It is called blind via because when the PCB's outermost circuit is connected with adjacent inner circuit layer by electroplating holes and the opposite side cannot be seen.The blind via is used to increase the utilization of space between circuit layers in PCB.It is namely a via hole extending to one surface of the printed board.
Characteristics: It is put on the surfaces of the top and bottom layers of the circuit board.It has a certain depth,which is used to connect the surface circuit and under inner circuits, and its depth normally isn’t more than a fixed ratio( aperture). This kind of production method requires makers to pay attention to getting drill holes an exact depth(Z-axis), otherwise the process of electroplating in holes will be so difficult that no factories will use the board. Another approach is that individual circuit layer among those which need connecting can be drilled in advance and then bond together. However, relatively precise location and para-position devices are needed to achieve that.
It connects any circuit layers in PCB but doesn’t extend to the outer layer,which also means it doesn’t extend to the PCB via hole on its surface.
Characteristics:In the manufacturing operation, the approach of drilling after bonding is inaccessible.Therefore,the step of drilling has to be realized in individual circuit layer. First, we need to use electroplating treatment after the partial bonding of inner layers,then we can bond all the layers.The production of the buried via takes more efforts and time than that of via holes and blind via, therefore, buried via is most expensive.But the manufacturing operation is usually used only to make high-density PCB in order to increase the usable space of other circuit layers.
Drilling is an important step in the production of PCB, which can not be careless. it is a process to drill via holes needed on CCL(copper-Clad Laminate) in order to provide electrical connection and fix the device. If the operation is improper, there will be problems in the process of via holes, and the device cannot be fixed on the circuit board, which will affect the use, and even the whole board will be scrapped. Therefore, the drilling process is very important.