Flexible circuits, also known as flex circuits, are the technology used for depositing, arranging and assembling electronic devices on flexible plastic substrates. The major purpose of this technology is to interconnect rigid boards, displays, connecters and various other components in flexible substrates for products ranging from computers to automobiles. Polyimide or Polyester films are the base material used in the making of flex circuits. Flexible films and thin layers of conductive circuit traces are essential in the construction of these circuits.
Flex Circuit Types
There are seven different types of flex circuit available for the production of cameras, cell phones, computer keyboards, printers and medical applications. These circuits are classified based on the design and construction. The 7 major types are:
Single-Sided – It comprises of a single conductive layer made up of metal or conductive polymer on a flexible film.
Double-Access – It also has a single-conductive layer but allows access from both sides to gain access to some features of the conductor pattern. Even though, it has features similar to single-sided circuits, it is not as commonly manufactured as single-sides because of the special processing involved. These kinds of circuits are also known as back-bared flex.
Sculptured Flex– These circuits are made up of copper conductors, wherein, the thickness of the conductors varies at different places like thin in flexible areas and thick at points of interconnection. The major application of these kinds of circuits relies in the creation of bare contacts.
Double-Sided – As the name implies, these flex circuits have two conductor layers. They can be constructed with or without plated through holes. Double-sided circuits without plated through holes allow access from only one side making it suitable for some military applications.
Multilayered – These circuits are made up of three or more conductor layers. Plated through holes are used to interconnect conductor layers. Laminating the layers together is a common practice in the construction of these circuits; however, discontinuous lamination is done to ensure maximum flexibility.
Rigid-Flex – These kinds of circuits contain both rigid and flexible substrates laminated together as a single structure. Usage of plated through holes are mandatory in these types of circuits as they are used to electrically charge the substrates. Rigid-flex types are commonly used in military products. However, the last few years has witnessed the use of rigid flex in the commercial world.
Polymer Thick Film Flex- In this type, conductors are printed on a polymer film. They contain single layer of conductors. These flex circuits are cost-effective compared to others and most commonly used in the making of keyboards.
The use of all the circuit types are widely acknowledged especially in automotive, telecommunications, aviation industries.
Introduction to Flex-circuit and Its Types