FR4 Glassfiber Rod

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Product details

Ⅰ. Definition of FR4 Fiberglass Rod

FR4 fiberglass rod is a rod-shaped composite material composed of glass fiber cloth and epoxy resin. It is an extension of the FR4 (Flame Retardant 4) family. Its core materials are:

• Reinforcement phase: Alkali-free glass fiber cloth (E-type glass fiber, alkali metal oxide content <0.8%), providing high mechanical strength and temperature resistance;

• Binder phase: Epoxy resin (such as bisphenol A epoxy resin), which fills the gaps between the glass fibers and forms a three-dimensional network structure through cross-linking, imparting insulation, chemical resistance, and processability.

FR4 fiberglass rod is typically manufactured as a cylindrical or square rod with a diameter of 6-130mm and a length of 1000mm (customizable). It features a smooth surface and internal fibers arranged in a continuous layer (mainly in a 0°/90° orthogonal weave). It is a fundamental material used in precision machining in the electronics and industrial sectors.

AHD FR4 G10 Epoxy Fiberglass Rod

II. Core Properties of FR4 Fiberglass Rods

The performance of FR4 fiberglass rods is determined by their composite structure of "glass fiber + epoxy resin." These core properties can be categorized into four main categories: physical, mechanical, chemical, and process properties.

1. Physical Properties

• Excellent electrical insulation: Epoxy resin itself is a highly insulating material (volume resistivity ≥ 10¹⁴Ω·cm). The glass fiber is non-conductive and blocks charge transfer at the interface with the resin. Therefore, the breakdown voltage of FR4 rods is ≥ 15kV/mm (at a thickness of 1mm), making them suitable for high-voltage or high-frequency applications.

• Moderate density: approximately 2.0g/cm³, achieving a balance between mechanical strength and lightweight requirements.

• Temperature Resistance Classification: Based on the glass transition temperature (Tg) of the epoxy resin, FR4 rods are classified as follows:

Conventional (Tg ≈ 130-140°C): Long-term operating temperature ≤ 120°C, short-term resistance to 150°C;

Medium (Tg ≈ 150-170°C): Long-term operating temperature ≤ 140°C, short-term resistance to 180°C;

High (Tg > 180°C): Long-term operating temperature ≤ 160°C, short-term resistance to 200°C (e.g., wave soldering trays require resistance to 260°C solder).

2. Mechanical Properties

• High Strength and Fatigue Resistance: Glass fiber has a tensile strength exceeding 3000 MPa, while epoxy resin transfers load evenly to the fiber through interfacial bonding, resulting in FR4 rods with a flexural strength of 500-800 MPa and a tensile strength of 300-400 MPa. Furthermore, the toughness of glass fiber absorbs some impact energy, resulting in high fatigue resistance.

• Brittleness: Glass fiber is inherently hard and brittle. While epoxy resin has a certain degree of toughness, the overall material is susceptible to delamination or fracture (elongation at break <2%) when subjected to sharp impact or transverse shear. Sharp notches and dynamic impact loads should be avoided.

• High Dimensional Stability: The coefficient of thermal expansion (CTE) of glass fiber is approximately 6-10 ppm/°C, while that of epoxy resin is approximately 50-60 ppm/°C. The resulting composite CTE is approximately 10-15 ppm/°C (much lower than that of metal and plastic), resulting in minimal deformation in temperature fluctuations (e.g., -40°C to 150°C).

3. Chemical Properties

• Chemical Resistance: Epoxy resin exhibits excellent resistance to non-oxidizing acids (e.g., hydrochloric acid, dilute sulfuric acid), weak bases (e.g., sodium hydroxide), and most organic solvents (e.g., alcohol, acetone, gasoline). Its surface is not susceptible to corrosion or swelling (no significant weight change after long-term immersion). However, it is sensitive to strong oxidizing acids (e.g., concentrated nitric acid, concentrated sulfuric acid) and highly polar solvents (e.g., dimethyl sulfoxide) and should be avoided.

• Flame Retardancy: The "Flame Retardant 4" designation in FR4 indicates that it meets the UL94 V-0 flame retardancy standard (extinguishing within 3 seconds of exposure to flame, no dripping). Bromine-based or phosphorus-based flame retardants in epoxy resin are the primary contributors, making it suitable for applications requiring fire protection, such as electronic appliances.

4. Processing Characteristics

• High Machinability: FR4 rods can be formed into complex shapes through conventional machining processes such as turning, milling, drilling, and grinding (specialized tools are required), achieving surface roughnesses of Ra 0.8μm or less (precision machining).

• High Thermal Stability: Heat generated during machining is effectively dissipated by water-soluble cutting fluid, preventing resin softening or ablation due to localized high temperatures (control of cutting speed and feed rate is required).

III. Core Advantages of FR4 Fiberglass Rods

FR4 fiberglass rods' advantages stem from their comprehensive performance of "insulation, strength, temperature resistance, and stability," particularly in the electronics and industrial sectors:

1. High Insulation and Safety:

The volume resistivity and breakdown voltage of FR4 rods far exceed those of ordinary plastics. They can maintain insulation even in high-voltage (e.g., above 10kV) or high-frequency (e.g., microwave) environments, eliminating risks such as leakage and arcing.

2. High Strength and Fatigue Resistance:

The flexural strength of FR4 rods (500-800MPa) is close to that of aluminum alloys, and their tensile strength is over 10 times that of ordinary plastics. Their density is only two-thirds that of aluminum alloys. In applications requiring both lightweight and high strength, their strength-to-density ratio surpasses that of most engineering plastics, even approaching that of some aluminum alloys. Furthermore, their fatigue resistance makes them suitable for industrial components subject to long-term reciprocating motion.

3. Temperature Resistance and Dimensional Stability:

The high-Tg version of FR4 rod can withstand short-term temperatures exceeding 200°C, while the conventional version can also operate stably at 120°C for extended periods, outperforming ordinary plastics. Furthermore, its low CTE minimizes deformation under temperature fluctuations, ensuring precise fit with electronic components and mechanical structures (for example, preventing chip displacement due to expansion in PCB fixtures).

4. Chemical Resistance and Cost Balance:

FR4 rod exhibits superior corrosion resistance to non-oxidizing acids, weak bases, and organic solvents to metals and ordinary plastics, making it suitable for use in corrosive environments such as chemical pump and valve seals and electroplating hangers. Furthermore, its raw material cost is significantly lower than that of high-performance engineering plastics and metals, offering an excellent overall cost-effectiveness.

5. Mature Processing and Design Flexibility:

The processing technology for FR4 rod is highly mature. Using specialized tooling, high-precision machining (tolerance ±0.05mm) is achieved, making it suitable for mass production on automated production lines. In addition, the weaving method of the fiberglass cloth (such as unidirectional cloth, plain cloth) and the epoxy resin formula (such as adding fillers) can be customized to meet the personalized needs of strength, temperature resistance or insulation in different scenarios.

Ⅳ. Summary

FR4 fiberglass rod is a high-performance rod material composed of a composite of glass fiber and epoxy resin. Its core properties include high insulation, strong mechanical properties, heat resistance, dimensional stability, and corrosion resistance. Its advantages lie in the insulation safety of electronic appliances, the structural strength of industrial equipment, adaptability to harsh environments, and a balance between cost and process. Despite its limitations of greater brittleness and slightly higher density, its comprehensive performance makes it one of the most commonly used basic materials for "insulation-structural integration" in the electronics, industrial, and automotive sectors.

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