Ntawv luam tawm hauv Circuit Court board (PCB) muaj nyob hauv yuav luag txhua yam khoom siv hluav taws xob. 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. Tus qauv PCB zoo ib yam li qhov no. 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. Ntawm ib qho yooj yim PCB, cov ntu tau mloog zoo rau ntawm ib sab thiab cov xov hlau tau tsom mus rau lwm qhov. 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.

Yog tias muaj qee qhov ntawm PCB uas tuaj yeem tshem tawm lossis muab rov qab rau tom qab tsim khoom, Lub qhov (socket) yuav siv los teeb tsa cov khoom. 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.

Txhawm rau txuas ob lub PCBS rau ib leeg, ib qho txuas txuas feem ntau siv. Cov ntiv tes kub muaj ntau tus tooj liab liab liab uas yog ib feem ntawm PCB thaiv. Feem ntau, txhawm rau txuas, peb ntxig cov ntiv tes kub ntawm ib qho PCB rau hauv qhov tsim nyog (feem ntau hu ua nthuav qhov) ntawm lwm PCB. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Cov xim ntsuab lossis xim av ntawm PCB yog xim ntawm daim npog qhov ncauj. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Lwm qhov lo lo ntxhuav yuav luam tawm ntawm txheej txheej txheej tsis kam. 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

Lus dab neeg).

Single-sided Boards

Raws li peb tau hais, ntawm qhov yooj yim PCB, cov ntu tau tsom mus rau ib sab thiab cov xov hlau tau tsom mus rau lwm qhov. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Vim tias ib lub vaj huam sib luag muaj ntau qhov kev txwv nruj rau kev tsim qauv hauv Circuit Court (vim tias tsuas muaj ib sab xwb, cov xov hlau tsis tuaj yeem hla thiab yuav tsum tau taug txoj kev sib cais), tsuas yog siv cov kab hluav taws xob thaum ntxov xwb.

Ob tog ob tog

Lub rooj tsav xwm hluav taws xob muaj cov xov hlau ntawm ob sab. But in order to use both wires, there must be proper electrical connections between the two sides. Qhov “choj” nruab nrab ntawm cov kab hluav taws xob no hu ua daim qhia kev (VIA). Phau ntawv qhia qhov yog qhov me me hauv PCB uas tau ntim lossis coated nrog cov hlau uas tuaj yeem txuas nrog cov xov hlau ntawm ob sab. 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

Txhawm rau txhawm rau txhawm rau thaj tsam uas tuaj yeem txuas tau, ntau dua ib leeg-lossis ob tog thaiv kab thaiv kab thaiv tau siv. Lub rooj tsav xwm ntau txheej siv ob peb lub vaj huam sib luag, thiab txheej txheej rwb thaiv tsev tau muab tso nruab nrab ntawm txhua lub vaj huam sib luag thiab glued (nias). 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. Feem ntau cov supercomputers loj siv ob peb txheej ntawm motherboards, tab sis lawv tau poob ntawm kev siv vim lawv tuaj yeem hloov los ntawm pawg ntawm cov khoos phis tawj zoo tib yam. 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.

Ib feem ntim tshuab

Los Ntawm Qhov Tshuab

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. Yog li lawv cov pob qij txha tau siv qhov chaw ntawm ob sab, thiab cov pob qij txha txuas tau zoo dua. Ntawm qhov tod tes, THT ntu txuas nrog PCB zoo dua li Nto Mounted Technology (SMT) ntu, uas peb yuav tham txog tom qab. 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.

Qhov chaw nplaum ntu tuaj yeem txuas rau ob sab.

SMT kuj muaj qhov me dua li 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

Hauv PCB tsim, muaj cov kauj ruam ntev heev uas yuav tsum tau ua ua ntej txuas txoj haujlwm. Cov hauv qab no yog txheej txheem tsim qauv tseem ceeb:

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

Cov kauj ruam tom ntej yog los tsim cov kab kos ua haujlwm ntawm lub system. Kev sib raug zoo ntawm cov xwm txheej kuj tseem yuav raug cim.

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.

Txiav txim siab txoj kev ntim khoom uas yuav siv thiab qhov loj ntawm txhua 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. Qhov zoo thiab nrawm ntawm daim duab qhia chaw yuav tsum raug txiav txim siab thaum xaiv cov thev naus laus zis.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. PCB hauv txhua lub tshuab yuav tsum tau piav qhia, thiab feem ntau ntawm lawv siv CAD (Khoos phis tawj Pab Tsim) tam sim no. Here is an example of a CircuitMakerTM design.

Schematic daim duab ntawm PCB Circuit

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. Lawv yuav tsum txuas nrog txoj hauv kev kom zoo tshaj plaws. 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

Qee qhov khoos phis tawj niaj hnub no tuaj yeem tshawb xyuas seb qhov kev tso kawm ntawm txhua qhov khoom tuaj yeem txuas nrog kom raug, lossis tshawb xyuas seb nws puas tuaj yeem ua haujlwm raug. Cov kauj ruam no hu ua kev npaj ntu, tab sis peb yuav tsis mus dhau qhov no. Yog tias muaj teeb meem nrog kev tsim hluav taws xob, cov khoom kuj tseem tuaj yeem rov kho dua ua ntej cov khoom xa tawm mus rau tom teb.

Export Circuit hauv PCB

The connections in the sketch will now look like wiring in the field. Cov kauj ruam no feem ntau yog siv lub tshuab tiav, txawm hais tias yuav tsum tau hloov phau ntawv. Below is the wire template for 2 laminates. Cov kab liab thiab xiav sawv cev rau txheej txheej PCB txheej thiab txheej txheej vuam feem. The white text and squares represent the markings on the screen printing surface. Cov dots liab thiab cov voj voos sawv cev rau qhov drilling thiab qhia qhov. On the far right we can see the gold finger on the welding surface of the 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. Cov lus qhia tshwj xeeb no sib txawv raws li qhov nrawm ntawm Circuit Court, lub zog ntawm lub teeb liab kom xa mus, qhov nkag siab ntawm Circuit kom siv lub zog thiab suab nrov, thiab qhov zoo ntawm cov khoom thiab cov cuab yeej tsim khoom. 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. Yog tias xav tau ntau dua 2 txheej, txheej fais fab thiab txheej hauv av feem ntau yog siv kom tsis txhob kis kab mob ntawm cov teeb liab txheej tau cuam tshuam, thiab tuaj yeem siv ua qhov thaiv ntawm txheej txheej teeb liab.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Qhov kev ntsuas no tseem txheeb xyuas qhov kev sib txuas tsis raug, thiab txhua qhov kev sib txuas ua raws daim duab qhia chaw.

Tsim thiab ua ntaub ntawv

Vim tias tam sim no muaj ntau yam cuab yeej CAD siv rau tsim PCBS, cov tuam txhab tsim khoom yuav tsum muaj cov ntaub ntawv uas ua tau raws cov qauv ua ntej lawv tuaj yeem tsim cov laug cam. 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

Cov cuab yeej hluav taws xob uas tsis tau tsim rau EMC cov lus qhia tshwj xeeb yuav ua rau muaj hluav taws xob sib nqus thiab cuam tshuam nrog cov khoom siv nyob ze. EMC txwv qhov txwv ntau tshaj ntawm kev cuam tshuam hluav taws xob (EMI), thaj chaw hluav taws xob (EMF) thiab kev cuam tshuam hauv xov tooj cua (RFI). Txoj cai no tuaj yeem ua haujlwm zoo ntawm cov khoom siv thiab lwm yam khoom siv nyob ze. EMC tau txwv nruj rau qhov muaj zog uas tuaj yeem tawg lossis kis tau los ntawm ib lub cuab yeej mus rau lwm qhov, thiab tau tsim los txhawm rau txo qis kev raug rau sab nraud EMF, EMI, RFI, thiab ntxiv rau. 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. Sab hauv EMI, xws li tam sim no poob ntawm cov neeg ua haujlwm, nce ntxiv raws li qhov nce. Yog tias qhov sib txawv tam sim no ntawm ob qho loj heev, nco ntsoov ua kom ntev li deb ntawm lawv. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Tus nqi qeeb ntawm cov xov hlau kuj tseem ceeb, yog li qhov luv dua qhov ntev, zoo dua. Yog li PCB me me nrog cov xov hluav taws xob zoo yuav ua haujlwm tau zoo dua ntawm qhov nrawm dua li PCB loj.