korero o Poari 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.

Ka taea te wehe te poari PCB ki te papa paparanga kotahi, te papa papanga rua me te papa papanga maha. Kua whakauruhia nga waahanga hiko ki roto i te PCB. I runga i te PCB paparanga-takitahi noa, ko nga waahanga kei te kaha ki tetahi taha ka huri nga waea ki tetahi taha. Na me huri he poka ki te papa kia uru ai nga titi ki roto i te papa ki tera taha, na ka paiherea nga titi o nga waahanga ki tera taha. 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. I etahi wa ka tika te hono atu i tetahi waea kotahi mai i tetahi taha ki tetahi atu taha o te papa ma te poka aratohu (ma te). Ko nga rua aratohu he kohao iti i te PCB kapi kapi ranei i te maitai ka taea te hono atu ki nga waea i nga taha e rua. I tenei wa he maha nga papahiko rorohiko e whakamahi ana i te 4, te 6 ranei o nga papa PCB, i te wa e whakamahia ana e nga kaata whakairoiro nga papa e 6 o te poari PCB. He maha nga kaari whakairoiro teitei penei i te raupapa nVIDIAGeForce4Ti e whakamahi ana i nga papa 8 o te poari PCB, e kiia nei ko te poari PCB maha-papa. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Na te mea he PCB paparanga maha, i etahi wa kaore e hiahiatia e nga kohao aratohu kia uru ki te PCB katoa. Ko nga kohinga aratohu pera ko nga Buriedvias me nga Blindvias na te mea ka uru noa ki etahi papa. Ko nga poka matapo e hono ana i etahi papa o PCBS o roto ki te papa PCBS me te kore e kuhu ki te papa katoa. Ko nga rua tanu ka hono noa ki te PCB o roto, na reira kaore e kitea te marama mai i te mata. I roto i te PCB multilayer, ko te waahanga katoa e hono tika ana ki te waea whenua me te mana hiko. Na ka whakariteritehia e maatau nga paparanga hei Tohu, Hiko, Whenua ranei. Mena ko nga waahanga kei runga i te PCB e hiahia ana kia rereke te mana o te hiko, i te nuinga o te waa neke atu i te rua nga hiko me nga papa waea. 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. Ko te PCB o te poari matua e 4 nga papa. I te wa e hangaia ana, ka hurihia nga waenganui e rua, ka tapahia, ka whakairihia, ka whakaarahihia, ka hikohia hoki. Ko nga papa e wha he waahanga waahanga, he paparanga mana, he stratum me te raima whakarewa. Ko nga papa e wha ka taatuhia kia hangaia he PCB mo te papa matua. Then the holes were punched and made. Whai muri i te horoi, ka taia nga papa e rua o waho o te raina, te parahi, te whakairo, te whakamatautau, te paparanga aukati maitai, te taarua mata. Hei whakamutunga, ko te PCB katoa (tae atu ki te maha o nga papapuna) ka takahia ki te PCB o ia kaupapa matua, katahi ka whakatutukihia te kohinga miihini i muri i te paahotanga o te whakamatautau. 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. Ko te mahi tinihanga ko te hora i tetahi apa parahi o te parahi parahi ki runga i te mata o te whenua ka tango i tetahi taikaha. Ko te taapiri i te whakawhitinga tetahi atu tikanga kaore i tino whakamahia, ko te tono waea waea parahi anake ki te waa e hiahiatia ana, engari kaore maatau e korero mo konei.

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. Ko te hood he tauira noa mo te hanga paparanga PCB. Ko te potae e hipoki ana i te kaiwhakaahua whakaahua i runga i te PCB ka aukati i etahi waahanga o te kaitoro whakaahua kia kore e kitea kia kitea ra ano te kaiwhakaahua ki te rama UV. These areas, which are covered with photoresist, will become wiring. Ko etahi atu waahanga parahi e whanau ana kia whakairihia i muri i te whanaketanga whakaahua. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Whakamahia ai hei whakarewa etching ma te whakamahi i te ferric chloride etc. After etching, remove the remaining photoresist.

1. Te whanui waea me te waa

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).

I te wa o te matotoru o te papa parahi e tata ana ki te 50um, ko te whanui waea he 1 ~ 1.5mm (60mil) = 2A

Ko te tikanga noa 80mil, ina koa mo nga tono me nga miihini.

2. Pehea te teitei o te papa o te papa tere?

A, no te pikinga / hinga o te wa tohu “3 ~ 6 wa te wa tuku tohu, ka kiia he tohu tere tere.

Mo nga huringa matihiko, ko te mea nui kia titiro ki te pari pari o te tohu, te waa e piki ana, e hinga ai.

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! – – – – – – ara! 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 taatai ​​me te paparanga

The four – layer plate has the following stacking sequence. Ko nga painga me nga huakore o te whakamaramatanga rereke e whakamaramatia ana i raro:

Ko te keehi tuatahi ko te mea pai rawa o nga papa e wha. 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. Heoi, ko te keehi tuatahi kaore e taea te whakamahi i te wa e tino teitei ana te poari. Na te mea hoki, ko te pono o te paparanga tuatahi kaore e tau, ana ko te tohu tuarua he kino ake. 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. Mai i te hanganga o te papa, kaore e pai mo te tere-tere te hanga huringa hikoi. He uaua ki te pupuri i te hiko iti i roto i tenei hanganga. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Na ko te papa tohu me te waenganui o te hanganga he 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. EMI whakangungu rakau. 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

Ko te kaha o te tohu ngaohiko e whakaatuhia ana ka whakatauhia e te whakarea whakaata o te puna ρ S me te whakarea whakaata kawenga ρL

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

I roto i te whārite i runga ake nei, mena ka RL = Z0, te whakarea whakaata kawenga ρL = 0. Mena he RS = Z0 whakarea whakaata-mutunga ρS = 0.

Na te mea ko te raina whakawhiti noa a Z0 te tikanga kia tutuki nga whakaritenga o te 50 ω 50 ω, a ko te kawenga a te kawenga i te nuinga o nga mano ohm ki te tekau mano mano ohm. Na reira, he uaua ki te mohio ki te taatai ​​impedance i te taha uta. Heoi, na te mea ko te putake tohu (putanga) impedance he iti tonu te ahua, i roto i nga tekau ohm. No reira he maamaa ake ki te whakamahi i nga taarua o te impedance i te putake. Mena ka hono tetahi parenga ki te pito kawenga, ka uru te parenga ki te wahanga o te tohu ki te whara o te tuku (taku maarama). Ka tohua ana te TTL / CMOS paerewa taraiwa 24mA o naianei, ko tona aukati whakaputa he 13 ω. Mena ko te raina whakawhiti i te Z0 = 50 ω, katahi ka honoa he parenga whakautu-a-toa 33 ω. 13 ω +33 ω = 46 ω (tata ki te 50 ω, ko te ngoikoretanga ngoikore ka awhina i te waa whakarite)

Ka tohua etahi atu paerewa whakawhiti me nga rerenga taraiwa, ka rereke te aukati takirua. I roto i te arorau tere-tere me te hoahoa ara iahiko, mo etahi tohu matua, penei i te karaka, tohu tohu, ka tūtohu atu me tapiri te parenga whakaōritenga pūtake.

Ma tenei, ko te tohu hono ka whakaatuhia mai i te taha uta, na te mea ka takirua te aukatinga o te putake, kaore e hoki mai te tohu whakaata.