fr4 pcb manufacturer
FR4 PCB

FR4 PCB

Meaning of FR-4: Composite PCB Manufacturing Material and Rating Unit.

In electronic engineering, different substrate materials are chosen based on their application characteristics. For instance, high-frequency circuits use Rogers, while RF circuits use Teflon (a comparison of FR4 with other PCB materials is provided below). Typically, we refer to circuit boards based on the substrate material name. FR-4 in PCB has a dual meaning:

  • As a substrate material, it refers to the glass fiber-reinforced epoxy laminate.
  • As a fire resistance rating, including FR-1, FR-2, FR-3, and FR-4.
 

For cost-effective projects, using FR-4 to construct circuit boards is a wise choice. It complies with the UL94V-0 standard, providing sufficient mechanical strength and self-extinguishing capabilities. Here, we not only elaborate on FS Technology’s manufacturing capabilities but also provide FR-4 material specifications. Whether you are in the process of selecting substrate materials for your project or seeking FR-4 PCB solutions, you will find this information helpful!

Reliable FR4 PCB Manufacturer - FS Technology

Unlike traditional Chinese companies that separate trade from manufacturing, FS Technology is an integrated PCBA manufacturer with various departments, including Engineering, Procurement, Sales, Production, and Assembly. This integration helps us meet the comprehensive needs of customers both domestically and internationally. With traditional substrate materials like FR-4, we have a strong experience base and set ourselves apart from other manufacturers through breakthrough technologies.

As a manufacturer that focuses on long-term cooperation,  “Quality”, “Service” and “Price” as three pillars, that is, providing better services at lower costs so that customers can obtain high-quality products. Based on our service philosophy, we have received a high volume of orders and consistent praise. Our main advantages include:

  • Broad Services: We have dedicated personnel to handle everything from design to delivery, so you can concentrate on sales.
  • Customized Solutions: Tailored solutions based on the specific stage of your project.
  • Flexible Customization: 1-56 layer FR-4 PCB, blind/buried/micro vias, SMT+THT, fine-pitch processing, various surface finishes, and more.
  • Cost-Effective: Close cooperation with supply chain partners and design optimization solutions.
  • Quality: 24/7 Online Customer Service + Point to Point Support + Well Defined Processes + High Quality Materials
  • Certifications: Providing industry-required certifications such as IATF16949 and ISO13485.
  • Speed: Digital Automated Production + Simplified Processes + High Production Capacity + Customized Shipping Solutions.
AOI inspection FR4 PCB board

FR4 Substrate Material Parameters

Selecting the right circuit board type for your project based on the parameters of the substrate material is the best strategy. Below is the parameter table for conventional FR4 provided by FS Technology:

Parameters Table

Test ItemsProcessing ConditionsUnitPerformance Parameter
Reference ValueTypical Values
TgDSC≥130140
CombustibilityC-48/23/50V-0V-0
E-24/125
Volume ResistivityAfter ImmersionMΩ-cm≥10^62.0*10^8
E-24/127≥10^35.0*10^8
Surface ResistivityAfter Immersion≥10^43.0*10^7
E-24/125≥10^35.0*10^7
Anti ARCD-48/50+D-0.5/23S≥60115
Dielectric BreakdownD-48/50+D-0.5/23KV≥4055
Dielectric Constant (1MHZ)C-24/23/50≤5.44.7
Dielectric Loss Angle (1MHZ)C-24/23/50≤0.0350.01
Bending StrengthHorizontalAMpa≥415450
Portrait≥345400
Water AbsorptionD-24/23%≤0.50.1
ClJPCA-ES-01-2003-Standard%≤0.090.05
BrJPCA-ES-01-2003-Standard%≤0.090

Remark:

  • All test data comply with IPC-4101/92 standard
  • Sample thickness: 1.6 mm
  • C=humid condition
  • D = Immersion in distilled water condition
  • E=temperature condition
  • Tg=Glass transition temperature, the plate undergoes softening deformation at high temperature and is accompanied by a sharp decline in mechanical and electrical properties

Parameter Explanation

Glass Transition Temperature

Temperature is an important measurement in electronic projects, Here, we primarily discuss the glass transition temperature, known as the TG value. A higher TG value indicates that the circuit board can operate continuously in higher-temperature environments without affecting its physical and electrical properties. Typically, the highest operating temperature for FR4 PCBs is around 130 °C, but FS Technology recommends not exceeding 100 °C, as components may need to be assembled on the FR4 PCB for specific functions, and the maximum operating temperature of these components may be lower than 130 °C.

Thermal Conductivity

The thermal conductivity of FR4 material is one of its drawbacks, with a thermal conductivity coefficient of approximately 0.3 W/(m·K), while metal substrate materials can reach 385 W/(m·K) (like copper). This represents a significant gap in material properties that, despite optimization in design, cannot be entirely bridged. One measure to improve heat dissipation is by increasing the number of heat dissipation holes. However, the benefit diminishes once a certain number is reached. Additionally, optimization in routing, increasing trace thickness, and well-distributed placement of heat-generating components can be employed to address this issue.

Thickness

The thickness can vary depending on the specific application and design requirements. Generally, FR4 PCB is available in thicknesses ranging from 0.2 mm to 6.0 mm or more. Thinner PCB is often used in applications where space is limited, such as in mobile devices or wearable technology, while thicker PCB is used in applications that require greater durability and strength, such as in industrial or military equipment. The thickness of an FR4 PCB can also affect its electrical properties, such as impedance and capacitance, so it’s important to carefully consider the design requirements and choose the appropriate thickness for the application.

Density

The density of FR4 PCB depends on the thickness and number of layers of the board. Typically, the density of FR4 material is 1.85g/cm³, but the actual density of the PCB may vary depending on the design and manufacturing process.

The number of layers in the PCB can also affect its density. A single-layer FR4 PCB will have a lower density than a multi-layer FR4 PCB because the latter has more layers of copper and insulating material. The thickness of the copper layers can also contribute to the density of the PCB, with thicker copper layers increasing the overall weight and density of the board.

Hygroscopicity

Hygroscopicity refers to the amount of moisture absorbed by a substrate in a humid environment. A lower hygroscopicity indicates that the material absorbs less moisture, allowing it to maintain dielectric performance in humid conditions and prevent issues like corrosion, delamination, microcracks, and electrical short circuits.

Mechanical Properties

FR4 substrate material exhibits excellent mechanical properties, with a tensile strength ranging from 345-414 MPa and a flexural strength ranging from 483-586 MPa. This results in better dimensional stability, vibration resistance, and physical impact resistance.

Types of FR4 PCB Boards

High TG FR4

High-TG PCB is an improved FR4 material with a higher glass transition temperature, which is the temperature at which the material transitions from a rigid, glass-like state to a more flexible, rubbery state. This is typically achieved by altering the material’s composition or upgrading the production process. While traditional FR4 materials have a TG value of approximately 130-140 °C, High-TG FR4 boasts a TG range of 170-180 °C. This change enhances its ability to withstand high temperatures, making it well-suited for applications in power electronics, LED lighting, and automotive electronics.

Halogen-Free FR4

The term “halogen-free” is commonly used to refer to circuit board substrates that do not contain halogen elements from the periodic table, such as bromine, iodine, and chlorine. While these halogen elements can enhance the flame retardant properties of circuit boards, they release harmful gases when burned, which is in violation of the RoHS directive.

To avoid the use of halogen elements without compromising performance, FS Technology employs alternative materials like phosphorus and phosphorus-nitrogen. The glass transition temperature of these halogen-free FR4 PCBs is typically around 150°C, with a decomposition temperature of approximately 330°C. This makes this type of FR4 substrate highly suitable for devices that aim to reduce harmful smoke during combustion.

Multilayer Circuit

One of the reasons why FR-4 is so popular in the PCB industry, aside from its excellent cost-effectiveness, is its ease of processing. As you may know, the more complex the layering in a circuit, the more challenging it is to construct. However, FR-4 material possesses adequate mechanical properties, and most manufacturers have a strong command of processing techniques. As a result, they can often achieve the construction of multi-layer circuits. For instance, at FS Technology, you can easily obtain 1-56 layer FR4 multi-layer PCB at a low cost. This advantage allows for the realization of higher-density circuit structures. Furthermore, the ease of processing in bare board manufacturing extends to assembly.

Thick Copper FR-4 PCB​

Thick copper FR4 PCB refers to the technology of significantly enhancing the conductivity and heat dissipation of the circuit board by adding thicker copper layers to the traditional FR4 substrate material. This is especially suitable for high-current and high-power applications, such as power circuits and motor control circuits.

However, it’s important to note that the improvement in performance may come with increased weight and costs. When designing FR4 PCBs with thicker copper, it is advisable to consider controlled impedance routing to ensure impedance matching in the circuit. Additionally, selecting the appropriate copper thickness is crucial for the success of your project. You can refer to FS Technology’s PCB Copper Thickness Guide, which provides valuable guidance for your design projects.

Bendable Board

First, there is the combination of rigid-flex PCB, which cleverly connects the rigid and flexible parts, giving the circuit board bending and flexing capabilities while maintaining a high level of reliability. Typically, we choose FR4 as the material for the rigid portion because it possesses the required mechanical properties, and its cost is relatively lower, contributing to cost-effective projects.

The other option is semi-flex PCB, which use deep milling techniques to process the areas that need a certain degree of flexibility. This approach is based on the ease of processing associated with FR4 materials.

Fr4 PCB or Others

FR Series

The FR (Flame Retardant) series currently includes five different materials, namely FR1, FR2, FR3, FR4, and FR5. The numbers represent the flame retardant rating, with higher numbers indicating stronger flame retardant capabilities.

  • FR1: Composed of phenolic resin and paper, it is the most cost-effective and is commonly used for low-voltage, low-frequency applications.
  • FR2: Made from phenolic resin and cotton, it offers better mechanical performance and has a wider range of applications compared to FR1.
  • FR3: Constructed using epoxy resin and paper, it can be used for high-voltage and high-frequency applications, although its capabilities are limited.
  • FR4: Comprised of epoxy resin and glass fiber, it is the most widely used in the FR series due to its cost-effectiveness.
  • FR5: Composed of epoxy resin and glass fiber, its performance is slightly better than FR4 but the price is higher.

VS Ceramic

Ceramic PCB is constructed using substrate materials such as aluminum oxide, aluminum nitride, and silicon carbide. They find extensive use in applications with stringent signal transmission requirements.

  • Compared to FR4, ceramic-based PCB offer significantly higher thermal conductivity. Whether using aluminum oxide, aluminum nitride, or silicon carbide, ceramic PCB excel in heat dissipation, obviating the need for features like vias and metal layers used for thermal management in FR4 PCB.
  • While FR4 provides adequate electrical performance, it pales in comparison to ceramics. However, it’s essential to note that ceramic PCBs come at a higher construction cost. As such, they are better suited for electronic projects with high pricing and profitability, such as those in the medical, military, or base station construction sectors.
  • Due to the inherent fragility of ceramic materials, constructing multi-layer ceramic PCB can be challenging. For multi-layer structures, it’s advisable to consider Rogers’ ceramic series as a viable alternative to ceramic-based.

VS Aluminum

Aluminum PCB use aluminum as the substrate material and is the most common among metal PCB. Usually, it appears silvery white, has bending properties at some point, and is commonly used in the LED industry.

  • In terms of pricing, FR4 is more cost-effective compared to aluminum PCB, which are one of the more budget-friendly options among metal PCB.
  • Aluminum-based PCB is challenging to process and, due to their primary purpose of achieving heat dissipation, are typically single or double-layer structures.
  • When it comes to thermal performance, aluminum PCB far outperform FR4 PCB. This is their main advantage, helping high-power projects with heat dissipation.
  • Aluminum is a material with excellent radiation shielding capabilities, which can prevent components on the board from being affected by electromagnetic radiation.

VS Rogers

Rogers laminate is a high-performance material developed and produced by Rogers Corporation. Due to its higher cost, it is typically used in more advanced electronics to compensate for the limitations of traditional materials in terms of signal transmission and signal integrity.

  • In terms of cost-effectiveness, FR4 significantly outperforms Rogers.
  • In terms of performance, whether it’s heat management, impedance control, dielectric constant, or dielectric loss, Rogers excels.
  • In terms of applications, FR4 is suitable for general electronics like phones and computers, while Rogers PCB shine in the communication field.
  • The Rogers material series provides more options to help you achieve your project’s design goals.

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