How many types of holes are on the PCB board?

To prevent losses, it is essential to operate the drilling of holes in printed circuit boards correctly, as even a small error can cause significant damage in this complex process that requires a high degree of expertise.

PCBs require specific holes. Some holes help to mount the components, while others connect the different layers of the board, with all drilled into the board.

Through Hole

It is called “through hole” because it runs from one side of the board to the other side. There are two types of through holes: Plating Through Holes (PTH) and Non-Plating Through Holes (NPTH).

(1) How can PTH and NPTH holes be distinguished?

It is effortless to distinguish between PTH and NPTH holes. The hole wall with bright plating marks is PTH, and the hole without plating marks is NPTH, as shown in the picture below.

(2) What is the use of NPTH (non-electroplated through holes)?

If you look closely at the PCB, you will find that the aperture of the NPTH is usually more significant than that of the PTH. NPTH is mostly used for locking screws, and some are used for installing connectors outside the links.

In addition, some NPTHs will be designed at the edge of the board (will break away) to be used as a test fixture positioning. In the early days, it was also used to fix the circuit board when SMT printing/attaching parts. Now, SMT printing machines mostly use the clamping way to fix the circuit board rather than the thimble.

(3) What is PTH used for?

Generally, PTH holes on the circuit board are used in two ways. One way is used for welding the feet of traditional DIP parts. The aperture of these holes must be larger than the diameter of the welding feet of the parts so that the parts can be inserted into the holes.

Another type of PTH. known as a via, is used to connect different layers of copper foil on a PCB for signal conduction. The PCB is made up of multiple layers of copper foil separated by insulation layers, and vias allow for communication between these layers.

2.Blind Hole

Blind hole – is the connection between the outermost circuit in the printed circuit board (PCB) and the adjacent inner layer by electroplating holes. Because it cannot see across, we called Blind Hole.

The blind holes are located on the top and bottom surfaces of the circuit board and have a certain depth. For the connection between the surface line and the inner line below, the depth of the hole generally has a specified ratio (aperture). This method of production requires special attention. Drilling depth must be just right, do not pay attention to it will cause difficulties in the hole electroplating.

3.Buried Hole

Buried hole is the connection between any circuit layers in the printed circuit board (PCB), but it is not connected with the outer layer.

That is, there is no through hole extending to the surface of the circuit board.

This manufacturing process cannot be achieved by drilling holes after the circuit board is bonded.

It is necessary to drill holes at individual circuit layers. The inner layer shall be partially bonded and then electroplated, and finally fully bonded.

Because the operation process is more laborious than the original through hole and blind hole.

the price is also the most expensive. This manufacturing process is usually only used for high-density circuit boards to increase the space utilization of other circuit layers.

4.Advantages of blind hole and buried hole

Due to limited space in small PCBs, circuit board designers often use blind holes and buried to increase available space and options. Buried vias, for example, help free up surface area without interfering with surface components or top/bottom layer wiring.

Blind holes are also useful for fine-spaced BGA components .

reduce signal residue by only passing through a portion of the board.

Using hidden through holes, such as blind holes and buried vias, can help make circuit boards smaller and lighter.

making them ideal for use in small electronic products like medical devices, tablets, laptops, and mobile phones.

These types of holes are especially popular for high-density interconnect PCBs or HDI.

which offer better power transmission and higher layer density.

During the production of printed circuit boards (PCBs), drilling is a crucial step. It involves creating the required through holes on the copper-clad plate to provide electrical connection. fix devices. If not done correctly, it can lead to issues in the via process.

making it impossible to fix the device on the circuit board. This can affect the use of the circuit board, and even result in scrapping the entire board. Hence, the drilling process is critical.