Flex Circuit Boards
Flexible electronics is a technology for assembling electronic circuits by mounting electronic devices to a flexible substrate. They can be manufactured using identical components used for rigid printed circuit boards, allowing them to conform to a desired shape or flex during use.
Flex circuits are often used as connectors in various applications where flexibility, space, or production restraints limit the service ability of rigid circuit boards. Most flexible circuits are passive wiring structures that are used to interconnect electronic components such as IC’s, Resistors, and Capacitors. However some are used only for making interconnections between other electronic assemblies either directly or by means of connectors. Flexible circuits are found in industrial and medical devices where many interconnections are required in a small package. They can also be found in computer keyboards and cell phones.
There a few basic constructions of flexible circuits but there is significant variation between them.
Single sided flex circuits have a single conductor layer made of either metal or conductive polymer on a flexible dielectric film. Component termination features are accessible only from one side.
Double access or back bared flex circuits are flexible circuits having a single conductor layer but which is processed so as to allow access to selected features of the conductor pattern from both sides. While this type of flex circuit has its benefits, the specialized processing requirements for accessing the features limits its use.
Double-sided flex circuits are flex circuits having two conductor layers. They can be fabricated with or without plated through holes. Many single sided circuits are built on double sided substrate just because they have one of two crossover connections. An example of this would be the circuit that connects the mouse pad to the motherboard of a laptop.
Multilayer flex circuits are flex circuits that have three or more layers of conductors. The layers of the multilayer flex circuit may or may not be continuously laminated together throughout the construction.
Rigid-flex circuits are a hybrid construction flex circuit consisting of rigid and flexible substrates which are laminated together into a single structure. The layers of a rigid flex are also normally electrically interconnected by means of plated through holes. Rigid-flex boards are normally multilayer structures, however, two metal layer constructions are sometimes used.