—Edited by JDB PCB COMPNAY.

PCB engineers often encounter various safety clearance issues when doing PCB design. Usually these spacing requirements are divided into two categories, one is electrical safety clearance, and the other is non-electrical safety clearance. So, what are the spacing requirements for designing PCB circuit boards?

1. Electrical safety distance

1. The spacing between wires: the minimum line spacing is also line-to-line, and the line-to-pad spacing must not be less than 4MIL. From a production point of view, of course, the bigger the better if possible. The conventional 10MIL is more common.

2. Pad aperture and pad width: According to the PCB manufacturer, if the pad aperture is mechanically drilled, the minimum should not be less than 0.2mm; if laser drilling is used, the minimum should not be less than 4mil. The aperture tolerance is slightly different depending on the plate, generally can be controlled within 0.05mm; the minimum width of the land should not be less than 0.2mm.

3. The distance between the pad and the pad: According to the processing capacity of the PCB manufacturer, the distance should not be less than 0.2MM.

4. The distance between the copper sheet and the board edge: preferably not less than 0.3mm. If it is a large area of copper, there is usually a retracted distance from the edge of the board, generally set to 20mil.

2. Non-electrical safety distance

1. The width, height and spacing of characters: The characters on silk screen generally use conventional values ​​such as 5/30, 6/36 MIL, etc. Because when the text is too small, the processed printing will be blurred.

2. The distance from the silk screen to the pad: the silk screen is not allowed to be on the pad. Because if the silk screen is covered with the pad, the silk screen will not be tinned when it is tinned, which will affect the component placement. It is generally required to reserve 8mil spacing. If the area of ​​some PCB boards is very close, 4MIL spacing is also acceptable. If the silk screen accidentally covers the pad during design, the part of the silk screen left on the pad will be automatically eliminated during manufacturing to ensure that the pad is tinned.

3. 3D height and horizontal spacing on the mechanical structure: When mounting components on the PCB, consider whether the horizontal direction and space height will conflict with other mechanical structures. Therefore, when designing, it is necessary to fully consider the adaptability of the space structure between the components, and between the finished PCB and the product shell, and reserve a safe distance for each target object.

The above are some of the spacing requirements that need to be met when designing PCB circuit boards. Do you know everything?