PCB Technical - PCB layout related technical points and design experience, skills and other knowledge

PCB layout related technical points and design experience, skills and other knowledge
PCB is the abbreviation for Printed Circuit Board. The printed circuit board is a substrate for assembling electronic parts. It is a printed board that connects dots and prints components on a common base material according to a predetermined design. The main function of the product is to connect various electronic components to a predetermined circuit, and play the role of relay transmission. It is the key electronic interconnection of electronic products and is known as the "mother of electronic products".

This content organizes relevant technical points, design experience, skills and other knowledge for PCB layout beginners, so that beginners can get started quickly.

One, what is a PCB layout
PCB is the abbreviation for Printed Circuit Board. The printed circuit board is a substrate for assembling electronic parts. It is a printed board that connects dots and prints components on a common base material according to a predetermined design. The main function of the product is to connect various electronic components to a predetermined circuit, and play the role of relay transmission. It is the key electronic interconnection of electronic products and is known as the "mother of electronic products". Printed circuit boards are used as substrates and key interconnects for electronic parts, and any electronic equipment or products must be equipped. Its downstream industries cover a wide range, involving general consumer electronics, information, communications, medical, and even aerospace technology (information market forum) products and other fields. With the development of science and technology, the demand for electronic information processing of various products is gradually increasing, and new electronic products continue to emerge, which makes the use and market of PCB products continue to expand. The upgrading of emerging 3G mobile phones, automotive electronics, LCD, IPTV, digital TV, and computers will also bring about a larger PCB market than the current traditional market.

LAYOUT means layout planning.

Combined: PCB LAYOUT is the Chinese meaning of printed circuit board layout and routing.

2. Commonly used electronic components based on PCB layout in English

Especially when drawing schematic diagrams with PADS9.3 or allegro16.3, it is an indispensable part to understand the English of commonly used electronic components. We often use the first three English letters of a part to replace a part. In PCB design training, for example: RES for resistors, CAP for capacitors, IND for inductors, etc. Below are some examples that I believe can help you.

voltage

current

Ohm Ohm

Volt Volt

AMP Ampere

Watt Watt

circuit circuit

circuit element,

resistance resistance

resistor

inductance

inductor

capacitance

capacitor

Ohm’s law Ohm’s law

Kirchhoff’s law Kirchhoff’s law

Kirchhoff’s voltage law (KVL)

Kirchhoff’s current law (KCL)

loop

network network

passive two-terminal network passive two-terminal network

active two-terminal network active two-terminal network

Three, the issues that must be considered in the PCB layout

PCB design and draw the circuit frame, the shortest distance between the frame line and the component pin pad should not be less than 2MM, (generally 5MM is more reasonable) otherwise it is difficult to blank. In the same circuit board, the power line. The ground line is thicker than the signal line.

Component layout principle

General principle: In PCB design, if the circuit system has both digital circuits and analog circuits. PCBlayout training and high-current circuits, they must be laid out separately to minimize the coupling between the systems. In the same type of circuit, according to the signal flow direction and Function, block, and place components in divisions.

Input signal processing unit, output signal drive components should be close to the PCB design training circuit board, make the input and output signal lines as short as possible to reduce the interference of input and output.

Component placement direction: Components can only be arranged in two directions, horizontal and vertical. Otherwise, they cannot be inserted into the plug-in. When the potential difference between the components is large, the component spacing should be large enough to prevent discharge.

Component spacing. For medium-density boards, small components, such as low-power resistors, capacitors, diodes, and other discrete components, the spacing between each other is related to the plug-in and welding process. When wave soldering, the component spacing can be 50-100MIL (1.27-2.54MM) The manual can be larger, such as taking 100MIL, integrated circuit chip, the component spacing is generally 100-150MIL, but the IC is used to go to the lotus. The capacitor should be close to the power supply and ground pin of the chip. Otherwise, the filtering effect will be worse. In the digital circuit, In order to ensure the reliable operation of the digital circuit system,

An IC decoupling capacitor is placed between the power and ground of each digital integrated circuit chip. The decoupling capacitor generally uses ceramic capacitors with a capacity of 0.01~0.1UF. The selection of the decoupling capacitor capacity is generally selected according to the reciprocal of the system operating frequency F In addition, a 10UF capacitor and a 0.01UF ceramic capacitor should also be added between the power line and the ground line at the entrance of the circuit power supply.

The clock circuit components should be as close as possible to the clock signal pins of the microcontroller chip to reduce the wiring length of the clock circuit. And it is best not to route the wires below. The resistance of the printed wire is large, the voltage drop on the wire is also large, which affects the performance of the circuit, If the line width is too wide, the wiring density is not high, and the board area increases. In addition to increasing the cost, it is also not conducive to miniaturization.

If the current load is calculated at 20A/mm2, when the thickness of the copper clad foil is 0.5MM, (usually so much), the current load of the 1MM (about 40MIL) line width is 1A, so the line width is 1-2.54MM (40-100MIL) can meet general application requirements. The ground wire and power supply on the high-power equipment board can be appropriately increased according to the power level. On the low-power digital circuit, in order to increase the wiring density, the minimum line width It is sufficient to take 0.254-1.27MM (10-15MIL).

Four, several modules that PCB layout engineers should be familiar with

The following are several modules that are often encountered in PCB design. As a PCB layout engineer, you should be familiar with these.

I-mode and CHTML

I-mode is a wireless communication service launched by DoCoMo, a subsidiary of Japan Telecom (NTT), in the Japanese market. It is currently the most used wireless Internet service in the world (all in Japan). I-mode and WAP

The main difference of is that the content of I-mode is written in CHTML, so most of the current network content can be used with minor modifications; while WAP uses WML, PCB

Layout training Existing web content must be converted to WML before it can be used by WAP.

CHTML (Compact HTML) A variant of HTML. Most compatible with HTML.