In PCB board copying, PCB modification and PCB design, the width of the printed wire, line spacing, circuit frame and component layout will affect the quality and performance of the circuit board.
The minimum width of a printed wire is related to the current flowing through the wire. Line width is too small, the resistance of just printed wire is large, and the voltage drop on the line is large, affecting the circuit’s performance.If the wire 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/ MM square, the current load of 1MM(about 40MIL) wireline is 1A when the thickness of the copper clad foil is 0.5mm (generally this much). Therefore, the line width of 1– 2.54mm (40–100MIL) can meet the general application requirements, the ground wire and power supply on the high-power equipment board, according to the power size, can be appropriately increased line width, and in the low-power digital circuit, to improve the wiring density, the minimum line width of 0.254-1.27mm (10–15MIL) can be full The foot. In the same circuit board, the power cord. The ground wire is thicker than the signal wire.
When it is 1.5mm (about 60MIL), the insulation resistance between wires is greater than 20M ohms, and the maximum voltage between wires can reach 300V. When the line spacing is 1MM(40MIL), the maximum voltage between the lines is 200V, therefore, in the low and medium voltage (the voltage between the lines is not greater than 200V) on the circuit board, the line spacing is 1.0- 1.5mm (40- 60MIL) in the low voltage circuit, such as digital circuit system, do not have to consider the breakdown voltage, as long as the production process allows, can be very small.
Pad lead diameter of 28MIL is sufficient for 1/8W resistance, For 1/2W, with a diameter of 32MIL, the lead hole is too large, and the width of the copper ring of the pad is relatively reduced, which leads to the decrease of the adhesion of the pad. Easy to fall off, lead hole is too small, component seeding is difficult.
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 blanching.
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