There are many kinds of PCB, but most of them can be divided into rigid and flexible PCB. Today, we will talk about the structure of flexible PCB. Generally, circuit boards are divided into layers according to the number and thickness of conductive copper foils. They can be divided into single-layer boards, double-layer boards, multilayer boards and double-sided boards. Their structures are also different. Here we will introduce their different properties.
Structure of single layer board: this is the most simple flexible board, which is usually purchased as a set of raw materials including base material, transparent adhesive and copper foil, while protective film and transparent adhesive are another kind of raw materials; First, the copper foil needs to be etched to obtain the required circuit. The protective film needs to be drilled to expose the corresponding bonding pad. After cleaning, the rolling method is used to combine the two, and then the exposed bonding pad is electroplated with gold or tin for protection. In this way, the large board is ready, and then the small circuit board with the corresponding shape needs to be stamped.
Double layer board structure: When the circuit is too complex, the single layer board cannot be wired, or copper foil is required for grounding shielding, double layer board or multilayer board is required. Multilayer board structure: the most typical difference between multilayer board and single-layer board is that the via structure is added to connect each layer of copper foil. Generally, the first processing process of substrate+transparent adhesive+copper foil is to make via; First, drill holes on the base material and copper foil, and then coat a certain thickness of copper after cleaning. In this way, the vias are ready. The subsequent manufacturing process is almost the same as that of the single-layer plate.
Double sided board structure: both sides of the double sided board have pads, which are mainly used for connection with other circuit boards. Although its structure is similar to that of a single-layer board, its manufacturing process is very different. Its raw materials are copper foil, protective film+transparent adhesive. First, drill holes on the protective film according to the location requirements of the bonding pad, then stick the copper foil, and then stick another protective film with drilled holes after the bonding pad and lead are corroded. Although these types of structures of FPCs are different, many manufacturing processes have the same features, but different processes are added in some basic places to correspond to different fields.