diomongkeun tina Dewan 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 tiasa dibagi kana papan lapisan tunggal, papan lapisan ganda sareng dewan multi lapisan. Komponén éléktronik diintegrasikeun kana PCB. Dina PCB hiji-lapisan dasar, komponénna konséntrasi dina hiji sisi sareng kabel-kabelna konséntrasi dina anu sanésna. Janten urang kedah ngadamel liang dina papan supados pin tiasa ngalangkungan papan ka sisi sanésna, janten pin bagéan na dilas ka sisi sanésna. 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. Kadang-kadang perlu nyambungkeun hiji kawat tina hiji sisi ka sisi anu sanés papan ngaliwatan liang pituduh (ngalangkungan). Liang Pitunjuk nyaéta liang leutik dina PCB dieusian atanapi dilapis ku logam anu tiasa disambungkeun kana kabel dina dua sisi. Ayeuna seueur motherboard komputer nganggo 4 atanapi bahkan 6 lapisan papan PCB, sedengkeun kartu grafik umumna nganggo 6 lapisan papan PCB. Seueur kartu grafik high-end sapertos siri nVIDIAGeForce4Ti nganggo 8 lapisan papan PCB, anu disebat dewan 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.

Kusabab éta PCB multi-lapisan, sakapeung liang panduan henteu kedah nembus sadayana PCB. Liang pituduh sapertos kitu disebat Buriedvias sareng Blindvias sabab ngan nembus sababaraha lapisan. Liang buta nyambung sababaraha lapisan PCBS internal kana PCBS permukaan tanpa nembus sakabéh dewan. Liang anu dikubur ngan nyambung ka PCB internal, janten lampu henteu katingali tina beungeut cai. Dina PCB multilayer, sadaya lapisan langsung nyambung kana kawat taneuh sareng catu daya. Janten urang ngagolongkeun lapisan salaku Signal, Power atanapi Ground. Upami bagian-bagian dina PCB meryogikeun suplai listrik anu béda, biasana ngagaduhan langkung ti dua lapisan listrik sareng kawat. 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 dewan utama kalobaannana 4 lapisan. Nalika ngadamel, dua lapisan tengah digulung, diteukteuk, dipahat, dioksidasi sareng dielektropkeun masing-masing. Opat lapisan nyaéta permukaan komponén, lapisan kakuatan, stratum sareng laminasi solder masing-masing. Opat lapisan teras dipencet janten PCB pikeun papan utama. Then the holes were punched and made. Saatos beberesih, dua lapisan luar garis dicitak, tambaga, etsa, tés, lapisan résistansi las, percetakan layar. Tungtungna, sacara gembleng PCB (kalebet seueur motherboard) dicap kana PCB unggal motherboard, teras bungkusan vakum dilaksanakeun saatos lulus tés. 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. Trikna nyaéta nyebarkeun lapisan ipis tina foil tambaga kana sadaya permukaan sareng miceun kaleuleuwihan naon waé. Nambahkeun transfer mangrupikeun cara anu sanés dianggo, nyaéta nerapkeun kawat tambaga ngan ukur dimana diperyogikeun, tapi kami moal nyarios ngeunaan éta di dieu.

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. Tiung na ngan ukur témplat pikeun nyieun lapisan PCB. Tiung anu nutupan fotoresis dina PCB nyegah sababaraha daérah fotoresist tina kakeunaan dugi fotoresis kakeunaan sinar UV. These areas, which are covered with photoresist, will become wiring. Bagéan tambaga bulistir sanésna tiasa diukir saatos ngembangkeun fotoresis. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Umumna dianggo salaku ét pangleyur nganggo ferric klorida jsb. After etching, remove the remaining photoresist.

1. Lebar kabel sareng ayeuna

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 kandel foil tambaga sakitar 50um, lebar kawatna 1 ~ 1.5mm (60mil) = 2A

Titik umumna umumna 80mil, khususna kanggo aplikasi sareng mikroprosesor.

2. Sakumaha jangkungna frékuénsi papan gancang-luhur?

Nalika naékna / turunna waktos sinyal “3 ~ 6 kali dina waktos transmisi sinyal, éta dianggap salaku sinyal gancang.

Pikeun sirkuit digital, konci na nyaéta pikeun ningali sisi tanjakan sinyalna, waktosna naek sareng turun,

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! – – – – – – nyaéta! 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 sareng lapisan

The four – layer plate has the following stacking sequence. Kaunggulan sareng karugian tina laminasi anu béda dipedar di handap ieu:

Kasus anu mimitina kedah anu saé tina opat 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 anu munggaran henteu tiasa dianggo nalika kapadetan papan relatif luhur. Kusabab éta, integritas lapisan kahiji henteu dijamin, sareng sinyal lapisan kadua langkung parah. 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. Tina struktur papan, éta henteu cocog pikeun desain sirkuit digital gancang-gancang. Hésé pikeun ngajaga impedansi kakuatan low dina struktur ieu. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Janten lapisan sinyal sareng tengah formasi na nyaéta 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 taméng. 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 tina sinyal voltase anu ditangtukeun ditangtukeun ku koefisien pantulan sumber ρ S sareng koefisien pantulan beban ρL

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

Dina persamaan di luhur, upami RL = Z0, koefisien refleksi beban ρL = 0. Upami RS = Z0 koefisien refleksi sumber-akhir ρS = 0.

Kusabab impedansi jalur transmisi biasa Z0 biasana kedah nyumponan sarat 50 ω 50 ω, sareng impedansi beban biasana rébuan ohm dugi ka puluhan rébu ohm. Kusabab kitu, sesah pikeun ngawujudkeun patandingan impedansi dina sisi beban. However, because the signal source (output) impedance is usually relatively small, roughly in the tens of ohms. Kituna langkung gampang pikeun nerapkeun pencocokan impedansi dina sumberna. If a resistor is connected at the load end, the resistor will absorb part of the signal to the detriment of transmission (my understanding). Nalika arus drive TTL / CMOS 24mA standar dipilih, kaluaran impedansi na sakitar 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 (sakitar 50 ω, underdamping lemah ngabantosan waktos pangaturan sinyal)

Nalika standar transmisi sanés sareng arus drive dipilih, impedansi anu cocog tiasa béda. Dina logika kecepatan tinggi sareng desain sirkuit, pikeun sababaraha sinyal konci, sapertos jam, sinyal kontrol, kami nyarankeun yén résistor cocog sumber kedah ditambihan.

Ku cara kieu, sinyal anu nyambung bakal dibayangkeun deui ti sisi beban, kusabab sumber impedansi cocog, sinyal anu dicerminkan moal dibayangkeun deui.