FPC circuit board is also called flexible circuit board, referred to as "soft board", commonly known as FPC in the industry. Battery FPC is a printed circuit board made of flexible insulating substrate (mainly polyimide or polyester film). It has many advantages that hard printed circuit board does not have. For example, it can be bent, wound and folded by itself. Using FPC can greatly reduce the volume of electronic products and is suitable for electronic products With the development of high density, miniaturization and high reliability , FPC has been widely used in aerospace, military, mobile communication, laptop, computer peripherals, PDA, digital camera and other fields or products.
The production process of FPC is complicated. There are more than 20 processes from drilling to packing. In this long production process, a variety of auxiliary materials will be used according to the needs of customers. The base material of FPC is usually double-sided or single-sided copper foil, which is the basis of the whole FPC, and the electrical performance of FPC is determined by it. Other auxiliary materials are only used to assist the installation and adapt to the environment. There are mainly the following:
1. FR4-is hard, with different thickness of 0.15-2.0 mm. It is mainly used in the back of FPC welding, as reinforcement, convenient for welding, stable and reliable.
FR-4 is a code of fire-resistant material grade, which means that the resin material must be able to extinguish itself after burning. It is not a material name, but a material grade. Therefore, there are many kinds of FR-4 grade materials used in general circuit boards, but most of them are so-called Tera function epoxy resin Add filler and glass fiber to make the composite.
2. PI tape-soft and flexible, mainly used for thickening and strengthening in the golden finger area, easy to insert and remove;
PI tape, full name is polyimide tape. PI tape is based on polyimide film, using imported silicone pressure sensitive adhesive, with high and low temperature resistance, acid and alkali resistance, solvent resistance, electrical insulation (grade H), radiation resistance and other properties. It is suitable for wave soldering shielding of electronic circuit board, protection of gold finger and high-grade electrical insulation, motor insulation, and fixation of positive and negative electrode ears of lithium battery.
3. Steel sheet-hard texture, the same function as FR4, used for welding reinforcement, more beautiful than FR4, can be grounded, higher hardness than FR4.
The steel sheet is made of original imported stainless steel by heat treatment and fine grinding. It has the characteristics of high precision, strong tension, good finish, toughness and not easy to break.
4. TPX film is a kind of high performance and high temperature resistant resin release film, which is used in the circuit board lamination process. Through special process design, it can be used to block the multiple lamination process of buried hole and blind through hole after resin overflow, with good effect of blocking and plugging.
5. EIM electromagnetic film is pasted on the surface of FPC to shield signal interference;
EIM electromagnetic film is a method of vacuum sputtering, which can be coated on different substrates (PET / PC / glass, etc.) to achieve EMI shielding with very low resistance.
6. Conductive adhesive-used for the connection and pressing of steel sheet and FPC, conductive, can realize the function of steel sheet grounding;
Conductive adhesive is a kind of adhesive with certain conductivity after curing or drying. It is mainly composed of resin matrix, conductive particles, dispersing additives and additives. It can connect a variety of conductive materials together to form an electrical path between the connected materials. In the electronic industry, conductive adhesive has become an indispensable new material.
7. 3M adhesive tape-mainly used for bonding FR4 and FPC with the thickness of 0.4mm and above, and assembling and fixing FPC with customers' products.
The use of FPC auxiliary materials is ultimately determined according to the customer's use environment and functional requirements.http://www.china-polyimide.com