ngandika Papan 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.

Papan PCB bisa dipérang dadi siji lapisan papan, papan lapisan kaping pindho lan papan multi lapisan. Komponen elektronik digabungake ing PCB. Ing PCB lapisan siji dhasar, komponen kasebut musatake ing sisih siji lan kabel dadi luwih fokus ing sisih liyane. Dadi kita kudu nggawe bolongan ing papan supaya pin bisa ngliwati papan menyang sisih liyane, mula pin bagean kasebut dipasang ing sisih liyane. 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. Kadhangkala perlu nyambungake kabel siji saka sisih menyang sisih liyane papan liwat bolongan pandhuan (liwat). Bolongan pandhuan yaiku bolongan cilik ing PCB sing diisi utawa ditutup nganggo logam sing bisa disambungake menyang kabel ing loro-lorone. Saiki akeh motherboard komputer nggunakake 4 utawa malah 6 lapisan papan PCB, dene kertu grafis umume nggunakake 6 lapisan papan PCB. Akeh kertu grafis mewah kaya seri nVIDIAGeForce4Ti nggunakake 8 lapisan papan PCB, sing diarani papan PCB multi-lapisan. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Amarga iku PCB multi-lapisan, kadang bolongan pandhuan ora perlu nembus kabeh PCB. Bolongan pandhuan kaya kasebut diarani Buriedvias lan Blindvias amarga mung nembus sawetara lapisan. Bolongan wuta nyambungake sawetara lapisan PCBS internal menyang PCBS ing permukaan tanpa nembus kabeh papan. Bolongan sing dikubur mung disambungake karo PCB internal, mula cahya ora katon saka permukaan. Ing PCB multilayer, kabeh lapisan langsung nyambung menyang kabel lemah lan catu daya. Dadi, kita ngelasake lapisan minangka Signal, Power utawa Ground. Yen bagean ing PCB mbutuhake pasokan listrik sing beda, umume duwe luwih saka rong lapisan listrik lan kabel. 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 papan utama biasane 4 lapisan. Nalika nggawe, rong lapisan tengah digulung, dipotong, diukir, dioksidasi lan dielektropasi masing-masing. Papat lapisan kasebut yaiku permukaan komponen, lapisan tenaga, stratum lan laminasi solder. Papat lapisan kasebut banjur dipencet dadi PCB kanggo papan utama. Then the holes were punched and made. Sawise diresiki, rong lapisan njaba dicithak, tembaga, etsa, pengujian, lapisan resistansi las, cetakan layar. Pungkasane, kabeh PCB (kalebu akeh motherboard) dicap ing PCB saben motherboard, banjur bungkus vakum ditindakake sawise lulus tes. 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. Caranya yaiku nyebar lapisan foil tembaga sing lancip ing kabeh permukaan lan mbusak kaluwihan. Nambah transfer minangka cara liyane sing kurang digunakake, yaiku nggunakake kabel tembaga mung ing endi sing dibutuhake, nanging ora bakal dibahas ing kene.

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. Hood mung minangka template kanggo nggawe lapisan PCB. Hood sing nutupi fotoresist ing PCB ngalangi sawetara area fotoresist supaya ora kapacak nganti fotoresist kena cahya UV. These areas, which are covered with photoresist, will become wiring. Bagean tembaga gundhul liyane sing bakal diukir sawise pembangunan fotoresist. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Umume digunakake minangka pelarut etsa nggunakake klorida klorida lsp. After etching, remove the remaining photoresist.

1. Jembaré kabel lan saiki

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).

Nalika ketebalan foil tembaga udakara 50um, jembaré kawat 1 ~ 1.5mm (60mil) = 2A

Umumé umume 80mil, utamane kanggo aplikasi karo mikroprosesor.

2. Sepira dhuwur frekuensi saka papan kecepatan tinggi?

Nalika munggah / mudhun wektu sinyal “3 ~ 6 kaping wektu transmisi sinyal, bisa dianggep minangka sinyal kacepetan dhuwur.

Kanggo sirkuit digital, kuncine yaiku kanggo ndeleng tajem sinyal, wektu sing dibutuhake kanggo munggah lan tiba,

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! – – – – – – yaiku! 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 tumpukan lan lapisan

The four – layer plate has the following stacking sequence. Kaluwihan lan kekurangan laminasi sing beda diterangake ing ngisor iki:

Kasus pisanan kudu paling apik saka papat lapisan. 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. Nanging, kasus pisanan ora bisa digunakake nalika kepadatan papan cukup dhuwur. Amarga integritas lapisan pisanan ora dijamin, lan sinyal lapisan liya luwih elek. Kajaba iku, struktur iki ora bisa digunakake ing kasus konsumsi daya gedhe saka kabeh papan.

The second case is the one we usually use the most. Saka struktur papan, ora cocog kanggo desain sirkuit digital kanthi kecepatan tinggi. Iku angel kanggo njaga impedansi daya sithik ing struktur iki. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Dadi lapisan sinyal lan tengah tatanan yaiku 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 tameng. 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

Amplitudo sinyal voltase sing dibayangke ditemtokake dening koefisien refleksi sumber ρ S lan koefisien refleksi beban ρL

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

Ing persamaan ing ndhuwur, yen RL = Z0, koefisien refleksi beban ρL = 0. Yen RS = koefisien refleksi sumber pungkasan ρS = 0.

Amarga impedansi jalur transmisi biasa Z0 biasane nyukupi sarat 50 ω 50 ω, lan impedansi momotan biasane nganti ewonan ohm nganti puluhan ewu ohm. Mula, angel kanggo nyadari cocog impedansi ing sisih beban. Nanging, amarga impedansi sumber sinyal (output) biasane rada sithik, nganti puluhan ohm. Mula luwih gampang kanggo ngetrapake pencocokan impedansi ing sumber kasebut. Yen resistor disambungake ing ujung beban, resistor bakal nyedhot bagean sinyal kanggo ngrusak transmisi (pangertenku). Nalika drive drive 24mA standar TTL / CMOS dipilih, impedansi output udakara 13 ω. Yen impedansi garis transmisi Z0 = 50 ω, mula kudu ditambah resistor pencocokan 33-sumber. 13 ω +33 ω = 46 ω (udakara 50 ω, underdamping sing lemah mbantu wektu persiyapan sinyal)

Yen standar transmisi lan arus drive liyane dipilih, impedansi sing cocog bisa beda. Ing desain logika lan sirkuit kecepatan tinggi, kanggo sawetara sinyal utama, kayata jam, sinyal kontrol, disaranake resistor pencocokan sumber kudu ditambahake.

Kanthi cara iki, sinyal sing disambungake bakal dibayangke maneh saka sisih beban, amarga impedansi sumber cocog, sinyal sing dibayangke ora bakal dibayangke maneh.