Guide to Manufacturing Rigid-Flex Circuit Boards

Guide to the Research and Manufacturing Methods of Rigid-Flex Circuit Boards

This research guide aims to help you understand and review the described rigid-flex circuit boards and their manufacturing methods.

Quiz

Please briefly answer the following questions in 2-3 sentences.

1. What is the technical field described in the patent document?
2. What advantages do rigid-flex circuit boards have compared to traditional multilayer FPC products?
3. What are the main steps included in the manufacturing method described in the patent?
4. What material options are available for the first substrate in the first step?
5. What techniques are used to form the first conductive wiring layer and the third conductive wiring layer in the fourth step?
6. What is the purpose of removing the dry film in the fifth step?
7. How is the opening window formed in the sixth step?
8. How is the protective layer in the opening window area handled in the eighth step?
9. What materials are typically used for the protective layer in the ninth step?
10. What main structures of the final product rigid-flex circuit board are shown in Figure 9?

Answer Key

1. The technical field described in the patent document is rigid-flex circuit boards and their manufacturing methods.
2. Compared to traditional multilayer FPC products, rigid-flex circuit boards have advantages such as thin design, lightweight, easy assembly, better electrical signal transmission, and improved product reliability.
3. The manufacturing method described in the patent mainly includes providing the first circuit board, first substrate, first adhesive layer, first copper layer, forming the conductive wiring layer, removing the protective layer, forming the opening window, and covering the protective layer.
4. In the first step, the material options for the first substrate include polyimide (PI), liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).
5. In the fourth step, techniques such as electroplating, etching, pressing film, exposure, and stripping process (Developing Etching Stripping, DES) are used to form the first conductive wiring layer and the third conductive wiring layer.
6. The purpose of removing the dry film in the fifth step is to expose the protective layer of the third conductive wiring layer and the fourth conductive wiring layer for subsequent removal of the protective layer.
7. In the sixth step, the opening window is formed on the semi-finished rigid-flex circuit board through pre-window processing.
8. In the eighth step, the protective layer in the opening window area can be removed by etching, laser, or mechanical stripping methods.
9. In the ninth step, the protective layer is typically composed of commonly used solder mask or cover layer (CVL) in the industry.
10. Figure 9 shows the main structures of the final product rigid-flex circuit board, including the first circuit board, second substrate, first adhesive layer, second adhesive layer, conductive wiring layer, protective layer, and opening window.

Paper Format Issues

Please choose one of the questions and write a paper to answer it.

1. Detail the differences and advantages of the manufacturing method of rigid-flex circuit boards described in the patent document compared to traditional FPC manufacturing methods in terms of process flow, material selection, and product performance.
2. Analyze the technical principles and practical effects of the patent method in solving the copper foil damage problem encountered in traditional cover film processes.
3. Based on the manufacturing steps and illustrations described in the patent document, explore how each key step affects the performance of the final rigid-flex circuit board.
4. Compare the characteristics of various first substrate materials and protective layer materials mentioned in the patent and discuss their impact on the application scenarios and performance of the circuit board.
5. In conjunction with Figures 1 to 9, explain in detail the internal structure of the rigid-flex circuit board and the functions and interrelationships of its components.

Glossary of Keywords

• Rigid-flex circuit board: A circuit board that combines rigid and flexible circuit boards, possessing characteristics of both rigidity and flexibility.
• Circuit board: Generally refers to a substrate that contains conductive wiring.
• Substrate: Material used to support the circuit layer or adhesive layer.
• Conductive wiring layer: A layer formed of conductive material used for transmitting electrical signals.
• Protective layer: A material layer used to protect the conductive wiring from environmental impacts or damage, such as solder mask or cover layer.
• Adhesive layer: A layer of adhesive used to bond different material layers together.
• Copper layer: A conductive layer formed of copper material.
• Opening window: An area reserved or formed on layers such as the protective layer for connection or other functions.
• Pre-window processing: Processing performed in the manufacturing process to form openings on certain layers.
• Shadow processing: A technique used in certain manufacturing steps, possibly involving illumination or shading.
• Electroplating: A method of depositing a metal layer on a surface through electrolysis.
• Etching: The process of removing material through chemical or physical methods.
• Pressing film: The process of pressing film material onto the substrate.
• Exposure: The process of irradiating photosensitive materials with light or other radiation.
• Stripping process: The process of removing specific films or material layers.
• Via hole: Holes that connect conductive wiring across different layers.
• Copper plating: The deposition of copper in areas such as via holes to form conductive connections.
• Peelable film: A film that can be peeled off from the surface.
• Seed layer: A thin layer used to promote metal deposition before electroplating.
• Solder mask: A protective layer covering the surface of the circuit board to prevent solder spread during soldering.
• Cover layer: A thin film covering the surface of flexible circuit boards, providing protection and insulation, usually referred to as CVL.
• Polyimide (PI): A commonly used flexible circuit board substrate material.
• Liquid crystal polymer (LCP): A material with excellent electrical and mechanical properties, suitable for high-frequency applications.
• Polyetheretherketone (PEEK): A high-performance thermoplastic material.
• Polyethylene terephthalate (PET): A commonly used polymer material.
• Polyethylene naphthalate (PEN): A high-performance polyester material.
• Ni/Cr/Ti/Cu/Ag/Al/Zn/Sn/Fe: The selection of protective layer materials mentioned in the patent.
• Polypropylene: A polymer material.
• Epoxy resin: A commonly used adhesive and insulating material.
• Polyurethane: A polymer material.
• Cellulose acetate butyrate: A polymer material.
• Polyester resin: A polymer material.
• Melamine-formaldehyde resin: A thermosetting resin.
• Polyamide-imide: A high-performance polymer material.
• Etching Stripping: A process that combines etching and stripping.
• DES (Developing Etching Stripping): A photolithography process flow that includes developing, etching, and stripping.

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