PCB Engineers are doing PCB When the design , We often encounter the problem of various safety distances , Generally, these spacing requirements are divided into two categories , One is electrical safety clearance , Another kind of : Non electrical safety clearance . that , Design PCB What spacing requirements do circuit boards have ？
One 、 Electrical safety clearance
1、 Spacing between conductors ： Minimum line spacing , It's also line to line , The distance between wire and pad shall not be less than 4MIL. From a production point of view , If there are conditions, of course, the bigger the better . General routine 10MIL More common .
2、 Pad aperture and pad width ： according to PCB Manufacturer information , If the pad hole diameter is drilled mechanically , The minimum shall not be less than 0.2mm; If laser drilling is used , The minimum shall not be less than 4mil. The hole diameter tolerance is slightly different according to different plates , Generally, it can be controlled in 0.05mm within ; The minimum pad width shall not be less than 0.2mm.
3、 Spacing between pads ： according to PCB Manufacturer's processing capacity , The spacing shall not be less than 0.2MM.
4、 The distance between copper sheet and plate edge ： Preferably not less than 0.3mm. If it is a large area of copper , There is usually an inward distance from the edge of the plate , General set to 20mil.
Two 、 Non electrical safety clearance
1、 Width, height and spacing of characters ： For the characters of silk screen printing, general values are generally used, such as ：5/30、6/36 MIL etc. . Because when the text is too small , Processing and printing will be blurred .
2、 The distance from the silk screen to the pad ： No pad is allowed for silk screen printing . Because if the silk screen is covered with a pad , When tin is applied, the silk screen printing place will not be tin , Thus affecting the installation of components . commonly PCB The manufacturer requires to reserve 8mil The distance between . If some PCB The board area is very close , Achieve 4MIL The spacing is also acceptable . If the silk screen is accidentally covered by the pad in the design ,PCB When manufacturing, the manufacturer will automatically eliminate the silk screen part left on the pad to ensure that the tin on the pad .
3、 Mechanical structure 3D Height and horizontal spacing ：PCB When installing the upper device , Consider whether the horizontal direction and space height will conflict with other mechanical structures . Therefore, when designing , Fully consider the relationship between components , as well as PCB Between the finished product and the product shell , Adaptability in spatial structure , Reserve a safe space for each target object .
The above is the design PCB Some spacing requirements that circuit boards need to meet , Do you understand ？
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