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What is FR5 PCB ?

Why are Printed Circuit Boards important?

Electronic items/appliances become functional due to Printed Circuit Boards. These PCBs are made of non-conducive material (the substrate or physical, insulating structure that holds the traces and components on it) covered in copper. PCBs have electric pathways connecting the different electronic components to each other through pads, traces, lines, and other features etched onto the copper plating.

PCBs are used in electronic devices and appliances across many different sectors, from handheld consumer devices to huge machinery and heavy parts. This blog entails details about the FR-5 as PCB substrate and why it is great for your PCB production needs.

Using high quality materials promotes longevity and performance of printed circuit boards. The FR5 Laminate is a NEMAcertified board, known for its immense strength, chemical resistance, excellent electrical properties, and low moisture absorption capabilities. Its natural color is a yellow-green-tan blend, and it is made of fiber-glass fabric reinforced with high temperature epoxy resin binder similar to G10 / FR4. As you read along, you will receive more information about PCBs in general and FR-5 in particular.

Types of PCBs

PCBs can be differentiated according to their flexibility, number of layers, frequency, and substrate used. Some popular types are discussed below.

PCBs Types according to Flexibility

They can be:

Rigid PCBs are solder masked during production, while flexible PCBs are usually overlaid or cover-layered to protect exposed circuitry. The rigid flex combines the flexibility and lightweight of flex PCBs with the strength of rigid PCBs. Its small size makes it perfect as a space-saving circuit board. FR-5 is a rigid PCB.

PCBs Types according to Number of Layers

PCBs are designed and manufactured in many ways, dependent on their use as:

  • Single-sided (one copper layer). These PCBs are used for simple circuits, as sensors, power sensors, relays, and electronic toys.
  • Double-sided (two copper layers on both sides of one substrate layer). These PCBs are used in mobile test equipment, power monitoring, amplifiers, phone systems, and many other applications.
  • Multi-layered (inner and outer copper layering, alternating with layers of substrate). They are used in high speed circuits as they offer better spacing options for conductor pattern and power.FR-5 falls under this category.

PCBs Types according to Frequency

  • High-Frequency PCBs which are used in the frequency range of 500MHz – 2GHz. These PCBs are used in for communication systems, microwave PCBs, micro-strip PCBs, etc.
  • Aluminum backed PCBs are used in high power applications, as the aluminum dissipates heat. They are great for applications requiring high mechanical tolerance such LEDs and power supplies, because they offer high rigidity and low thermal expansion.

PCBs Types according to Substrate

PCBs are most often made as substrate, copper, solder mask, and silkscreen. PCBs substrates come in a large variety of options. The most popular substrate of a printed circuit board (PCB) is a thin board made from fiberglass, reinforced with composite epoxy resin, or other laminate materials with a copper foil layer on one or both sides: FR-4 and FR-5 PCB Substrate Materials. However, for classification purposes, there are three major types of materials used for fabrication of PCBs:

FR-5, FR-4 PCB Substrate Materials 

These both are the most common materials used in PCB manufacturing. FR-5 and FR-4 substrates are made of woven fiber glass reinforced material and a flame-resistant epoxy resin binder. The epoxy used is flame retardant and water resistant, and provides a notable ratio of strength to weight. Lastly the tensile strength of both is very high.

PTFE (Teflon) PCB Substrate Materials

PTFE is a plastic-like material used for high speed, high frequency applications because it does not offer resistance in conductivity. PTFE is very lightweight and flexible, making it suitable for tight tolerance applications. It is also strong and flame resistant, versatile and provides temperature stability.

Metal PCB Substrate Materials

Metals such as iron, aluminum, and copper, amongst others are still used in PCBs because they allow easy integration of components in Surface Mount Technology (SMT). They have a long product life and provide mechanical durability.

The FR-5 Features and Advantage

fr4 PCB vs fr5 pcb

In order to understand the benefit of using the FR-5 PCB, here are some of its noteworthy features.

Moisture Absorption

Moisture can greatly lower the quality of lamination, solder mask, metallization, and production process of PCB board manufacture and assembly. Dampness and humidity inside a PCB also reduces the glass-transition temperature (Tg) resulting in excess thermal stresses that can damage the board or components causing PCB failure. In the FR5 PCB, the moisture absorption is low making it a prime choice when selecting a PCB material.


The FR5 circuit board can resist many things, which lowers the risk of faulty PCB functioning or PCB failure. FR5 PCB is impressively Heat and Radiation Resistant, and Chemical Resistant. It also has a low dielectric loss.

Mechanical Properties

We have already mentioned that FR-5 has low dielectric loss. This means it has high dielectric strength, which can be defined as the maximum voltage needed to produce a dielectric breakdown through the insulating material. FR-5 also has High Tensile Strength which indicates the stress threshold that can be applied to it before it breaks. Its High Flexural Strength is its ability to resist breaking when pressure is applied. These features determine its application and ensure its longevity.

Excellent Performance

Investing in the FR5 PCB is the right thing to do considering the excellent performance. One way of monitoring of the FR5 PCB performance is during the lead-free soldering process. It can be easily applied to the following fields:

  • Circuit Board Holders
  • End Plates
  • Solder Frames
  • Antennal Isolators
  • Test Boards
  • Electrical Equipment
  • Aerospace


Why are FR-4 and FR-5 popular as PCB substrates?

There are many substrate materials used in PCB production. NEMA (National Electrical Manufacturers Association, USA) classification has named a group of laminates as FR. FR stands for Flame – Retardant or Fire Resistant and signifies that the material complies with UL94VO, and the ensuing numbers 1 till 5 differentiate the different materials in the same class. The group comprises of FR-1, FR-2, and FR-3, FR-4, and FR-5, and are popularly used for single sided, double sided and multilayer printed circuit boards, dependent on compliance with strict requirements for mechanical strength.

From single to multilayer PCBs (going up to 40 to 50 layers of substrates and copper layering: theoretically even 100 layer PCBs can be made)  FR-1, FR-2, and FR-3 materials have all been used to manufacture PCBs. FR-4 and FR-5 are used the most. Despite the fact that FR2 and FR3 materials are cheaper than FR4 and FR5 PCB materials, PCB designers prefer these more expensive options because of their reliability and other key features that we will discuss as we go along.

There are many ways in which FR-4 and FR-5 composite materials based on woven glass-epoxy compounds out-perform their older counterparts. Boards made from FR-4 and FR-5 are water resistant, flame-resistant, strong, and provide good insulation between copper layers. This minimizes electromagnetic interference and supports good signal integrity. Their flammability rating is UL94-V0.

FR-5 vs FR-4. Why is the FR-5 CCL (PCB Substrate) Material Better?

The FR5 PCB has many features that make it a popular option in PCB Design and Manufacture. Its maximum operating temperature is 140 degrees, ensuring the circuit board doesn’t overheat or go above recommended temperatures. Also, because of the thermosetting fiberglass composite no additional improvement is required to enhance its flame resistance.

FR-5 has improved functionality as compared to the FR-4 due to its higher operating temperature, giving it superior mechanical properties at raised temperatures, and in humid or dry conditions. The FR-5 laminate has an expansion coefficient of 14 ppm/XC (25XC to 130XC) in the xy plane and the expansion coefficient of the epoxy resin in the z plane ranges from 50XC to 288XC and is approximately 4%. FR5’s glass transition temperature (Tg) ranges from 170-180°C. Continuous operating temperature for FR5 is typically 140° degrees C.

Because of its high Tg, the FR-5 laminate is best used for higher layer count, multilayer PCBs in the medical, automotive and OEM industries.

Why are FR-4 and FR-5 fierce competitors?

There is a vast similarity between the two FR-4 and FR-5 substrates. Both FR-4 and FR-5 have multiple use cases, including high-temperature applications. Both are compliant with lead-free technology PCB assembly. Additionally, both have a UL flammability rating of 94 V-0.

However, the primary difference between the two lies in the heat resistance and the number of layers that each of the materials can be used.

Epoxy resin + glass fiber fabricEpoxy resin + thermostable glass fiber fabric
FR4 has a Tg of 130° C (266° F)FR5 has a Tg of 160° C (320° F)
Maximum operating temperature of 110° C (230° F)Maximum operating temperature of 140°C – 160° C (284° F)

Made of special electronic fiber-glass cloth strengthened with epoxy phenolic resin and other materials, compressed and solidified at high temperature and pressure, both have:

  • high mechanical and dielectric properties,
  • good insulation properties,
  • heat resistance and moisture resistance, and
  • good machinability.

However the FR-5 CCL has better heat resistance, almost twice the FR-4. With a smaller Z-CTE is, the FR-5 is prime for high multilayer boards. The FR-5 has higher Tg (Temperature of Glass Transition) and Td (Time to Delaminate) than FR-4. T288 (Time to delamination) is the time it take for the FR-5 base material to delaminate when subjected to a temperature of 288°C.

Price wise the FR-5 is much more expensive than an FR-4, but the material is that much better. Creating better PCBs with better efficiency and applications comes choosing the right materials. The FR-5 is a very viable option of high purpose PCB manufacturing and can be used to make double-sided PCBs, rigid PCBs and multi-layer PCBs. We hope this blog helped you in making informed choices for your PCB design and manufacturing processes.