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 What is The Flex Circuit Coverlay?

What is The Flex Circuit Coverlay?


During the production process of Flexible Printed Circuit Boards. the copper structure, which includes the exterior circuitry and wiring. and enclosed and protected with flex circuit coverlay. It is an overlay film made of a flexible adhesive layer. bonded at high temperatures over a thick sheet of acrylic or polyimide. which is subsequently pressed onto the circuit surface. The FPC’s substrate is mostly protected by the flexible circuit board coverlay. It works well in ovens and heaters and is heat resistant.

The Flex Circuit Coverlay: What Is It?

Flex circuit coverlay is a crucial element in the construction of FPCs. It serves as a protective layer that encapsulates the circuitry. providing insulation and shielding against external elements. Typically made from a flexible polyimide material. Coverlay designed to enhance the mechanical and electrical properties of the FPC.

flex circuit coverlay
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Key Functions of Flex Circuit Coverlay


Coverlay acts as an insulating layer that protects the underlying circuitry from environmental factors. preventing short circuits and electrical interference.


One of the primary advantages of using Coverlay is its flexibility. It allows the FPC to bend and conform to different shapes without compromising the integrity of the circuit.


Coverlay shields the circuit from moisture, dust, and other contaminants. ensuring the reliability and longevity of the flexible PCB.


Coverlay applied using advanced adhesion techniques. ensuring a strong bond with the underlying circuit layers. This enhances the overall structural integrity of the flexible PCB.

How is Coverlay Applied?

The application of Coverlay involves a lamination process. where the polyimide film is precisely aligned and bonded to the flexible circuit layers. This process requires precision and expertise, areas where Gesflex Circuit excels.

What Is The Thickness of Flex Circuit Coverlay?

The thickness of flexible PCB coverlay can vary based on specific requirements. and the design considerations. Coverlay thickness is typically measured in micrometers (μm) or mils (1 mil = 0.001 inches). Commonly used coverlay thicknesses for flexible printed circuits (FPCs). That can range from about 12.5 micrometers (0.5 mils) to 75 micrometers (3 mils). although these values customized based on the needs of a particular project.

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The Differences FPC Coverlay and Solder Mask Layer

Material Composition:

  • Flexible PCB Coverlay:Coverlay is typically made of a flexible polyimide material. It serves as a protective layer applied over the flexible circuit. providing insulation, environmental protection, and additional structural support.
  • Solder Mask Layer: The solder mask, also known as solder resist, is a layer applied to the surface of the circuit board. It is usually made of epoxy-based materials. that provide insulation and protection for the copper traces and pads. preventing unintended solder bridges during the assembly process.

Function and Purpose:

  • Flexible PCB Coverlay:The primary function of the coverlay is to insulate and protect the flexible circuit. It provides a protective barrier against environmental factors. such as moisture and dust, while also offering mechanical support and enhancing the overall flexibility of the FPC.
  • Solder Mask Layer: The solder mask layer primarily serves as a protective coating for the exposed copper traces on the circuit board. It prevents solder from adhering to areas where it shouldn’t during the soldering process. ensuring proper electrical isolation and preventing short circuits.

Application Areas:

  • Flexible PCB Coverlay:Coverlay is specifically designed for use in flexible PCBs. where its flexibility is essential. It applied over the entire flexible circuit or specific areas. depending on the design requirements.
  • Solder Mask Layer: Solder mask used in both rigid and flexible PCBs. It applied to the surface of the circuit board to protect the copper features during the soldering process. While it is more common on rigid PCBs, flexible circuits with rigid portions may also use solder mask.

Manufacturing Process:

  • Flexible PCB Coverlay:The coverlay is typically applied in a lamination process. where a layer of flexible polyimide is precisely aligned and bonded to the flexible circuit layers. This process requires precision to ensure proper alignment and adhesion.
  • Solder Mask Layer:Solder mask applied using a screen printing process. After the application, the board undergoes a curing process to harden the solder mask material.
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How to Choose the Right Flex Circuit Coverlay?

Choosing the correct Coverlay for your flex PCB is a critical decision that can significantly impact the performance, reliability, and longevity of your flexible circuit. Here’s a guide to help you navigate the process:

Consider the Environmental Conditions:

  • Temperature Range: Evaluate the operating temperature range of your application. Ensure that the chosen Coverlay material can withstand the extremes of your environment.
  • Chemical Exposure:If your flex PCB will be exposed to chemicals, choose a Coverlay material with resistance to those specific substances.

Evaluate Mechanical Requirements:

  • Flexibility Requirements:Different applications demand varying levels of flexibility. Select a Coverlay material that aligns with the bending and flexing needs of your design.
  • Thickness:Consider the thickness of the Coverlay, as this can impact the overall flexibility and formability of the flex PCB.

Assess Electrical Properties:

  • Dielectric Strength:Ensure that the chosen Coverlay material provides sufficient dielectric strength to prevent electrical interference and short circuits.
  • Surface Resistivity: Evaluate the surface resistivity of the Coverlay to understand its impact on the electrical performance of the flexible PCB.

Evaluate Moisture Resistance:

  • Humidity Exposure: If your flex PCB will be exposed to high humidity or moisture, choose a Coverlay material with excellent moisture resistance to prevent damage to the circuit.

Compatibility with Other Materials:

  • Adhesion Compatibility: Ensure that the chosen Coverlay material is compatible with the adhesives and materials used in the lamination process to achieve a strong bond.
  • Compatibility with Substrates:Consider the compatibility of the Coverlay material with the base materials used in your flex PCB.

Consider Manufacturing Processes:

  • Ease of Processing:Choose a Coverlay material that aligns with your preferred manufacturing processes, ensuring ease of handling, cutting, and lamination.

Expert Consultation:

  • Collaborate with Experts:Seek advice from experienced flexible PCB manufacturers like Gesflex Circuit. Leverage their expertise to choose the most suitable Coverlay for your specific application.

Explore Options with Gesflex Circuit:

  • Customization: Gesflex Circuit offers customizable Coverlay solutions tailored to your project’s unique requirements.
  • Quality Assurance: Trust in Gesflex Circuit’s commitment to delivering Coverlay solutions that meet the highest industry standards.
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Why Choose Gesflex Circuit for Coverlay Applications?


With our extensive experience in flexible PCB manufacturing. Gesflex Circuit has the expertise to ensure precise and reliable Coverlay applications.

Quality Assurance: 

We adhere to stringent quality standards, guaranteeing. that our Coverlay solutions meet the highest industry benchmarks.

Flexible Solder Mask Materials:

Flexible solder mask materials used in combination with various substrate materials. to provide protection and insulation for flexible circuits. These materials enhance the performance and reliability of flexible PCBs.


At Gesflex Circuit, we understand that every project is unique. We offer customizable Coverlay solutions to meet the specific requirements of your FPC.

Learn More with Gesflex Circuit

Explore the world of flexible PCBs with Gesflex Circuit. For inquiries, quotes, or to learn more about our Coverlay solutions, contact us today. Trust Gesflex Circuit for cutting-edge technology and unwavering commitment. to excellence in flexible PCB manufacturing.d

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