What Are Buried Vias in PCB and Their Purpose

Printed circuit boards are a mysterious entity. On one hand, their high complexity makes them challenging for those outside the industry to comprehend. On the other hand, beyond the visible components and circuits on the surface, there are hidden elements, and one of these is the buried via. So what is buried via, and what purpose does it serve?

What Are Buried Vias in PCB

Buried vias are a concept in multilayer PCB. They have no connection to the outer layers and are plated through holes between two or more inner layers. This means they are not visible from the surface of the PCB. A typical PCB contains numerous holes, most of which are used for mounting components. However, buried vias, lacking space on the PCB surface, do not accommodate component pins. Unlike other PCB vias, the purpose of buried vias is to create more interlayer connections, enhancing circuit performance and signal transmission efficiency.

buried via hole

Applications and Characteristics of Buried Vias

Among various types of vias, buried vias pose the greatest manufacturing challenges, resulting in higher costs. Naturally, users would not want to incur additional expenses for something without meaningful benefits.

Firstly, high-density interconnects aim to achieve higher circuit density and more intricate line designs, especially in high-performance computers, communication equipment, and other miniaturized electronic devices. These applications deal with high-frequency and high-speed data transmission, where buried vias shine by significantly shortening signal transmission paths, thereby reducing signal latency.

Secondly, in multilayer PCB, the purpose of buried vias is to serve the inner layers, which single and double layers lack. As demand for high-tech products increases, more PCB layers are often required to enhance board performance. Although constructing buried vias adds extra manufacturing costs, in highly competitive markets, this cost increase is relatively negligible as the product itself holds higher value.

It’s crucial to recognize that buried vias exist within the PCB’s internal layers and do not enter from the surface. This makes manufacturing more challenging. Typically, laser equipment is used during manufacturing to penetrate a thin insulating layer, followed by plating a thin metal layer inside the hole. Finally, these layers are stacked together to form the entire PCB structure.

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