1. With the evolution of time and the advancements in science and technology, electronic products are undergoing constant transformation. In the realm of electronic assembly technology, it confronts successive challenges. To keep pace with the dynamic landscape of electronic technology, individuals engaged in electronic assembly must harness their expertise and embrace bold innovation and research. It is within this milieu that flexible circuits, comprised of delicate wires embedded within thin, pliable polymer films, have emerged as a pivotal breakthrough. These circuits facilitate the application of surface mount technology while accommodating bending without compromising functionality.
2. Present-day flexible electronics leverage Surface Mount Technology (SMT), enabling the creation of ultra-thin, highly intricate circuits with insulation thicknesses of less than 25μm. Such flexibility allows these circuits to be contorted and even rolled into cylinders, exploiting three-dimensional space efficiently. This departure from traditional notions of fixed usage areas empowers the utilization of volume shapes to their fullest extent, markedly enhancing the density of conductor length employed per unit area. Consequently, this yields a form of assembly characterized by high density.
3. In recent years, flexible circuit technology has found application across diverse sectors including radio communication, computing, and automotive electronics. Unlike earlier applications where flexible circuits merely served as substitutes for rigid cables, they have now evolved into viable alternatives for rigid circuits and printed circuit boards, particularly in contexts necessitating thin or three-dimensional circuitry. To cater to the demands of both rigid and flexible applications, the integration of rigid circuit boards with flexible circuits has become prevalent. Among these, flexible circuit boards reign supreme in terms of usage. These boards serve four primary functions: facilitating lead lines, hosting printed circuits, enabling connectors, and integrating various functionalities. Their applications span across computing, peripheral systems, consumer electronics, automobiles, and beyond.
Flexible Circuit Material: The Destiny of the Film
1. Insulation film possesses the essential trait of flexibility, serving as the insulation platform for circuit boards and constituting the foundational layer of circuits. When selecting a flexible dielectric film, thorough examination and testing of its heat resistance, cladding efficacy, thickness, mechanical attributes, and electrical properties are imperative. Predominantly, the materials of choice are polyimide and polyester, readily available in the commercial sphere. In the United States, approximately 80% of flexible circuit manufacturers utilize polyimide film, with around 20% combining it with polyester film. Polyimide materials are distinguished by their non-flammability, geometric stability, high tear resistance, and capacity to endure elevated temperatures during welding.
2. Material of Flexible Circuit: Adhesive Sheet
3. The adhesive sheet’s function encompasses bonding the film to the metal foil and facilitating inter-film bonding. Adhesive-backed reinforcement strips are affixed to the flexible circuit to furnish mechanical support and mitigate stress during component and connector insertion. It comprises two film-coated sides adhered with adhesive. This sheet not only offers environmental protection and electrical insulation but also aids in film removal and bonding in multi-layer circuits. Different adhesive sheets are tailored for distinct film substrates; for instance, those used for polyester and polyimide substrates vary. Adhesive sheets for polyimide substrates can be categorized into epoxy and acrylic variants.
4. Material of Flexible Circuit: Copper Foil
5. Copper foil serves as the conductive layer overlaying the bonding on the insulation substrate, subsequently etched selectively to delineate conductive lines. The predominant types of copper foil are calendered and electrolytic. Calendered copper foil outperforms electrolytic copper foil in ductility and bend resistance. Calendered copper foil typically exhibits an elongation of 20%-45%, whereas electrolytic copper foil ranges from 4% to 40%. The standard thickness for copper foil is 35um (1oz), with variations including 18um (0.5oz), 70um (2oz), or even 105um (3oz). Selection of copper foil form depends on specific applications; for instance, in reactive circuit boards aimed at wire and connector replacement to reduce manufacturing time and costs, electrolytic copper foil proves optimal. Additionally, electrolytic copper foil enhances current carrying capacity by augmenting copper weight, particularly suited for scenarios necessitating wider copper sheets.
6. Material of Flexible Circuit: Cover Layer
7. The coating’s primary function is to shield surface conductors and enhance substrate strength. The cover layer envelops the surface of the flexible printed circuit board, completing a functional layer of insulation protection. Two primary protective materials for exterior graphics are prevalent. The NovaClad brand, developed by Sheldahl, employs a proprietary technology based on vacuum metal-spraying, applying a thin layer of pure copper onto a polyimide film surface. Subsequently, the material undergoes electroplating to achieve a specific thickness, forming NovaClad’s base material. NovaClad base materials are integral in Novaflex flexible circuit production, eliminating the need for adhesives. Following circuit imaging, a Novaflex insulation coating is applied. Engineered to endure harsh environmental conditions, Novaflex flexible circuitry offers superior flexibility, chemical resistance, high-temperature resilience, and optimal heat dissipation.
8. Material of Flexible Circuit: Reinforcement Plate
9. The reinforcement plate is affixed to specific locations on the flexible plate to fortify the flexible film substrate and facilitate connection, fixation, or other PCB functions. Reinforcement board materials vary depending on application, commonly including polyester and polyimide sheets, epoxy glass fiber cloth boards, phenolic paper boards, or metallic plates such as steel or aluminum.
2. Present-day flexible electronics leverage Surface Mount Technology (SMT), enabling the creation of ultra-thin, highly intricate circuits with insulation thicknesses of less than 25μm. Such flexibility allows these circuits to be contorted and even rolled into cylinders, exploiting three-dimensional space efficiently. This departure from traditional notions of fixed usage areas empowers the utilization of volume shapes to their fullest extent, markedly enhancing the density of conductor length employed per unit area. Consequently, this yields a form of assembly characterized by high density.
3. In recent years, flexible circuit technology has found application across diverse sectors including radio communication, computing, and automotive electronics. Unlike earlier applications where flexible circuits merely served as substitutes for rigid cables, they have now evolved into viable alternatives for rigid circuits and printed circuit boards, particularly in contexts necessitating thin or three-dimensional circuitry. To cater to the demands of both rigid and flexible applications, the integration of rigid circuit boards with flexible circuits has become prevalent. Among these, flexible circuit boards reign supreme in terms of usage. These boards serve four primary functions: facilitating lead lines, hosting printed circuits, enabling connectors, and integrating various functionalities. Their applications span across computing, peripheral systems, consumer electronics, automobiles, and beyond.
Flexible Circuit Material: The Destiny of the Film
1. Insulation film possesses the essential trait of flexibility, serving as the insulation platform for circuit boards and constituting the foundational layer of circuits. When selecting a flexible dielectric film, thorough examination and testing of its heat resistance, cladding efficacy, thickness, mechanical attributes, and electrical properties are imperative. Predominantly, the materials of choice are polyimide and polyester, readily available in the commercial sphere. In the United States, approximately 80% of flexible circuit manufacturers utilize polyimide film, with around 20% combining it with polyester film. Polyimide materials are distinguished by their non-flammability, geometric stability, high tear resistance, and capacity to endure elevated temperatures during welding.
2. Material of Flexible Circuit: Adhesive Sheet
3. The adhesive sheet’s function encompasses bonding the film to the metal foil and facilitating inter-film bonding. Adhesive-backed reinforcement strips are affixed to the flexible circuit to furnish mechanical support and mitigate stress during component and connector insertion. It comprises two film-coated sides adhered with adhesive. This sheet not only offers environmental protection and electrical insulation but also aids in film removal and bonding in multi-layer circuits. Different adhesive sheets are tailored for distinct film substrates; for instance, those used for polyester and polyimide substrates vary. Adhesive sheets for polyimide substrates can be categorized into epoxy and acrylic variants.
4. Material of Flexible Circuit: Copper Foil
5. Copper foil serves as the conductive layer overlaying the bonding on the insulation substrate, subsequently etched selectively to delineate conductive lines. The predominant types of copper foil are calendered and electrolytic. Calendered copper foil outperforms electrolytic copper foil in ductility and bend resistance. Calendered copper foil typically exhibits an elongation of 20%-45%, whereas electrolytic copper foil ranges from 4% to 40%. The standard thickness for copper foil is 35um (1oz), with variations including 18um (0.5oz), 70um (2oz), or even 105um (3oz). Selection of copper foil form depends on specific applications; for instance, in reactive circuit boards aimed at wire and connector replacement to reduce manufacturing time and costs, electrolytic copper foil proves optimal. Additionally, electrolytic copper foil enhances current carrying capacity by augmenting copper weight, particularly suited for scenarios necessitating wider copper sheets.
6. Material of Flexible Circuit: Cover Layer
7. The coating’s primary function is to shield surface conductors and enhance substrate strength. The cover layer envelops the surface of the flexible printed circuit board, completing a functional layer of insulation protection. Two primary protective materials for exterior graphics are prevalent. The NovaClad brand, developed by Sheldahl, employs a proprietary technology based on vacuum metal-spraying, applying a thin layer of pure copper onto a polyimide film surface. Subsequently, the material undergoes electroplating to achieve a specific thickness, forming NovaClad’s base material. NovaClad base materials are integral in Novaflex flexible circuit production, eliminating the need for adhesives. Following circuit imaging, a Novaflex insulation coating is applied. Engineered to endure harsh environmental conditions, Novaflex flexible circuitry offers superior flexibility, chemical resistance, high-temperature resilience, and optimal heat dissipation.
8. Material of Flexible Circuit: Reinforcement Plate
9. The reinforcement plate is affixed to specific locations on the flexible plate to fortify the flexible film substrate and facilitate connection, fixation, or other PCB functions. Reinforcement board materials vary depending on application, commonly including polyester and polyimide sheets, epoxy glass fiber cloth boards, phenolic paper boards, or metallic plates such as steel or aluminum.
