1. Spacing between wires

　　As far as the processing capabilities of mainstream Shenzhen PCB manufacturers are concerned, the minimum distance between wires should not be less than 4mil. 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 Shenzhen PCB manufacturers are concerned, if the pad diameter is mechanically drilled, the minimum should not be less than 0.2mm, and if the laser drilling method is used, the minimum should not be less than 4mil. The hole diameter tolerance is slightly different according to the different plates. Generally, it can be controlled within 0.05mm, and the minimum pad width should not be less than 0.2mm.

　　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.

　　Double-sided pcb circuit board

　　There are many ways to deal with this copper skin shrinking, 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.

　　Non-electrically related safety distances

　　No changes can be made to the text film during processing, but the width of the character lines whose D-CODE is less than 0.22mm (8.66mil) is thickened to 0.22mm, that is, the width of the character line is L=0.22mm (8.66mil).

　　The width of the whole character is W=1.0mm, the height of the whole character is H=1.2mm, and the spacing between characters is D=0.2mm. When the text is smaller than the above standard, the processing and printing will be blurred.

　　Via-to-via spacing

　　The silk screen is not allowed to cover the 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 circuit board factory requires a spacing of 8 mils to be reserved. If the area of the circuit board is limited, the spacing of 4mil is barely acceptable. If the silk screen accidentally covers the pad during the design, the circuit board factory will automatically eliminate the silk screen part left on the pad during manufacture to ensure that the pad is tinned.

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