Multilayer PCB: three categories of PCB vias

Multilayer PCB: three categories of PCB vias

A friend asked the editor, what are the vias in the circuit board, there are several types of PCB vias, and what are the advantages, here I will talk about it in detail.

Buried, blind, through-hole technology Buried, blind, through-hole combination technology is also an important way to increase the density of printed circuits. Generally, the buried and blind holes are tiny holes. In addition to increasing the number of wiring on the board, the buried and blind holes use the "closest" inter-layer interconnection, which greatly reduces the number of through holes formed and the isolation plate setting will also be greatly Reduction, thereby increasing the number of effective wiring and inter-layer interconnections in the board, and increasing the density of interconnections.

Therefore, the multi-layer board combining buried, blind, and through-holes has a interconnection density of at least 3 times higher than that of the conventional full-through-hole board structure at the same size and number of layers. The size of the printed board combined with through holes will be greatly reduced or the number of layers will be significantly reduced.

Therefore, in high-density surface-mounted printed boards, buried and blind hole technologies are increasingly used, not only in surface-mounted printed boards in large computers and communication equipment, but also in civil and industrial applications. It has also been widely used in the field, even in some thin boards, such as various PCMCIA, Smard, IC cards and other thin six-layer board blind buried via multilayer PCB circuit processing.

These vias are generally divided into three categories, namely blind vias, buried vias, and through vias. The blind holes are located on the top and bottom surfaces of the printed circuit board and have a certain depth. They are used for the connection between the surface layer circuit and the inner layer circuit below. The depth of the hole usually does not exceed a certain ratio (aperture). Buried hole refers to the connection hole located in the inner layer of the printed circuit board, it will not extend to the surface of the circuit board.

The above two types of holes are located in the inner layer of the circuit board, which is completed by the through-hole molding process before lamination, and several inner layers may be overlapped during the formation of the via hole. The third type is called a through hole. This hole penetrates the entire circuit board and can be used for internal interconnection or as a component positioning hole. Semi-hole multilayer PCB circuit processing

Through hole: Plating Through Hole is referred to as PTH, which is the most common one. As long as you hold the PCB to the light, the hole where you can see the bright light is the "through hole." Through hole multilayer PCB circuit processing

Blind via: Blind Via Hole, connects the outermost circuit of the PCB to the adjacent inner layer with a plated hole. Because the opposite side cannot be seen, it is called "blind pass".

Buried hole: Buried hole, the connection of any circuit layer inside the PCB but not connected to the outer layer. This process cannot be achieved by drilling after bonding. Drilling must be performed on individual circuit layers. After the inner layer is partially bonded, it must be plated first before it can be fully bonded. It is better than the original "through hole" and "Blind hole" takes more time, so the price is also the most expensive. This process is usually only used on high-density (HDI) circuit boards to increase the usable space of other circuit layers.