1. Electrical related safety distance

　　1. Spacing between wires

　　As far as the processing capabilities of mainstream PCB manufacturers are concerned, the minimum spacing between wires should not be less than 4 mils. The minimum line spacing is also the line-to-line and line-to-pad distance. From the production point of view, the bigger the better under conditions, the more common one is 10mil.

　　2. Pad aperture and pad width

　　As far as the processing capabilities of mainstream PCB manufacturers are concerned, if the pad diameter is mechanically drilled, the minimum should not be lower than 4 mils. The hole diameter tolerance is slightly different according to the different plates, which can generally be controlled within, and the minimum width of the pad shall not be lower than that.

　　3. Spacing between pads and pads

　　As far as the processing capabilities of mainstream PCB manufacturers are concerned, the spacing between pads and pads should not be lower.

　　4. The distance between the copper sheet and the edge of the board

　　The distance between the charged copper sheet and the edge of the PCB should preferably not be smaller than that. As shown in the figure above, set the spacing rules for this item on the Design-Rules-Board outline page.

　　If it is a large area of copper, usually there is a shrinking distance from the edge of the board, which is generally set to 20mil. In the PCB design and manufacturing industry, under normal circumstances, for the sake of mechanical considerations of the finished circuit board, or to avoid the occurrence of curling or electrical short circuit due to the exposed copper skin on the edge of the board, engineers often place copper on a large area. Instead of laying copper all the way to the edge of the board, the block is indented by 20 mils relative to the edge of the board. There are many ways to deal with this copper skin shrinkage, such as drawing the keepout layer on the edge of the board, and then setting the distance between the copper and the keepout. Here is a simple method, that is, to set different safety distances for the copper objects, for example, set the safety distance of the whole board to 10mil, and set the copper to 20mil, you can achieve the effect of shrinking the edge of the board by 20mil. Removed dead copper that may have occurred within the device.

　　2. Non-electrical related safety distance

　　1. Character width, height and spacing

　　No changes can be made to the text film during processing, but the line width of the characters whose D-CODE is less than () is thickened, that is, the line width of the character L=(), the width of the entire character =, the height of the entire character H = , the spacing between characters D=. When the text is smaller than the above standard, the processing and printing will be blurred.

　　2. Via-to-via spacing (hole edge to hole edge)

　　Via (VIA) to via spacing (hole edge to hole edge) is preferably greater than 8mil.

　　3. Silkscreen to pad distance

　　Silkscreen does not allow to cover pads. Because if the silk screen is covered with the pad, the silk screen will not be able to be tinned when tinning, which will affect the mounting of components. Generally, the board factory requires a spacing of 8mil to be reserved. If the area of the PCB board is limited, the spacing of 4 mil is barely acceptable. If the silk screen accidentally covers the pad during design, the board factory will automatically remove the silk screen part left on the pad during manufacture to ensure that the pad is tinned.

　　Of course, the specific situation in the design of specific analysis. Sometimes the silkscreen is intentionally close to the pad, because when the two pads are close together, the silkscreen in the middle can effectively prevent the solder connection from short-circuiting during soldering. This situation is another matter.

　　4. 3D height and horizontal spacing on the mechanical structure

　　When mounting devices on the PCB, it is necessary to consider whether there will be conflicts with other mechanical structures in the horizontal direction and space height. Therefore, in the design, it is necessary to fully consider the compatibility between components, between the finished PCB and the product shell and the spatial structure, and reserve a safe distance for each target object to ensure that there is no conflict in space.

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