As a professional supplier of packaging machinery parts, Hansheng Automation's CNC capabilities include: Ordinary turning and milling reaches an accuracy of ±0.01mm, precision grinding reaches an accuracy of ±0.005mm, precision turning and milling reaches an accuracy of ±0.005mm, and super mirror finishing reaches an accuracy of ±0.002mm. Below, we will introduce you to the relevant knowledge of FR-4 glass epoxy plastic that can be used for CNC machining.
What is FR-4 (also known as G10) glass epoxy?
FR-4 glass epoxy (FR4 for short) is a thermosetting composite material made by laminating and curing fiberglass cloth and epoxy resin. It is a typical example of a glass-reinforced epoxy system. Due to its excellent overall performance, it is often mentioned alongside G10 material (G10 is the base grade, while FR-4 adds flame retardancy to G10). It is widely used in applications requiring high strength, insulation, and stability.
As the core form of FR4 material, its common products include sheets (G10 material sheet) and rods. It is a fundamental material in the electronics, machinery, and aerospace industries, and holds an irreplaceable position in the printed circuit board industry.
What are the characteristics of FR-4 material? (Technical parameters)
| Property Category | Specific Property | Value/Description |
|---|---|---|
| Mechanical Properties | Tensile Strength | ~38,000 psi (≈262 MPa) |
| Flexural Strength | ~60,000 psi (≈414 MPa) | |
| Flexural Modulus | 2,400,000 psi (≈16.5 GPa) | |
| Wear Resistance | Rockwell hardness 110 M scale, resistant to wear during long-term use | |
| Electrical Properties | Dielectric Strength | ＞50 kV |
| Dielectric Constant (1 GHz) | ~4.4 | |
| Dissipation Factor (1 GHz) | 0.017–0.018 | |
| Thermal Properties | Flame Retardancy Rating | UL94 V0 (self-extinguishing) |
| Coefficient of Thermal Expansion (x/y-axis) | 1.2–1.4×10⁻⁵ K⁻¹ | |
| Glass Transition Temperature (Tg) | ＞120 ℃ (varies slightly by formulation) | |
| Physical Properties | Density | 1.85 g/cm³ (1850 kg/m³) |
| Water Absorption (24-hour immersion) | ＜0.10% |
FR-4 Glass Epoxy Plastic Manufacturing Process
Continuously woven E-type glass fiber cloth is cut and cleaned to remove impurities to enhance the bond with the resin.
The glass cloth is immersed in liquid epoxy resin to form a "prepreg" (prepreg). The resin content is controlled (typically 30%-40%).
Multiple layers of prepreg are stacked according to the desired thickness and pressed at a temperature of 150-200°C and a pressure of 100-300 psi to allow the resin to flow and fill the gaps between the fibers.
The epoxy resin undergoes a cross-linking reaction at high temperature, forming a rigid structure. After cooling, a basic form such as a G10 material sheet is obtained.
CNC milling, drilling, and other processes are used to transform the sheet into FR-4 PCB substrates or customized structural components.
What are the advantages and disadvantages of FR-4 glass epoxy plastic compared to similar plastics?
| Comparative Materials | Advantages (FR-4 vs. Comparative Materials) | Disadvantages (FR-4 vs. Comparative Materials) |
|---|---|---|
| Phenolic Plastics (PF) | Superior electrical insulation, mechanical strength over 30% higher, and lower brittleness. | More complex manufacturing process; cost approximately 20%-30% higher than PF. |
| POM (Acetal) | Significantly better electrical insulation and thermal stability than POM, suitable for high-voltage scenarios. | Slightly lower impact toughness than POM; density 31% higher than POM (1.41 g/cm³). |
| PEEK (Polyether Ether Ketone) | Cost only 1/3 to 1/5 of PEEK, suitable for large-scale applications. | Slightly lower temperature resistance (PEEK Tg ≈ 143℃ vs. FR-4 ≈ 120℃); slightly inferior chemical corrosion resistance. |
| General Epoxy Boards | Better flame retardancy (UL94 V0) and mechanical strength, suitable for high-risk scenarios. | Dielectric properties of some batches slightly lower than general epoxy boards due to flame retardant addition. |
As can be seen from the table, material fr 4 has significant advantages in scenarios where both electrical performance and structural stability need to be taken into account.
Applications of FR-4 Glass Epoxy Plastic
FR-4 has a wide range of applications due to its multiple performance dimensions.
In the electrical and electronics sector
Printed circuit boards (PCBs): FR-4 serves as the substrate for circuit wiring and provides insulation, accounting for over 90% of the global PCB substrate market.
Insulating structural parts: Components such as motor end caps, transformer partitions, and high-voltage switch insulation sheets utilize its high dielectric strength.
Connector housings: FR-4 protects internal circuitry while withstanding the mechanical stress of plugging and unplugging.
In mechanical manufacturing
Precision tooling fixtures: FR-4 utilizes its high rigidity and low expansion properties to ensure machining accuracy.
Automation equipment components: FR-4 includes robotic arm joint gaskets and guide rail insulation, ensuring both strength and insulation.
Aerospace and medical
Avionics components: Such as satellite antenna brackets and cabin insulation panels, meeting lightweight requirements and extreme environmental resistance;
Medical equipment: Such as MRI equipment housings and insulated surgical instrument handles, meeting biocompatibility and stability requirements.
References
The following are the reference sources for this article：
Baidu Encyclopedia. FR-4 [EB/OL]. (2025-08-21) [2025-08-21].
Wikipedia. FR-4[EB/OL]. (2025-03-16)[2025-08-21].
FAQ
Q: What is the core difference between FR-4 and G10?
A: Both are based on glass fiber and epoxy resin, but FR-4 incorporates flame retardants, achieving a UL94 V0 (self-extinguishing in case of fire) flame retardancy rating, making it suitable for high-risk applications such as electronic equipment. G10, however, lacks a flame retardant design and is more suitable for mechanical components where flame retardancy is not a mandatory requirement. Other mechanical and electrical properties are essentially the same, and there is no significant difference in processability between G10 and FR-4 sheets.
Q: Why is FR-4 the mainstream choice for PCB circuit boards?
A: The key reason lies in its precise balance of performance and cost: its dielectric constant (~4.4 @ 1GHz) and dissipation factor (0.017-0.018) ensure stable high-frequency signal transmission; its low moisture absorption (<0.10%) prevents insulation failure in humid environments; and its flame retardancy and low cost make it a perfect fit for mass production of FR4 PCBs. Currently, over 90% of PCB substrates worldwide are made of FR-4.
Q: 3. What is the service life of FR-4 material? Will it degrade due to environmental factors?
A: Under normal operating conditions (temperature -40°C to 120°C, humidity <85%), FR-4 has a service life of up to 10-15 years. However, long-term exposure to extreme environments (such as temperatures > 150°C, strong acid/alkali corrosion, and continuous vibration) can cause resin aging or fiber breakage, leading to gradual performance degradation (e.g., reduced insulation and strength). Therefore, it is recommended to select a customized formulation (such as a heat-resistant enhanced formulation) based on the application scenario.
Q: Can G10/FR-4 sheet materials be used directly outdoors?
A: Yes, but precautions are necessary: FR-4 is inherently resistant to UV and rain (low water absorption), but for long-term outdoor use, it is recommended to apply an anti-UV coating to the surface to prevent accelerated aging of the resin due to direct sunlight. In environments exposed to salt spray (such as in coastal areas), it is recommended to select a product with anti-corrosion additives to prevent electrochemical corrosion between the glass fiber and metal connectors.
Q: What details should be taken into consideration when processing FR-4 material to avoid damage?
A: When drilling/milling, use high-speed tools (speed ≥ 3000 rpm) to avoid softening the resin due to frictional heat.
When cutting thick boards (>1 inch), cut in steps to prevent excessive instantaneous stress and fiber delamination.
It is recommended to remove surface burrs after processing to prevent tip discharge during subsequent assembly, which could affect the insulation properties of the FR4 circuit board.
Q: What are the most reliable ways to connect FR-4 to metals (such as aluminum and copper)?
A: Mechanical connections: Fastening with screws or rivets is suitable for removable structures. Insulating gaskets are required at the contact points to prevent electrochemical corrosion.
Adhesive connections: Bonding with epoxy resin is suitable for permanent attachment, with bond strengths exceeding 1000 kg (compared to the inherent strength of the FR4 material).
Embedded metal parts: Metal inserts are integrally molded into the board during production. This is suitable for high-load scenarios (such as robotic arm joints) and offers the highest reliability.
Q: Is FR-4 an environmentally friendly material? How is it disposed of after disposal?
A: FR-4 itself contains no heavy metals, is RoHS-compliant, and is a low-toxic material. Discarded FR-4 can be disposed of in two ways:
Mechanical recycling: Crushed FR-4 is then used as filler and incorporated into new composite materials (such as concrete or plastic). Suitable for non-structural components.
Pyrolysis: Heat-decomposition is performed under an inert environment to recover epoxy resin and glass fiber. This process is suitable for industrial-scale processing, but the cost is relatively high.
Q: How can I tell if FR-4 on the market is genuine? Are there simple testing methods?
A: Flame retardancy testing: Continuously burn the board with a lighter. Authentic FR-4 should extinguish within 3 seconds after removal from the flame (UL94 V0 rating).
Density testing: Calculate the density by weighing. Authentic FR-4 should be 1.80-1.85 g/cm³. Substandard FR-4, due to reduced glass fiber content, often has a density of less than 1.7 g/cm³.
Appearance inspection: Authentic FR-4 should have a smooth surface, free of bubbles or delamination, and evenly distributed glass fiber cross-sections. Substandard FR-4 often exhibits resin accumulation or exposed fibers.