PCB Technical - PCB common three kinds of drilling

Let's first introduce the common drill holes in PCB: plated through hole, blind via hole, buried via hole.

The meaning of these three kinds of holes and their unique place. plated through hole (PTH), which is a common hole, is used to conduct or sign copper foil circuit between conductive patterns in different layers of circuit board.
For example (such as blind hole, buried hole), but it is not allowed to insert components. The guide leg is copper plated hole of other reinforcement materials.

Because PCB is formed by the accumulation of many copper foil layers, each layer of copper foil will be laid with a layer of insulation layer, so you and I can not communicate with each other, and the signal link depends on the via, so there is the name of Chinese character through hole.

The unique place is: in order to meet the needs of customers, the through hole of circuit board must be plugged. In this way, in changing the traditional aluminum plug hole process, the white mesh is used to complete the solder mask and plug hole on the circuit board surface, so that the production is stable, the quality is reliable, and the use is more complete.

With the rapid development of electronic industry, higher requirements are put forward for the manufacturing process and surface mounting technology of printed circuit board.

The technology of plug hole for through-hole is applied, and it should meet the following requirements:

1. Copper can be used in the through hole, but the solder mask can be plugged.

2. There must be tin and lead in the through hole. There is a certain thickness requirement (4um) and no solder paste can enter into the hole, resulting in tin beads hidden in the hole.
3. Through hole must have solder resist ink plug hole, opaque, no tin ring, solder bead and leveling requirements.

Blind via hole(BVH): it is to connect the outermost circuit in PCB with the adjacent inner layer by electroplating hole. Since the opposite side cannot be seen, it is called blind pass.

At the same time, in order to increase the space utilization between PCB layers, blind holes are applied. That is, a through hole on the surface of the printed circuit board.

Unique: the blind hole is located on the top and bottom surface of the circuit board, and has a certain depth. It is used to link the surface circuit and the inner circuit below. The depth of the hole is generally not more than a certain ratio (aperture).

This kind of manufacturing requires that the depth of drilling (Z axis) should be just right to the benefit. Inadvertently, electroplating in the hole will be difficult, so almost no factory thinks it is suitable to use. It can also drill holes in the circuit layer that needs to be connected in advance, and then bond them at the moment of individual circuit layer. However, it needs more accurate positioning and positioning device.

Buried via hole(BVH) refers to the connection between arbitrary circuit layers in PCB, but it does not conduct to the outer layer, and it also means that the through hole does not extend to the outer surface of the circuit board.

Unique: in this process, there is no way to use the form of bonding and drilling. Drilling must be carried out at the moment of individual circuit layer. First, the inner layer is partially bonded, and then electroplating treatment is carried out. Finally, all bonding is possible. It takes more time than the original through-hole and blind hole, so the price is also the most expensive.

This process is generally only used in high density circuit boards to increase the available space of other circuit layers. In PCB production process, drilling is very important and can not be confused.

Because drilling is to drill the required through holes on the copper clad laminate to supply the electrical co sign and fix the parts. If the operation is not appropriate, the through-hole process shows problems. The parts can not be fixed on the circuit board. If it is light, it will affect the use, and if it is heavy, the whole wrench will be discarded. Therefore, the drilling process is quite tight.