Polyimide (PI) film is the dominant substrate, valued for its high-temperature resistance and bendability. When laminated with copper foil, it forms the performance foundation of FPCs, making it suitable for products in complex operating environments.
Two methods are common:
- Dry film: Applied via heat pressing, requiring bubble-free, wrinkle-free adhesion to ensure uniformity.
- Wet film: Applied as a liquid, with strict controls on thickness and precision—directly impacting pattern transfer accuracy.
Ultraviolet exposure transfers circuit patterns to the photoresist, which is then developed to reveal the desired circuit layout. Line width precision is critical, especially in high-density circuits, where tight tolerances (often ±0.01mm) must be maintained.
Using specialized etchants (e.g., cupric chloride), parameters like temperature, immersion time, and solution concentration are tightly controlled to minimize undercutting. This ensures line width deviations stay within acceptable ranges (typically <5% of nominal width), a key step in forming precise circuits.
After etching, residual photoresist is stripped, followed by thorough cleaning to remove etchant residues. This prevents degradation of electrical performance and long-term reliability.
- Lamination (for multi-layer FPCs): Requires tight adhesion between layers and precise alignment to avoid delamination or short circuits.
- Reinforcement: Stiffeners (e.g., FR4, stainless steel) are added to areas needing extra strength (e.g., connector interfaces), enhancing overall durability.
- Laser drilling: Creates microvias with high precision (diameters as small as 0.1mm) for layer-to-layer connections.
- Plating: Chemical copper deposition followed by electrolytic plating thickens copper in vias, ensuring reliable conductivity.
- Surface finishes: Options include ENIG (gold immersion), OSP (organic solderability preservative), and tin plating—chosen based on solderability, corrosion resistance, and cost requirements.
- Testing: 100% electrical testing (e.g., continuity, insulation resistance) and environmental testing (e.g., thermal cycling, bend testing) validate performance and reliability.
From copper foil to finished FPC, every step is interconnected. Strict control over materials, processes, and inspections is essential to produce high-quality FPCs that meet evolving market demands.
Founded in 2009, our company has deep roots in the production of various circuit boards. We are dedicated to laying a solid electronic foundation and providing key support for the development of diverse industries.
Whether you are engaged in electronic manufacturing, smart device R&D, or any other field with circuit board needs, feel free to reach out to us via email at sales06@kbefpc.com. We look forward to addressing your inquiries, customizing solutions, and sincerely invite partners from all sectors to consult and collaborate, exploring new possibilities in the industry together.
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