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FR4 Stiffener Flexible PCB: Enhancing Durability and Performance

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Item Flexible PCB
Max Layer 8L
Inner Layer Min Trace/Space 3/3mil
Out Layer Min Trace/Space 3.5/4mil
Inner Layer Max Copper 2oz
Out Layer Max Copper 2oz
Min Mechanical Drilling 0.1mm
Min Laser Drilling 0.1mm
Aspect Ratio(Mechanical Drilling) 10:1
Aspect Ratio(Laser Drilling) /
Press Fit Hole Ttolerance ±0.05mm
PTH Tolerance ±0.075mm
NPTH Tolerance ±0.05mm
Countersink Tolerance ±0.15mm
Board Thickness 0.1-0.5mm
Board Thickness Tolerance(<1.0mm) ±0.05mm
Board Thickness Tolerance(≥1.0mm) /
Impedance Tolerance Single-Ended:±5Ω(≤50Ω),±7%(>50Ω)
Min Board Size 5*10mm
Max Board Size 9*14inch
Contour Tolerance ±0.05mm
Min BGA 7mil
Min SMT 7*10mil
Surface Treatment ENIG,Gold Finger,Immersion Silver,Immersion Tin,HASL(LF),OSP,ENEPIG,Flash Gold;Hard gold plating
Solder Mask Green Solder Mask/Black PI/Yellow PI
Min Solder Mask Clearance 3mil
Min Solder Mask Dam 8mil
Legend White,Black,Red,Yellow
Min Legend Width/Height 4/23mil
Strain Fillet Width 1.5+0.5mil
Bow & Twist /
Table of Contents
Primary Item (H2)

In the dynamic world of electronics, flexible printed circuit boards (PCBs) have become a staple for their versatility and efficiency. However, their flexibility often requires additional support to ensure durability and functionality in various applications. Enter the FR4 stiffener, a critical component in reinforcing flexible PCBs without compromising their inherent flexibility. 

What Are Flexible PCB Stiffeners?

Think of flexible PCB stiffeners as the skeleton that provides structure to the otherwise flexible body of a printed circuit board (PCB). They're like the supportive friend that ensures the PCB doesn't flex or bend more than it should, especially around critical components like connectors. This support helps maintain the integrity of electrical connections in dynamic environments.

What Is The Stiffener Material?

Stiffener materials can vary but typically include polyimide (PI), stainless steel, and FR4. Each material brings its own set of advantages to the table, depending on the specific needs of the PCB application, like thermal management, mechanical strength, or cost-efficiency.

What is an FR4 Stiffener?

An FR4 stiffener is a reinforcement material from the same glass-epoxy composite used in traditional rigid PCBs. When attached to specific areas of a flexible PCB, it provides the necessary rigidity to support components, connectors, and other stress points, effectively marrying the best of both rigid and flexible PCB technologies.

Benefits of Using FR4 Stiffeners

  • Cost-Effectiveness: FR4 is generally less expensive than other stiffening materials, offering a budget-friendly solution without compromising quality.
  • Mechanical Strength: It provides substantial mechanical support, ensuring components remain securely attached to the PCB.
  • Thermal Stability: FR4 has high thermal resistance, which is crucial for PCBs exposed to varying temperatures.
  • Versatility: Suitable for various applications, from consumer electronics to automotive systems.

The Role of FR4 Stiffeners in Flexible PCBs

  • Enhanced Support and Durability

FR4 stiffeners are strategically placed to offer support where it's most needed, such as under heavy components or along connector sites. This reinforcement prevents damage during assembly, handling, and operation, extending the lifespan of the PCB.

  • Improved Assembly Process

The added rigidity makes the assembly process smoother and more efficient. Stiffened areas facilitate easier soldering of components and provide a stable base for automated pick-and-place processes, reducing the risk of errors and defects.

  • Versatility in Design

With FR4 stiffeners, designers have more freedom to incorporate flexible PCBs into a broader range of applications. Stiffeners can be customized in shape and size, allowing for precise reinforcement that meets the specific needs of each project.

Applications of FR4 Stiffener Flexible PCBs

FR4 stiffener flexible PCBs are utilized in a variety of industries, including:

  • Consumer Electronics: In devices like smartphones and tablets, space is at a premium, and the PCB must conform to specific shapes.
  • Automotive: For applications requiring durable and flexible electronics, such as dashboard displays or control systems.
  • Medical Devices: The flexibility of the PCB allows for innovative device designs without sacrificing durability or reliability.
  • Wearable Technology: Enabling compact, flexible designs that can withstand the wear and tear of daily use.


FR4 stiffener flexible PCBs represent a perfect marriage of flexibility and strength, allowing designers to create innovative and reliable electronic devices. Whether it's a wearable gadget or a high-tech automotive display, FR4 stiffeners ensure that flexible PCBs can meet the demands of modern electronics without breaking a sweat (or a solder joint).

Ready to Elevate Your PCB Projects to New Heights?

At GlobalWellPCBA, we’re not just experts in PCB assembly and fabrication; we're your partners in innovation and success. Our commitment to quality, efficiency, and unparalleled customer service has supported countless projects across diverse industries, ensuring they meet their goals with the highest standards.

Don’t let PCB challenges slow you down. Whether you're in the military, medical, power, or commercial sectors, our seasoned team is here to provide tailored solutions that fit your unique needs. From rapid prototyping to high-volume production, we have the expertise and capabilities to bring your ideas to life precisely and quickly.
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