As modern electronic devices become more micro and complicated, the accuracy and reasonableness of PCB design which is the bridge of electronic components, appear very important. PCB design is connected with performance stability, manufacturing costs and efficiency. The minimum distances between wires and minimum distances between holes and wire are one of key factors that ensure normal work, avoid short circuit and improve manufacturing success rate.
Distances between wires and distances between holes and wire
Distances between wires and distances refer to minimum allowable distances between center wires of any two conductive wires. The minimum allowable distances must be big enough to prevent accidental electrical connections (i.e., short circuits) caused by breakage of insulation materials during manufacturing or circuit operation. The value of the wire spacing is affected by a variety of factors, such as the material used, the manufacturing process, the operating voltage, the expected current, and the expected operating environment.
Distances between holes and wire refer to minimum allowable distances between the holes edge that are adopted to install component pins and achieve connection from one layer to another layer, and the edge of the nearest wires. Proper hole spacing ensures that adjacent wires would not be damaged during the drilling and copper plating process, meanwhile crosstalk between signals can be decreased, so that signal integrity of the circuit can be ensured.
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Why minimum allowable distances are necessary?
1. Electrical safety: Excessively small wire spacing and hole spacing may lead to current leakage, causing short circuits, and in severe cases, the circuit boards or even the entire system would be damaged.
2. Manufacturing feasibility: manufacturing are limited by techniques, such as etching accuracy, drilling accuracy and so on, and too small spacing can add production difficulty and reduce qualification rate.
3. Signal integrity: if two conductors are too close, electromagnetic interference would occur, which will affect signal transmission quality, and cause signal attenuation, delay, or distortion.
4. Heat management: Dense layouts can hinder heat dissipation, so the long-term reliability and longevity of components would be affected.
The factors that affect the minimum spacing
Operating voltage and current in circuit: high voltage or current circuits need larger wire spacing to lower breakdown risk.
Signal frequency: high frequency signal is more sensitive to wire distances in order to decrease crosstalk and ensure signal quality.
Manufacturing: advanced production technique supports smaller distances between wires and between hole and wire, but the cost will rise.
Environmental factors: temperature cycling, humidity, harsh environments require more conservative designs to improve reliability.
Suggestions for designs
1. Manufacturer guide should be obeyed: each PCB manufacturer provides specific manufacturing capability parameters, including minimum distances between wires and between hole and wire, and all these parameters should be obeyed strictly during design.
2. Use design software to assist: modern PCB design software often has a built-in DRC (Design Rule Check) feature that helps designers automatically detect and adjust the distances between wires and between hole and wire that do not satisfy specification.
3. Margin: wire spacing and hole spacing can be increased to some extent to allow for manufacturing tolerances and potential design modifications, and performance requirements should be met at the same time.
4. Multi-layer board design: It is also necessary to consider the impact of layer alignment and via penetration on adjacent layers for a comprehensive design.
In short, the distances between wires and between hole and wire are one of the most key factors in PCB design, and these distances are directly associated with circuit board performance, reliability and manufacturing costs. The designers can avoid common errors and create efficient and reliable electronic products through the knowledge of these distances, project requirements and production capability.
