What is the polyimide PI film production process?

Polyimide Film Thickness Uniformity AnalysisPolyimide Film, or PI Film for short, is the world's best insulating polymer material. Because the polyimide molecule contains very stable aromatic ring structural units, the film has high thermal stability, tensile strength, low coefficient of linear expansion, appropriate elastic modulus and excellent resistance to high temperature, low temperature, insulation, dielectric and other polymer materials, and is known as a gold film. Therefore, it is widely used in the electrical and electronic field (flexible printed circuit boards) FPC, self-adhesive tape, cable insulation materials, etc. ), aerospace, solar photovoltaic, electronic products (mobile phones, computers, audio, etc.). as well as barcodes, radars, fire covers, etc

1. The production process of polyimide film The preparation of polyimide film is divided into impregnation method, casting method and cast stretching method according to different processes. The impregnation method is one of the most traditional methods, in which a polyamic acid solution is impregnated on an aluminum foil base and baked to dry to form a polyamic acid film. The substrate and film are placed in a high-temperature baking oven for dehydration and imidization, and then made into a polyimide film by peeling, trimming, rolling, pickling, washing, drying. The production process and operation of this method are the simplest, but the thickness uniformity and mechanical strength of the film are poor, and it is difficult to meet the quality requirements of high-performance films. The casting method is to cast the polyamic acid solution through the casting port onto the stainless steel strip running below, and dry it through the drying channel to form a self-supporting gel film. The gel film is stripped from the rigid band, imitated at high temperature, and the polyimide film is rolled, which significantly improves the uniformity and mechanical properties of the film. The difference between the flow elongation method and the flow elongation method is that a biaxial stretching process is added before collection, which not only greatly improves the physical properties of the film but also greatly improves the electrical properties and thermal stability. Analyzing the development trend of the polyimide film market, the field of microelectronics will become one of the most potential application fields, and its light and fine requirements will inevitably promote the large-scale production of electronic engineering (electronic grade) polyimide films, in order to meet the requirements of high quality, the flow extension method and the flow extension method will become a common preparation method in the industry, and further improve in practice.
   

   2. Polyimide film thickness uniform flexible printed circuit board (FPC) is one of the key areas of polyimide film application, the biggest feature of FPC is that it can move, bend, fold and expand arbitrarily in three-dimensional space, so the base polyimide film is light and thin, with good tensile properties and insulation. The national standard GB 1355-92 flexible copper-clad foil polyimide film for printed circuits GB/T 13542.6-2006 "Electrical Insulating Film Part VI: Polyimide Film for Electrical Insulation" also clearly stipulates the thickness, tensile peeling properties and electrical properties of polyimide film. GB/T 13542.6-2006 uses polyimide films (μm) according to the nominal thickness of polyimide films (μm) divided into 7.5, 13, 20, 25, 40, 50, 75, 100, 1259 categories, and puts forward the corresponding tensile strength, elongation at break and alternating current strength value requirements for various materials. It can be seen that thickness is the basic key index of the performance standard, which is of great significance to the stability of the physical properties of the film and the operation of the subsequent process. First of all, the uniformity of the thickness of the film affects its mechanical properties to a certain extent. When the thickness of the polyimide film is less than 20μm, and when the thickness is greater than 20, the transverse and longitudinal tensile strength and elongation at break show a positive correlation with the thickness, and the transverse and longitudinal tensile strength and elongation at break tend to be stable. Second, the uniformity of the film thickness is closely related to the strength performance of the AC electrical. When the polyimide film thickness is 20-25 μm, the AC electrical strength reaches the highest value of -200 V/μm, and when the polyimide film thickness is less than 20 μm or higher than 25 μm, the overall trend of the relationship between the two decreases. Thirdly, the poor uniformity of film thickness will greatly reduce the quality and efficiency of later winding. Fourth, the uniformity of film thickness will lead to an abnormal increase in production costs, which will reduce the market competitiveness of products to a certain extent.