Application of polyimide film in the manufacture of flexible copper clad laminates

The largest application area of polyimide (PI) film is currently flexible printed circuit boards. With the rapid and rapid development of electronic products, electronic assembly technology has presented severe challenges one after another. In order to meet the development of electronic technology, people have made bold innovations in electronic assembly technology. Against this background, a flexible circuit (flexible circuit) containing delicate wires and made of a thin, compliant polymer film was applied. However, it can be applied to surface mounting technology and can be bent into countless desired shapes.

 

The flexible circuit board (FPC) using SMT technology can be made very thin and delicate, with an insulation thickness of less than 25 μm. This flexible circuit can be arbitrarily bent and can be rolled into a cylinder to make full use of three-dimensional volume. It breaks the traditional mindset of using the area, thereby forming the ability to make full use of the volume shape. This can significantly enhance the effective use density on the conductor length per unit area currently conventionally used, and form a high-density assembly. form. In recent years, the use of flexible circuits has expanded to radio communications, computers, and automotive electronics. In the past, flexible circuits were used exclusively as a substitute for rigid cables. It has maturedly used as a substitute for rigid circuits and printed circuit boards in applications requiring thin circuits or three-dimensional circuits. In order to meet the requirements of rigid-flex applications, rigid-flex technology combines flexible circuits (that is, rigid-flex printed circuit boards) on rigid circuit boards.

 

的 The main materials used in general flexible circuits (FPC with 3-layer method) are insulating films (insulating layers), adhesives, and wires (conductive layers). The insulating film forms the basis of the circuit and forms the insulating layer of the flexible circuit board. The adhesive glues the copper foil to the insulating film. In the design of the multilayer structure, many layers are glued together. Use an outer protective layer (cover film) to isolate electricity from sand, dust, and moisture, while reducing the stress on flexing. The conductive layer is provided by a copper foil. In some flexible circuits, reinforcing plates (consisting of aluminum, stainless steel, composite materials, etc.) are used as reinforcing ribs to ensure the stability of geometric dimensions. It can also provide mechanical support during component and connector insertion, and eliminate stress.

 

The flexible substrate materials currently used in flexible printed circuit boards are generally flexible copper clad laminates (FCCL). FCCL is divided into adhesive type (ie, three-layer type, 3L-FCCL) and non-adhesive type (ie, two Layer type, 2L-FCCL). Although the types of FCCL are different, most of the insulating films used in FCCL are polyimide (PI) films. At the same time, in the process of manufacturing flexible printed circuit boards and rigid-flexible printed circuit boards, in addition to the use of FCCL and great demand for PI films, PI is also used in the above-mentioned cover films and reinforcement boards. Films (or products made from PI films). In order for FCCL manufacturers to supply flexible substrate materials to FPC manufacturers, the above three types of flexible materials are generally produced simultaneously.

 

Flexible printed boards have a wide range of applications, and can be used in almost all kinds of electronic products. There is a tendency to replace rigid printed boards.