FPC (Flexible Printed Circuit) refers to flexible circuit boards, commonly known as flexible printed circuit boards, flexible circuit boards, or soft boards. These circuit boards offer benefits such as high wiring density, lightweight construction, and thin profiles. They are widely utilized in devices such as mobile phones, laptops, PDAs, digital video cameras, LCMs, and many other products. In recent years, PCB manufacturing technology has advanced rapidly, leading to increased industry demands for FPC. Precision PITCH is identified as a key area for future breakthroughs in FPC development. The need for dimensional stability and precision has also contributed to rising costs of FPC. Finding a balance between these competing factors has become a significant challenge in managing the expansion and contraction of FPC materials during production. Below, we outline the main points for effective control in this process.

1. Design

1. Regarding wiring: Since FPC tends to expand due to temperature and pressure during ACF crimping, it is essential to account for the expansion rate of the crimping fingers in the initial circuit design and implement pre-compensation measures.


2. Typesetting: Design elements should be distributed evenly and symmetrically across the layout whenever possible. The minimum spacing between each PCB product should exceed 2MM, and the copper-free areas alongside the dense via holes should be staggered as much as feasible. These two components significantly influence the subsequent manufacturing process, particularly regarding material expansion and contraction.

3. Material Selection: The adhesive for the cover film should not be significantly thinner than the copper foil’s thickness to prevent inadequate adhesive filling during the pressing process, which can lead to product deformation. Both the adhesive thickness and its uniform distribution are critical factors contributing to the expansion and contraction of the FPC material.

4. Process Design: The cover film should ideally cover all copper foil sections. Avoid sticking the cover film down to prevent uneven pressure during pressing. For PI reinforcement bonding surfaces above 5MIL, the area should not be excessively large. If unavoidable, apply the PI reinforcement after the cover film has been pressed and baked.

2. Material Storage: The importance of proper material storage cannot be overstated. Materials must be stored strictly according to the conditions specified by the supplier.

3. Manufacturing:

1. Drilling: It is advisable to bake the substrate before drilling to minimize expansion and shrinkage during subsequent processing due to high moisture content.

2. Electroplating: Utilize short-side splints to reduce deformation caused by water stress during swing. Minimize swing amplitude and ensure the number of splints is adequate. Use asymmetrical splints as needed, and when entering the tank, apply power gradually to prevent sudden high current impacts on the board, avoiding adverse effects on the electroplating process.

3. Pressing: Traditional presses are larger and operate differently than fast presses. Traditional presses employ constant temperature curing, while fast presses utilize heat curing. Control the glue application in traditional presses to maintain stability. The laminated board is also a crucial element.

4. Baking: For fast-pressed products, baking is essential. Ensure that baking conditions allow for complete curing of the adhesive; otherwise, it can lead to ongoing issues in production or usage. The baking temperature curve should gradually increase to the point where the adhesive completely melts, maintained until it solidifies, followed by a gradual cooldown.

5. Throughout the production process, strive to keep temperature and humidity stable across all stations, particularly during transitions, with special attention to product storage conditions.

Fourth, Packaging: The completion of a product does not guarantee success; it’s vital to ensure that customers face no issues in subsequent usage. Prior to packaging, it’s best to bake and dry the substrate to remove moisture absorbed during manufacturing. Use vacuum packaging and provide customers with storage instructions.

To ensure consistent quality of these products, it’s imperative to adhere to specific requirements from material storage through process control to packaging and customer guidance.

Five, Concluding Remarks: In the coming years, smaller, more complex, and higher-cost flex circuits will necessitate innovative assembly methods, along with the integration of hybrid flex circuits. The flexible circuit industry faces the challenge of leveraging its technological strengths to keep pace with advancements in computing, remote communications, consumer demand, and active markets. The PCB production and processing service department is staffed with highly skilled technicians and frontline operators, providing a reliable foundation to ensure product quality exceeds 99% (in accordance with IPC-A-610C CLASS 2 and company standards).