The process of PCB fabrication is impressive, and even those familiar with PCB design might not know all the ins and outs of how PCBs are made. Learn more about the different PCB fabrication techniques that make your design go from the virtual image on your computer screen to the tangible, green board in your toaster.

The Basics

Before diving into PCB fabrication, it’s important to know what makes up a PCB. Often, people will describe PCBs as a layered cake. The most basic PCB designs have four layers: the substrate (base), copper, solder mask, and silkscreen. These layers all work together and must be in total alignment for the final product to work.

Once you’ve designed a PCB and sent your PCB design off to the manufacturer, what will they do with it? For starters, they use your PCB design as the blueprint for the entire process.

Through-Hole Method

One of the earliest forms of PCB fabrication was the through-hole method. This tried-and-true method is quickly being replaced by a more modern PCB fabrication, known as surface mount technology (SMT). While each has its advantages and disadvantages, SMT PCB manufacturers seem to be able to produce smaller and cheaper PCB boards.

We’ll take a look at the intricate work that goes into a through-hole PCB design first. The most significant difference of the through-hole method is that manufacturers drill a hole into the board so that factory workers can double-check that each layer is aligned before moving onto the next step. With the through-hole method, manufacturers will print your PCB design onto special laminate paper. The manufacturers can attach a thin sheet of copper once the design is captured onto this special paper. This will be the basis of your substrate, or the base of the PCB.

Creating Layers

The next step is to start working on the copper that will form the layers of your PCB. This process is a bit similar to how photographs are developed – to the point that at-home PCB makers will use the same processing chemicals. Essentially, the special laminate paper is covered with photo-reactive chemicals, and when a UV light passes over it, it hardens the desired areas. This shows manufacturers which parts, based on your design, should be kept for the final PCB board and which bits of copper should be chipped away.

When the chemicals dry and harden, the board is washed in an alkaline solution and is ready to be inspected. If the board is good to go, a technician uses a powerful chemical to remove unnecessary copper, leaving behind only the copper needed per your PCB design.

Next, the copper layers are laminated together. Technicians must keep a keen eye for detail and always watch that each layer is perfectly aligned with the last. The result is a beautiful, half-finished board.

Factories can use an x-ray machine to uncover where the holes are meant to be drilled and then use a high-powered drill for precise execution. The board is finally plated, and the layers are fused with a series of chemicals. There is one last etching that occurs before the solder mask is attached. This etching ensures that your PCB has the right connections to make your creation function.

Surface Mount Technology

Surface mount technology (SMT) has become more commonplace in the PCB fabrication process because it allows for easier mass production. With an SMT outfit, the PCB fabrication process is more automated and thus less prone to human error. SMT-designed PCBs also do not have the same hole that is prominent in the through-hole method. Here’s a brief glimpse into how these PCBs are produced.

Simple As a Stencil

By using high-powered computers and technology, machinery takes your PCB design and creates a stencil. The stencil contains all the information the automated process will need to finish up your design. The stencil also allows machines to trace solder paste onto the board only in the designated areas.

The board is now ready to run through a pick-and-place machine, which takes the guesswork and error out of the PCB design process. The pick and place machine holds various components in their reels and reads the solder paste to place the proper components onto the board as directed by the PCB’s design. The solder paste will also hold everything in place so that components cannot be knocked off-kilter, thus resulting in a faulty product.

Once this process finishes, the PCB is heated and melts the soldering paste so that the layers meld together. The PCB is then ready for a clean-up, to ensure there is no residual solder paste on the board. At last, the board will receive an inspection of any potential defects.

Advantages of Surface Mount Technology

As you can see, SMT is a much more straightforward and more automated process. Its simplicity is what makes it best for the mass production of PCBs. Once a stencil is created for a design, you can print countless boards. Since the process relies on computers and machines rather than technicians, it’s also less vulnerable to human error. If there’s a mistake with a PCB board, it’s likely because the pick and place machine needs some reconfiguration.

Another big advantage of SMT fabrication is that they tend to allow for higher density component placement while still maintaining smaller boards. Since the board is smaller, the connections have a shorter distance to travel for better power.

The most significant disadvantage of the stencil-based process is that it makes it more challenging to produce prototypes quickly. This system works best if the same stencil is being used repeatedly, rather than creating one stencil that will change.

However, given the automation of the SMT process, it’s no wonder that the SMT fabrication method has gained greater momentum in the PCB world than the through-hole. Whichever route you go, make sure you’re aware of the PCB fabrication process that your manufacturer uses. In today’s world of making everything faster and smaller, you’ll want to make a decision that gives you the best return on investment.

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.

Before Sending

Before you send your design to the PCB manufacturer, there are a few things that you should do. Remember – this is your final chance to make sure that your board design lives up to your expectations. To that end, make sure that you:

• Print Out the Layout: Physically print the board design on paper and make sure that everything fits. If there is even a small amount out of tolerance, it’s time to address that.

• Check for Functionality: Make sure that your components are all in place, that your traces are properly sized, that you have no 90-degree angles (to avoid partial etching and the resulting shorts), and more. As much as you can, check functionality and placement one last time before sending the design out.

• Double Check Tolerances: Verify with your PCB manufacturer what their tolerances are and then ensure that your design meets those requirements. In most cases, you can simply build those tolerances into your design with your PCB software, such as our free PCB Artist software. Just run a quick manufacturability check based on those tolerances and you should be alerted to any issues, which can then be rectified.

• Double Check the Space Requirements: When adding components to your PCB, make sure that you leave enough space between them. You need to account for traces, but also to help alleviate heat buildup, to reduce resistance, and more. Don’t forget that you will also need to leave room for things like buttons and other components that are not part of the PCB layout, too. Accurate size estimation from the beginning stages is essential to success.

Know the PCB Manufacturing Process

It is important to understand the process followed by the PCB manufacturer once you send your design to them. After design, which is the part you handle, the next step is printing. The PCB manufacturer will check your design to ensure that it meets design tolerances. Note that this check does not necessarily mean that your board works to your expectations – most DFM checks are strictly to ensure that the board fulfills the tolerances necessary for manufacturing. (When you work with Advanced Circuits you can take advantage of our FreeDFM tool, to ensure your design is free of manufacturability issues.)

A plotter printer will then be used to print the PCB. This type of printer uses a transparent film to create a negative image of the board. Black and clear ink are used to represent traces and circuits, as well as non-conductive areas of the board (clear ink). With outer board layers, the colors are reversed, with black indicating non-conductive parts and clear ink used for components. A soldering mask is added, and then a registration hole is punched through the film to help align each one into the appropriate layer.

Next up, the manufacturer prints the copper layer for the board’s interior layers, then unnecessary copper is removed. Finally, the entire thing is sandwiched together into a single board and inspected, the layers are laminated, drilling takes place, and plating occurs. A final etching then occurs, followed by the application of the solder mask, silk-screening, and a final reliability test.

Of course, it helps if you have chosen the right PCB manufacturer in the first place. What should you consider when choosing one?

Choosing a PCB Manufacturer

You’ll find many important considerations when choosing a PCB manufacturer. There are numerous fabricators available, but they are by no means created equal. Some are budget-oriented options, while others are geared for working with major tech companies. Here are a few of the more critical considerations to make before choosing a partner:

• Lead Time: Some PCB manufacturers have very long lead times. Make sure you know the lead time requirements of any you are considering working with, as this will have a huge impact on your overall project.

• File Type: Make sure that the PCB manufacturer that you choose accepts the file type(s) that you want to send. Some of the more common types used today include KiCad, Gerber, and EAGLE.

• Minimum Time to Shipment: In addition to lead time, you’ll need to think about the company’s minimum time to shipment. Basically, this is a specified period that occurs before your order can be shipped. Some companies have very low requirements, but others have lengthy periods that may be a week or more.

• Order Quantity: How many boards do you need to print? Are you interested in one or two prototypes for testing? Do you need a full production run? Make sure that the PCB manufacturer you choose is able to meet your quantity requirements. Some companies will only print larger quantities, while others are more flexible.

• Software Availability: Ideally, you’ll work with a PCB manufacturer that makes design software available to you. At Advanced Circuits, we offer one of the most robust design tools in the industry – PCB Artist – free of charge. It can handle all of your design needs and seamlessly export the design when you’re ready to print.

Our Position as an Industry Leader

Ultimately, the right PCB manufacturer will help you bring your designs to life. Make sure that you check their reputation, the quality of their manufacturing process, their lead time and minimum time to shipment, minimum order quantity, and whether they offer access to free design software or not. At Advanced Circuits, we’re proud of our position as an industry leader, as well as our ability to offer our customers the flexibility they need. Whether you’re printing off a handful of prototypes, or you’re ready to go to market with a full production run, we can help.

PCBs for Any Application at Advanced Circuits

Working with Advanced Circuits allows you to get the exact PCBs that you need for any project. You are able to get the custom spec PCBs you are looking for with your choice of plating finishes, laminates and more. For more information on placing your order or for help during your designing process, contact the PCB experts at Advanced Circuits today.

Advanced Circuits is a Top Manufacturer for Engineering Students

Advanced Circuits is the industry leader in providing PCBs to engineering students at major colleges and universities across the country. By investing in the future of the industry and helping students get the experience they need, the profession benefits and is infused with talent and commitment that will show its positive effects on the marketplace as a whole. For more information about the Advanced Circuits student program and to see new customer specials, talk with a representative today.

Working with the top manufacturer for printed circuit boards is vital so that you can get the PCBs you need on your timetable. Advanced Circuits specializes is speedy turn times so you are not stuck waiting for your PCBs. Since your PCBs are fabricated and assembled in one continuous operation, you get consistent and high quality products with expedited turn times. The best part of the process is that you get all of the convenience you expect without sacrificing on the functionality and usability of your PCBs. Advanced Circuits can produce PCBs of up to 14 layers and has lead-free (RoHs compliant) SMT assembly available.

Referral Rewards Available from Advanced Circuits

Referring your friends and colleagues to Advanced Circuits does more than just help them get the high quality PCBs they need for their application. For every new customer you refer, Advanced Circuits will reward you with a $25 gift card to Outback Steak House. Learn more about the referral program and other deals and specials by contacting a representative at Advanced Circuits today