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PAN1322
Application Note
47
Revision 1.2, 2013-12-18
Design Guide
Figure 18. Example of a four layer stack-up
7.2.1.1
Via Holes
Before starting with routing, the layout engineer must know what kinds of via are available. The choice
depends from budget considerations: micro via are the most expensive, through via are the cheapest,
the others are in the middle.
Figure 19. Via Types
Micro via:
they have a diameter between 50
m and 100
m and can be placed directly into the pads
of BGA and similar components. The availability of this technology must be verified with the
manufacturing factory. Because of the small diameter much PCB’s space can be saved and power and
ground planes are less discontinuous.
Buried via:
they are connecting two or more inner layers (for example from 2
nd
to 3
rd
layer). The
diameter is ≥ 100
m. Since is not required to drill all the PCB they can help to save space for routing.
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