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Flex Circuit Design

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • Polyamide and polyester films are commonly used substrate materials in flexible circuit boards.

  • Flex boards are capable of undergoing bending, rolling, folding, twisting, etc.

  • Flex circuits replace wires and cables with flexible interconnects, thereby saving space, size, and weight.

Flex Circuit Design

Flex circuit design is popular in many industries due to its durability and space-saving abilities

Flexibility is an important factor when you are placing your printed circuit boards in a system that vibrates. If your board is designed to be rigid, there is a good probability that the board will break under shock and vibrations, leading to the failure of the system. For this reason, flex circuit design is popular in many industries due to its durability and space-saving abilities. 

Flex Circuits

Just like rigid PCBs, the basic function of flex circuits is to establish electrical connections between various components. Unlike rigid boards, in flex circuits, the electronic devices, components, and circuits are mounted on a flexible substrate. Polyamide and polyester films are the commonly used substrate materials in flexible circuit boards.

Generally, flex circuit applications require single-layer circuits. Multilayer circuits printed using circuit boards are also fabricated depending on the application, usually with plated through holes.

Flex Circuit Design Advantages

Offers mechanical flexibility and design freedom - Generally, flex circuits are ductile and have low mass. They can withstand shape change, strains, etc. to a great extent without breaking. They are suitable for applications involving vibrations. Flex boards are capable of undergoing bending, rolling, folding, and twisting. They fit in tight spaces and allow design as well as packaging freedom.

Saves weight and space - Flexible circuits replace wires and cables with flexible interconnects, thereby saving space and reducing weight. The larger surface-to-volume ratio of flexible current improves the heat dissipation from the circuit.

Increases signal integrity - In high-speed digital systems, the use of flex circuits increases signal integrity, as these circuits can handle rapid rise times.

Durable and reliable - The customization of routing paths in flexible printed circuit boards improves the reliability and durability of the boards.

Saves time and money - Flex circuits seamlessly integrate into the product shape and size, so time spent on assembling the system is reduced. Less manual labor in designing flex circuits is required, meaning fewer errors. And, money is saved with the elimination of the routing, wrapping, and soldering of the wires.

Flex Circuit Design Steps

  •  Understand the project

    Identify all specific requirements, both mechanical and electrical, such as currents, voltages, capacitance, impedance, shielding, wiring, types of components, location of components, signal types, etc.

  1.  Create the schematic  

    Accounting for the bendability of the PCB based on the application (static or dynamic), create the schematic design of the flex circuit board.

  1.  Design the PCB layout and identify the location of the components

    Use PCB layout software to design the layout of the PCB board. The decision on the placement of the components should be made at this step. Here, you can collaborate with the additive manufacturing or mechanical engineer to check whether the flex PCB will fit into the device. The flex circuit board layout may be designed as single-sided, double-sided, or multi-layered. The flex substrate material should also be considered when designing the layout. The coverlay and adhesive materials can also be chosen along with the substrate. When designing traces and routing, adhere to the IPC standard corresponding to the electrical parameters of the board. Holes can be drilled on the edges for mounting. Similarly, labels and identifiers can be added.

  1.  Verify the flex circuit design

    Simulation software can be utilized for verifying the flex circuit board design or you can physically build one prototype to validate the circuit board layout.

  1.  Generate the files to send to the PCB manufacturer

    Gerber files are generated and sent to the manufacturer at this stage.

  1.  Fabricate, assemble, and test

    The flex circuit board is fabricated, components are assembled onto the circuit, and then the board is sent for testing to validate that the flex circuit design meets all project requirements.

Cadence offers tools to help designers create flex circuit designs that meet their application requirements. Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.