How is a Buried Via Designed in PCB Software?

Buried Via Designed in PCB Software

In printed circuit boards (PCBs), vias provide electrical connections between layers of the board. While basic through-hole vias span the entire PCB, more advanced via structures called blind and buried via connect between adjacent layers without passing completely through the PCB. This article provides an in-depth overview of these two types of vias, including their definitions, PCB technology enabling their fabrication, key benefits and applications, design considerations, reliability factors, and comparison to other via types.

A buried via is a copper-plated hole in a printed circuit board that connects internal layers of the PCB. It is not accessible by external layers of the circuit board, therefore, it is referred to as “buried” because it cannot be seen from outside the PCB. As such, a buried via can be used to increase the density of a PCB by eliminating the need for through-hole components, or it can reduce the number of layers in an HDI PCB.

The PCB manufacturing process can be a complex and time-consuming task, which is why it’s important to carefully consider your PCB design and routing before placing any vias. In particular, buried vias require careful attention as they can impact signal integrity. In addition, they can cause thermal stress in high-speed applications if they are not placed properly.

How is a Buried Via Designed in PCB Software?

When designing a buried via, you should ensure that the drilled holes are correctly positioned on the inner layers. Also, you should check that the ratio of the drilled hole depth to its drill diameter is correct for the layer it is connecting to. For example, a buried via that connects to an inner layer with a large hole will create unnecessary stresses in the board and may lead to failure.

Another critical factor in buried via design is ensuring that there are no unnecessary holes between the drilled holes. This will prevent the accidental connection of multiple signals to each other. Additionally, it is important to avoid placing any component pads or traces too close to the buried via. Finally, you should ensure that the buried via has an annular ring that is at least 0.1 mm thick to protect it from damage during manufacturing.

In addition to reducing the amount of space required for components, buried vias can help improve the overall quality of a PCB’s electrical performance. This is because they can be placed at heat-generating areas and travel the heat to a different layer where it can dissipate more easily. This can help to improve the performance of a PCB under harsh thermal conditions. Moreover, buried vias can help to eliminate signal stubs, which can improve impedance matching and signal integrity. As such, they are an essential part of any HDI PCB design.