In the field of PCB manufacturing, FR4 material has become the first choice of PCB designers due to its excellent performance and wide application. So what is the charm of FR-4 that makes it stand out among many materials? This article will introduce the material FR4 in detail.
1. What is FR4 Material in PCB?
FR-4, the full name of Flame-Retardant 4, is a composite material made of glass fiber and flame-retardant epoxy resin. It has become the main raw material for printed circuit board manufacturing with its excellent flame-retardant performance and stable electrical properties. Among China’s A-level PCB raw material brands, Shengyi and Kingboard, FR-4 is their star product.
FR4 material
2. What are FR4 material properties?
Excellent flame-retardant performance
Material FR4 contains special chemicals that can effectively slow down the spread of fire in the event of a fire, thereby protecting electronic equipment from damage. The “FR” in FR-4 stands for flame retardant, which represents its excellent flame retardant ability. The flame retardant rating of material FR4 is as high as 94V-0, which is the highest rating in the UL94 standard. This means that after two 10-second burning tests, the flame can be extinguished within 30 seconds, and no burning objects can fall off.
High mechanical strength
FR4 PCB material has high strength and high toughness mechanical properties. Glass fiber as a reinforcing material can enhance the strength and rigidity of the material. Epoxy resin as an adhesive can enhance the toughness of the material, can withstand various external loads, and is not prone to breakage or bending. Even if it is affected or vibrated, it can maintain good integrity and is not easy to break.
Stable electrical properties
The dielectric constant (Dk) of FR4 material is stable, generally between 4.2 and 4.8, which is suitable for medium frequency and high-speed signal transmission. Although the dielectric constant changes with temperature and frequency, FR4 can still meet most application requirements. It has high insulation resistance and stable electrical properties and can maintain good insulation properties whether in dry or humid environments. The dissipation factor (Df) is usually 0.02-0.035. Although it is not as low as some special high-frequency materials, it is sufficient to meet most application scenarios. FR4 also has good anti-electromagnetic interference ability, which can ensure the stability and integrity of the signal during transmission.
dissipation factor of various PCB materials
High stability
FR4 material can withstand temperatures up to 160℃~180℃, and can even be used at higher temperatures for a short time without deformation or melting. It has good corrosion resistance to most chemicals and can resist corrosion by acids and organic solvents. The high-temperature resistance and corrosion resistance of FR4 material makes it widely used in electronics, communications, aviation, aerospace, and other fields.
3. When to Use FR4?
PCB designers often face an important decision: should we choose economical FR4 PCB material or expensive high-frequency laminates? This seemingly simple choice actually contains in-depth considerations of performance, application, and cost requirements.
Performance: FR4 materials have good electrical performance and mechanical strength and are suitable for low-frequency applications. FR4 can be used for PCB working below 1 GHz operating frequency. High-frequency laminates have lower losses and higher signal integrity and are suitable for high-frequency microwave RF applications.
Application requirements: Select the appropriate PCB material based on the product’s transmission distance and electromagnetic compatibility (EMC) requirements. FR4 PCB material is widely used in various general electronic devices, such as computers and consumer electronics. High TG FR4 material is suitable for automotive electronics, aerospace, smart homes, medical equipment, etc. However, high-frequency materials perform better in complex electromagnetic environments and can ensure long-term stable equipment operation. Therefore, high-frequency material is widely used in communication systems, automotive ADAS systems, satellite communication systems, and other fields to meet the needs of high-frequency and high-speed signal transmission.
Cost: Material FR4 is relatively cheap and is suitable for cost-sensitive applications. High-frequency laminates have a high production cost, but in critical applications, their performance and reliability far outweigh cost considerations.
4. How to Choose FR4 Material Thickness
The common thicknesses of FR4 material PCBs are 0.3 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.4 mm, 3.0 mm, and 3.2 mm. The material thickness tolerance depends on the production capacity of FR4 PCB material manufacturers. The common FR4 PCB copper thicknesses are 0.5 ounce, 1 ounce, and 2 ounces, and other copper thicknesses are also available.
● The standard thickness is 1.6 mm, which is the most commonly used FR4 PCB thickness and is suitable for a wide range of electronic products, such as computer motherboards (and home appliances).
● The ultra-thin FR4 thickness ranges from 0.3 mm to 0.8 mm. Due to its lightweight and softness, it is more suitable for small electronic products, such as smartphones, smart wearable devices, and laptops.
● The thickness of thick PCBs is generally between 2.4 mm and 3.2 mm. Compared with the standard FR4 PCB thickness, thick PCB boards have a high load-bearing capacity and rigidity, and are used for products with high power and large electronic components, such as industry, automobiles, and aerospace.
When selecting FR4 PCB thickness, you need to consider whether your circuit board meets the scene requirements, clarify the product characteristics, and ensure safety while meeting performance requirements such as mechanical properties. At the same time, don’t forget the impact of cost. Generally speaking, the price difference of PCBs with thicknesses of 1.2 and 1.6 mm is not much, but if the thickness is above 2.0 mm, the cost will increase accordingly. The thicker the board is, the more sheets of fiberglass fabric are needed, so the cost will increase accordingly.
5. How to Select FR4 TG Value
TG value is Glass Transition temperature. It is an important technical indicator of FR4 PCB material, which determines the stability and reliability of the FR4 PCB at high temperatures. Generally speaking, the higher the TG value, the better the FR4 material’s high temperature resistance and the higher the reliability. The TG value of standard FR4 is usually between 130–140°C, the median TG is 150°C, and the high TG is greater than 170°C.
When choosing the FR4 TG value, the specific application needs to be considered. For example, for motherboards, consumer electronics, etc., TG135℃ FR4 can be selected; while for applications with higher requirements such as CPU motherboards and DDR3 memory substrates, TG180℃ or higher FR4 should be selected. In addition, the production process conditions will also affect the stability and improvement of the TG value, so comprehensive considerations are required to select the most suitable FR4 materials.
6. FR4 Material Datasheet (TG150)
Here we share the commonly used FR4 material (S1000H from Shengyi manufacturer) datasheet.
You can download the Fr4 datasheet from here: FR4 datasheet
