When it comes to PCB (Printed Circuit Board) design and manufacturing, one of the most critical considerations is FR4 thickness. FR4, a widely used material in PCB production, refers to a type of glass-reinforced epoxy laminate that provides structural stability, electrical insulation, and resistance to heat and moisture. Selecting the right FR4 thickness for a PCB impacts its mechanical durability, electrical performance, signal integrity, and thermal management.
In this article, we’ll explore everything you need to know about FR4 thickness, including common standards and specific measurements for 2-layer and 4-layer PCBs. Whether you’re an engineer working on electronic product development or a designer tackling your next custom electronic design, understanding FR4 thickness is essential for successful PCB manufacturing.
What Is FR4 in PCB Manufacturing?
FR4 is the most commonly used core material in PCB fabrication. It’s a composite material made from woven fiberglass cloth and epoxy resin, often with additional flame-retardant additives. The “FR” stands for “Flame Retardant,” and the number “4” signifies that it’s part of the NEMA (National Electrical Manufacturers Association) standard for laminate grades.
FR4 provides:
- Mechanical strength
- Electrical insulation
- Resistance to moisture and chemicals
- Thermal stability
- Flame retardance (self-extinguishing properties)
These characteristics make FR4 suitable for a wide range of applications, including industrial control systems, automotive electronics, consumer gadgets, and high-speed communication devices.
Why FR4 Thickness Matters
The thickness of the FR4 core and the overall PCB plays a crucial role in:
- Electrical performance: Impedance control, capacitance, and signal propagation speed are affected by dielectric thickness.
- Mechanical stability: Thicker boards provide increased rigidity and durability, while thinner boards offer flexibility and are useful in lightweight applications.
- Thermal performance: Heat dissipation can be influenced by the thickness of the board and copper layers.
- Manufacturability and cost: Thicker boards may require different processes and materials, impacting manufacturing costs and turnaround times.
Choosing the right FR4 thickness is an important consideration during electronic design and electronic product development, ensuring optimal performance and reliability.
How Thick Is a 2-Layer FR4?
Standard Thickness Range
A 2-layer FR4 PCB typically consists of two layers of copper with an FR4 core in between. The standard thickness for a 2-layer PCB generally falls within 0.8 mm to 1.6 mm, though this can vary depending on the application and customer requirements.
Common Thickness Options for 2-Layer PCBs:
- 0.8 mm (0.031 inches)
- 1.0 mm (0.039 inches)
- 1.2 mm (0.047 inches)
- 1.6 mm (0.063 inches) – This is the most common thickness for standard applications.
- 2.0 mm (0.079 inches) – Less common but used in boards requiring extra rigidity or for specific design needs.
Applications for 2-Layer FR4 Boards
- Consumer electronics (remote controls, toys, small appliances)
- Industrial control systems
- Basic power supplies
- LED lighting products
The 1.6 mm FR4 thickness is widely considered the industry standard for 2-layer boards because it offers a good balance between durability, mechanical strength, and manufacturability.
What Is the Standard Thickness of a PCB Board?
The standard thickness of a PCB board—whether it’s single-layer, double-layer, or multilayer—traditionally refers to 1.6 mm (0.063 inches). This standard emerged from early PCB industry practices and has continued due to its versatility, mechanical strength, and compatibility with many electronic assembly processes.
Factors That Influence PCB Thickness
- Number of layers – More layers generally increase the overall board thickness.
- Copper thickness – Heavier copper weights add to the overall thickness.
- Dielectric material and prepreg layers – These insulating layers vary in thickness based on design and electrical requirements.
- Application-specific requirements – Some industries (e.g., aerospace or automotive) may specify different thicknesses for environmental or performance reasons.
Standard Thickness Options Beyond 1.6 mm
- 0.2 mm (0.008 inches) for ultra-thin applications
- 0.4 mm (0.016 inches) for flexible PCBs or low-profile products
- 2.0 mm (0.079 inches) and above for heavy-duty, high-current applications
- Boards thicker than 3.2 mm (0.126 inches) are rare but used in specialized applications such as high-current busbars or rugged industrial systems.
The 1.6 mm standard works well in most electronic product development scenarios, providing a practical balance between mechanical strength and design flexibility.
What Is the Thickness of a 4-Layer PCB?
A 4-layer PCB is a multilayer board consisting of four conductive copper layers, separated by insulating layers of FR4 material (core and prepreg). The additional layers provide enhanced routing options, better signal integrity, and improved power distribution for more complex electronics.
Typical Thickness for 4-Layer PCBs
- 1.6 mm (0.063 inches) is also the default standard thickness for 4-layer PCBs.
- Thicknesses can range from 0.8 mm (0.031 inches) to 3.2 mm (0.126 inches) depending on the design.
Layer Stackup Example:
- Top Layer (Signal)
- Inner Layer 1 (Ground Plane)
- Inner Layer 2 (Power Plane)
- Bottom Layer (Signal)
Each conductive layer is separated by prepreg (pre-impregnated) fiberglass cloth and FR4 core material, whose thicknesses are adjusted based on the impedance requirements and overall board thickness.
Applications for 4-Layer PCBs
- High-speed digital circuits
- RF applications
- Medical devices
- Automotive control systems
- Industrial automation equipment
Factors That Influence 4-Layer PCB Thickness:
- Copper thickness – Thicker copper layers (e.g., 2 oz instead of 1 oz) increase the overall board thickness.
- Prepreg and core thickness – Adjusted based on electrical and mechanical performance needs.
- Impedance control – The dielectric thickness is fine-tuned to maintain specific impedance values for high-speed signal transmission.
How to Choose the Right FR4 Thickness for Your PCB
When selecting FR4 thickness, consider these factors:
- Mechanical Strength Requirements: Thicker boards resist bending and mechanical stress.
- Electrical Characteristics: Thinner dielectric layers influence impedance and signal propagation.
- Thermal Performance: Thicker boards can dissipate heat better but may trap heat in certain designs.
- Assembly Requirements: Boards that are too thick may be challenging to assemble, while those too thin can be fragile during soldering.
- Cost and Manufacturing Limitations: Custom thickness may lead to increased costs and longer lead times.
For custom electronic design projects, it’s essential to collaborate with experienced PCB manufacturers or electronic product development teams to balance these requirements.
Why FR4 Thickness Matters for Your Project: Insights from Arshon Technology
At Arshon Technology, we understand how critical FR4 thickness is in the electronic design and electronic product development process. Whether you’re working on a simple 2-layer board or a complex multi-layer PCB, selecting the right materials and thicknesses can impact the success of your project.
Our team of engineers works closely with clients to ensure optimal PCB stackups, impedance control, and thermal management—all while considering manufacturing efficiency and cost. From standard 1.6 mm FR4 PCBs to custom thickness boards designed for specialized applications, we offer tailored solutions that align with your product goals.
By leveraging our expertise in custom electronic design services, we help companies across industries—including medical devices, industrial automation, and consumer electronics—navigate the complexities of PCB material selection, stackup design, and manufacturability. If you’re looking for reliable guidance on FR4 thickness or end-to-end PCB design and development, Arshon Technology is your trusted partner.
Conclusion
Understanding FR4 thickness is essential for successful PCB design and manufacturing. Whether you are developing a 2-layer PCB, a 4-layer PCB, or a complex multilayer system, choosing the appropriate FR4 thickness impacts your product’s electrical, mechanical, and thermal performance.
The standard PCB thickness of 1.6 mm works for many applications, but there’s flexibility to customize the thickness based on project requirements. Factors such as layer count, copper weight, and design complexity will influence your decision.
By partnering with a knowledgeable electronic product development firm like Arshon Technology, you gain access to the expertise necessary to optimize every aspect of your PCB design, including material selection and FR4 thickness. Whether you need a rugged industrial control board or a sleek consumer device, our team ensures your PCB meets the highest standards for performance, reliability, and manufacturability.
Contact Arshon Technology today to learn how we can help with your next project!
