1. Where Did Flex Circuits Originate?
The flexible circuit has just recently come of age as an interconnection device, although it was originally developed over twenty years ago.
Designers of applications from car stereos and cameras, to heart pacemakers and disk drives, have all reaped the benefits of flex circuits. More applications are being discovered every day.
The flexible circuit was originally designed as a replacement for bulky wire harnesses. Simple circuit designs helped to solve space and weight problems that could not be resolved using traditional wiring methods.
As technology advanced in leaps and bounds, new products required more compact packaging, minutely defined electrical impedances, and error-free product performance. Flexible circuitry gave the package engineer ways to miniaturize circuits, increase functional capacity, and improve reliability.
In addition to being flexible, flex circuits can be designed to meet highly complex special con figurations, and hostile operating environments are easily withstood by flex.
New products demand savings in space and weight with greater reliability. Because of these demands, the twenty-year-old technology of flexible circuits has come of age.
2. What Makes Up A Flexible Circuit?
A basic flexible circuit is made of a flexible polymer film laminated to a thin sheet of copper that is etched to produce a circuit pattern.
Patterns can be created on both sides of the film. Interconnections are achieved with plated through-holes, yielding an almost unlimited adaptability between various component parts. A polymer overcoat is often added to insulate and environmentally seal the circuit.
Flexible circuits can also combine several single- or double-sided circuits with complex interconnections, shielding, and surface mounted devices in a multi-layer design. These multi-layer designs can also be combined with rigid circuit boards to create a rigid/flex circuit capable of supporting devices as needed.
The most widely used polyimide film is KAPTON, because of its high heat resistance, dimensional stability, dielectric strength, and flexural capability. The characteristics of this raw material help the flex circuit maintain a high degree of durability, and also help it survive hostile environments.
3. How Does The Makeup Of A Flexible Circuit Compare To A Rigid Board?
One thing that flexible circuits and rigid printed circuit boards have in common is that they both allow repeatable connections. Conductor routings in a flexible circuit are determined just like a rigid PC board by a single artwork, rather than by individual wirings.
Flexible circuits also allow extra-fine lines, as low as 2 mils on 4-mil centers, allowing high -density device population and reduced circuit size and weight.
But flexible circuits have one important advantage over rigid PC boards in that they give designers a third dimension with which to work. Flexible circuits can bend and shape around two or more planes during installation. They can solve space and weight problems by replacing several bulky boards with a single thin one. While in use, flexible circuits can also bend and flex up to 500 million times without a failure. This is something a rigid PC board simply cannot do.
4. What Types of Flexible Circuits Are Available?
There are four basic types of flexible circuits, varying in degrees of complexity. These three types of circuits can be used in different combinations to solve most every interconnection design problem.
The simplest circuits are single-sided flexible circuits. They provide maximum flexibility for dynamic applications and can withstand hundreds of millions of flex cycles These simple circuits are also the most easily adaptable to SMT, TAB, and other developments in circuit technology.
Double-sided circuits are somewhat limited in their capacity to flex because of a thicker, more complex level of design. The ability to interconnect between sides using through-hole plating helps double-sided circuits carry complex designs, and still maintain flexibility
Multilayer circuits are ideal for complex, highly populated design requirements. Large numbers of conductors can be designed into a small package. Flexibility may be somewhat limited, de pending on the number of layers in the design. These multi-layer circuits are ideal for rigid/flex designs, combining a multilayer flex circuit with a hard board.
Multilayer circuits are the ideal problem-solving technology when confronted with design challenges like unavoidable crossovers, specific impedance requirements, elimination of crosstalk in sensitive circuits, additional shielding or ground planes, and high component density.
Rigid-Flex circuits are circuits combination of Rigid circuit and Flex circuits. So it have both the advantage of each other and it's newest types used in various applications