What are the FPC Stiffener Materials

Why should FPC be stiffened? Because the FPC itself is only flexible, and the application scenarios of individual FPC are different, in order to meet the use requirements, it is necessary to increase a certain thickness and rigidity in the designated position. The main purpose is to improve the strength of the FPC plug-in part; or to solve the local flexibility of the FPC, to facilitate the overall assembly of the product. Generally, the materials used for FPC stiffener need to meet the requirements of high and low temperature resistance, acid and alkali resistance, corrosion resistance, etc. So what are the FPC stiffener materials?

1. PI

As a special engineering material, PI has been widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separation membrane, laser and other fields. It is resistant to high and low temperatures and flame retardant. PI protective film or PI stiffener film is mainly used in FPC stiffener. PI protective film is generally used for circuit insulation, while PI stiffener sheet is generally used in areas such as the back of FPC gold fingers. The thickness is based on the design drawings and the use environment to select different thicknesses of PI stiffener and FPC for pressing.

2. FR4  

FR4 itself, as a kind of flame-resistant material, has higher mechanical properties, dimensional stability, impact resistance and moisture resistance than paper substrates. It has excellent electrical properties, high operating temperature, and its performance is less affected by the environment. The FR4 stiffener sheet is mainly used as the back of the FPC welding area to strengthen the hardness of the welding area and will not be damaged by the continuous bending and stretching of the FPC.

3. Steel sheet stiffener

Steel sheet stiffener mainly refers to 303 stainless steel stiffener, free-cutting stainless and wear-resistant acid steel containing sulfur and selenium, which is used for occasions requiring easy-cutting and high surface finish. FPC stiffener often has different shapes, and 303 stainless steel is easy to etch, so in FPC products that require high stability, this kind of steel sheet is mostly used as stiffener. Steel sheet stiffener cannot be drilled by CNC, nor can it be cut by FPC laser. It is mainly made by potion etching, so its cost is relatively high.

No matter what kind of stiffener, it needs to be pressed on the FPC circuit board in the end. It is self-evident to improve the quality of FPC by selecting different stiffened materials, adjusting the pressing parameters correctly, and controlling the pressing time according to different needs and use environments.

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