PCB Technical - Commonly used die-cutting auxiliary materials in FPC

FPC circuit board is also called flexible circuit board, abbreviated as "soft board," commonly known as FPC in the industry. It is a printed circuit board made of flexible insulating substrates (mainly polyimide or polyester film) and has many rigid printed circuits. The board does not have the advantages, such as it can be bent, wound, and folded freely. The use of FPC can greatly reduce the volume of electronic products, and is suitable for the needs of electronic products to develop in the direction of high density, miniaturization and high reliability. Therefore, FPC is used in aerospace, It has been widely used in military, mobile communications, laptop computers, computer peripherals, PDAs, digital cameras and other fields or products.

The process of producing FPC is complicated, from cutting and drilling to packaging and shipping, there are more than 20 processes required in the middle. In this long production process, according to customer needs, a variety of auxiliary materials will be used. The base material of FPC is generally double-sided or single-sided copper foil, which is the basis of the entire FPC, and the electrical performance of the FPC is determined by it. Other auxiliary materials are only used to assist in installation and adapt to the use environment. There are mainly the following:

1FR4

The texture is hard, with different thicknesses of 0.15-2.0mm, mainly used on the opposite side of the FPC welding place, as a reinforcement, facilitating stable and reliable welding;

FR-4 is the code name of a flame-resistant material grade. It represents a material specification that the resin material must be able to extinguish by itself after burning. It is not a material name, but a material grade. Therefore, the current general circuit There are many types of FR-4 grade materials used in the board, but most of them are composite materials made of so-called Tera-Function epoxy resin, Filler and glass fiber.

2PI tape

The texture is soft and bendable. It is mainly used for thickening and strengthening the golden finger area, which is convenient for plugging and unplugging;

PI tape, its full name is polyimide tape. PI tape is based on polyimide film and imported organic silicon pressure-sensitive adhesive. It has the properties of high and low temperature resistance, acid and alkali resistance, solvent resistance, electrical insulation (level H), and radiation protection. Suitable for electronic circuit board wave soldering tin shielding, protection of gold fingers, high-end electrical insulation, motor insulation, and fixing the positive and negative ears of lithium batteries.

3 steel sheets

Hard texture, the same function as FR4, used to strengthen the welding place, more beautiful than FR4, groundable, higher hardness than FR4;

The steel sheet is made of imported stainless steel after heat treatment and fine grinding. It has the characteristics of high precision, strong pulling force, good smoothness, toughness and not easy to break.

4TPX Adhesive Film

A high-performance and high-temperature resistant resin barrier release film, used in the circuit board pressing process. After a special process design, it can be used to block the multiple lamination processes of buried holes and blind vias after resin overflow. Glue resistance and plug hole effect.

5EIM electromagnetic film

Attached to the surface of the FPC to shield signal interference;

EIM electromagnetic film is a vacuum sputtering method, which can plate shielding materials on substrates of different substrates (PET/PC/glass, etc.) to achieve EMI electromagnetic interference shielding with extremely low resistance.

6 conductive adhesive

It is used for the connection and pressing of steel sheet and FPC, conductive, and can realize the function of steel sheet grounding;

Conductive adhesive is an adhesive that has certain conductivity after curing or drying. It is mainly composed of resin matrix, conductive particles, dispersing additives, auxiliary agents, etc. It can connect a variety of conductive materials together to form an electrical path between the connected materials. In the electronics industry, conductive adhesive has become an indispensable new material.

73M tape

Mainly used for bonding FR4 and FPC with a thickness of 0.4mm and above, and assembling and fixing FPC and customer products;

The use of FPC auxiliary materials will ultimately be determined according to the customer's use environment and functional requirements.