Introduction to Adhesiveless Flexible Copper Clad Laminate (FCCL)

Flexible Printed Circuit Boards (FPC) have gained prominence due to their notable advantages, including flexibility, lightweight design, thinness, and versatility. As electronic devices continue to shrink in size and demand for lighter and thinner products increases, FPCs are gradually supplanting rigid PCBs. Notable applications include notebook computers, smartphones, cameras, and tablets.

Traditional Flex PCB Challenges

Traditional flex PCB materials typically feature a three-layer structure comprising a polyimide (PI) film adhesive and copper foil. The adhesive, commonly Epoxy or Acrylic, poses limitations in terms of heat resistance and dimensional stability. With a maximum operating temperature of 200°C, traditional flex PCBs are unsuitable for high-reliability applications.

Adhesiveless FCCL: Overcoming Limitations

Adhesiveless FCCL emerges as a compelling alternative, offering three key features:

1. Heat Resistance: Adhesiveless FCCL, devoid of adhesives, exhibits exceptional heat resistance, with a long-term use temperature surpassing 300°C. This is crucial for applications involving SMT soldering and the pressing process in rigid-flex board production, where temperatures often exceed 200°C.
2. Dimensional Stability: Adhesiveless FCCL experiences minimal dimensional changes even at high temperatures, maintaining a change rate below 0.1% at 300°C. In contrast, traditional three-layer rubberized flexible boards are significantly affected by temperature fluctuations, impacting their dimensional stability.
3. Chemical Resistance: The absence of adhesive in adhesiveless FCCL contributes to excellent chemical resistance, ensuring consistent tear strength over time. Conversely, traditional three-layer rubberized flexible boards, due to adhesive presence, demonstrate poor chemical resistance and fluctuating tear strength.

Manufacturing Methods of Adhesiveless FCCL

Three main manufacturing methods for adhesiveless FCCL include:

1. Sputtering Electroplating Method: Utilizes PI film as the base material, employing vacuum sputtering for an attribute layer and electroplating to increase copper thickness. This method is ideal for producing ultra-thin adhesiveless FCCLs and double-sided flexible boards with varying thicknesses.
2. Coating Method: Involves using copper foil as the base material, extruding and coating synthesized polyamic acid on the copper foil, followed by drying and imidization to form adhesiveless FCCL. Primarily employed for single-sided flexible boards.
3. Hot Pressing Method: Encompasses coating PI film with a thin layer of thermoplastic PI resin, hardening at high temperatures, and then remelting the resin using high temperature and pressure. Suitable for manufacturing rubber flexible board substrates.

Adhesiveless FCCL Applications and Market Trends

Projections suggest that adhesiveless FCCL will gradually replace traditional three-layer adhesive flexible boards in the high-end flexible board market. In the Japanese market alone, the adhesiveless FCCL market has grown substantially, showcasing a shift from 290,000 square meters in 1997 to 1.72 million square meters in 2000. Market estimates indicate a steady increase in market share from 3.4% to 16.8%.

Conclusion

With the increasing emphasis on portable and user-friendly electronic products, adhesiveless FCCL emerges as a pivotal solution aligning with market trends. The elimination of adhesives, enhanced heat resistance, dimensional stability, and chemical resistance positions adhesiveless FCCL as a key player in meeting the evolving demands of the electronics industry.