FPC flexible circuit board is a highly reliable and excellent flexible printed circuit board made of PI polyimide or polyester film as the substrate. It has the characteristics of high wiring density, light weight, thin thickness, and good bending performance. PI, as a special engineering material, has been widely used in fields such as aviation, aerospace, microelectronics, nanomaterials, liquid crystals, separation membranes, lasers, etc.

　　The long-term use temperature is between -200 ℃ and 426 ℃. PI polyimide is common in FPC flexible circuit boards, as it exists in substrates, covering films, and even reinforcement. Some people may be confused about this, so today let's discuss the difference between them?

　　The functional differences between the substrate, covering film, and PI reinforcement of FPC flexible circuit boards are as follows: 1 PI substrate: For FPC flexible circuit board substrates, there are two types: adhesive substrate and non adhesive substrate. PI polyimide is essential for both adhesive and non adhesive substrates. 2. PI covering film: Its main function is for circuit insulation. 3. PI reinforcement: often used in the area on the back of FPC gold fingers. PI reinforcing ribs are used to increase the thickness and hardness of fingers, making it easy to insert and remove.

　　Differences in thickness between the substrate and covering film of FPC flexible circuit boards: 1 PI substrate: For PI in the substrate, 1/2mil and 1mil are common, and their thickness can even reach 4mil and 5mil (DuPont adhesive free PI material). 2. PI coating film: There are two options for the PI thickness on the coating film, 1/2mil or 1mil. 3. PI reinforcement: There are multiple options for the thickness of PI reinforcement according to customer needs, such as 0.075mm, 0.1mm, 0.125mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm, etc.

　　Differences in color selection between the substrate and covering film of FPC flexible circuit boards: 1 PI substrate: No color selection. 2. PI covering film: PI covering film has three colors to choose from: yellow, white, and black. 3. PI reinforcement: Changes with thickness, with thicker colors becoming darker. For example, a 0.075mm PI reinforcement looks brown, while a 0.25mm PI reinforcement is closer to black.

　　FPC flexible circuit boards are printed circuits made of flexible insulating substrates, which have many advantages that hard printed circuit boards do not have. It can be freely bent, wound, folded, arranged according to spatial layout requirements, and moved and expanded freely in three-dimensional space, thus achieving the integration of component assembly and wire connection; The use of FPC can greatly reduce the volume and weight of electronic products, which is suitable for the development of electronic products towards high-density, miniaturization, and high reliability.