PCB with Hole

We often see PCB with Hole, but there are many kinds of holes on PCB. Do you know?Let’s introduce it today

PTH and NPTH

In terms of whether it plays the role of electrical connection, we divided the hole into PTH hole and NPTH hole (PTH: Plating through hole, NPTH: no Plating through hole)

PTH (Plating Through Hole) is a metalized hole, so the layer connected to it is conductive; there is an electrical connection.

The metal tube passes through the surface of the circuit board hole, connects the two-sided circuits on the double-sided board, and also plays a role in connecting the internal circuit in the multilayer board. As shown below:

The opposite is NPTH (Non Plating Through Hole)

Which means that there is no copper inside the hole; electrical isolation. Generally, they are positioning holes and gongs holes. As shown below:

Conclusion： Whether it is PTH or NPTH, it is the classification of through holes. Through holes refer to through the top and bottom layers of the PCB. There are similar holes and blind holes and buried holes. The through holes can be PTH or NPTH, depending on specific needs. Certainly. For example, the hole used to connect the wire needs PTH, and the hole used for fixing function, such as screw hole, may be NPTH

Laser drilling hole and Ordinary machining pcb with holes

Laser drilling

From the processing equipment, laser drilling and ordinary machining holes (ordinary machining holes, which can cover holes processed by beer machines and milling machines), the former type of holes often appear in ANY Layer (any layer interconnected Multilayer board) and HDI (High Density Interconnect Board),

Mechanical drilling

In the production of circuit boards, actrally, in the past the engineer was like design the mechanical drilling. Mechanical drilling is the most effective and cost-effective method for printed circuit boards. For the specified through-hole size, the diameter of mechanically drilled and plated through-holes can reach 100μm to 150μm (4-6 mils).

However, it is more practical to choose a drill with a diameter of 200μm (8 mil). Because the drill tip is pointed and has a long service life, so it is unlikely to damage the drill.

With the rapid development of microelectronics technology, the wide application of large-scale and super-large pcb circuit boards, and the advancement of micro-assembly technology, the manufacturing of printed circuit boards is developing in the direction of multi-function and layering. The hdi circuit board has fine wires, micro holes and narrow spacing. Mechanical drilling technology can no longer meet the requirements of a new micro-hole processing method in processing.

Laser is a kind of strong light beam. When the “light” is stimulated by external energy, it will be excited. Infrared light and visible light have heat energy, and ultraviolet light has light energy. When this light reaches the surface of the workpiece, there are three phenomena: reflection, absorption and penetration. HDI cicurit board always use laser drilling hole.

Laser drilling machine. Mainly used in the connection between the inner layer and the inner layer, and the outer layer and the inner layer of the printed circuit board. The high-precision laser is used to penetrate the copper plate and the inner resin, and then pass the copper plating to complete the circuit connection.

Laser drilling machine is the earliest practical laser processing technology, and it is also one of the main application fields of laser processing.

Traditional processing methods can no longer meet certain process requirements, because we choose use more and more materials with high hardness and high melting point. With the rapid development of modern industry and science and technology. For example, the processing of micron-level apertures on the high melting point metal molybdenum plate, and the processing of small holes of tens of microns on the hard tungsten carbide

Through holes, buried holes and blind holes

From where the holes appear, we can add through holes, buried holes and blind holes

Through Hole:

Plating Through Hole, or PTH for short, is the most common one. You only need to pick up the PCB and face the light, and the hole that can see the bright light is the “through hole”.

This is also the simplest type of hole, because when making it, you only need to use a drill or a laser to directly drill the circuit board, and the cost is relatively cheap. But on the other hand, some circuit layers do not need to connect these through holes. For example, we have a six-story house.

I bought its third and fourth floors. I want to design a staircase inside that only connects the third floor to the third floor. It’s fine between the fourth floor. For me, an existing staircase connecting the first to sixth floors invisibly occupies the fourth floor. So although through holes are cheap, they sometimes use up more PCB space.

Blind Via Hole

which connects the outermost circuit of the PCB with the adjacent inner layer with electroplated holes. Because we cannot see the opposite side, it is called “blind via”. In order to increase the space utilization of the PCB circuit layer, a “blind via” process has emerged.

This production method requires special attention to the depth of the drilling (Z axis) to be just right. No manufacters want to use this because this method often causes difficulties in electroplating in the hole; The designer can also pre-place the circuit layers that need to be connected in a separate circuit layer.

At that time,the worker should drilled first, and then glued together, but he need a more precise positioning and alignment device.

Buried hole:

Buried hole, the connection of any circuit layer inside the PCB but not conducting to the outer layer. We cannot achieved this process by drilling after bonding. It must be drilled on the individual circuit layers. After the inner layer is partially bonded, it must be electroplated before it can be fully bonded.

Compared with the original “through hole” and “Blind holes” take more time, so the price is the most expensive. We not only use this process on high-density (HDI) circuit boards, we alse use it as space of other circuit layers.

There is a sample picture below, you can refer to it for understanding: