What’s a Via?
Via is one of the important components of a multi layer PCB, the cost of drilling can be up to 30% to 40% of the total board cost.
As we all know, printed circuit board is superimposed by copper foil circuit layer upon layer, and the connection between the different circuit layers is the via.
The three most common via are plating through hole, blind hole and buried hole. Below are the details of these three kinds of PCB via hole.
Plating Through Hole(PTH)
Plating through hole is the most common via, just take up PCB and face to the light, if you can see the light, then it is the “through hole”. PTH is also the simplest kind of hole because it just need to use drill or laser light to make a full borehole, and the cost is relatively cheap. But some circuit layer do not need plating through hole. Although PTH is much cheaper, sometimes, it may use some more PCB space.
Blind Via Hole(BVH)
Connect the outermost circuit of the PCB and the adjacent inner layer with plated through-hole, since we cannot see the opposite, so it is called “blind pass”. In order to increase the space utilization of PCB circuit layer, blind via hole came into being. Please note that this production method requires special attention to the depth of the hole (Z axis) should be appropriate. Almost no PCB manufacturer adopt this kind of method because the difficult of hole plating.
Buried Via Hole (BVH)
Buried via hole connects to any circuit layer of PCB but do not pass to the outer layer. This process cannot be done using the method of bonding after drilling, it must be in the individual circuit layer when the implementation of drilling, the first part of the internal bonding after the first plating treatment, and finally all the bonding. Buried via hold need more time than the original “through-hole” and “Blind hole”, so its’ price also the most expensive. This process is usually used in high-density (HDI) circuit boards to increase the other circuit layer can be used space.