Pc Board Fabrication For High-speed Circuits In Pcb Assembly

By Author: Sam Sangani
Total Articles: 3
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PC Board Fabrication for High-Speed Circuits?
PC Board Fabrication
If you have seen printed circuit boards (well, I am sure you have seen one) then you must wonder how they are made and how they are managing your electrical devices. Nowadays, a multiple-layer printed circuit board is managing the most critical electronic devices. From your laptop to your phone and other devices are relying completely on printed circuit boards. Printed circuit boards may seem uninteresting to you but once you get deep into it, it’s an interesting and worth knowing subject. Let’s imagine, how a printed circuit board is working in the device you are using right now, and it will boost your interest. Now the question may arise about the manufacturing of the circuit board. How is a printed circuit board manufactured and prepared?

There are few rules in the designing and manufacturing of printed circuit boards that need to be followed. The material being used in the circuit board matters a lot. The main purpose of the material is to provide insulation between the conducting layers of the copper foil and pass electricity. Essentially ...
... four basic layers need to be followed in manufacturing a printed circuit board. The format of these layers is:
• Silkscreen
• Solder mask
• Copper
• Substrate

Initially, there were only two choices available for the PCB’s. One is a rigid circuit and the oter is a flexible circuit. Now as the electronics industry has been developed the boom in printed circuit boards can also be seen easily. Now we have a choice of different printed circuit boards for different devices. For example, various frequency ranges and antennas.

But the thing that needs attention is that the base material used in the manufacturing process of printed circuit boards is still the same. And the material used as a base for the printed circuit board still falls into the rigid category of the printed circuit boards. Now let’s understand what a substrate is.

What is the substrate?
Let’s imagine a building. What is the base of the building on which it is relying entirely? The ground, right? Similarly for the manufacturing of printed circuit boards, we need to build a base first. And the same as the building should have a reliable and strong ground, the printed circuit board also requires a good and efficient material with a number of characteristics in order to stand out in the world of electronics.

The substrate is the first physical layer of the circuit board on which the traces and components are relying. If you want to manufacture a reliable and high-quality printed circuit board, choosing the right and recommended material for the substrate layer is the first step you should go for. There are a variety of choices available when you get to choose the material of the substrate. But first, let’s understand why it is important to give this much attention to substrates.

Importance Of Substrate
There should be a solid shape and structure for the PC Board so that the other layers, traces, and components can easily rely on it. A strong canvas and platform are required to better hold all the components. The overall performance of the printed circuit board would be affected by the quality of the substrate. A soft substrate offers more space for designing options. On the other hand, hard and rigid substrates increase the durability of the circuit board. Similarly, if we need multiple designs on the printed circuit board then we may use multiple substrates for each layer. As we need to be concerned about the non-conductive material so the substrate decided should be able to withstand heat and dielectric constant also.

Now let’s have a look at different types of substrate with an explanation so you can understand how substrates are suitable in particular circuit boards. Moreover, the substrate is the reason for the stability of the printed circuit boards. It protects the board from bending by providing it with a hard or flexible surface. For example, the computer motherboard is probably the most common substrate you can see now. The motherboard is a multiple-layer printed circuit board. You can see that other components and traces are connected to the surface in such an efficient and best way.

Rigid Substrate:
As we have discussed before, the rigid substrate is always a good choice when we want a strong and dielectric circuit. Also, the rigid substrate can cross up to 350 degrees, so it is a noteworthy operating temperature. Rigid substrates are preferred when you want a PCB in a way that it can be repaired and maintained easily. It is easy to mark the affected area because of the clear view of the board. Rigid substrates are the best choice for critical situation usage devices for example LEDs used in medical surgeries. Ceramic-based substrates are the most common these days. Common examples are aluminum nitrate and aluminum. Rigid substrates offer high thermal stability and low expansion and are easier for the pcb assembly process.

Soft Substrate:
There are renowned benefits of using soft substrate in a printed circuit board. Soft substrate act as a shield in a hazardous environment. You can make a corrosion-proof, waterproof, and shockproof printed circuit board by using the soft substrate. This advantage is not provided by most rigid substrates. The dielectric material or glass material can be protected by epoxy coating around the filler. The soft substrate also provides resistance against chemicals and radiations. The melting point is high in them. Soft substrates have made the wearable concept possible. It is now possible to enable printed circuitry in tight areas just because of the soft substrate used in it. Although flexible material used in circuit boards is expensive, it provides better functionality by reducing the weight of the overall circuit.

Flex-Rigid Substrate:
Sometimes a PCB requires easy fixation. Lightweight can also be a condition to follow. In this case, flex-rigid can accommodate the requirement perfectly. Specific flexible substrates such as R0400 are used in circuit board manufacturing; they are simple to machine and precision built. They are the most lightweight substrate, so it is possible to reduce weight and space up to 50 percent. Because of these features, flexible substrates are the best available choice for most printed circuit boards.

FR-4:
If you want to build a complex and multilayer printed circuit board then FR-4 is the way to go. They are also known as fire retardants, and they offer high resistance against flames because of the bromide present in them. There are several subcategories of FR-4 such as TG and FR-4 Roger. The other advantage of this substrate is that it is cost-friendly. Highly optimal performance of microwave frequency in the printed circuit board can be achieved by using RF-4 because of their strength to weight ratio. This is also a reason for their affordable design.

Now we have analyzed the reasons why we should go for good substrates. Let’s also understand the materials of the substrate. Because the quality of the substrate plays an important role in deciding the efficiency and reliability of the PCB as well as the end product.
Ceramic substrates are usually preferred because of the high magnitude of the thermal conductivity as compared to conventional printed circuit board material.

Commonly used substrate materials are Al2O3, AIN and FRx. alumina is preferred because it offers high resistivity, the best dielectric strength, good thermal and corrosion stability, and the best mechanical power. Its major disadvantage is a delay in propagation signal because of the relatively high rate of dielectric constant. It is also difficult to draw away heat and the reason is low thermal conductivity.

That’s why ceramic materials are under development. The main purpose of these developments is to improve the existing material. Integrated circuits are one of the best examples. As they perform complex functionality, it is important to build a printed circuit board with multiple layers. The low dielectric material is used in these circuits.

Similar polyimide is also used as a substrate in printed circuit boards. It offers wide temperature ranges and better chemical resistance. Its electrical properties are also good. Typically, these PCBs are used in cameras, antennas, entertainment devices, calculators, and instrumental panels. The other material that is recommended in the substrate is PTFE, this offers low dissipation and maximum temperature stability and would require a fixture for the printed circuit board assembly process. These are used in antennas, the aerospace industry, and power amplifiers.

There are many other examples of the best substrate materials that many industries are using for manufacturing better-printed circuit boards. The end goal is to provide stability and reliability under severe conditions. Also, it is preferred to use substrate material that is beneficial for critical industries and helpful in industries such as medical and aerospace.

The entire printed circuit board is relying on the substrate as it provides the basic foundation. The other components such as silkscreen, copper foils, and traces can do good if the basic physical layer is good. That’s the reason you should take some more time in deciding your substrate material and type. This will be a key to your PCB’s better performance.

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We are capable of meeting all of your requirements for design, fabrication and assembly. For the last 48 years, we have served a diverse group of industries like contract manufacturing, telecommunication, medical, data processing, recorders, controllers, audio, video and aerospace.