Editorial Team - PCB Directory
A Staggered Via is a type of via structure that consists of multiple (two or more) vias in an arrangement such that they are never in direct contact with each other as their drill axes are separate which offsets their position on adjacent layers. As staggered vias have a different position in each layer they form a zigzag pattern when the PCB is viewed from the top or bottom of it. They are most often used in multi-layer printed circuit boards (PCBs), and high-density interconnect (HDI) designs.
How are Staggered Vias Made?
The staggered configuration can include a combination of different types of vias, such as micro vias, buried vias, and through-hole vias, depending on the design requirements. They can be made primarily by two methods:
Advantages of Staggered Vias
There are several reasons why designers choose to use staggered vias in PCB designs. Here are some of the key advantages:
Challenges of Staggered Vias
Staggered vias in PCB designs are tougher to design and manufacture. While designing a staggered via structure, the spacing between the laser-drilled holes is the primary concern. The possibility of the staggered via design depends on the vertical distance between the centers of two adjacent vias. A viable staggered design requires the vertical separation to be more than the diameter of the via. This needs to be done precisely to avoid any issues, making the process more challenging.
Although less complex, staggering makes them use up more space on the board. Hence, if the PCB design has space constraints, staggered vias may not be the right choice. Staggering also introduces more discontinuity in the signal path. This makes it difficult to maintain a uniform via impedance requirement in a high-speed design.
HDI designs already have a high aspect ratio of vias. A staggered via structure may cause additional complexity in these designs resulting in manufacturing errors. There can potentially be more drilling and plating errors also due to the offset vial scoring which can result in higher production costs.
In some instances, staggered vias may even boost the complexity of a heat control system by introducing more thermal interfaces and potential hot point locations mainly because of the positions of staggered vias.
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