Circuit boards are thin boards made of insulating material to which all the other components are attached. They’re the physical structure for mounting and connecting other electronic components. If you know anything about desktop computer configurations, the best analogy would be to compare it to the motherboard. All the other components (CPUs, GPUs, SSDs, etc.) will be connected to this board.
This part is used in all modern electronics, and understanding it might be vital to understanding all modern technology. With that in mind, here is how understanding PCB (printed circuit boards) assembly may help you develop a far better understanding of today’s technology as a whole.
1. What is a printed circuit board?
In the introduction, we’ve given you a simplified explanation of what a PCB is and even used an analogy to make it a bit clearer. Well, in order to understand the way modern technology is manufactured, you need to have a deeper understanding of the subject matter.
There are two components in creating a PCB. The first one revolves around creating a fiberglass board as a mechanical support. It’s like a background on a painting, a key part that’s supporting and holding everything else together. The problem is that its functionality ends with it being a “holder.” It’s like when there’s a new iPhone out, and everyone talks about the camera and the CPU, with no one actually paying much attention to the casing.
Thin layers of copper are then laminated onto the board. Think of a board as a field and these copper lines as canals through which the water is supposed to go. It cannot just overflow the field; it needs to be carefully guided so that it fulfills its purpose and doesn’t damage the field itself.
Once the copper layers are placed, you need to apply the solder mask, also known as the conformal coating of PCB. Most commonly, this will be green, and it gives these circuit boards the copper and green look that you most likely know them for. They’re there to protect the copper from oxidation (seeing as how it’s made of metal).
Finally, you need to understand the importance of the human component in using these circuit boards. Silkscreening applies labels and symbols to the circuit board, making it easier to identify. This is especially useful during manufacturing and testing points. More often than not, the color used for this marking is white.
2. Types of PCBs
While there are many different designs of PCBs, it is possible to classify them all into three different types.
First, you have single-layer PCBs. These are single-sided PCBs, which have only one layer of conductive copper on just one side of the board. These are the simplest and the most cost-effective to produce.
These are really the simplest PCBs made with an FR4 fiberglass substrate, a single layer of copper, a solder mask, and a silkscreen. These are most commonly used for the simplest consumer electronics (like calculators and remote controls). In other words, consumer electronics might soon be made obsolete.
In addition to this, they’re also used in simple circuits (a power supply is a perfect example) and LED lighting. The latter is what they’ll be used for the most in 2024.
Then, you have double-layer PCBs, which are a bit different. They have conductive copper layers on both sides of the board, allowing for a more complex and higher-density circuit design.
The structure is, more or less, the same. A FR4 fiberglass substrate with copper layers, with a big difference in the fact that these copper layers are laminated on both sides of the substrate.
These are used in a bit more complex and common user electronics, like smartphones and computers. They are also used in industrial control, power monitoring, and point-of-sale systems. The reason why this is possible is because they’re suitable for more complex circuits and have superior electrical performance.
Finally, you have multi-layer PCBs. They’re similar to their predecessors, with a major difference in the fact that there are three or more layers of copper with internal layers connected by vias. These are used in advanced electronics (servers), aerospace and military installations, and medical devices (like MRI machines).
3. Functions of circuit boards
In the previous section, we’ve listed a few applications for each of these types of PCBs; however, here’s a bit longer list to help you develop a better sense of what’s going on here exactly.
- Consumer electronics: These are the simplest electronic devices. We’re talking about smartphones, tablets, televisions, and home appliances. This includes everything from common home appliances all the way to simple devices like remote controllers and calculators.
- Computers: We already used a motherboard as an example of what a fiberglass substrate does in a PCB; however, it’s also worth mentioning that motherboards are made out of PCBs. This makes the analogy a bit strange (albeit not inaccurate). Graphic cards and other computer peripherals also consist of a number of PCBs.
- Automotive parts: Control systems, navigation systems, and entertainment units in vehicles are made using PCBs. In other words, all car electronics rely on it.
- Medical devices: Diagnostic equipment and monitoring systems couldn’t work without PCBs. The same goes for all the modern surgical instruments (which rely on electronics).
- Industrial equipment: Automation systems, control panels, and all the electrical machinery in modern factories are made with PCBs.
Overall, wherever you need a physical structure and electrical connectivity, you cannot achieve it without PCBs. Well, as it happens, this is true for all modern electronic devices.
4. Design and fabrication of PCBs
The first step on this journey of a thousand miles lies in the design and fabrication. Designers usually project this in specialized software in order to ensure that the dimensions fit the amount of space these PCBs will take in an electronic device.
The schematic design is really difficult to make, which is why specialists usually design it via CAD software. After this is done, you have to create a PCB layout, which can be difficult if there are multiple layers involved.
Most commonly, these boards will be made out of fiberglass, which acts as a base, then they’ll be coated with copper. This copper is usually etched away in order to form a pattern of electrical pathways. Think of it as roads connecting settlements (electrical components) on a landscape.
The main reason fiberglass is used is that it’s strong, stable, and non-conductive (opposite to copper). This means that it acts as a great basis for these boards. The most commonly used type of fiberglass is FR4, which is a composite material made out of woven fiberglass cloth with an epoxy resin binder. This material also provides amazing insulation and decent thermal stability, which is crucial under extreme circumstances.
Copper is used to create conductive traces, seeing as how it’s amazing for electrical conductivity. Just think about the reason why so many electrical cables and cords are made out of copper. On top of this, it’s relatively inexpensive (compared to other materials that are as conductive). Remember that the amount of these boards is so incredible that a difference in cost actually determines the viability of the process itself.
The fabrication itself involves processes like etching, drilling, plating, soldering, silkscreen printing, and more. In the end, the product has to be tested.
5. Testing and quality control of PCBs
Finally, before PCBs can be used in a product, they have to be tested. The last thing you want is to cause damage to an expensive product because a single PCB was faulty.
There are several types of testing. First, you have the visual inspection. This means that you have someone inspect the product for misaligned components, missing parts, etc. Now, in the modern day and age, this visual inspection doesn’t mean that there’s a human out there visually inspecting every PCB. Instead, this task is entrusted to a tool conducting automated optical inspection.
Next, because it’s so important that these PCBs are solid at a structural level, you often have 2D and 3D X-ray inspections of PCBs. This is used to determine the quality of solder joints and the alignment of internal layers.
Finally, you have the electrical testing and environmental testing, where all the flaws in the product will be fleshed out.
Lastly, it’s important to assess the manufacturing process itself from the standpoint of manufacturability, quality assurance, and process control.
PCBs are the backbone of modern industry
Understanding how PCBs work is important for understanding modern technology as a whole. While understanding their components, the manufacturing process, and quality testing may not have much practical application; it’s still crucial to understand what’s going on in this field. They’re what makes miniaturization and functionality of modern devices possible, which means that they’re vital to the way modern technology works.
