To distribute electricity, PCBs are made with a series of copper wires (called traces) that connect components and allow electrons to flow. Understanding PCB fabrication is important, whether you’re teaching students the basics of electronic device operation or you’re designing the next hit Internet of Things device. In this guide, we’ll explore some of what you need to know about PCB fabrication.

Types of PCBs

Today, there are three types of PCBs manufactured. The PCB fabrication process is similar for each, although the more complex the board, the more complicated the fabrication process will be. The three types you’ll find today include the following:

• Single – Single-sided PCBs are the simplest of the lot and are made with an FR4 base and a rigid laminate made from woven glass epoxy. One side of the laminate is covered with copper, while the other side is left uncovered. The copper layer can be of varying thickness to suit the usage needs and design of the board.

• Double – Double-sided PCBs use the same epoxy as single-sided PCBs. The primary difference here is that both sides have copper added so that traces can be etched. Each side has the potential to either act as a separate circuit board, or to integrate with the other, creating a more compact form factor for what would be a larger board if it were only single-sided.

• Multi-Layer – Some PCBs have multiple layers. They begin with the same substrate material, but use copper foil instead of a copper coating. Foil and base material are interleaved to create a sandwich effect that allows multiple layers of functionality.

Of course, the PCB fabrication process is more complex than this. There are four primary parts to a PCB. These are the substrate, or base material, the copper layer (or foil), the solder mask, which protects the copper from damage during the soldering process, and silk-screening, which denotes part numbers, symbols, and other important information. Getting these four components into place is the purpose of PCB fabrication, and there are multiple steps involved.

Design

The first step is to design the PCB. Usually, you’ll use design software, such as PCB Artist, which is a free, full-feature tool that delivers powerful capabilities and ease of use. During this process, you lay out the board, indicate where components go, route traces, add capacitors, and more. However, this is all theoretical. No actual PCB fabrication occurs during this stage – it’s all about planning, prep, and basic testing for functionality.

The Design and Fabrication Process

With the design work out of the way, you now need to choose the bare PCB boards and create the traces. This process will remove unwanted/unneeded copper, leaving you with the characteristic thin lines to carry current from component to component. In most cases, a chemical etching process is used – ferric chloride is the most common etching agent, although there are other agents, and even other etching processes that may be used.

On top of the base material, copper is laid, either as a full layer, or as a foil. Over that, a film is placed. This film has a photograph/image of the completed circuit. The film is exposed to light to detail the traces and component mounting locations, creating what is called a photo-resist. This is then placed in a developer solution that removes any unneeded material.

The next step in the PCB fabrication process is to use ferric chloride to etch the area without copper. If the ferric chloride solution is too strong, or if the PCB is left in the solution for too long, damage may occur, so timing and proper solution mixing are both critical considerations.

Note that this is just one option when it comes to PCB fabrication. There are other methods that do not rely on ferric chloride at all. For instance, milling machines are able to remove copper from the areas where it is not needed without damaging the underlying board. Another option is to use inks that resist the etching solution rather than a film.

Drilling Holes/Vias

Numerous holes, or vias, must be drilled through the PCB during the fabrication process. These are used for a couple of different things. One is obvious – mounting components by their pins. However, another is to ensure that the individual layers of the board can be lined up. This is particularly important with multilayer PCBs.

Soldering and Silk-Screening

The final two steps of the PCB fabrication process are soldering and silk-screening. A soldering mask is put in place over the PCB to protect the copper from damage and to ensure that soldering is done accurately. Then, the board is flipped over and names, numbers, symbols, part identification information, and other text elements are silk-screened onto the board.

Decades of PCB Manufacturing Experience

In the end, PCB fabrication is a complex process. Accuracy and proper planning are essential from the very beginning. Whether you’re designing your first PCB ever or you’re hard at work on yet another prototype, it pays to have the right PCB design software, as well as the right manufacturing partner.

At Advanced Circuits, we have decades of experience working with clients ranging from individuals to international corporations. We can help with prototyping, design, testing and offer full PCB fabrication services with minimal lead time and highly flexible minimum order requirements. Contact us today to learn more about how we can help.

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.