Covering film of flexible printing circuit board and flexible printing circuit board structure and manufacturing method thereof

Abstract

The invention discloses a covering film of a flexible printing circuit board, a flexible printing circuit board structure provided with the covering film, and a manufacture method. The covering film is provided with a liquid baking type polyamide imide film directly formed on the surface of a formed circuit substrate. The formed circuit substrate and the liquid baking type polyamide imide film form the flexible printing circuit board, the flexible printing circuit can be matched with a reel-to-reel printing machine table for continuous production, the liquid baking type polyamide imide film can be adopted and matched with a photoreception polyimide protective film to form the covering film which can improve reserved opening precision of a flexible printing circuit board welding plate or a circuit. The covering film has the advantages of being ultra-thin, good in softness and flexibility, conforming to environment-friendly operation without separating paper, producing and machining in a non-scrap mode, being high in TG and the like. Moreover, the flexible printing circuit board provided with the covering film is suitable for flip phones, slide phones, digital cameras, digital photographic cameras, tablet personal computers, intelligent mobile phones and the like.

Description

technical field [0001] The invention belongs to the field of flexible printed circuit boards, and in particular relates to a covering film of a flexible printed circuit board, a structure of a flexible printed circuit board with the covering film and a manufacturing method thereof. Background technique [0002] Small electronic products not only need to be smaller and lighter, but also more freedom in design is also a major factor. Most of the wiring materials for small electronic products use flexible printed circuit boards (Flexible Printed Circuit, hereinafter referred to as FPC) with high design freedom and good flexibility. In the field of FPC, it is not only for mainstream smart phones, but also for touch panels. New requirements for design are also expanding. Flexible printed circuit board (FPC) is generally composed of two parts: a substrate with a formed circuit and a polyimide (PI) protective film, and FPC has developed various thicknesses while continuously devel...

AI Technical Summary

Problems solved by technology

It is then laminated on the circuit substrate. Generally, it is pressed at a high temperature of 160°C to 190°C in a fast pressing method, and then baked and hardened at a temperature of 160°C. In addition, it is made in a pressure transmission method, generally at 160°C to 175°C. Pressing and curing for a long time, the advantages of this pressure transmission production are large quantities and no additional baking time is required, but the production elasticity of the fast pressing method is relatively poor

[0010] It can be seen from the above that the structure and operation method of the traditional PI film + adhesive protective film are prone to the following defects: due to the adhesive layer, the thickness of the protective film is relatively thick; the storage environment of the protective film is harsh due to epoxy glue; Not good; need to use release paper, and the release paper is easy to shed and produce foreign matter; high temperature processing is easy to explode; the amount of glue overflow is not easy to control

[0011] (2) Non-photosensitive polyimide protective film: During operation, a layer of non-photosensitive polyimide protective film is covered on the surface of the circuit substrate, and then a UV photosensitive photoresist film is covered on the surface of the protective film. Using the principle of UV exposure, remove the light group and protective film at the reserved opening with liquid medicine, and then harden it by baking. The disadvantage of this protective film and operation method is that the manufacturing process of flexible printed circuit boards is cumbersome and costly. high, and poor flexibility

The disadvantages of this protective film and working method are high cost, poor flexibility and harsh storage environment of the protective film

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