FPCWAY

In the information age, people transmit and process data through various electronic products every day. As the carrier medium, the demand for Printed Circuit Boards (PCBs) is also increasing year by year [1-3]. Flexible Printed Circuits (FPCs) have the characteristics of high wiring density, lightness, and good bendability, so they are increasingly occupying a larger proportion of PCBs [4]. FPCs usually refer to printed circuit boards made with flexible plastic films as substrates, which can be directly applied in three-dimensional working environments, accelerating the development of fields such as biomedical and human-machine information exchange, and further broadening the application areas of current electronic products .

The earliest FPC technology appeared in a British patent published in 1898, which described flat conductor circuits made on paraffin paper substrates. However, it was not until the late 20th century that FPCs began to be widely researched both domestically and internationally after being used in modern consumer electronic products such as car dashboards, instruments, mobile phones, and OLED (Organic Light Emitting Diode) flexible screens.

Flexible single-sided boards are currently the most widely used type of FPCs. The main production methods for this kind of printed board at home and abroad are sheet-to-sheet and roll-to-roll (R2R) [8]. Sheet-to-sheet production involves cutting flexible substrates into individual pieces and producing them on a piece-by-piece basis. Its advantages include low investment and flexible product variety, but it is inefficient. Roll-to-roll production involves winding the product into rolls and driving it through positioning holes at the edges for continuous operation. The European Flex-o-Fab project used the roll-to-roll process to produce flexible OLED prototypes. This method has a high degree of automation, suitable for mass production, but requires a large investment in production equipment and lacks flexibility in product variety changes [9]. Although there are two methods for producing flexible single-sided boards, their production processes are basically the same, with the most commonly used being printing and etching. The process includes lamination, exposure, development, and etching. The etching process not only wastes resources but also causes certain damage to the environment. Therefore, finding a method that can effectively solve these problems is particularly important.

This article proposes a design that uses ultrasonic atomization spraying to coat conductive layers on flexible substrates. A metal mask is placed on the flexible substrate, and the required conductive traces and electrodes are produced according to design requirements. By using the principle of ultrasonic atomization, conductive ink is atomized into nano-sized particles, which are then guided by airflow to coat the substrate along a specific path. Using this method, the coating thickness can reach the nanometer level, allowing for convenient control of the coating thickness according to actual production needs. Ultrasonic spraying can flexibly change the types of products, ensure full automation of equipment, and guarantee production efficiency. Moreover, excess ink can be recycled, reducing waste and environmental damage. Introducing ultrasonic spraying into the manufacturing of flexible printed circuits will have a promising application prospect.