The different kinds of Vias used in PCB designs
Vias are used as electrical connections between layers on a PCB (printed circuit board). They can carry signals or power between layers.
Here are the types of Via configuration that we can encounter in a PCB design:
Stub Via
The Stub Via is the most common via configuration found in PCBs aside from the Through hole Vias. The two variations of a stub vias are illustrated as Stub Via A and Stub Via B.
Figure 1 Stub Via A
For the Stub Via A example, it shows the through portion starting from the top layer and ending at some inner layer. The stub portion is the remaining portion continuing from the inner layer junction to the bottom layer.
Figure 2 Stub Via B
The Stub Via B example shows the through portion originating from one internal signal layer and terminating on another internal signal layer. In this scenario, there are two stubs. The first stub is from the first internal layer junction to the top layer; the second stub is from the second internal layer junction to the bottom layer.
Through Hole Vias
Figure 5 Through Hole Via ( Image courtesy en.wikipedia.org )
Through vias are the oldest and simplest via configurations originally used in 2-4 layer PCB designs. Since the signals originate and terminate from the outer layers of the PCB, there are no stubs. In multi-layer PCB applications, they are an inexpensive way to eliminate the resonance effects caused by stubs where other mitigation techniques are not practical or are too expensive.
Blind Vias
Figure 3 Blind Via ( Image courtesy www.microconnex.com )
Blind vias are just like any other via, except that they don’t cross through the entire PCB. A Blind Via connects one or more internal layers to only one external layer. Controlled-depth drilling is used to form the holes prior to plating.
Buried Vias
Figure 4 Buried Via
A buried via, is a plated hole which is completely buried within the board. It connects one or more internal layers and does not connect to an external layer. A disadvantage of using buried via technology is that it is expensive since the inner layers being interconnected need to be fully fabricated and plated before final lamination of the entire PCB.
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