Through hole, blind hole, buried hole
Through Hole: Plating Through Hole, PTH for short
This is the most common type of through hole. You just hold the PCB up to the light and the hole where you can see the light is the "through hole". This is also the simplest type of hole because it is relatively inexpensive to drill the circuit board directly using a drill or laser light. But relatively, some circuit layer does not need to connect the hole, for example we have a house of six stories, work bears deep pockets, bought its third and fourth floor, and then work Xiong Ziji in between the third and fourth floor design a staircase connected to each other, and work bears don't need to be connected to the other floors, if to design a stair well versed in each floor to the sixth floor, it will form the waste, today's boards, to treasure land, should not be allowed. Therefore, although the through-hole is cheap, sometimes more PCB space will be lost.
Blind Via Hole (BVH)
Connect the outermost circuit of the PCB with the adjacent inner layer by electroplating hole. Since you can't see the opposite side, it is called "blind hole". In order to increase the space utilization of PCB circuit layer, "blind hole" manufacturing process came into being. This method requires special attention to the depth of the hole (the z-axis) to be just right, but it often makes the hole difficult to electroplate and is rarely used by manufacturers.
It is also possible to drill holes in individual circuit layers that need to be connected in advance and then glue them together. For example, 2+4+2 can be used to guide the outermost two layers or the board of 2+4 at the same time. However, this requires precise positioning and alignment devices.
For example, a six-story house only connects the first floor to the second floor, or the stairs from the fifth floor to the sixth floor. This is called a blind hole.
Buried Hole: Buried Via Hole (BVH)
Any circuit layer inside the PCB is connected but not connected to the outer layer. This process can not be achieved by the way of drilling after bonding, it must be performed in individual circuit layer drilling, first local bonding inner layer after electroplating treatment, and finally all bonding, than the original "through hole" and "blind hole" more time, so the price is also the most expensive. This process is usually used only on high density (HDI) circuit boards to increase the usable space of other circuit layers. With above buy building when example, the house of 6 storeys building connects the stair of 3 storeys and 4 storeys only, call bury hole.