Electronics is ruling the civilization at present and many efforts are being made to make this technology more suitable and adoptable to the users. Electronics circuits till now are used to be fabricated on rigid/hard substrates and this rigidity imposes shape limitations for electronic equipments. Though miniaturization of integrated circuits has helped to a large extent in giving the desired shape to electronic equipments but still this can be more exploited with the latest developments in the fabrication of flexible circuits. Flexible circuitry reduces the size and weight of a finished product. It allows increased circuit density and eliminates bulky connections and wiring. And the added ability to fold the circuit expands the boundaries of design and packaging.
Flexible electronics, also known as flex circuits or flex circuit boards, is a technology for assembling electronic circuits by mounting electronic devices on flexible high-performance plastic substrates, such as polyimide. Circuits can be designed in configurations from simple, single-sided conductive paths to complex high density three-dimensional assemblies utilizing a variety of fabrication materials from low cost polyester to mid range PEN to high density adhesiveless polyimide Novaclad. Additionally, flex circuits can be screen printed silver circuits on polyester. Flexible electronic assemblies may be manufactured using identical components used for rigid printed circuit boards, allowing the board to conform to a desired shape, or to flex during its use.
Developments:
The original recipe for flexible CMOS circuits comprised a 2- to 3-micrometer circuit layer sitting atop a plastic substrate as much as 100 µm thick. It could curve around a small roll of coins. But the new version has a total thickness of only 1.7 µm, including the plastic, which gives it the ability to wrap around a rod whose diameter is roughly 85 µm. In LCD fabrication, glass is used as a substrate. If thin flexible plastic or metal foil is used as the substrate instead, the entire system can be flexible, as the film deposited on top of the substrate is usually very thin, on the order of a few micrometres. OLEDs are normally used instead of a back-light for flexible displays, making a flexible organic light-emitting diode display. Flexible solar cells have been developed for powering satellites. These cells are lightweight, can be rolled up for launch, and are easily deployable, making them a good match for the application.
The development of bendable, twistable electronic circuits has been reported whose performance nearly matches that of conventional CMOS chips. The new circuits, developed by a team of researchers at the University of Illinois at Urbana-Champaign (USA) are built from ribbons of silicon only a few nanometers thick that are mounted on flexible plastic substrates. Same group or researchers has developed an improved plastic circuit that is not only flexible but also stretchable and foldable. To make it foldable, the researchers looked at the behavior of everyday objects so they decided to make the circuit much thinner.
Researchers at the University of Illinois at Urbana-Champaign (USA) make plastic circuits by transferring thin ribbons of silicon onto glue-coated plastic using a patterned rubber stamp. But before the ultrathin silicon layer is applied to the substrate, the plastic is heated, causing it to expand. Once the circuit layer is deposited and chemically bonded to the expanded substrate, the plastic is allowed to cool and contract. Relaxing the strain causes the circuit layer to buckle and form wavy patterns like the bellows of an accordion. It's the folds and wrinkles that give the circuit the ability to stretch and bend without breaking. Researchers say that in laboratory tests, the circuits, after a few hundred stretch-and-release cycles, showed no signs of fatigue.
Applications:
Flex circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring. In addition to cameras, a common application of flex circuits is in computer keyboard manufacturing; most keyboards made today use flex circuits for the switch matrix. Flexible circuit offers value added services that will help with bringing the design to reality with following advantages:
* Tightly assembled electronic packages, where electrical connections are required in 3 axis, such as cameras (static application).
* Electrical connections where the assembly is required to flex during its normal use, such as folding cell phones (dynamic application).
* Electrical connections between sub-assemblies to replace wire harnesses, which are heavier and bulkier, such as in rockets and satellites.
* Electrical connections where board thickness or space constraints are driving factors.
Further, the researchers are proceeding with partnerships with physicians who are developing biomedical devices incorporating the circuits for the use of flexible circuits which will help to create flexible biomedical devices suitable to be implanted inside the body in more comfortable manner, for example, an implantable sensor that will monitor electrical activity in the brain to help predict the onset of epileptic seizures. The device may also work in reverse, sending electric pulses that head off the seizures. This requires a device that will conform to the rippled geometry of the brain.
Dr SS Verma, -Dept of Physics, SLIET Longowal
Print This Page
Terms
and Conditions