Which PCB Substrate Should I Use?

Traces, components, and PCB substrate are the components of a printed circuit board, or PCB. However, a PCB substrate is one of the essential components required to make a printed circuit board. It is one of the initial decisions made when designing a printed circuit board and acts as the base of the board. However, several PCB substrates are available on the market, making it hard for humans to choose the ideal one for their printed circuit board.

Each PCB substrate type has unique qualities and advantages, though. So choosing a PCB substrate that suits your needs is a very crucial step that can affect the overall performance of a printed circuit board.

If you need clarification about which PCB substrate is ideal for your needs, you must read this article. It will help you decide wisely on choosing a PCB substrate and provide all the necessary information. 

What is a PCB substrate?

A PCB substrate is a critical element of the printed circuit board. It is responsible for holding components and traces that make up the foundation of a printed circuit board. This crucial material is also responsible for the success or failure of the printed circuit board. Yes, you read it right! It is responsible for the failure of the PCB project if you select the wrong type of PCB substrate. 

PCB substrate is often created similarly to a sandwich because it consists of several layers. Below are the detail of the layers of this substrate-

• The core is a rigid base PCB substrate material that acts as the main insulating material on the printed circuit board and typically has copper foil as an inner ground plane.
• Prepreg, dielectric material binding agent, covers the core.
• The surface is coated with an outer layer of foil, forming the surface area to which parts will be attached and traces will be etched.
• At last, a solder mask is applied to the surface that protects the copper traced from oxidation and solder bridge and assists in visually inspecting the printed circuit board.
• Silkscreen indicates where parts are located on a board, and while it is considered its layer, it provides no material benefit.

However,  core and prepreg bis refer to the actual PCB substrate. It is available in several options that are designed to give satisfaction to every need of ended-users.

How are PCB substrates made?

A PCB substrate is organized in the layer during creation. These layers alternate between the metal foil and dielectric material. Most PCB substrate materials are mixed with epoxy due to the superior electrical performance of lower dielectric constants and loss tangents compared to other materials. Because of environmental concerns about lead-based printed circuit boards, resin chemistry has changed over time to identify the lead-free soldier’s higher temperature.

It is crucial to understand that the cost of PCB substrate increases with the improvement of its performance because of the kind of PCB substrate material used to build it. The printed circuit boards needed for telecommunications, military hardware, and aerospace engineering must perform much better than a phone that will be discarded in a few years. When looking at the list, consider the end-use before prioritizing optimal performance.

Types of PCB substrate 

If you’re familiar with PCB substrate, you’ll know that there are several varieties available on the market. Each type of substrate is built with a unique or different PCB substrate material. Material plays an integral part in the performance and reliability of these substrates. Below are the main types of the substrate of PCB-

• FR – 2

FR-2 is the least famous print circuit board substrate because it needs to perform better. However, this substrate is flame retardant. Remember, FR-2 is referred to as flame retardant 2. FR-2 is made from phenolic material, an impregnated paper deposited on top of glass fiber. This substrate only works in some economic customer products, like affordable radios.

•  FR-4

FR-4 is also the ideal substrate for PCBs. It is lightweight, has good moisture resistance, performs well, and comes at a low cost. While this substrate is excellent for customer electricity because it has a dielectric loss, it is unsuitable for high-frequency applications. This substrate comprises the epoxy laminate sheet, which is fireproof, water resistant, and moisture resistant. The tensile strength of this substrate is very high and has a high strength ratio and electrical isolation. FR-4 comes in the following types-

• FR-4 standard – It is the most common type of FR-4 and has a heat resistance of up to 150’ C.
• FR-4 high tg – This FR-4 version has a high Tg (glass transition temperature), allowing the substrate to reach temperatures up to 1180°C.
• FR-4 halogen-free – it is a material with a low halogen content (which produces toxic substances when burned). Halogens are one of the most commonly used fireproofing elements.

If you have a low budget, consider choosing FR-4 because it can help you get a better result at the lowest price.

•  Flex substrate 

Flex substrate can fit a ton of surface area into a limited, shaped space. This made them ideal for everything, like calculators, video games, and medical devices. They can even work in environmentally hazardous conditions. 

The most prominent feature of this substrate is that it can bend because this PCB substrate material is soft and formed with epoxy shaped around a glass wafer. Below are some flex PCB substrates-

• Polyimide – it has a good temperature range, solid conductive properties, and high chemical resistance. This material suits small consumer products, like video games, calculators, and more.
• Polytetrafluoroethylene – Polytetrafluoroethylene, also known as PTFE, is a good option for flex PCB material. They can be found in products like cruise control, antennas, and more due to their low dissipation and good temperature stability.
• Polyether Ether Ketone – Polyether Ether Ketone, also known as PEEK, is highly recommended for use in extreme conditions. It can handle high melting points, high radiation, and excellent chemical resistance.

•  Rigid substrate 

Rigid substrates are immobile, durable, powerful, and affordable. This substrate is also less shockproof, corrosion-resistant, and waterproof. These substrates are generally ceramic-based. It has a high operating temperature and thermal conductivity. They can fit in less space, and some of their counterparts can be easily repaired. Aluminum, beryllium oxide, and Aluminium nitride are popular PCB substrate material.

The rigid aluminum substrate can be found in LEDs, circuits, and sensors because of its low expansion and high thermal dielectric. In comparison, aluminum nitrate rigid substrate can be found in high-power LED, integrated circuits, and more. Moreover, its potential applications are more advanced because beryllium oxide has a higher thermal conductivity than aluminum nitride.

• Rigid-flex substrate 

The combination of rigid and flexible substrates produces the rigid-flex substrate. They mainly rely on polytetrafluoroethylene components due to their ability to create them quickly and their low dielectric loss at microwave frequencies. This substrate can be used in aerospace, medical, and military products.

Conclusion

Choosing a suitable PCB substrate is a challenging task. It requires a lot of research, expertise, and professional skill. We have clarified all your doubts about the types of these substrates in this article. If you still need clarification, contact the PCB substrate manufacturer to get help with your confusion.