadiga ah buuxisaa shuruudaha 50 ω 50 ω, iyo culeyska culeyska wuxuu badiyaa ku jiraa kumanaan ohms illaa tobanaan kun oo ohms. Sidaa darteed, way adag tahay in la xaqiijiyo is -waafajinta is -waafajinta ee dhinaca culeyska. However, because the signal source (output) impedance is usually relatively small, roughly in the tens of ohms. Sidaa darteed aad bay u sahlan tahay in laga hirgeliyo isbarbar -dhigga is -beddelka. If a resistor is connected at the load end, the resistor will absorb part of the signal to the detriment of transmission (my understanding). Marka la doorto heerka TTL/CMOS ee 24mA wadista wadista hadda, soo -saaristeeda wax -soo -saarku waa qiyaastii 13 ω. If the transmission line impedance Z0=50 ω, then a 33 ω source-end matching resistor should be added. 13 ω +33 ω =46 ω (approximately 50 ω, weak underdamping helps signal setup time)

Marka la doorto heerar kale oo gudbinta iyo durdurrada wadista, carqaladaynta u dhiganta way ka duwanaan kartaa. Caqli-xawaaraha sare iyo naqshadda wareegga, qaar ka mid ah calaamadaha muhiimka ah, sida saacadda, calaamadaha koontaroolka, waxaan ku talineynaa in isha ku-habboonaanta isbarbar-taaga waa in lagu daraa.

Sidan oo kale, signalada ku xiran ayaa dib uga soo muuqan doonta dhinaca culeyska, maxaa yeelay is -hortaagga illaha ayaa la jaanqaadaya, signaalka ka muuqda dib looma soo celin doono.