Almost all electronics devices in use today have printed circuit boards (PCBs) embedded within, which work like their nucleus. PCBs are crucial to the point where they contribute to their performance and functionality, and hence they must be flawless. As part of this, the material to make the PCBs must be chosen carefully depending on various. Today, PCB designers and manufacturers have many options in terms of the materials used in their construction, ranging from fiberglass, copper, and silicone to plastic and FR4. Among all, FR4 have gained immense traction, and is the most preferred material used to make circuit boards. What makes it so popular, and what are the beneficial properties of FR4? This post discusses some pointer considerations when selecting FR4 material in the PCB fabrication process.

Gain understanding of FR4 material and its beneficial properties

In FR4, FR stands for flame retardant, and the number 4 indicates a rating that differentiates the material from others. FR4 is a thin, woven fiberglass-reinforced epoxy laminated sheet used in PCB fabrication. Also written as FR4, it is a composite structure of fiberglass layers that offers stability and rigidity to the material.

Here are some beneficial properties of FR4 that make it a popular material among OEMs and PCB manufacturers alike. So, let’s have a look at them.

Good Electrical Properties
The electrical properties of circuit board material play a key role in signal integrity and impedance considerations as they are important for the speed of the electrical signal that propagates through the material. FR4 has a high dielectric strength that contributes to its electrical insulation properties. Depending on the fiberglass weaving style, resin, and thickness, the FR4 dielectric constant (Dk) varies in the range of 3.8-4.8 MHz.

Flame Retardant
Flame retardants are extremely versatile for various manufacturing procedures, and produce predictable results. FR4 has great thermal, electrical, and mechanical properties, making them a preferred choice for several electronics applications.

Moisture Absorption
This is one of the important properties of FR4 material. When immersed in water, the material has a low moisture absorption rate of 0.10%. Also, FR4 is temperature resistant and can withstand a wide temperature range, apart from being largely moisture resistant.

Cost Effectiveness
FR4 is a commonly used circuit board base material owing to its relatively low-cost feature aside from stable physical and chemical properties. This benefits several cost-concerned PCB manufacturers and designers.

Important Guidelines for Selecting FR4 Material in PCB Fabrication

Material thickness plays a key role in FR4 circuit board manufacturing. Some common units used to measure material thickness include inches, millimeters, and thousands. Apart from material thickness, there are several important pointers that need to be considered while choosing FR4 material for a circuit board assembly.

It is always a good practice to select a high-performance FR4 laminate when the operating temperature exceeds 150°C. As discussed earlier, these materials offer better thermal resistance and low expansion rates while retaining manufacturability.

Consider thin FR4 material with space constraints to make the PCBs reliable in terms of functionality. These lightweight materials support delicate components to make devices such as USB connectors, Bluetooth accessories, and much more. Thin FR4 material is widely preferred for applications where space is always a constraint. These materials are known for offering better flexibility, and hence they are used for building complex yet thin PCBs used in the medical and automotive sectors.

Choose a material having a uniform dielectric constant over varied frequencies, and FR4 fits into this aspect.

Avoid using other thin PCB materials that feature grooves as there may be a high risk of board fracture or damage.