Printed circuit boards have long been an integral part of several electronic circuits. Therefore, most electrical engineers involved in the production of these circuit boards are familiar with the different materials used to make them. FR4 PCB material is one of the most popular materials used to manufacture PCBs.
The FR in FR4 stands for flame retardant, and the number 4 distinguishes this material from others in this class. FR4 PCB material is a glass fiber reinforced epoxy laminate that looks like a thin woven cloth board. FR4 also represents the grade used to make these laminates. The fiberglass structure provides structural stability to the material, and the fiberglass layer is covered with a flame retardant epoxy resin. This brings durability and strong mechanical properties to the material. All these characteristics make FR4 printed circuit boards popular among electronics contract manufacturers.
FR4 PCB material has been the most successful and widely used material in PCB processing for many years. This is mainly due to the wide range of FR4 PCB materials, although they contain similar properties and are mostly epoxy systems. As a result, FR4 materials are now commonly used in the most common terminations.
FR4 PCB material acts as the base of any PCB circuit board. The material is laminated with layers of copper foil, which is laminated using heat as well as adhesive. Copper foil can be used to laminate the material from one or both sides. For relatively simple applications, an FR4 PCB material with a TG value of 130-140°C can be selected. For multi-layer or thicker circuit boards, products that have higher requirements for heat resistance should choose FR4 PCB materials with a TG value of 170-180. With the advent of lead-free soldering processes, in addition to TG, TD and additional indicators also need to be considered together. Also, in lead-free soldering process applications, higher TG values do not always mean better performance. In other words, as end applications expand, so will the range of available FR4 PCB materials.
FR4 PCB material is popular for the following reasons:
- FR4 PCB material is a low-cost material.
- FR4 PCB material has high dielectric strength, which contributes to its electrical insulating properties.
- FR4 PCB material has a high strength-to-weight ratio and is light in weight.
- FR4 PCB material is moisture resistant and also has relative temperature.
- FR4 PCB material has good electrical loss performance.
- FR4 PCB material does not absorb water, so it is also suitable for various marine PCB applications.
- FR4 PCB material is yellow to light green, ideal for any application.
- All these characteristics of FR4 PCB material make it suitable for various environments.
FR4 acts as the base of any PCB. The material is laminated with a copper foil layer. Lamination is performed using heat and adhesive. Copper foil can be used to laminate material from one or both sides.
Choosing the Right FR4 PCB Material
Using the correct thickness of material is very important for building FR4 PCBs. Thickness is measured in inches, such as thousands, inches or millimeters. There are several things to consider when choosing FR4 PCB material for your PCB.
- Choose thin FR4 PCB material for building boards with space constraints. The thin material can support the various delicate components needed to build the device, such as Bluetooth accessories, USB connectors, etc. They are also suitable for larger projects where engineers want to focus on space-saving designs.
- Thin FR4 PCB material is suitable for applications requiring flexibility. For example, thin materials are ideal for automotive and medical PCBs, which require regular flexing.
- Avoid choosing thinner FR4 PCB material for PCB designs with grooves, as this increases the risk of damage or board breakage.
- The thickness of FR4 PCB material will affect the weight of the printed circuit board and may also affect the compatibility of components. This means, thin FR4 PCB material will logically help to make lightweight circuit boards, resulting in lightweight electronics. These lightweight products are attractive and easy to transport.
When should FR4 PCB material not be used?
FR4 PCB material is not the right choice if your application requirements meet any of the following:
- Excellent heat resistance: If the PCB is to be used in a high temperature environment, it is recommended not to use FR4 PCB material. For example, for PCBs in aerospace applications, FR4 PCB material is not the right choice.
- Lead-free soldering: If your customer needs a RoHS compliant PCB, lead-free soldering must be used. During lead-free soldering, the reflow temperature can peak and reach 250°C, and FR4 PCB material cannot withstand it due to its low temperature resistance.
- High frequency signal: FR4 board cannot maintain stable impedance when exposed to high frequency signal. As a result, fluctuations can occur and can affect the integrity of the signal.
Due to the popularity and widespread use of FR4 PCB materials, at present, it is easy to find FR4 PCB materials with various specifications and functions in the market. Therefore, it is necessary to discuss the requirements of the board with the PCB manufacturer during pcb processing.