What is a Via?

A via is simply a hole, drilled or plated, that is in the PCB that will allow a signal to pass to the inner layer of the board or to the other side of the board. Vias often connect component leads to planes or signal traces. These allow a change to the signal layers. If the via goes completely through the PCB board, it is often called a through-via. You might also hear people refer to this as a through-hole.

Blind and buried vias are only available on boards that have at least four layers. They connect the inner layers with other inner layers that are adjacent to them or to adjacent surface layers.

A Closer Look at Blind Vias

When examining blind and buried vias, there are several different types of blind vias to be considered. There are photo-defined blind vias, controlled-depth blind vias, sequential-lamination blind vias, and laser-drilled blind vias.

• Photo-defined blind vias. The creation of photo-defined blind vias requires laminating a photosensitive resin to a core. The photosensitive sheet will have a pattern on it that indicates the areas where the holes will be made. It is then exposed to light that causes the remaining material on the board to harden. The PCB is then put into an etching solution that removes the material from the holes that were created, which creates pathways. Copper is then plated in the hole and on the outer surface, which creates the outer layer of the PCB.
• Controlled-depth blind vias. The creation of controlled-depth blind vias is very similar to creating through-hole vias. The only difference is that the drill used to make the holes is set so that it will only go partially through the PCB. Modern technology makes it possible to do this accurately so that the features below the hold will not come into contact with the drill. Once the hole is drilled, it will then be plated in copper. This is the least expensive option, but it does require that the holes are large enough that they can be made with a drill. While this will work for many PCB needs, it might not always be the right solution for everyone.
• Sequential-lamination blind vias. Sequential-lamination blind vias are created using a piece of laminate that is extremely thin. The process is similar to creating a two-sided PCB, where the laminate will be drilled, plated, then etched. This method creates elements in the side that will form the second layer of the board. On the other side will be a copper sheet, which forms the first layer. This assembly is then laminated with the other layers of the board before going through the remaining steps to becoming a complete PCB. This method is not used as much today as it was in the past, because it is expensive.
• Laser-drilled blind vias. Laser-drilled blind vias are made after the PCB has been laminated, but before the outer layer undergoes etching and lamination. There are different types of lasers used to make the holes today, but the results are the same.

A Closer Look at Buried Vias

When a via goes between two inner layers of a PCB but does not touch the surface of either side, it is called a buried via. Buried vias create connections between the inner layers. As the name suggests, vias are literally “buried” within the PCB. The functionality of a buried via is similar to that of a blind via, as the goal is to make sure that the PCB has the full functionality that is required. Buried vias help free up space in other areas of the board. To create buried vias, the inner layers with the vias are created first, and then other layers are added to the outside to build up the board.

The Benefits of Blind and Buried Vias

Because PCBs have limited amounts of space, blind and buried vias can be a huge benefit. They allow you to keep the PCB small, which is essential when working with electronics. The use of vias frees up space on the surface of the board; that space can then be used for other functions. Vias are a relatively simple solution, but you will need to be aware that the addition of blind and buried vias will add to the cost of the board.

Because there are many factors that go into getting the right PCBs with the correct blind and buried vias, it is important to work with a quality manufacturer.

Choose the Right PCB Manufacturer for Blind and Buried Vias

Adding blind and buried vias to your PCBs is a delicate process that’s best left to professional manufacturers. This means finding the right manufacturer for the job becomes very important. Advanced Circuits has led the PCB field for more than a quarter of a century and provides a range of services and technologies that can help to make your life easier. We can provide simple designs or complex boards according to your needs.

There are many benefits to working with us. We offer round-the-clock support, and we provide fast turnaround times. We also have instant online quotes available to give you an idea of how much your project will cost, as well as a way to track your order. Give us a call today with any questions you may have regarding blind and buried vias.

It can often be difficult to fit all the needed connections on a PCB onto a single layer. A way around this problem is with vias. They are conductive holes that are shaped similar to a barrel, which allows for connections across multiple layers of the PCB. While there are several vias, there are two that are used most often. These are the blind and buried vias, and we believe they can provide some excellent benefits to those who use them in their PCBs.

What is the Difference Between Blind and Buried Vias?

A blind via will connect an outer layer of the board to one of the inner layers. However, it does not go all the way through the entire PCB. A buried via is located within the board and will connect the inner layers without reaching the outer layers. There is also a through-hole, which goes through the entire board vertically and will connect all the layers. It is a relatively simple concept to understand, and it can provide some excellent benefits.

Many Benefits of Blind and Buried Vias

Many PCB boards are small and have a limited amount of space, so the blind and buried vias can provide additional room and options for the board. The buried vias, for example, will help to free up space on the surface of the board without affecting the surface components or traces that are on the top or bottom layers. The blind vias can help to free up some additional space. They are often used for fine pitch BGA components. Since the blind vias only go through a portion of the board, it also means that there will be a reduction of signal stubs.

While the blind and buried vias can be used with many various PCBs, they tend to be used most often for high-density interconnect PCBs, or HDIs. The HDIs are popular because they can offer better power delivery and an added layer density. Through the use of the hidden vias, it will also help to keep the board smaller and lighter, which is very helpful when you are creating electronics. They are commonly used in medical devices, tablets, laptops, cellphones, and similar small electronics.

While the blind and buried vias can be helpful for those who need them, they can also add to the cost of the PCB. This is due to the added work that is required to add them to the board, along with the testing and manufacturing that will need to go into them. This means that you should only use them when it is truly necessary; because you want to have a great board that is tight and efficient.

How Are the Blind and Buried Vias Built?

The vias can be made either before or after the multilayer lamination. The blind and buried vias are added to the PCB through drilling, which can be precarious. It is important that the builder understands and is aware of the depth of the drill. If the hole is not deep enough, it might not provide a good connection. On the other hand, if the hole is too deep, there is a chance that it could degrade the signal or cause distortion. If any of these things were to occur, it would not be viable.

In a blind via, the hole will need to be defined using a separate drill file. The ratio of that hole diameter to the drill diameter needs to be equal to one or less. With a smaller hole, the distance between the outer layers and the inner layers will be smaller.

With a buried via, each of the holes needs to be made using a separate drill file. This is because they connect to different parts of the inner layer of the boards. The hole depth to drill diameter ratio will need to be no larger than 12. If it is larger than that, it will run the risk of touching other connections within the board.

We recommend working with Advanced Circuits for PCB manufacturing. This will help to ensure that the design and the build of the board, including the blind and buried vias, are feasible. Failure to prepare and to work with a quality board manufacturer could end up in added costs.

Our experts have the tools and techniques to ensure proper drill depths. We can ensure that there is no air trapped in the PCB during the process. The plating will be applied properly to connect the internal layers.

Choosing a Printed Circuit Board Manufacturer

Because it is so important to ensure blind and buried vias are added to the PCB properly, finding the right manufacturer becomes essential. We at Advanced Circuits provide reliable PCB manufacturing and assembly that meets your specifications.

We own a large printed circuit board manufacturing facility that uses state-of-the-art equipment and procedures to provide quality and consistency. All orders placed with us go through a free engineering file review before they go into production. This helps to ensure that the boards are created properly and that they work. No one wants to receive boards that are unusable. It would be a waste of time and money.

Also, we know how important it is for you to get your boards on time. We can provide you with PCBs with blind and buried vias with fast turnaround time, not to mention fast shipping.

When you are choosing a manufacturer, you will also want to have an understanding of how much the order will cost. We offer instant PCB quotes.

If you need PCBs that have blind and buried vias, the right company can make getting what you need fast and easy. Advanced Circuits offers excellent manufacturing, reliable products, and superior customer service.