PCBNEW: Routing PCBs
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The choice is made in the menu: Dimensions ->Tracks et Vias.
The dimensions are given in inches or mm, depending upon the active units.
Reminder: 2.54 cm = 1 inch (or " ) = 1000 mils = 10000 tenths of mils.
Use the largest possible value and conform to the minimum sizes given here:
Units |
CLASS 1 |
CLASS 2 |
CLASS 3 |
CLASS 4 |
CLASS 5 |
mm |
0,8 |
0,5 |
0,4 |
0,25 |
0,15 |
1/10mils |
310 |
200 |
160 |
100 |
60 |
Unité |
CLASS 1 |
CLASS 2 |
CLASSE3 |
CLASS 4 |
CLASS 5 |
mm |
0,70 |
0,5 |
0,35 |
0,23 |
0,20 |
1/10mils |
270 |
200 |
140 |
90 |
80 |
Usually, the minimum clearance is very similar to the minimum track width.
Clearance: 0.35mm (0.0138 inches).
Track width: 0.8mm (0.0315 inches).
Pad diameter for ICs and vias: 1.91mm (0.0750 inches ).
Pad diameter for discrete components: 2.54mm (0.1 inches).
Ground track width: 2.54mm (0.1 inches).
Clearance: 0.35mm (0.0138 inches).
Track width: 0.5mm (0.0127 inches).
Pad diameter for ICs: make them elongated in order to allow tracks to pass between IC pads and yet have the pads offer a sufficient adhesive surface (1.27 x 2.54 mm -->0.05x 0.1 inches).
Vias : 1.27mm (0.0500 inches).
Manual routing is recommended, because it is the only method offering control of routing priorities. For example, is is preferable to start by routing power tracks, making them wide and short and keeping analog and digital supplies well separated. Then sensitive signal tracks should be routed. Amongst other problems, automatic routing often requires many vias. However, automatic routing can offer useful insight into the positioning of modules. With experience, you will probably find that the automatic router is useful for quickly routing the 'obvious' tracks, but the remaining tracks will best be routed by hand.
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