Buried Via Save PCB Space

A buried via is a PCB hole that runs from one inner layer to another without reaching the outer layers of the circuit board. These vias allow designers to increase the connectivity of their traces, which improves the function of a multilayer printed circuit board and can also reduce the amount of space required for signal transmission.

To achieve this, buried vias are usually filled with copper to improve their electrical conductivity and allow them to connect a higher number of layers, which makes them an essential component for high-performance, compact electronics. However, they can create impedance discontinuities and substantial energy losses, especially for large currents. Fortunately, there are some steps that can be taken to minimize these issues.

A PCB is made from several copper foil circuits layered on top of each other, and the connections between these layers are established through vias. These are conductive holes that look like barrels and serve as the channels for signals to pass through different layers of the board.

The connectivity of a PCB via depends on how it is made and where it is located in the circuit board. The two most common types of vias are blind and buried. Blind and buried via allow a greater number of connection points while consuming less space than through-hole (TH) vias. They are also known as controlled-depth vias because they have a specific depth that is controlled during fabrication.

How Does a Buried Via Save PCB Space?

Blind and buried vias are used to increase the wiring density on a multilayer PCB. They are drilled in the PCB’s core, which is usually made of FR-4, and then the photosensitive side is laminated to it. The holes are then filled with a thin layer of copper, and they can be etched to expose the metal. Finally, the plated copper can be cut to size with lasers, and the PCB is ready for assembly.

These vias save space on the PCB by connecting more internal layers than through-hole (TH) vias can. However, they can be difficult to use in a multilayer board because the process of drilling and stacking multiple layers around them is complicated. Furthermore, there is a risk of stress concentration at the vias, which can cause cracking and delamination.

Using a buried via can help to prevent this problem by reducing the stress at the vias and keeping them away from heat sources. It also allows designers to use a smaller aspect ratio for the PCB, which can help to improve its thermal performance.

The selection of a blind or buried via should be determined by the design requirements of the circuit board. Choosing the simplest form that meets these needs optimizes cost and manufacturability. This can be done by minimizing the thickness of the copper plating and by reducing the aspect ratios of the vias. It is important to consider the impact of this decision on other aspects of the PCB, such as metallization and assembly. The selection of a blind or buried hole can also have an effect on the quality of solder joints.