Preparation method of size-stable polyimide film

Abstract

The invention discloses a preparation method of a size-stable polyimide film. The preparation method comprises the following steps: 1) obtaining a defoamed polyamide acid resin solution; (2) casting the obtained resin solution onto a support body to form a liquid film, and sequentially heating the liquid film by hot air within the temperature ranges of T1, T2 and T3 to obtain a gel film, wherein the solvent content of the gel film is less than or equal to 35 percent and the imidization rate is more than or equal to 60 percent; 3) longitudinally stretching the obtained gel film through at leastsix rollers under a specific roller speed ratio condition without heating to obtain a longitudinally stretched gel film; 4) feeding the obtained longitudinally-stretched gel film into an imine furnace, and carrying out transverse stretching, imidization and a shaping treatment to obtain a polyimide film; and 5) feeding the obtained polyimide film into a gradient heating treatment at 150-400 DEG Cunder a condition of no stress, and then performing gradient cooling treatment at 400-50 DEG C. The provided method can guarantee a good heat shrinkage rate and low thermal expansion, and at the sametime, improves the continuity and yield of production.

Description

technical field [0001] The present invention relates to polyimide film, be specifically related to a kind of preparation method of dimensionally stable polyimide film. Background technique [0002] With the rapid development of electronic technology, the output of flexible copper-clad laminates has grown steadily, and the production scale has continued to expand. Especially, the demand and growth trend of flexible copper-clad laminates with polyimide film as the base material are more prominent. Polyimide (PI) film is combined with copper foil as an important insulating substrate of flexible printed circuit boards, and the film is required to have a thermal expansion coefficient similar to that of copper foil (18×10 -6 / K), lower thermal shrinkage rate (<0.05%), that is, high dimensional stability, to reduce the thermal stress accumulation of the two and cause problems such as peeling, cracking, and warping. At present, domestic polyimide films can only be used in the lo...

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Problems solved by technology

[0006] Though this method can obtain the polyimide film that meets the thermal shrinkage rate of relevant requirement, low coefficient of thermal expansion, because in the actual production of longitudinal stretching (longitudinal stretching process is by oil heating roller and control roller speed, The gel film passing through the roller is stretched and shaped longitudinally at a certain temperature (usually 60-150°C), and the gel film with a large solvent content is easily deformed, so that there are many defects in the longitudinal stretching process. Problems, for example, the orientation and deformation of the gel film with uneven thickness are different when stretching in the longitudinal direction, which intensifies the deformation of the gel film in the subsequent transverse stretching, resulting in poor dimensional stability, poor appearance flatness, and uneven tension of the film. The problem of equalization; the extreme edge of the gel film is easy to form small cracks when it is heated, and when it is subjected to longitudinal tension, it will tear and break the film or even wrap the roll; changes in the ambient temperature during the production process, solvent recovery efficiency, etc. will affect the solvent content of the gel film , small changes in the solvent content of the gel film will make the matching degree of the longitudinal stretching process parameters abnormal, resulting in abnormal problems such as white spots, pulling fine lines, and scratch marks on the gel film surface

The above problems lead to low product yield

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