achitaura Pcb bhodhi, 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 bhodhi inogona kuganhurwa kuita rimwe rukoko bhodhi, yakapetwa kaviri bhodhi uye yakawanda dura bhodhi. Zvemagetsi zvigadzirwa zvakabatanidzwa muPCB. Pane yakakosha imwechete-rukoko pcb, izvo zvikamu zvinoiswa kune rumwe rutivi uye mawaya akaiswa pane imwe. Saka isu tinofanirwa kugadzira maburi mubhodhi kuitira kuti mapini akwanise kupfuura nepabhodhi kuenda kune rimwe divi, saka hoko dzezvikamu dzakasungirirwa kune rimwe divi. 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. Dzimwe nguva zvinodikanwa kubatanidza tambo imwechete kubva kune rumwe rutivi kuenda kune rumwe rutivi rwebhodhi kuburikidza negomba rinotungamira (kuburikidza). Makomba ekuperekedza makomba madiki muPCB izere kana kuputirwa nesimbi inogona kusunganidzwa newaya pamativi ese. Iye zvino mazhinji emakomputa emabhodhi ari kushandisa 4 kana kunyange matanhatu matete ePCBboard bhodhi, nepo mifananidzo yemakadhi inowanzo shandisa 6 matete ePCBboard bhodhi. Mazhinji makadhi ekumusoro-ekupedzisira akaita seNVIDIAGeForce6Ti akateedzera anoshandisa masere masere epcb board, inonzi multi-layer PCB board. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Nekuti iri yakawanda-yakaturikidzana pcb, dzimwe nguva maburi anotungamira haadi kupinda mukati mePCB yese. Makomba anotungamira akadaro anonzi Buriedvias neBlindvias nekuti anongopinda muzvikamu zvishoma. Makomba mapofu anobatanidza akati wandei akaturikidzana emukati maPCBS kumusoro PCBS pasina kupinda mukati mebhodhi rese. Maburi akavigwa anongobatana nePCB yemukati, saka mwenje hauoneke kubva kumusoro. Mune multilayer pcb, hwese hwakazara hwakabatana zvakananga netambo yepasi uye magetsi magetsi. Saka isu tinopatsanura zvidimbu seSignal, Simba kana Ground. Kana zvikamu zviri paPCB zvichida zvakasiyana magetsi, zvinowanzove neanopfuura maviri magetsi uye waya matete. 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. The pcb of chikuru bhodhi iri zvikuru 4 akaturikidzana. Kana uchigadzira, iwo maviri epakati akaturikidzana akamonerwa, akachekwa, akachekwa, akaiswa oxidized uye electroplated zvichiteerana. Iwo mana akaturikidzana ari epamusoro pevhu, simba rukoko, stratum uye solder lamination zvakateerana. The four layers are then pressed together to form a PCB for the main board. Then the holes were punched and made. After cleaning, the outer two layers of the line is printed, copper, etching, testing, welding resistance layer, screen printing. Chekupedzisira, iyo pcb pese (inosanganisira akawanda mamaboards) yakadhindwa muPCB yebhodhi rimwe nerimwe, uye wozorongedza kuputira kunoitwa mushure mekupasa bvunzo. 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. The trick is to spread a thin layer of copper foil over the entire surface and remove any excess. Kunyorera kuendesa imwe nzira isinganyanyo shandiswa, iri yekuisa waya yemhangura chete pazvinodiwa, asi isu hatichataura nezvazvo pano.

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. Iyo hood ingori template yekugadzira PCB matete. Hood inovhara fotoresist paPCB inodzivirira dzimwe nzvimbo dzefresresist kubva pakuburitswa pachena kusvikira iyo fresresist yafumurwa kune UV 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. Inowanzo shandiswa seyetching solvent uchishandisa ferric chloride nezvimwe. After etching, remove the remaining photoresist.

1. Wiring width and current

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).

Kana iyo hukobvu hwemhangura foil ingangoita 50um, iyo waya upamhi ndeye 1 ~ 1.5mm (60mil) = 2A

Iyo yepasi pevhu inowanzo kuve 80mil, kunyanya kune zvinoshandiswa nema microprocessors.

2. Yakakwira sei iyo frequency yeiyo-yekumhanyisa bhodhi?

Kana kusimuka / kudonha kwechiratidzo nguva “3 ~ 6 nguva yekutumira chiratidzo, inoonekwa seyakanyanya kumhanya chiratidzo.

Kune macircuit edhijitari, kiyi ndeyekutarisa kumucheto kwakadzika kwechiratidzo, iyo nguva inotora kusimuka nekudonha,

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! – – – – – – izvo! 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 kuisira uye kuisa

The four – layer plate has the following stacking sequence. Izvo zvakanakira nekuipira kweakasiyana lamination zvinotsanangurwa pazasi:

Mhosva yekutanga inofanira kuve yakanakisa pamatanho mana. 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. Nekudaro, kesi yekutanga haigone kushandiswa kana huwandu hwebhodhi hwakati kurei. Because then, the integrity of the first layer is not guaranteed, and the second layer signal is worse. 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. Kubva pakuumbwa kwebhodhi, haina kukodzera kumhanya-mhanya yedhijitari wedunhu dhizaini. Izvo zvinonetsa kuchengetedza yakaderera magetsi impedance mune ino chimiro. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Saka chiratidzo cheyadhi uye pakati pekuumbwa i0.14mm. 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. EMI kudzivirirwa. 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

Ukuru hweratidziro yemagetsi inoratidzwa neyakagadziriswa fosi ρ S uye mwero wekuratidzira mwero ρL

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

In the above equation, if RL=Z0, the load reflection coefficient ρL=0. If RS=Z0 source-end reflection coefficient ρS=0.

Because the ordinary transmission line impedance Z0 should usually meet the requirements of 50 ω 50 ω, and the load impedance is usually in thousands of ohms to tens of thousands of ohms. Naizvozvo, zvinonetsa kuona impedance inoenderana padivi remutoro. However, because the signal source (output) impedance is usually relatively small, roughly in the tens of ohms. Saka zviri nyore kwazvo kuita impedance inoenderana nekwairi. If a resistor is connected at the load end, the resistor will absorb part of the signal to the detriment of transmission (my understanding). When the TTL/CMOS standard 24mA drive current is selected, its output impedance is approximately 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)

When other transmission standards and drive currents are selected, the matching impedance can be different. In high-speed logic and circuit design, for some key signals, such as clock, control signals, we recommend that the source matching resistor must be added.

In this way, the connected signal will be reflected back from the load side, because the source impedance matches, the reflected signal will not be reflected back.