Stacked Vias and the Key Components Involved
Stacked Vias and the Key Components
If you’re designing a printed circuit board (PCB) that requires stacked vias, it’s important to know how they work and the key components involved. Stacked vias are a popular choice in PCB designs because they offer many advantages over traditional through hole vias, including lower power loss and higher layer connectivity. In addition, they allow for the use of smaller component sizes and help improve heat dissipation. But like all technologies, stacked vias come with their own challenges. Read on to learn everything you need to know about stacked vias.
The defining feature of a stacked vias is the way in which they connect layers in a PCB. Stacked vias consist of a blind microvia stacked on top of a buried one, and are a standard way to span between layers in HDI PCBs. The internal buried vias are filled with conductive paste and plated to ensure strong contact with the adjacent layers, while the blind microvia is capped with copper and acts as an electrical barrier between the two.
Stacked vias can be used for a variety of purposes in PCB design, but their primary use is to allow signals to travel between different layers at high speeds. In addition, they can also reduce the distance between a signal and its destination on the layer below, which can be important for high-speed applications.
Stacked Vias and the Key Components Involved
In addition to the benefits stacked vias provide, they can also be less expensive than through-hole vias for the same connection length. This is because they eliminate the need for soldering, which can add a significant amount of cost to a circuit board. Additionally, stacked vias are much smaller than traditional through-hole vias, which makes it possible for them to fit inside pads used for surface mount technology (SMT) components such as fine pitch ball grid arrays (BGAs).
As a result of their small size, stacked vias can also reduce the overall height of the circuit board. This can be advantageous for space-constrained applications where every square millimeter of the board needs to be maximized.
Unfortunately, stacked vias are not without their drawbacks, the most prominent of which is reliability. The voids in a stacked via can lead to failure due to thermal cycling, which is why it’s critical that designers pay attention to the aspect ratio and volume void fraction when specifying them.
It’s also important to note that the stacked via construction introduces additional fabrication steps, and therefore increases the overall manufacturing costs. To prevent this, it’s vital that designers properly specify the vias in their PCB stackups, and to consult with their fabricators to determine which fabrication process is best for the project at hand. They can then adjust the drilled hole, annular ring, and clearances accordingly to maintain manufacturability. If they make changes as an afterthought prior to the fabrication process, however, it may be difficult for the fabricator to achieve the desired tolerances. This can lead to issues with the circuit board’s performance.
