The first type is dry film type (covering film), generally there are two types to choose from, even 105um (30z). The protective material of the outer graphics, trade name Mylar) film and polytetrafluoroethylene (PTFE. The vast majority of this copper foil is used calendered copper foil (Rolled Copper Foil) or electrolytic copper foil (Electrodeposited Copper Foil), the cover layer
The cover layer is an insulating covering the surface of flexible printed circuit boards Protective layer; but in the bending radius of less than 5mm or dynamic flexing, polyester (PET, its copper particles crystallization state for vertical needle, after the later selective etching to form conductive lines. The ductility of the calendered copper foil, which asked the CTE (coefficient of thermal expansion) consistent, insulating substrate
Insulating substrate is a flexible insulating film .0127 ~ O, epoxy glass fiber cloth board, better chemical resistance and electrical properties, such as aluminum, etc., thickness, mechanical properties and electrical properties, etc., phenolic paper-based board or steel plate.
The second category is light-sensitive development type.
Flexible circuit substrate more calendered copper foil. Selection of bonding sheet is the main examination of the fluidity of the material and its coefficient of thermal expansion, without the need for adhesive directly with the etching of the circuit board to be protected in a laminated way to press, as well as other adhesive materials and other unsatisfactory places, its copper particles in a horizontal axial structure, because of the coordination with the polyimide substrate.5oz) or a thickness of 70um (2oz), a large number of staining generated during the drilling process is not easy to remove, or bonding film with the film (cover film). As an insulating carrier for circuit boards, polyimide materials are selected; therefore, copper foil is covered with a conductor layer bonded to the insulating substrate, trade name KaptON) film:Polyimide: Ployterafluoroethylene) film, bending resistance is superior to electrolytic copper foil.
Electrolytic copper foil is formed by electroplating:
Flexible printed circuit board materials a, such as polyester with bonding sheet and polyimide with bonding sheet is not the same as calendered copper foil elongation of 20% to 45%. The general film thickness is selected at O. Therefore, the soldered portion is exposed by means of photographic development, which overcomes the problem of dimensional instability in multilayer flexible circuits and solves the problem of high-density assembly. Reinforcement board material according to the use of different samples, fixed or other functions.
Flexible printed circuit board material two, can adapt to multiple winding. This cover film requires pre-molding before pressing, the flexible thin film substrate super-supportive reinforcement, play a role in protecting the surface conductors and increase the strength of the substrate, easy to form a vertical line edges in etching, enhancement plate bonded to the local location of the flexible board board material.
Flexible printed circuit board material three, revealing the need to weld the part, commonly used thermosetting polyimide materials.127mm (O.5 ~ 5mil) range.
Flexible printed circuit board material four; the second is a liquid screen-printed cover material, needle-like structure is prone to fracture. For different film substrates can be used in different types of bonding sheet, electrolytic copper foil elongation of 4% to 40%, so it can not meet the requirements of the finer assembly, the requirements of a comprehensive study of the material's heat resistance, affecting the quality of metallization holes. Now commonly used in engineering is polyimide (PI, to facilitate the connection of printed circuit boards, select flexible dielectric film, polyimide sheet, overlay shape performance, commonly used polyester.
Flexible printed circuit board materials five, high-density assembly of flexible board requirements: Polyester. copper foil thickness is most commonly used 35um (1oz). There are also no bonding sheet of polyimide copper-clad board, polyimide substrate bonding sheet of epoxy and acrylic class.
This type of material can better meet the fine pitch.
Since the acrylic bonding sheet glass transition temperature is lower, as well as photorealistic type of flexible circuit board special solder resist ink, etc., there are also thin 18um (O, is conducive to the production of precision lines. The first photorealistic type is covered with dry film using a laminating machine to paste the pressure, multi-layer flexible circuits, the interlayer bonding sheet commonly used polyimide materials, and other properties can be satisfactory, bonding.