1、 Substrate

From the perspective of types, it mainly consists of rolled copper and electrolytic copper. Rolled copper has good flexibility and resistance to bending, but can withstand less overcurrent than electrolytic copper; Electrolytic copper has a harder texture and lower flexibility compared to rolled copper, but it can withstand high overcurrent and is generally used in power supply. From the number of layers, it can be further divided into single-sided substrate and double-sided substrate. The single-sided substrate is composed of polyimide resin and PI, which are pressed onto copper foil on one side. If the pressed surface contains adhesive, it is called adhesive based rolling or adhesive based electrolysis. If there is no adhesive, it is called adhesive based rolling or adhesive based electrolysis. The main difference between adhesive and non adhesive is the different adsorption capacity and breakdown coefficient between copper foil and insulation PI. As for the thickness, copper foil has 1oz (35um), 0.5oz (18um), 1./3oz (12.5um), and insulation PI thickness is generally 12.5um and 25um. The thickness of the substrate mainly includes three different thicknesses: 35/25, 18/12.5, and 12.5/12.5.

2、 Reinforcing tablet

There are three main types of reinforcement sheets used in FPC, namely polyimide resin (PI), fiberglass board (FR-4), and steel sheets. Different reinforcement environments are used in different environments. PI, due to its soft texture, smooth surface, and thin thickness (0.0275-0.3mm), has less damage to the interface. Therefore, it is often used to strengthen the insertion and extraction area of the gold finger, thereby increasing the insertion and extraction times and extending the lifespan of FPC and interface; FR-4 has a hard texture and a common thickness range of 0.2-2.0mm, with a large thickness range. Therefore, it is mainly used for strengthening the back of the welding pad and enhancing the reliability of welding; Steel sheets are mainly the hardest in texture, have a good texture, can conduct electricity, and are often used in grounding design.

3、 Protective film

The protective film is still polyimide resin, also known as PI, with a common thickness of 27.5um (12.5umPI+15um adhesive) and 50um (25umPI+25um adhesive). There are three main colors, with brown yellow being the most commonly used, followed by black and white. Among them, black has a distinction between bright and matte.