Printed circuit board Ang (PCB) ay matatagpuan sa halos lahat ng uri ng elektronikong aparato. 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. A standard PCB looks something like this. 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. Sa isang pangunahing PCB, ang mga bahagi ay nakatuon sa isang gilid at ang mga wire ay nakatuon sa kabilang panig. 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.

Kung may mga bahagi sa PCB na maaaring alisin o ibalik pagkatapos gawin, ang Socket ay gagamitin upang mai-install ang mga bahagi. 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.

To connect two PCBS to each other, an edge connector is commonly used. Naglalaman ang gintong daliri ng isang bilang ng mga hubad na tanso pad na talagang bahagi ng mga kable ng PCB. Karaniwan, upang kumonekta, inilalagay namin ang gintong daliri sa isang PCB sa naaangkop na Slot (karaniwang tinatawag na Slot ng pagpapalawak) sa kabilang PCB. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Ang berde o kayumanggi na kulay sa PCB ay ang kulay ng solder mask. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Ang isa pang sutla na screen ay mai-print sa layer ng paglaban ng solder. 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

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Single-sided Board

Tulad ng nabanggit namin, sa isang pangunahing PCB, ang mga bahagi ay nakatuon sa isang gilid at ang mga wire ay nakatuon sa kabilang panig. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Dahil ang solong mga panel ay may maraming mahigpit na paghihigpit sa disenyo ng circuit (dahil may isang gilid lamang, ang mga kable ay hindi maaaring tumawid at kailangang kumuha ng isang hiwalay na landas), mga maagang circuit lamang ang gumamit ng gayong mga board.

Dobleng panig ng mga Lupon

Ang circuit board ay may mga kable sa magkabilang panig. But in order to use both wires, there must be proper electrical connections between the two sides. Ang “tulay” na ito sa pagitan ng mga circuit ay tinatawag na isang hole hole (VIA). Ang mga butas ng gabay ay maliit na butas sa PCB na puno o pinahiran ng metal na maaaring maiugnay sa mga wire sa magkabilang panig. 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

Upang madagdagan ang lugar na maaaring i-wire, mas maraming solong – o dobleng panig na mga board ng kable ang ginagamit. Ang multilayer board ay gumagamit ng maraming mga dobleng panel, at isang layer ng pagkakabukod ay inilalagay sa pagitan ng bawat panel at nakadikit (pinindot). 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. Karamihan sa mga malalaking supercomputer ay gumagamit ng ilang mga layer ng mga motherboard, ngunit hindi na sila ginagamit dahil maaari silang mapalitan ng mga kumpol ng mga ordinaryong computer. 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.

Teknolohiya ng bahagi ng packaging

Sa pamamagitan ng Hole Technology

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. Kaya’t ang kanilang mga kasukasuan ay talagang tumatagal ng puwang sa magkabilang panig, at ang mga solder joint ay medyo malaki. Sa kabilang banda, ang mga bahagi ng THT ay mas mahusay na konektado sa PCB kaysa sa mga bahagi ng Surface Mounted Technology (SMT), na pag-uusapan natin sa paglaon. 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.

Ang mga bahagi ng malagkit na pang-ibabaw ay maaaring kahit na welded sa magkabilang panig.

Ang SMT ay mayroon ding mas maliit na mga bahagi kaysa sa 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

Sa disenyo ng PCB, talagang may napakahabang mga hakbang upang dumaan bago pormal na mga kable. Ang sumusunod ay ang pangunahing proseso ng disenyo:

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

Ang susunod na hakbang ay upang lumikha ng isang gumaganang diagram ng block ng system. Ang relasyon sa pagitan ng mga parisukat ay dapat ding markahan.

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.

Tukuyin ang paraan ng pag-iimpake na gagamitin at ang laki ng bawat 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. Ang kalidad at bilis ng circuit diagram ay dapat ding isaalang-alang kapag pumipili ng teknolohiya.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. Ang PCB sa lahat ng mga system ay dapat na inilarawan, at karamihan sa kanila ay gumagamit ng CAD (Computer Aided Design) sa kasalukuyan. Here is an example of a CircuitMakerTM design.

Scagram diagram ng 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. Dapat silang konektado sa landas sa pinaka mahusay na paraan. 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

Ang ilan sa mga software ng computer ngayon ay maaaring suriin kung ang pagkakalagay ng bawat bahagi ay maaaring konektado nang tama, o suriin kung maaari itong gumana nang tama sa mataas na bilis. Ang hakbang na ito ay tinatawag na pag-aayos ng mga bahagi, ngunit hindi kami masyadong malayo rito. Kung mayroong isang problema sa disenyo ng circuit, ang mga bahagi ay maaari ding maiayos muli bago mai-export ang circuit sa patlang.

I-export ang circuit sa PCB

The connections in the sketch will now look like wiring in the field. Ang hakbang na ito ay karaniwang ganap na awtomatiko, kahit na karaniwang kinakailangan ang mga manu-manong pagbabago. Below is the wire template for 2 laminates. Ang pula at asul na mga linya ay kumakatawan sa layer ng mga bahagi ng PCB at ang layer ng hinang ayon sa pagkakabanggit. The white text and squares represent the markings on the screen printing surface. Ang mga pulang tuldok at bilog ay kumakatawan sa mga butas sa pagbabarena at paggabay. Sa dulong kanan makikita natin ang gintong daliri sa ibabaw ng hinang ng 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. Ang mga pagtutukoy na ito ay nag-iiba ayon sa bilis ng circuit, ang lakas ng signal na ililipat, ang pagiging sensitibo ng circuit sa pagkonsumo ng kuryente at ingay, at ang kalidad ng materyal at kagamitan sa pagmamanupaktura. 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. Kung higit sa 2 mga layer ang kinakailangan, ang layer ng kuryente at ground layer ay karaniwang ginagamit upang maiwasan ang signal ng paghahatid sa signal layer ay apektado, at maaaring magamit bilang isang kalasag ng layer ng signal.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Sinusuri din ng pagsubok na ito ang mga maling koneksyon, at lahat ng mga koneksyon ay sumusunod sa diagram ng eskematiko.

Itaguyod at i-file

Because there are currently many CAD tools for designing PCBS, manufacturers must have a profile that meets the standards before they can manufacture boards. 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

Ang mga elektronikong aparato na hindi idinisenyo sa mga pagtutukoy ng EMC ay malamang na naglalabas ng electromagnetic na enerhiya at makagambala sa mga kalapit na kagamitan. Nagpapataw ang EMC ng maximum na mga limitasyon sa pagkagambala ng electromagnetic (EMI), electromagnetic field (EMF) at pagkagambala ng dalas ng radyo (RFI). This regulation can ensure the normal operation of the appliance and other nearby appliances. Nagpapataw ang EMC ng mahigpit na mga limitasyon sa dami ng enerhiya na maaaring makalat o mailipat mula sa isang aparato patungo sa isa pa, at idinisenyo upang mabawasan ang pagkamaramdamin sa panlabas na EMF, EMI, RFI, at iba pa. 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. Ang panloob na EMI, tulad ng kasalukuyang pagkawala sa pagitan ng mga conductor, ay tumataas habang tumataas ang dalas. If the current difference between the two is too large, make sure to lengthen the distance between them. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Ang rate ng pagkaantala sa mga kable ay mahalaga din, kaya’t mas maikli ang haba, mas mabuti. Kaya’t ang isang maliit na PCB na may mahusay na mga kable ay gagana nang mas mahusay sa mataas na bilis kaysa sa isang malaking PCB.