Types Of Flexible Circuits

Flexible circuit is a pattern of conductors created on a bendable film, often polymers, which acts as an insulating base material. The top is coated with an insulating cover layer. A flexible circuit is in fact a counterpart to a rigid printed circuit board.

There are four basic types of flexible circuits, varying in degrees of complexity that can be used in different combinations to solve almost every interconnection design problem.

1. Single-sided flexible circuits –
   
   This is the simplest of all types and provides maximum flexibility for dynamic applications. These simple circuits are also the most easily adaptable to SMT (surface mount technology), TAB (Tape Automated Bonding), and other developments in circuit technology. It is called single sided because the circuit allows access from one side only. Its applications are in the field of optical pick-up for computers, camera, camcorder, VCD players, vibration motors for mobile phones etc.
   
   They are the most least expensive, and produced in the greatest volume. Single-sided circuits find maximum application in appliances where dynamism is required like in case of printers and disk drive heads.
   
   Single layer circuit is created using a technique known as back baring or double access. This technique allows access to the metal conductors from both sides of the circuit. This method eliminates requirement of plate-through holes as required in multilayer circuits.
   
   
2. Double-sided flexible circuits –
   
   As the name suggests, these circuits have two conductive layers that are usually accessible from both sides. Their main features include component assembly on both sides. Although, their capacity to flex reduces because of their thickness and complexity in design but their ability to interconnect between sides using plate-through hole helps to implement complex designs without compromising on flexibility.
   
   These types of circuits are used when circuit density and layout cannot be routed on a single layer. Also used in shielding applications and dense surface mount assembly.
   
   
3. Multi-layer flexible circuits –
   
   These circuits are ideal for complex, highly dense design requirements. Large numbers of conductors can be interwoven into a small package. Flexibility may be reduced somewhat, depending on the number of layers in the design. Multilayer circuits are the ideal technology to overcome design challenges like unavoidable crossovers, specific resistance requirements, elimination of crosstalk in sensitive circuits, additional shielding of ground planes, and high component density.
   
   
4. Rigid-flex circuits –
   
   These are combination of rigid circuits and flex circuits. So it has the advantages of both. Rigid-flex circuits are a hybrid construction, consisting of rigid and flexible substrates laminated together into a single package and electrically interconnected by means of plate-through holes.
   
   Rigid-flex boards are normally multilayer designs, but double-sided (two-metal layer) constructions are possible as well, and, in fact, have been selected for certain microelectronic chip-packaging applications, such as in the construction of hearing aids.
   
   Such circuit types have been encouraged by military product designers, but in recent years, this type of construction has gained popularity in the commercial world, as well.
   
   

All the above-discussed types of flexible circuit technology offer numerous viable solutions for those challenged with packaging electronic products. The technology has come of age and become a strong contender in the arena of electronic packaging technologies.

Only sky is the limit in the advancement of electronics packaging with flexible circuits.