Apa itu PCB Circuit Board?

Papan litar PCB , juga dikenali sebagai papan litar bercetak, adalah penyedia sambungan elektrik untuk komponen elektronik. Perkembangannya mempunyai sejarah lebih dari 100 tahun. Reka bentuknya terutamanya reka bentuk susun atur, dan kelebihan utama menggunakan papan litar adalah untuk mengurangkan kesalahan pendawaian dan pemasangan, dan meningkatkan tahap automasi dan kadar buruh pengeluaran.

Komposisi papan litar PCB

1. Circuit and Pattern: The circuit is used as a tool for conduction between the originals. In the design, a large copper surface will be additionally designed as a ground and power layer. The lines and drawings are made at the same time.
2. Dielectric: used to maintain the insulation between the circuit and each layer, commonly known as the substrate.
3. Hole: The through-hole can make the lines above two levels to connect with each other, the larger through-hole is used as a part insert, and the non-through hole is usually used as a surface mount It is used for positioning and fixing screws during assembly.
4. Solder resistant /Solder Mask: Not all copper surfaces need to eat tin on the parts, so the non-tin eating area will be printed with a layer to isolate the copper surface eating tin material (usually epoxy resin) to avoid There is a short circuit between the lines not eating tin. According to different processes, it is divided into green oil, red oil and blue oil.
5. Screen printing (Legend / Marking/Silkscreen): This is a non-essential component. The main function is to mark the name and location frame of each part on the circuit board, which is convenient for maintenance and identification after assembly.
6. Surface finish: Since the copper surface is easily oxidized in the general environment, it can not be tinned (poor solderability), so it will be protected on the copper surface that will eat tin. The protection methods are HASL, ENIG, immersion silver, immersion tin, OSP. The methods have their own advantages and disadvantages, which are collectively called surface treatment.

PCB circuit board design steps

The basic design process of the circuit board can be divided into the following four steps:

The design of the circuit schematic diagram: The design of the circuit schematic diagram mainly uses the schematic diagram editor to draw the schematic diagram.

Generate a network report: A network report is a report that shows the relationship between the circuit principle and the various components in it. It is a bridge and link between the circuit schematic design and the circuit board design. Through the network report of the circuit schematic, you can quickly find the element The connection between the devices, thus providing convenience for the subsequent PCB design.

Printed circuit board design: The printed circuit board design is what we usually call the reka bentuk PCB. It is the final form of the circuit schematic. The related design of this part is more difficult than the design of the circuit schematic. We can complete this part of the design with the help of powerful design functions.

Generate printed circuit board reports: After the printed circuit board design is completed, various reports need to be generated. For example, generate pin reports, circuit board information reports, network status reports, etc., and finally print out the printed circuit diagram.

PCB circuit board design considerations

 1. Antenna design

•  The wiring from the Bluetooth IC to the antenna should be smooth or straight;
• There should be no devices, wiring and copper laying around the effective part of the antenna and its lower layer (ie the back);
• The antenna is required to be designed on the edge of the PCB , facing the front panel as much as possible, and it is required to avoid iron structural parts around;
•  Choose the type of antenna according to the size of the papan PCB, choose the inverted F antenna when the board is large, and choose the snake antenna when the board is small;

2. Second, the component placement principle

• The general order of component placement: First, place components that closely match the structure. Such as power sockets, indicators, switches, connectors, interfaces, etc. Second, place special components, such as large components, heavy components , Heat-generating components, IC, etc. Finally, place small components; layout should consider wiring, try to choose layout layout that is conducive to wiring;
• The crystal should be placed close to the IC;
• Susun atur kapasitor pemutus IC harus sedekat mungkin dengan pin bekalan kuasa IC, dan gelung terpendek terbentuk di antaranya dan bekalan kuasa dan tanah;
• Elemen pemanasan hendaklah diagihkan secara merata untuk memudahkan pelesapan haba papan tunggal dan keseluruhan mesin. Peranti yang peka suhu selain elemen pengesan suhu harus dijauhkan dari komponen yang menghasilkan sejumlah besar haba;

3. Prinsip pendawaian

• Jauhkan jejak isyarat berkelajuan tinggi sesingkat mungkin, dan jejak isyarat utama sesingkat mungkin;
• Jangan membuat terlalu banyak vias untuk satu jejak, dan jangan melebihi dua vias;
• Sudut penghala harus lebih besar daripada 90 darjah sebanyak mungkin, dan sudut di bawah 90 darjah harus dihapuskan, dan sudut 90 darjah harus digunakan sesedikit mungkin;
• Semasa pendawaian dua sisi, wayar di kedua-dua sisi harus tegak lurus, pepenjuru atau melengkung untuk mengelakkan selari untuk mengurangkan gandingan parasit;
• Kabel input audio harus sama panjang, kedua-dua wayar harus diletakkan berdekatan satu sama lain, dan wayar audio harus dibungkus dengan wayar tanah;
• IC penguat kuasa tidak dapat dialirkan di bawah IC penguat kuasa, dan banyak vias disambungkan ke GND;
• Tidak ada lapisan tanah di papan sisi dua. Kawat tanah kapasitor kristal harus disambungkan ke pin GND yang paling dekat dengan kristal pada peranti dengan wayar sesingkat mungkin, dan vias harus dikurangkan;
• Kabel kuasa, input pengecasan USB harus menjadi garis tebal (》 = 1mm), tembaga di kedua sisi lubang, kemudian buat beberapa lubang lagi di tembaga;

Under normal circumstances, the power cord and ground wire should be wired first to ensure the electrical performance of the circuit board. To the extent possible, widen the width of the power and ground wires as much as possible. It is better that the ground wire is wider than the power wire. Their relationship is: ground wire> power wire> signal wire, usually the signal wire width is: 0.2 ~ 0.3mm , The thinnest width can reach 0.05～0.07mm, the power cord is generally 1.2～2.5mm.

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