Flexibility and Reliability of FPC Flexible Circuits

Flexible Printed Circuit (FPC), also known as Flexible Electronics or Flex Circuits, is a versatile and highly reliable electronic interconnect technology. It consists of a thin, flexible, and bendable printed circuit board (PCB) that is made from various materials such as polyester, polyimide, or PEEK (Polyether Ether Ketone).

Currently there are four types of FPC: single-sided, double-sided, multi-layer flexible board and rigid flexible plate

①Single-sided flexible boards are low-cost printed boards when the requirements for electrical properties are not high. In the single-sided wiring, a single-sided flexible board is the first choice. It has a layer of chemically etched conductive patterns, and the conductive graphic layer on the flexible insulating substrate surface is a calendered copper foil.  The insulating substrate can be polyimide, polyethylene terephthalate, aramid fiber ester and polyvinyl chloride.

②Double-sided flexible board is a conductive graphic made by etching on each of the two sides of an insulating base film. Metallized holes connect the graphics on both sides of the insulating material to form a conductive pathway to meet the design and use of the function of the flex. And the cover film can protect single and double-sided conductors and indicate the location the placement of components.

③Multi-layer flexible boards are made by laminating 3 or more layers of single- or double-sided flexible circuits together and forming conductive paths between the different layers by drilling solenoids and plating to form metallized holes. This eliminates the need for complex soldering processes. Multi-layer circuits make a huge functional difference in terms of higher reliability, better thermal conductivity and easier assembly performance. When it comes to layout design, interaction of assembly size, number of layers and flexibility should be taken into consideration.

④ Conventional rigid-flexible boards are composed of rigid and flexible substrates selectively laminated together. The structure is tightly packed with metallized solitons to form conductive connections. If there are components on both the front and back sides of a printed board, a rigid-flexible board is a good choice. However, if all the components are on one side, it is more economical to choose a double-sided flexible board with a layer of FR4 reinforcement laminated to the back side.

⑤ Hybrid-structured flex circuits are multi-layer boards with conductive layers made of different metals. An 8-layer board uses FR-4 as the dielectric for the inner layer and polyimide as the dielectric for the outer layer, with leads protruding from the main board in three different directions, each made of a different metal. Copper alloy, copper and gold are used as separate leads. This hybrid structure is mostly used in the relationship between electrical signal conversion and heat conversion and low-temperature situation with harsh electrical property ,Hybrid-structured flex circuit is the only feasible solution. 

It can be evaluated by the convenience and total cost of the inline design to achieve the desired performance-price ratio.

Future Trends in FPC Technology

The development of Flexible Printed Circuit (FPC) technology continues to advance, driven by the increasing demand for smaller, more flexible, and high-performance electronic devices. Several exciting future trends are expected to shape the evolution of FPC technology. Let’s explore some of these trends:

Miniaturization: FPCs will continue to play a vital role in the miniaturization of electronic devices. With advancements in manufacturing techniques and materials, even smaller and thinner FPCs will be developed, enabling the creation of more compact and lightweight devices.

3D Flexibility: The implementation of three-dimensional (3D) flexibility in FPCs is anticipated to become more prevalent. This will allow FPCs to be folded, bent, or twisted in complex 3D shapes, expanding the design possibilities for flexible electronic devices.

Integration with IoT and Wearable Technology: As the Internet of Things (IoT) and wearable technology markets continue to grow, FPCs will play a crucial role in enabling the interconnection of various devices. FPCs will be integrated into wearable sensors, smart clothing, and IoT-enabled devices, providing flexibility, durability, and lightweight solutions.

Flexible Display Technology: FPCs will be instrumental in the advancement of flexible display technology. FPCs integrated with flexible OLED and AMOLED displays will enable the development of foldable smartphones, rollable screens, and other innovative display applications.

Stretchable Electronics: The development of FPCs with stretchable properties will enable the creation of electronic devices that can conform to irregular shapes and stretch with the human body. This technology holds great promise in applications such as healthcare, robotics, and consumer electronics.

Advanced Materials: The introduction of advanced materials, such as graphene and other nanomaterials, is expected to revolutionize FPC technology. These materials offer exceptional conductivity, flexibility, and durability, paving the way for enhanced performance and new applications for FPCs.

Advanced Manufacturing Techniques: Continuous improvement in manufacturing techniques, such as additive manufacturing (3D printing) and roll-to-roll (R2R) processing, will further streamline and enhance the production of FPCs. These advancements will reduce costs, improve efficiency, and expand possibilities for customization.

The future of FPC technology is incredibly promising, offering endless possibilities for innovative electronic devices. With ongoing research and development, FPCs will continue to evolve, delivering even more flexible, reliable, and high-performance solutions for a wide range of industries and applications.