What principles should be followed for pcb copy board

Abstract: PCB copying is a very tedious task. If you are not careful, mistakes will be copied and the circuit board can no longer be used. So, what are the principles to be followed in the process of PCB copying?Here are some tips when pcb copy board.

Table of content

1. Choose the appropriate printed wire width

2. Line spacing

3. Selection of pads

4. Draw the circuit border

5. Component planning criteria

 pcb copy board

1. Choose the appropriate printed wire width

The minimum width of the printed wire is related to the size of the current flowing through the wire: the line width is too small, and the resistance of the printed wire is large, and the voltage drop on the wire will be large, which affects the function of the circuit. 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 1-2.54 MM (40-100MIL) can meet the requirements of ordinary use. The ground wire and power supply on the high-power equipment pcb copy 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 The line width is 0.254–1.27MM (10–15MIL) to meet the requirements. In the same circuit board, the power line and the ground line are thicker than the signal line.

 

2.Line spacing

When it is 1.5MM (about 60MIL), the insulation resistance between the lines is greater than 20M ohms, and the maximum withstand voltage between the lines can reach 300V. When the line spacing is 1MM (40MIL), the maximum withstand voltage between the lines is 200V. For high-voltage (line-to-line voltage not greater than 200V) circuit boards, the line spacing is 1.0–1.5MM (40-60MIL). In high-voltage circuits, such as digital circuit systems, there is no need to think about the breakdown voltage, only the production process allows. It can be very small.

 

3. Selection of pads

For 1/8W resistors, the diameter of the pad lead is 28MIL, and for 1/2W, the diameter is 32MIL, the lead hole is too large, and the width of the copper ring of the pad is absolutely reduced, causing the pad to be damaged. Adhesion is reduced. It is easy to fall off, the lead hole is too small, and it is difficult to install the components.

 

4. Draw the circuit border

The shortest distance between the border line and the component pin pad cannot be less than 2MM, (usually 5MM is more reasonable) otherwise it is difficult to blank the material.

pcb board copy

 

5. Component planning criteria

A: Ordinary criterion: In PCB copy board design, if the circuit system has both digital circuits and analog circuits. And large current circuits, it must be planned separately to minimize the coupling between the various systems. In the same type of circuit, according to the signal flow direction and Function, block and place components in zones.

B: The output signal processing unit, the input signal driving component should be close to the edge of the pcb copy board, and the input and output signal lines should be as short as possible to reduce the interference of input and output.

C: Component placement direction: Component can only be displayed in the horizontal and vertical directions. Otherwise, it cannot be used in the plug-in.

D: Component spacing. Regarding 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 the welding process. During wave soldering, the component spacing can be 50-100MIL (1.27– 2.54MM) manual can be larger, such as taking 100MIL, integrated circuit chip, component spacing is generally 100-150MIL

E: When the potential difference between the components is large, the component spacing should be large enough to prevent the appearance of discharge.

F: The IC decoupling capacitor should be close to the chip’s power supply and ground line pins. Otherwise, the filtering effect will be worse. In the digital circuit, in order to ensure the reliable and reliable task of the digital circuit, it is placed between the power supply and the ground of each digital integrated circuit chip. IC decoupling capacitor. In addition, a 10UF capacitor and a 0.01UF ceramic capacitor are also required between the power line and the ground line at the entrance of the circuit power supply.

G: The clock circuit components are 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 wire them.


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