What are PCB Vias?
In a single-layer printed circuit board, all components can be connected to each other with portions of copper foil called PCB traces or tracks.
However, over the years, as PCBs became more complex and incorporated a greater number of components, the traditional method of interconnecting them would demand a significant amount of space. This would not only increase the board's weight and size but also pose challenges for printed circuit board manufacturers. Nonetheless, these manufacturers have leveraged technological advancements to overcome these obstacles and produce high-quality printed circuit boards.
To avoid it, manufacturers make 2-layer and multi-layer printed circuit boards. Such PCBs are smaller and lighter but, at the same time, have high capacity and speed. For such boards, along with using traces, engineers can use different types of vias in PCB design. They save space and perform other functions. So, the use of via is a crucial part of modern PCB design and layout.
Vias are electrical connections between PCB layers. They are copper cylinders placed inside holes drilled in the board. Simply put, vias are holes in printed circuit boards that conduct electrical signals between two or more layers of the board. One can regard them as vertical PCB traces as opposed to horizontal tracks. This is the main purpose of vias, but they can perform other tasks as well such as heat dissipation or printed circuit board fixation.
Main Types of PCB Vias
1. Through-hole vias
This is the most common type of vias used in PCB design. They penetrate all the layers of a board and go from its upper layer to its bottom layer. Simply put, if you can see what is behind the board by looking into the via, it’s a through-hole via. This is the cheapest type of vias, and they are easy to make but take a lot of space.
Most of them are plated through-holes capable of electrically connecting different layers. But some are non-plating though-holes and serve for mechanically fixing the board with screws or connectors.
2. Blind vias
Unlike through-holes, blind vias are drilled from an exterior layer of a board to one of its inner layers. In other words, they don’t go all the way through the board, and you cannot see what’s behind it.
Such vias require accuracy so that the hole does not penetrate any further than the PCB design allows. For this purpose, laser drilling is sometimes used. But this technique is complicated. So, the more common way to make a blind via is to drill through-holes in multiple layers and then pile them up.
3. Buried vias
Such vias only connect two or more inner layers of a board and have no access to its exterior layers. One cannot see them by looking at the PCB at all. The only way to create blind vias is to drill the necessary holes in layers before compiling them.
Other Types of PCB Vias
While all PCB vias belong to one of the types mentioned above, they can be further classified into the following categories.
1. Stacked vias
The term stacked via refers to a few blind or buried vias placed on top of each other. The manufacturer drills and electroplates through-holes in different layers, then compiles them so that these vias are layered on top of one another. Designing such vias is easier, but the cost is higher because placing must be extremely accurate. On the other hand, using this type of via in PCB design takes less space than through-holes and makes layer connectivity more flexible.
2. Staggered vias
Just like stacked vias, staggered vias are connected to each other but do not overlap. Instead, they simply touch each other with their annular rings. Since this connection method requires less accuracy than stacked vias, making staggered vias is cheaper. However, designing them is more difficult.
3. Skip vias
This term refers to stacked (blind or buried) vias that penetrate several layers but are not electrically connected to a specific layer or layers. In other words, they skip a few layers before connecting to another one.
As the name suggests, such vias are extremely small and do not exceed 150 microns in size. It is easy to recognize them by what they look like: microvias have the shape of cones. They require much less space than other types and are often used in high-density interconnect boards. They can be either blind or buried.
Microvias can penetrate not more than two layers. For deeper penetration, they must be stacked. However, making stacked microvias is very costly, so staggered microvias are more common.
5. Vias in Pad
Vias in pad are the same as other types of vias used in PCB design. However, as the name suggests, they are placed directly beneath the contact pad of a component. It allows manufacturers to save space, which is why this technology is commonly used for manufacturing small-scale PCBs and ball grid array packages.
If you want to know more about different types of vias or come up with your own printed circuit board design, take a look at Integra Source’s PCB design and layout development options. The full cycle of the PCB design process may also include testing, validation, and certification. If you’re interested in hiring an outsourcing development team, it’s useful to know that there actually can be various collaboration models available depending on the project requirements, shared areas of responsibility, and manufacturing options.
We also recommend that you check out our recent case studies by the link above. There you can see the scope of work, a solution for the initial problem, and a list of technologies used. Moreover, you can check our FAQ for a better understanding of the technologies we use, our abilities to build prototypes according to the required specifications, and additional information on PCB validation and cost of life estimation.
All this information will help you to better understand available printed circuit board development options and how to choose the best collaboration model to ensure that you get the best result in terms of time, money and functionality for your project. We have worked with successful startups, businesses, and research centers.