Surface Treatment Process in FPC Production Process (1)

With the increasing development of the electronic industry today, electronic products are moving towards light, thin, short, high-performance and multi-functional development, and perfect electronic device welding technology. Flexible printed circuit boards (FPC), as a circuit board also used for electronic interconnection, have been rapidly developed in China’s printed circuit board industry in the past two years. Due to the needs of electronic products for lightness, thinness, and small size, the application range of flexible PCBs is becoming wider and wider. Compared with other types of printed boards, flexible PCB has a large amount of wiring in a small space. The parts that need to be bent repeatedly have a longer bending life than other cables due to the selection of special materials.

Due to the characteristics of lightness and thinness, the selection of mechanical equipment and processing methods during the surface treatment of flexible boards has its own special requirements. In the production of flexible boards, surface cleaning treatment is a very critical link. Because it not only requires a good surface condition, but also has strict requirements on the dimensional stability of the board. The dimensional stability depends on the dimensional change rate of the laminated copper foil layer, and also has a great influence on the mechanical grinding during the production process. The running direction of the grinding brush roller is opposite to the conveying direction of the board to ensure uniform grinding effect. However, the base of the flexible board is thin and soft. If the pressure is too high during grinding, the base material will be stretched or broken due to great tension. This is one of the important reasons for dimensional changes. Scratches, tears and jams on the substrate should be avoided during the grinding process. If the equipment is not specialized in flexible board production conditions, it is recommended to use a pallet, which can avoid the large distance between the machine’s transmission wheels. The influence of high-pressure water washing and drying hot air causes the substrate card board to be deformed or even scrapped.

According to the requirements of the flexible board production process and the grinding comparison of the abrasive brush wheel, in the production process of the flexible printed board, the chemical cleaning method and the nylon needle brush roller is ideal for  transferring patterns, hole metallization, and cover the surface of the film. It can remove the oxide layer on the copper surface and achieve good roughness on the board surface.

In the pretreatment of surface processing technology such as chemical immersion gold, you can choose a non-woven brush roller with low cutting force. Because of its uniform and detailed grinding effect, it can ensure the removal of residual glue on the board and the pads are carefully and uniformly polished. This is a surface treatment effect that the nylon needle brush cannot achieve. Because the flexible board generally has small pads, ordinary nylon needle brushes cannot be completely polished to the pads, and strip-shaped scratches will be left during polishing. The scrarches will affact welding and beautiful surface. Choosing a soft non-woven brush roller with a lower cutting force than the conventional one can improve the effect that nylon needle brushes cannot achieve. The non-woven brush roller is the first choice for many manufacturers of high-precision circuit boards due to its uniform and detailed grinding effect. It is recommended to use 1000#+1200# red non-woven brush roller with a hardness of 30-45 degrees, and the wear scar is controlled at 8-10mm, which can ensure the removal of the dirt of the pad and the flatness of the surface coating.