FPC board composition material introduction
The insulating substrate is a flexible insulating film. As the insulation carrier of FPC flexible circuit board, the choice of flexible dielectric film requires a comprehensive inspection of the material’s heat resistance, shape, thickness, mechanical properties and electrical properties. Polyimide films, polyester films, and polytetrafluoroethylene films are now commonly used.
2, adhesive sheet
The function of the adhesive sheet is to bond the film and the metal foil, or to bond the film and the cover film. Different types of adhesive sheets can be used for different film substrates. For example, polyester adhesive sheets and polyimide adhesive sheets are different. The adhesive sheets of polyimide substrates are classified into epoxy and acrylic. Choosing a cohesive sheet mainly examines the fluidity of the material and its coefficient of thermal expansion.
3, copper foil
The copper foil is a conductor layer that covers the insulating substrate and is selectively etched to form a conductive line. The vast majority of such copper foils are rolled copper foils or electrolytic copper foils. The ductility and bending resistance of the rolled copper foil is better than that of the electrolytic copper foil. The elongation rate of the rolled copper foil is 20% to 45%, and the elongation of the electrolytic copper foil is 4% to 40%.
4, cover layer
The cover layer is an insulating protective layer covering the surface of the FPC flexible circuit board, which plays a role of protecting the surface wires and increasing the strength of the substrate. The protective material of the outer layer pattern generally has two types of dry film type (cover film) and photosensitive developing type.
5, enhanced board
The reinforcing plate is adhered to the local plate of the flexible plate, and the super-strength of the flexible film substrate is strengthened to facilitate the connection, fixing or other functions of the FPC flexible circuit board. Reinforcement plate materials are selected according to different applications. Commonly used are polyester, polyimide sheets, epoxy glass cloth sheets, phenolic paper plates or steel plates, and aluminum plates.