FR-4 is a highly versatile, cost-effective material widely used in printed circuit board (PCB) manufacturing. Its beneficial properties make it a standard choice, which is why we’re dedicating an article to explore its features, types, and practical considerations.

Overview of FR-4 Properties and Composition:

FR-4 is a standard defined by the National Electrical Manufacturers Association (NEMA) for a glass-reinforced epoxy resin laminate. The “FR” in FR-4 stands for “flame retardant,” indicating compliance with the UL94V-0 standard for flame resistance. All FR-4 PCBs feature a UL94V-0 code, ensuring flame resistance and rapid self-extinguishing properties.

FR-4’s glass transition (TG) temperature ranges from 115°C to 200°C, depending on manufacturing methods and resin types. Standard FR-4 PCBs consist of a layer of FR-4 sandwiched between two layers of laminated copper. Additionally, FR-4 includes bromine, a flame-resistant halogen, which has replaced the earlier G-10 composite due to its improved durability and fire resistance.

Key advantages of FR-4 include a favorable strength-to-weight ratio, water resistance, high mechanical strength, and excellent insulating capacity in both dry and humid conditions.

Types of FR-4:

1. Standard FR-4: Features heat resistance of approximately 140°C to 150°C.

2. High TG FR-4: Offers a higher glass transition temperature around 180°C.

3. High CTI FR-4: Has a Comparative Tracking Index above 600 volts.

4. FR-4 without Copper Lamination: Used in insulation plates and board supports.

More details on each type are discussed further here.

Choosing the Right FR-4 Thickness:

• Component Compatibility: FR-4 thickness affects the types of components you can use. For example, through-hole technology (THT) components may require thinner PCBs.

• Space Optimization: Thinner boards are ideal for compact designs, especially for USB connectors and Bluetooth accessories where space-saving is essential.

• Structural Design and Flexibility: Thicker boards offer greater flexibility, allowing for V-grooves, while thin boards can be at risk of breaking in larger dimensions.

• Environmental Suitability: Consider the application’s environment, as thin boards may be more susceptible to heat and warping, particularly in sensitive fields like medical electronics.

• Impedance Control: Thickness influences impedance control, which can be critical in specific designs.

• Connector Compatibility: The thickness of FR-4 must align with the types of connectors used in your circuit design.

Why Choose FR-4?

FR-4’s affordability makes it ideal for producing small PCB batches and for electronic prototyping. However, it may not be suitable for high-frequency circuits or applications where flexible PCBs are essential. In such cases, alternative materials like polyimide or polyamide might be preferable.

Proto-Electronics’ FR-4 Options

1. Standard FR-4

---    SHENGYI S1000H: Thickness from 0.2 to 3.2 mm.

---    VENTEC VT 481: Thickness from 0.2 to 3.2 mm.

2. FR-4 High TG

---    SHENGYI S1000-2: Thickness from 0.6 to 3.2 mm.

---    VENTEC VT 47: Thickness from 0.6 to 3.2 mm.

3. FR-4 High IRC

---    SHENGYI S1600: Standard thickness 1.6 mm.

---    VENTEC VT 42C: Standard thickness 1.6 mm.

4. FR-4 without Copper

---    Epoxy glass without copper, suitable for insulation plates, templates, and board supports.

---    Available thicknesses from 0.3 to 5 mm, manufactured from Gerber or DXF mechanical drawings.