Pengding Holdings has disclosed a flexible circuit board and its manufacturing method. The core innovation of this circuit board lies in the adoption of a unique dielectric structure, which uses air filled in a closed cavity as the primary medium surrounding the signal transmission lines. Compared to traditional dielectric materials, air has a lower dielectric constant and dielectric loss, significantly reducing losses during high-frequency signal transmission and improving signal quality. This design allows for the realization of low-loss characteristics under conventional manufacturing processes without the need for special materials.
Main themes and important ideas/facts:
Addressing the issue of dielectric loss in high-frequency signal transmission:
Background: The background section of Pengding clearly points out the main issue in high-frequency signal transmission: “The signal attenuation in high-frequency transmission lines mainly comes from the attenuation caused by dielectric loss.”
Disadvantages of traditional methods: Existing methods to reduce dielectric loss typically require the use of materials with low dielectric constants and low dielectric losses, such as liquid crystal polymers (LCP) or polytetrafluoroethylene (Teflon). However, “the transmission lines made from the aforementioned materials exhibit significant signal attenuation.”
Solution of the invention: By creating a closed cavity containing air around the signal line, “the medium surrounding the signal transmission line is filled with air, allowing the high-frequency signal transmission loss of this flexible circuit board to be nearly lossless as if transmitted in air, achieving ultra-low loss signal transmission and thereby enhancing transmission quality.” This method avoids the need for special dielectric materials.
Innovative circuit board structure:
This flexible circuit board consists of multiple layers, with the core structure including an inner circuit substrate, an outer circuit substrate, and bonding layers that connect and support these substrates.
The most important structural feature is that the signal line is placed in a “closed cavity,” which is formed through clever lamination and hole design, and “the closed cavity is filled with air.”
“The flexible circuit board includes: an inner circuit substrate, which includes a first conductive line layer that contains at least one signal line; two bonding layers, which include a first insulating layer and two pure adhesive layers formed on opposite sides of the first insulating layer; the first pure adhesive layer is bonded to the surface of the inner circuit substrate, and the bonding layer also includes a first opening that penetrates through the first insulating layer, the first pure adhesive layer, and the second pure adhesive layer, with the position of the first opening corresponding to the position of the signal line; and two outer circuit substrates formed on the bonding layer, with the two first openings and the two outer circuit substrates forming a closed cavity filled with air, which envelops the signal line.” (Claim 1)
This structure ensures that the signal line is effectively enveloped by air, minimizing contact with solid dielectric materials, thereby reducing losses.
Feasible manufacturing method:
Pengding provides a feasible step for manufacturing this flexible circuit board.
The core steps include: providing an inner circuit substrate and outer circuit substrates; creating bonding sheets with specific openings; laminating these layers together to form a closed cavity; and ensuring the cavity is filled with air.
“A method for manufacturing a flexible circuit board, which includes the steps of: providing an inner circuit substrate, two bonding layers, and two outer circuit substrates; the inner circuit substrate includes a first conductive line layer that contains at least one signal line; the two bonding layers include a first insulating layer and two pure adhesive layers formed on opposite sides of the first insulating layer; the first pure adhesive layer is bonded to the surface of the inner circuit substrate, and the bonding layer also includes a first opening that penetrates through the first insulating layer, the first pure adhesive layer, and the second pure adhesive layer, with the position of the first opening corresponding to the position of the signal line; stacking and laminating the inner circuit substrate, the bonding layer, the inner circuit substrate, the bonding layer, and the outer circuit substrates together to form a closed cavity, thereby forming the flexible circuit board; the closed cavity is filled with air, which envelops the signal line.” (Claim 7)
This method describes how to achieve the aforementioned special structure through conventional lamination and hole processes, making the technology highly implementable.
Advantages of the technology:
“In view of this, the invention provides a flexible circuit board and its manufacturing method that has ultra-low signal attenuation and relatively low cost.” (Invention content)
By utilizing air as the medium, this method avoids reliance on expensive low-loss materials, thereby reducing costs.
This technology can achieve ultra-low signal attenuation, improving the performance of high-frequency signal transmission.
Important facts and details:
Pengding details the composition of each layer, for example, the inner circuit substrate consists of a substrate, copper foil layer, and conductive line layer; the bonding layer consists of an insulating layer and pure adhesive layers.
The signal line is “enveloped by air,” which is key to achieving low loss.
“The position of the first opening corresponds to the position of the signal line,” ensuring that the signal line is within the formed air cavity.
“The closed cavity 80 is filled with air 81, which envelops the signal line 131.” (Specification [0026]) This again emphasizes the importance of air enveloping the signal line.
Conclusion:
Pengding Holdings provides an innovative and relatively low-cost design and manufacturing method for flexible circuit boards, significantly reducing dielectric loss in high-frequency signal transmission by creating and filling a closed cavity with air around the signal lines. This technology can be realized using conventional circuit board manufacturing processes, providing a new avenue for the development of high-performance flexible electronic products. The core value of Pengding lies in proposing and implementing an effective solution that uses air as the primary medium to enhance signal integrity.
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