Cover film with low rebound force and preparation method of film

Abstract

The invention provides a cover film with low rebound force. The film comprises a PI film with low rebound force, a release film arranged on one side of the PI film, and an adhesive layer with low rebound force between the PI film and the release film, wherein a PET carrier film is arranged on the other side of the PI film, and a glue blocking layer is arranged between the PI film and the PET carrier film; and the PI film is a film layer with a thickness of 1-7 um formed by directly casting and drying a polyamic acid solution with a molecular weight of more than 100,000 and a solid content of less than 25% without biaxial stretching, the elongation at break of the PI film is more than 60%, the tensile strength is less than 150 MPa, and the stripping temperature is lower than 390 DEG C. Theprocess of printing green oil separately in the bending area of the FPC is omitted, the effective efficiency is greatly improved, the production cost is reduced, and meanwhile, the defective rate caused by manual printing errors is avoided, and the product yield is greatly improved.

Description

technical field [0001] The invention relates to the field of FPC printed circuits, in particular to a covering film with low rebound force and a preparation method thereof. Background technique [0002] Printed circuit board (FPC for short) is an indispensable material in electronic products, and is currently widely used in computers and their peripheral equipment, communication products and consumer electronics products. FPC usually protects the circuit by attaching a cover film. However, the bending area of ​​the FPC has high requirements for bendability. If the existing cover film is attached, the rebound force of the cover film will be too large, causing The bending area is prone to rebound after bending, which will cause screen scratches and affect the service life of electronic products. [0003] In the prior art, the process of printing green oil on the FPC bending area is used to solve the problem of low rebound force, but there are the following disadvantages: (1) ...

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Problems solved by technology

FPC usually protects the circuit by attaching a cover film. However, the bending area of ​​the FPC has high requirements for bendability. If the existing cover film is attached, the rebound force of the cover film will be too large, causing The bending area is prone to rebound after bending, resulting in scratches and affecting the service life of electronic products

[0003] In the prior art, the process of printing green oil on the FPC bending area is used to solve the problem of low rebound force, but there are the following disadvantages: (1) Printing green oil requires a separate silk screen process, which increases the process of product production and processing, that is, reduces (2) Silk screen printing is to print green oil manually, which is not only time-consuming and labor-intensive, but also the operator's operation error can easily make the thickness of green oil printing uneven, resulting in inconsistent rebound force in the bending area, thus affecting the line quality. The protective effect of the circuit is easy to break, which reduces the yield of the product; moreover, the alignment accuracy of the silk screen is poor, which reduces the quality of the product; (3) the coating used in the silk screen printing process has certain toxicity, which pollutes the environment greatly and the working environment Poor, and even affect the health of workers; (4) With the user's pursuit of thinner and lighter mobile electronic products and a larger display surface, the size of the FPC bending area is becoming narrower and narrower, so the protective layer in this area has low resilience The requirements are getting higher and higher, and the existing green oil printing may not meet the requirements

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