Flex Circuit Boards
A flex circuit board, as its name suggests, is an electrical connection that can bend or flex during normal use. They are used in a variety of applications including phones, laptops, MP3 players and more. They are also used in medical devices and wearable electronics. This technology offers many benefits over traditional ribbon cables and rigid circuit boards including a significant decrease in assembly errors. The flex circuit is also much thinner and lighter which allows it to fit more easily in tight spaces.
The basic structure of a flex circuit board consists of a conductor layer, usually copper, which is bonded to a dielectric layer. The thickness of the dielectric can vary, but a common choice is polyimide. The metal can be bonded to the dielectric using an adhesive, but increasingly popular are adhesiveless constructions that offer both improved performance and lower costs.
There are a number of other materials that can be added to a flex circuit to improve its functionality and durability. For example, a stiffener can be added to selected areas of the flex circuit to give it extra mechanical stability. PCBWay provides stiffeners made from FR4 and metal (not specified what type of metal). The cost for this option will increase the manufacturing cost. For more protection from electromagnetic interference, a shielding film can be added to the circuit board. The shielding will help to prevent interference from sources such as power lines and radio signals.
How Flex Circuit Boards Are Used in Stretchable Electronics
A single-sided flex circuit is the most commonly used type. This consists of one layer of conducting material, with the other side being used for housing different electronic components. It can be a simple design or can have openings for through-holes. It can also be laminated with other materials such as a protective solder mask or silk screen.
More complex flex circuits are often designed with multi-layer constructions. The layers are often connected through plated through holes. The layers can be a combination of different materials, although a copper foil is the most commonly used material. The conductive copper can be etched to create the different traces that are needed for the circuit to function.
Other important components include the insulating material that separates different layers, the solder mask to protect the underlying traces and the silk screen that shows the manufacturer’s logo or other information. For a high quality product, the surface of a flex circuit must be polished before it is finished.
The bending and flexing that occurs with stretchable electronics requires the flex circuit to be able to withstand deformations without damaging the conductors. This can be accomplished with the use of dual-layer flex circuits and laser postprocessing. The resulting flex circuit can then be integrated into the actuator to perform its functions. In addition, the flex circuit can be reprocessed to accommodate further stretching and flexing without the risk of damage to the conductors or other components.