pacing between conductors

As far as the processing capacity of mainstream PCB manufacturers in Shenzhen is concerned, the minimum distance between conductors shall not be less than 4mil. The minimum line distance is also the distance from line to line and from line to pad. From the perspective of production, the larger the better if conditions permit, and the more common is 10mil.

2. Pad aperture and pad width

As far as the processing capacity of mainstream PCB manufacturers in Shenzhen is concerned, if the pad hole diameter is mechanical drilling, the minimum shall not be less than 0.2mm, and if laser drilling is used, the minimum shall not be less than 4mil. The hole diameter tolerance is slightly different according to different plates, which can be controlled within 0.05mm generally, and the minimum pad width shall not be less than 0.2mm.

In case of large-area copper laying, there is usually a shrink distance from the plate edge, which is generally set as 20mil. In PCB design and manufacturing industry, in general, due to the mechanical considerations of the finished circuit board, or to avoid the possibility of curling or electrical short circuit due to the exposure of the copper sheet on the board edge, engineers often shrink the large area of copper block with respect to the board edge by 20 mils, instead of always laying the copper sheet to the board edge.

There are many methods to deal with the copper skin shrinkage, such as drawing a keepout layer on the board edge, and then setting the distance between copper and keepout. A simple method is introduced here, which is to set different safety distances for the copper laying objects. For example, if the safety distance of the whole board is set to 10mil, and the copper laying is set to 20mil, the board edge can be shrunk by 20mil. At the same time, the possible dead copper in the device can be removed.

Non electrical related safety distance

The text film cannot be changed during processing, but the width of character lines with D-CODE less than 0.22mm (8.66mil) is thickened to 0.22mm, that is, the width of character lines L=0.22mm (8.66mil).

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

Clearance between vias

It is not allowed to cover the pad with silk screen. Because if the solder pad is covered with the silk screen, the silk screen cannot be coated with tin, which affects the assembly of components. Generally, it is better to reserve a space of 8mil for PCB manufacturers. If the area of PCB is limited, the spacing of 4mil is acceptable. If the silk screen accidentally covers the bonding pad during design, the PCB factory will automatically eliminate the silk screen left on the bonding pad during manufacturing to ensure tin on the bonding pad.