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Characteristics of Flexible Circuitry
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Characteristics of Flexible Circuitry


A Flexible Circuit is an arrangement of conductors mounted on a flexible circuit base or substrate and supported by a flexible dielectric film. These features distinguish flexible circuitry from rigid circuitry, and enable it to meet a broad range of application requirements. In order for a flexible circuit board to bend repeatedly, the conductors mounted on it, the adhesive used in binding, and any cover layer materials must be as flexible as the base board, and these types of circuits are often categorized according to the flexibility of their component parts. Aside from bending, the thinness of the dielectric material is one of the main properties of a flexible circuit, as it can support a high level of heat management and component strain relief in thermal cycling processes. Likewise, the potential for solder joint strain is greatly reduced in flexible circuitry.



Unlike standard circuit boards, flexible circuit boards are typically fabricated using polyimide (PI) or polyester materials instead of epoxy- and glass-based fabrics. Surface wiring can be done using acrylic or epoxy adhesive to bond copper foils and photolithography may be employed to establish a copper wiring pattern. Flexible circuitry benefits from having a relatively simple assembly that can be bent around components and attached to a chassis, the ability to create uniform electrical characteristics under specific positioning of conductors and insulation, and numerous other advantages that enable this technology to be a versatile solution for electronics and integrated circuit applications. The factors used in selecting a flexible circuit typically include cost, function, reliability, manufacturing requirements, and packaging efficiency.



Operational Features


In most cases, the weight and volume of flexible circuit wiring is significantly lower than interconnected round wiring alternatives. In addition, its flexibility enables this type of circuit to connect components that feature motion relative to one another and have them operate for an extremely high number of motion cycles. To better fit a chassis, a flexible circuit can be laid down flat and components can be inserted, soldered, and tested before the assembly is folded to conform to the shape of the intended chassis, but it can also be reverted back to a flat shape when in need of service or repair. With higher heat dissipation properties, flexible circuits can be designed with a higher current capacity than their rigid counterparts, while evenly positioning the conductors on its surface can provide uniform mechanical and electrical characteristics from part to part.


Due to wider variations in the proportional thickness of flexible circuitry dielectrics and adhesives, controlling the impedance for high-frequency transmission applications can be more difficult among flexible circuits than rigid ones. Similarly, the thin conductors and dielectrics in flexible circuitry tend to provide less shock absorption and shielding from vibrations for most components besides small, surface-mounted devices. However, the lack of shielding can be somewhat compensated through the use of adhesive stiffeners at component bonding points or by shifting support to the product chassis.



Reliability Characteristics


Flexible circuitry offers certain advantages in terms of reliability due to its unique design characteristics. Combining interconnecting cables with component mounting areas on a single flexible circuit can reduce the number of soldering joints and terminals, thereby strengthening device integrity. When exposed to shock, the flexibility and lower mass of a flexible circuit decreases the strain on solder joints, and terminal areas of the circuit can be polarized to reduce the potential for wiring errors. In flexible circuitry, the conductors can be placed closer to neutral surfaces and their bonding to insulators can be distributed over a larger surface area, effectively reducing the risk of damage from flexure. However, flexible circuit boards are more vulnerable than rigid devices to tearing from pressure at their edges, although reinforcement and careful packaging design can help alleviate the risk.



Cost Efficiency


Although the costs of flexible dielectrics and flexible circuit boards tend to be higher than those for rigid circuitry, flexible wiring typically has lower assembly and installation expenses due to more easily identifiable conductor paths and terminals. Additional tooling and processing stages make flexible boards and dielectrics more expensive, but savings can come in the form of lower material usage. Areas requiring less material in flexible circuitry include:


* Conductor Cross Sections: These cross sections can be made smaller as a result of efficient heat dissipation from flat conductors.

* Service Loops: The service loops in flexible circuitry can be made shorter without sacrificing effectiveness due to the greater physical elasticity of the boards.

* Signal Lines: Due to the mechanical support provided by conductors, the cross sections in flexible circuit signal lines can be decreased without reducing the terminal size.



Manufacturing Specifications


Under most circumstances, processing equipment is limited to producing flexible wiring assemblies within a range of 25 to 30 inches in width. Roll-to-roll manufacturing methods can, however, produce continuous lengths of up to several hundred feet with conductor patterns being set in small increments. Unless the entire length of the circuit board is covered with conductor patterns, it is generally less expensive to use flexible cable to connect a series of smaller boards into a composite fabricating unit. Flexible wiring can be hand- or wave-soldered, but at lower temperatures than those used for rigid boards.

Heros Electronics is a professional rigid /flex /flex-rigid PCB manufacturer Shenzhen with reasonable prices no matter for low size or high volume.

Sourcing: www.thomasnet.com/articles/automation-electronics/flexible-circuit-characteristics