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PCB the point settings
Mar 04, 2017

PCB the point settings:

Rational use of grid systems, can we play a multiplier role in PCB design. But what is reasonable? many people think that setting the smaller the better, but here we will concentrate on two issues: the first is the design grids at different stages of selection, and the second for the wiring of different points selected.

Design of different stages require different grid settings. Made in the layout can choose grid layout; IC, non-locating connectors and other devices can use 50~100mil to layout grid precision, resistance-Capacitance Inductance and small, passive devices 25mil grid layout. Grid accuracy of aesthetic in favour of alignment and layout. In the design of BGA, if 1.27mm BGA, the Fanout we set point accuracy 25mil to facilitate Fanout vias hit four pins in a central location; for 1.0mm and 0.8mm BGA, we'd better use mm for layout, so Fanout vias can be a very good set. The Fanout is also recommended for other IC design with large lattice design. We recommend Fanout grid best 50mil is even greater. If we can ensure that each can walk the line between the two through-hole is the best.

In the routing phase grid can select 5mil (not certain). Remember never to 1mil wiring grid, so that wiring is cumbersome and very time consuming. Now we talk about why 5mil is recommended in the design (or other grid points) accuracy. Usually determines the design points to two factors: factor of the line width and line spacing, and at design-time for our accuracy and our designs to match, can have a simple formula: (line width + spacing)/5=n, where n must be an integer greater than 1. From a realistic design, line width + line spacing can be greater than 10. Illustrated by 15 as an example. Such as line width for 6mil, line spacing is 9mil; when the line width to 7mil, line spacing for 8mil. Only in this way can be used only when the design grid Precision design rules to ensure accuracy. Wiring hole lattice it is best with over 25mil. We can size in ALLEGRO points set up cabling and through-hole lattice points is different. Can do is bigger than hole lattice and small linear lattice. Of course, the grid setting needed in the practical application of flexible hold.