User Guide

If micro vias are enabled in the Design Rules, EAGLE sets a micro via
when routing from an SMD and immediately changing to the next inner
layer.
Autorouter
TheAutoroutersupportsblindandburiedvias.
If you decide to use the Autorouter for a multilayer board that uses
blind and buried vias it is not allowed to work with automatically gener
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ated supply layers (see page 122). In this case inner layers can be defined
withthehelpofpolygons.
Already existing supply layers can be transformed into layers with sup
-
plypolygonsby
•
renamingthelayer(no$signatthebeginningofthename),
•
removingpossiblyexistingisolationwires,
•
drawingapolygoncoveringthewholelayout,and
•
namingthepolygonwiththefavoredsignalname.
MicroVia ¾ A SpecialCaseof BlindVia
In contrast to blind vias that can reach several layers deep into the board
the micro via connects an outer layer with the next inner layer. The drill
diameter of a micro via is relatively small. Presently the usual values are
about0.1to0.05mm.
For manufacturing resons micro vias, as blind vias, have to follow a cer
-
tain aspect ratio of depth to drill diameter. This ratio defines the maxi
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mumviadepthforacertaindrilldiameter.
Thepropervaluecanbelearnedfromyourboardhouse.
SetthisvalueintheDesignRules, Sizes tab, Min.BlindViaRatio.
Assumed the boardhouse demands the ratio as 1:0.5 you have to enter
0.5 for Min.BlindViaRatio.
Additionally the Design Rule Check verifies the minimum drill diame
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ter for mircro vias given in Min. MicroVia. If this value is higher than the
valuefor MinimumDrill (default),microviaswon'tbechecked.
The diameter of micro vias is set in the Restring tab of the Design Rules.
131
FromSchematictoFinishedBoard