1 Traditional Plated Through Hole;
Most common, cheapest inter-layer connected technology is traditional plated through hole technology. Below picture you can view the 6 layer plated through hole printed circuit board:
In this application, all the drill hole need to be through printed circuit board, no matter if they can be used as via or component lead hole. The drawback of this technology is the through hole will take over all the precious space of each layer. Without the consideration whether that layer need electric connection.
2 Buried via:
Buried via is a kind of through hole technology use to connect the 2 or more layers of multilayer printed circuit board, buried via is among the inner layer of printed circuit board, not on the surface of printed circuit board. See below picture, there is a multilayer printed circuit board with buried via.
Compare with traditional plated through hole structure, buried via can save more space. When the signal circuit density is very high, need more holes to connect the signal layers, and need more signal circuit simultaneously, buried via technology can be applied. However, because buried via technology need more process, so higher circuit density will increase printed circuit board cost.
3 Blind via
Blind via is a kind of through hole which help to connect layer from surface to inner layer, they won’t go through the whole printed circuit board, see below picture
It is a typical blind via technology, blind via technology can be applied on both side of multilayer printed circuit board, blind via can connect both through hole and component hole which will go through printed circuit board.
Blind via can overlay each other and can make smaller which can save more space and layout more signal circuit.
Refers to SMD and connector, blind via is extremely useful because they don’t need big component hole, only need small via which can connect surface layer to inner layer. On the very density and thick multilayer printed circuit board, through surface mount technology can effectively reduce the weight and provide more space for designer.