A dynamically stable shielded signal cable and its preparation method

Abstract

This invention discloses a dynamically stable shielded signal cable and its manufacturing method. The cable includes a conductor, an insulation layer covering the conductor, and a multi-layer shielding structure covering the insulation layer. The multi-layer shielding structure includes an inner shielding layer and a composite shielding layer. The composite shielding layer is a multi-layer composite tape, including a metallic conductive layer and at least two polymer adhesive layers. A molten blending interface exists between the inner shielding layer and the composite shielding layer. This molten blending interface is formed by the polymer adhesive layer located in the inner region bonding to and solidifying with the back side of the inner shielding layer in a molten state. This invention significantly improves the cable's shielding effectiveness under dynamic bending conditions by creating an integrated structure where the multi-layer shielding layers deform synergistically.

Description

Technical Field

[0001] This invention relates to the field of transmission cable technology, specifically to a dynamically stable shielded signal cable and its manufacturing method. Background Technology

[0002] In applications with extremely high signal integrity requirements, such as data centers, high-performance computing, precision measuring instruments, and industrial automation, transmission cables not only need to possess high shielding effectiveness under static conditions, but also face the severe challenge of maintaining stable electromagnetic shielding performance under dynamic mechanical stresses such as long-term equipment operation, repeated bending, or movement of cables. This is a key technical bottleneck in ensuring system reliability and data accuracy.

[0003] Currently widely used traditional multi-layer shielded cables (such as "metal wire braided layer + aluminum-plastic composite tape wrapping" or "double aluminum foil wrapping" structures) generally have the following defects under dynamic operating conditions:

[0004] Interlayer slippage leads to unstable electrical contact: In traditional shielding structures, the layers are usually only in physical contact or simply bonded together with low-tack tape, resulting in weak interlayer bonding. When the cable is repeatedly bent, the materials in each layer slip relative to each other due to differences in modulus. This leads to increased fluctuations in the contact resistance between the metal layers, and may even cause microscopic fatigue damage to the metal foil layer or braided wire, resulting in irreversible deterioration of the shielding effectiveness.

[0005] It is difficult to balance low-frequency magnetic field shielding materials with flexibility: Conventional copper and aluminum shielding layers have limited effectiveness against low-frequency magnetic field interference below 1MHz. Although high-permeability materials (such as permalloy) have good shielding effects, they are brittle and prone to micro-cracks when bent, which can damage the magnetic conductivity path and make it difficult to meet the reliability requirements of dynamic applications.

[0006] The "dynamic leakage" problem of high-frequency shielding: The metal wire braid layer mainly relies on reflection loss to function in the high-frequency band, but its shielding effect is extremely sensitive to coverage. When the cable is bent, the relative position and angle of the braided wires change, causing the local mesh to enlarge and the coverage to decrease, thus forming an electromagnetic leakage channel that changes with the bending state.

[0007] To address the aforementioned issues, common improvement approaches, such as increasing braiding density, increasing metal foil thickness, or adding conductive adhesive layers, while improving the initial shielding value to some extent, do not change the fundamental structural defect of "independent deformation of each layer." It was once widely believed in the field that a certain degree of relative displacement between shielding layers must be allowed to maintain the necessary flexibility of the cable; this understanding has limited the path to solving the dynamic shielding stability problem.

[0008] Therefore, there is a need for an improved shielding structure design that enables multiple shielding layers to deform collaboratively under dynamic bending conditions, reducing interlayer relative displacement, thereby maintaining long-term stability of shielding effectiveness under combined mechanical stress and electromagnetic interference environments. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a dynamically stable shielded signal cable and its manufacturing method. The present invention significantly improves the cable's shielding effectiveness under dynamic bending conditions by forming an integrated structure with multiple shielding layers that deform synergistically.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0011] In a first aspect, the present invention provides a dynamically stable shielded signal cable, comprising a conductor, an insulating layer covering the conductor, and a multi-layer shielding structure covering the insulating layer;

[0012] The multi-layer shielding structure includes an inner shielding layer and a composite shielding layer;

[0013] The composite shielding layer is a multi-layer composite strip, comprising a metal conductive layer and at least two polymer adhesive layers located inside the metal conductive layer; of the at least two polymer adhesive layers, the polymer adhesive layer located in the outer region has a first melting point Tm1, and the polymer adhesive layer located in the inner region and facing the inner shielding layer has a second melting point Tm2, ​​and Tm1 <Tm2;

[0014] The inner shielding layer and the composite shielding layer have a melt-blended interface, which is formed by the polymer adhesive layer located in the inner region bonding with the back of the inner shielding layer in a molten state and then solidifying; the inner shielding layer, the melt-blended interface and the composite shielding layer constitute an integrated shielding core.

[0015] The process of forming the melt blending interface includes: after wrapping the composite shielding layer around the inner shielding layer, first placing the composite shielding layer in a temperature range below Tm2 but above Tm1, and then placing the composite shielding layer in a temperature range not lower than Tm2.

[0016] Preferably, the inner shielding layer is a soft magnetic alloy foil or metal foil, and a thermoplastic adhesive layer is provided on the side facing the insulating layer, and the thermoplastic adhesive layer is bonded to the surface of the insulating layer.

[0017] Furthermore, the multilayer composite tape also includes a polymer carrier film, which is located between the polymer adhesive layer in the outer region and the polymer adhesive layer in the inner region.

[0018] Furthermore, the difference between the second melting point Tm2 and the first melting point Tm1 is not less than 15°C.

[0019] Preferably, the polymer adhesive layer in the outer region is an ethylene-vinyl acetate copolymer or an ethylene-acrylate copolymer; the polymer adhesive layer in the inner region is a copolyamide or a modified polyolefin.

[0020] Furthermore, the 180° peel strength of the melt blend interface, as tested according to ASTM D903 standard, is not less than 2.5 N / mm.

[0021] Furthermore, after undergoing 5000 dynamic bending cycles as specified in the IEC 61196-1 standard, the shielding effectiveness of the integrated shielding core at a frequency of 3GHz does not decrease by more than 3dB.

[0022] Furthermore, the insulating layer is composed of a low dielectric loss composite material, comprising, by weight: 40-60 parts of metallocene polyethylene, 20-30 parts of styrene-based thermoplastic elastomer, and 10-20 parts of spherical silica modified with a coupling agent.

[0023] Furthermore, the multi-layer shielding structure in the dynamically stable shielded signal cable also includes an outer shielding layer located outside the composite shielding layer. The outer shielding layer is a metal wire braided layer, and the outer surface of the metal wire braided layer has undergone a rolling process.

[0024] Secondly, the present invention provides a method for preparing the dynamically stable shielded signal cable, the method comprising the step of forming the integral shielding core in-line, the step comprising:

[0025] An inner shielding layer is formed outside the conductor covered with an insulating layer;

[0026] The multilayer composite tape is wrapped around the inner shielding layer, and the resulting wire core is sequentially passed through at least two heating zones at different temperatures, wherein:

[0027] The temperature of the first heating zone is controlled to be lower than Tm2 but higher than Tm1;

[0028] The temperature of the second heating zone is controlled to be no lower than Tm2, ​​so that the polymer adhesive layer located in the inner region melts and contacts the back of the inner shielding layer.

[0029] The wire core after passing through the second heating zone is cooled to solidify the molten polymer adhesive layer, forming the molten blend interface.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) The integrated shielding core of the present invention is composed of an inner shielding layer and a composite shielding layer, wherein the composite shielding layer includes a metal conductive layer, a polymer adhesive layer located in the outer region, and a polymer adhesive layer located in the inner region facing the inner shielding layer. Through a step-by-step melting process, in the first heating zone, the polymer adhesive layer in the outer region can be softened and shaped first, so that the composite shielding layer is flatly attached to the surface of the inner shielding layer. At this time, the polymer adhesive layer in the inner region remains solid, serving as a "skeleton" to support the overall shape of the composite strip and prevent wrinkling or slippage during wrapping. After entering the second heating zone, the polymer adhesive layer in the inner region melts and fully contacts the back of the inner shielding layer under pressure. The molten polymer wets the micro-pits on the metal surface to form a mechanical interlocking structure. At the same time, the active functional groups in the polymer chemically bond with the oxide layer on the metal surface. After cooling, a melt-blended interface is formed, eliminating the micro-gap between the layers and making the inner shielding layer and the composite shielding layer integrated.

[0032] (2) The 180° peel strength of the melt blend interface in this invention is not less than 2.5 N / mm according to ASTM D903 standard. The peel failure mode is cohesive failure rather than interfacial peel, indicating that the interfacial bonding strength is higher than the material bulk strength, ensuring that the interlayer will not become the failure starting point under repeated bending stress.

[0033] (3) In this invention, the polymer adhesive layer in the outer region forms a flexible transition layer between the metal conductive layer and the inner polymer adhesive layer, which buffers the interface stress caused by the difference in modulus between the metal conductive layer and the polymer layer when bending, and avoids interface damage caused by stress concentration.

[0034] (4) Based on the fused blend interface structure, the inner shielding layer and the composite shielding layer in this invention can deform together when bent, avoiding contact resistance fluctuations and metal layer fatigue caused by interlayer relative slippage in traditional structures, thereby maintaining the stability of shielding effectiveness. After 5000 dynamic bending cycles according to IEC 61196-1 standard, the shielding effectiveness attenuation value at the 3GHz frequency point does not exceed 3dB.

[0035] (5) The integrated shielding core of the present invention, as an integral structure, provides a flat and stable wrapping substrate for the outer shielding layer. It can be combined with constant angle rolling process to flatten and attach the outer shielding layer, further suppressing electromagnetic leakage caused by the deformation of the braided mesh of the outer shielding layer when bending. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the dynamically stable shielded signal cable of the present invention.

[0037] Figure 2 This is a schematic diagram of the composite shielding layer in the dynamically stable shielded signal cable of the present invention.

[0038] Figure 3 This is a comparison curve showing the attenuation value (ΔSE) of the shielding effectiveness (SE) of the cable in this embodiment and the cable in the comparative embodiment after a dynamic bending cycle test.

[0039] In the figure, 10: conductor; 20: insulating layer; 30: inner shielding layer; 40: composite shielding layer; 401: metallic conductive layer; 402: polymer adhesive layer; 403: polymer carrier film; 50: outer shielding layer; 60: sheath layer. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The present invention provides a dynamically stable shielded signal cable, which includes a conductor 10, an insulation layer 20 covering the conductor 10, and a multi-layer shielding structure covering the insulation layer 20.

[0042] The conductor 10 can be made of copper, silver-plated copper, or tin-plated copper, and preferably uses a multi-strand stranded structure to give the cable good flexibility while ensuring conductivity.

[0043] The insulating layer 20 covers the conductor 10, providing electrical insulation and ensuring low-loss signal transmission characteristics. Exemplarily, the insulating layer 20 can be composed of a low-dielectric-loss composite material. By weight, this composite material comprises: 40-60 parts of metallocene polyethylene, 20-30 parts of styrene-based thermoplastic elastomer, and 10-20 parts of surface-modified spherical silica. The metallocene polyethylene provides good processability and electrical properties; the styrene-based thermoplastic elastomer (such as SEEPS) imparts flexibility and elasticity to the insulating layer, reducing stress concentration during bending; and the surface-modified spherical silica reduces the dielectric constant of the composite material while improving filler dispersion. Through the synergistic effect of the above formulation, the dielectric constant Dk of the insulating layer 20 at a frequency of 1 GHz is no higher than 2.25, and the loss factor Df is no higher than 0.001, effectively reducing the transmission attenuation of high-frequency signals. The insulation layer 20 can be formed by extrusion molding process, in which the above-mentioned composite material is melted and mixed and then extruded onto the conductor 10, and after cooling and shaping, a uniform insulation layer 20 is formed.

[0044] The multi-layer shielding structure includes an inner shielding layer 30 and a composite shielding layer 40, which are combined into an integral shielding core through a melt-blending interface.

[0045] Among them, the inner shielding layer 30 is located outside the insulating layer 20, and its function is to provide low-frequency magnetic field shielding and serve as the base layer of the melt blending interface.

[0046] Exemplarily, the inner shielding layer 30 can be made of a soft magnetic alloy foil tape or a metal foil tape, preferably a soft magnetic amorphous alloy foil tape. This amorphous alloy foil tape has a high saturation magnetic induction intensity (Bs≥1.2T) and a high amorphous phase content (≥85%). Its amorphous structure eliminates grain boundaries, endows the material with excellent bending fatigue resistance, and overcomes the defect that traditional crystalline high-permeability materials (such as permalloy) are prone to generate microcracks when bent. The Vickers hardness HV of the amorphous alloy foil tape can be controlled within the range of 450-550, which not only ensures the shape retention ability during winding but also avoids being too hard to be processed.

[0047] One side of the inner shielding layer 30 facing the insulating layer 20 is provided with a thermoplastic adhesive layer. This thermoplastic adhesive layer can be made of thermoplastic polyurethane (TPU), polyamide (PA) or polyester-based hot melt adhesive, and the thickness is preferably 5-12μm. During the winding process, by heating and applying radial tension, the thermoplastic adhesive layer is softened and infiltrates the surface of the insulating layer, and a self-bonding interface is formed after cooling, realizing the tight fitting of the inner shielding layer 30 and the insulating layer 20.

[0048] The composite shielding layer 40 is a multi-layer composite tape, which is wound outside the inner shielding layer 30. Its function is to provide high-frequency electromagnetic shielding and form a melt blending interface with the inner shielding layer 30 through the polymer adhesive layer 402 on its inner side.

[0049] Exemplarily, the composite shielding layer 40 includes a metal conductive layer 401 and at least two polymer adhesive layers 402 located inside the metal conductive layer 401. The metal conductive layer 401 can be made of aluminum foil, copper foil or metal-plated plastic film, and the thickness is preferably 20-35μm, providing a continuous and seamless metal shielding layer to effectively reflect high-frequency electromagnetic waves.

[0050] The polymer adhesive layer 402 (close to the metal conductive layer) in the outer region has a first melting point Tm1, and the polymer adhesive layer 402 in the inner region facing the inner shielding layer 30 has a second melting point Tm2, and Tm1<Tm2. The difference between Tm1 and Tm2 is preferably not less than 15°C to ensure that there is a wide enough temperature window for the stepwise melting process.

[0051] The polymer adhesive layer 402 in the outer region can be made of ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EEA), or polyolefin elastomer (POE), with a preferred melting point Tm1 of 95-105℃. The preferred thickness is 10-20 μm. This layer softens and sets in the first heating zone of the step-melting process, imparting flexibility and initial shaping capability to the multilayer composite tape. Simultaneously, it serves as a flexible transition layer between the metal conductive layer 401 and the inner polymer adhesive layer 402 in the final structure, buffering bending stress.

[0052] The polymer adhesive layer 402 in the inner region can be made of copolyamide (CoPA), modified polyolefin, or polyester hot melt adhesive, with a preferred melting point Tm2 of 115-125℃ and a preferred thickness of 10-20μm. This layer melts in the second heating zone of the step-melting process and, under pressure, comes into full contact with the back side of the inner shielding layer 30 to form a melt-blended interface.

[0053] Furthermore, the composite shielding layer 40 also includes a polymer carrier film 403, located between the outer region polymer adhesive layer and the inner region polymer adhesive layer. The polymer carrier film 403 can be made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyimide (PI), and its thickness is preferably 8-15 μm. The function of the polymer carrier film 403 is to: prevent the softened outer region polymer adhesive layer 402 from prematurely mixing with the unmelted inner region polymer adhesive layer 402 during the step-by-step melting process; and in the second heating zone, when the inner region polymer adhesive layer 402 melts, the polymer carrier film 403 remains solid, isolating the molten inner region polymer adhesive layer 402 from the outer region polymer adhesive layer 402, ensuring that the inner region polymer adhesive layer 402 can form a pure melt-blended interface with the inner shielding layer 30.

[0054] There is a melt-blended interface between the inner shielding layer 30 and the composite shielding layer 40. This interface is formed by the polymer adhesive layer 402 located in the inner region being bonded to the back side of the inner shielding layer 30 in a molten state and then solidified.

[0055] The formation process of the melt blend interface includes a step-by-step melting process: First, after the composite shielding layer 40 is wrapped around the inner shielding layer 30, the composite shielding layer 40 is placed in a temperature range below Tm2 but above Tm1 (first heating zone). At this time, the polymer adhesive layer 402 in the outer region softens, allowing the multilayer composite tape to adhere smoothly to the surface of the inner shielding layer 30. Subsequently, the composite shielding layer 40 is placed in a temperature range not lower than Tm2 (second heating zone). At this time, the polymer adhesive layer 402 in the inner region melts and, under the action of wrapping tension, makes full contact with the back side of the inner shielding layer 30. The molten polymer wets the micro-pits and defects on the surface of the inner shielding layer 30, forming a mechanical interlocking structure after cooling. On the other hand, the active functional groups in the polymer undergo chemical bonding or hydrogen bonding with the oxide layer on the surface of the inner shielding layer 30. Finally, through rapid cooling, the molten polymer adhesive layer 402 is solidified, bonding the inner shielding layer 30 and the composite shielding layer 40 into one unit.

[0056] The 180° peel strength of the melt blend interface, tested according to ASTM D903, is no less than 2.5 N / mm, and the peel failure mode is cohesive failure (i.e., fracture occurs within the polymer adhesive layer material or the inner shielding layer material), rather than interfacial peeling. This indicates that the bonding strength of the melt blend interface is higher than the bulk strength of the material, and the interlayer is no longer a weak point in the structure, ensuring that the interlayer will not become the failure initiation point under repeated bending stress.

[0057] The inner shielding layer 30, the fused blend interface, and the composite shielding layer 40 together constitute an integrated shielding core. After undergoing 5000 dynamic bending cycles as specified in the IEC 61196-1 standard, the shielding effectiveness attenuation value ΔSE at the 3GHz frequency does not exceed 3dB.

[0058] To further improve the high-frequency shielding effect, the multi-layer shielding structure of the cable may also include an outer shielding layer 50 located outside the composite shielding layer 40. For example, the outer shielding layer 50 may be a braided metal wire layer, with a preferred braiding angle of 85°±2° and a braiding density of not less than 85%. After braiding, the braided layer is calendered using calendering rollers at a temperature of 70-90°C, causing the braided wires to flatten and tightly adhere to the surface of the composite shielding layer 40, reducing gaps between the braided wires and improving shielding consistency.

[0059] The outermost layer of the cable of the present invention is further provided with a sheath layer 60, which can be made of materials such as polyvinyl chloride (PVC), low smoke halogen-free flame retardant polyolefin (LSZH), thermoplastic elastomer (TPE) or polyurethane (TPU), and is extruded and molded to cover the multi-layer shielding structure, providing mechanical protection and environmental protection for the internal structure of the cable.

[0060] The present invention further provides a method for preparing the above-mentioned dynamically stable shielded signal cable, the method comprising the step of forming an integral shielding core in online.

[0061] This step includes:

[0062] An insulating layer 20 is formed on the outside of the conductor 10. Exemplarily, an extrusion molding process can be used: the insulating layer composite material is melt-blended in a twin-screw extruder, extruded through the extruder head onto the outside of the conductor 10, and cooled and shaped in a cooling water tank to form a uniform insulating layer 20.

[0063] An inner shielding layer 30 is formed outside the insulating layer 20. An inner shielding material (such as a soft magnetic amorphous alloy foil strip) with a thermoplastic adhesive layer is guided to the surface of the insulating layer 20 with the adhesive side facing inwards. Radial tension is applied at the wrapping point using a tension-heating coupling device, while the non-adhesive surface of the inner shielding material is simultaneously heated. The radial tension is preferably controlled at 8-12 N, and the auxiliary heating temperature is preferably 80-90 °C. The synergistic effect of heat and tension softens the thermoplastic adhesive layer, causing it to adhere tightly to the surface of the insulating layer 20 under pressure, forming a self-adhesive interface upon cooling.

[0064] The multi-layer composite tape is wrapped around the inner shielding layer 30, and the resulting wire core is passed through at least two heating zones at different temperatures in sequence, followed by cooling to form a molten blend interface.

[0065] Specifically, the temperature of the first heating zone is controlled to be lower than Tm2 but higher than Tm1, preferably 0-10°C higher than Tm1. At this temperature, the polymer adhesive layer 402 in the outer region softens but does not completely melt, and the composite tape obtains good flexibility and preliminary shaping ability, and adheres smoothly to the surface of the inner shielding layer 30; at this time, the polymer adhesive layer 402 in the inner region remains solid and plays a supporting role.

[0066] The temperature of the second heating zone is controlled to be no lower than Tm2, ​​preferably 0-5°C higher than Tm2 and not exceeding Tm2+10°C. At this temperature, the polymer adhesive layer 402 located in the inner region is completely melted and in a viscous flow state, making full contact with the back side of the inner shielding layer 30 under the action of wrapping tension. The wrapping tension is preferably controlled at 5-10N.

[0067] Subsequently, the core wire after passing through the second heating zone is cooled, preferably at a cooling rate of not less than 30°C / s, and more preferably by using a cooling medium (such as a water-cooled roller) at 15-25°C for rapid cooling. The molten polymer adhesive layer 402 rapidly solidifies, permanently bonding the inner shielding layer 30 and the composite shielding layer 40 together to form a melt-blended interface.

[0068] Through the above steps, the inner shielding layer 30, the molten blending interface, and the composite shielding layer 40 together constitute an integrated shielding core.

[0069] After forming the integrated shielding core, an outer shielding layer 50 can be formed on its exterior. For example, a constant tension braiding machine is used to braid metal wires (such as silver-plated copper wire) at a constant angle of 85°±2° to form a metal wire braided layer with a braiding density of not less than 85%. After braiding, the braided layer is calendered using calendering rollers at a temperature of 70-90°C, flattening the braided wires and tightly adhering them to the surface of the composite shielding layer 40.

[0070] Finally, sheath material is extruded over the outer shielding layer 50, and after cooling and shaping, sheath layer 60 is formed, completing the cable preparation.

[0071] The present invention will be further described below through specific embodiments.

[0072] Example

[0073] This embodiment provides a dynamically stable shielded signal cable and its preparation method.

[0074] First, conductor 10 and insulation layer 20 are prepared. Conductor 10 is made of Class 7 silver-plated annealed copper wire with a single wire diameter of 0.20 mm, which is stranded to form the conductor core. Insulation layer 20 is composed of a low dielectric loss composite material, which, by weight, includes: 55 parts of metallocene polyethylene (mPE, grade Exceed™ 1018), 25 parts of SEEPS (grade Septon™ 4055), 15 parts of vinylsilane-grafted modified spherical silica (average particle size 0.8 μm), and 2 parts of composite antioxidant (a 1:1 mixture of primary antioxidant 1010 and secondary antioxidant 168). The above materials are melt-blended and granulated in a twin-screw extruder, and then extruded onto the conductor on a tandem extrusion line, with the insulation layer 20 having a thickness of 0.8 mm. The extruder temperature is set in zones, with the highest temperature zone at 175°C.

[0075] An inner shielding layer 30 is formed outside the insulating layer 20. The inner shielding layer 30 is made of iron-based soft magnetic amorphous alloy foil (grade 1K107B), with a thickness of 0.025 mm, a saturation magnetic induction intensity Bs of 1.25 T, an amorphous phase content of more than 90%, and a Vickers hardness HV of approximately 500. The side of the foil facing the insulating layer 20 is coated with a thermoplastic polyurethane self-adhesive layer with a thickness of approximately 8 μm. During wrapping, the foil with the self-adhesive side facing inward is guided to the surface of the insulating layer 20, and a constant radial tension of 10 N is applied through a tension-heating coupling device. At the same time, the non-adhesive side is auxiliaryly heated to 85°C to soften the self-adhesive and make it tightly adhere to the insulating layer 20, with a wrapping overlap rate of 30%.

[0076] Next, a composite shielding layer 40 is wrapped around the formed wire core. The composite shielding layer 40 is a multi-layer composite tape, consisting of the following layers from the outside in: a metal conductive layer 401 (electrolytic aluminum foil, 30 μm thick), an outer polymer adhesive layer 402 (ethylene-vinyl acetate copolymer layer, EVA, 15 μm thick, melting point Tm1 = 100℃), a polymer carrier film 403 (polyethylene terephthalate carrier film, PET, 12 μm thick), and an inner polymer adhesive layer 402 (copolyamide layer, CoPA, 15 μm thick, melting point Tm2 = 120℃). The composite tape is wrapped with the inner CoPA layer facing towards the inner shielding layer 30, with an overlap of 35%.

[0077] The wrapped wire core undergoes a step-by-step melting process in two heating zones with different temperatures. First, it enters the first heating zone, where the surface temperature is controlled at 105℃. This softens the outer EVA layer but does not completely melt it, giving the composite tape good flexibility and initial shaping ability, allowing it to adhere smoothly to the surface of the inner shielding layer 30. At this point, the inner CoPA layer remains solid, providing support. Next, the wire core enters the second heating zone, where the surface temperature is controlled at 123℃. This completely melts the inner CoPA layer, creating a viscous flow state, and under the wrapping tension, it makes full contact with the back of the inner shielding layer 30. The molten CoPA wets the microscopic pits on the metal surface of the inner shielding layer 30, forming a mechanically interlocking structure. Simultaneously, the amide groups in its molecular chain chemically bond with the oxide layer on the surface of the inner shielding layer 30, forming a melt-blended interface. Next, the core wire is rapidly cooled in a 20°C water-cooling bath at a rate of approximately 60°C / s, which solidifies the molten blend interface and combines the inner shielding layer 30 with the composite shielding layer 40 into a single integrated shielding core.

[0078] An outer shielding layer 50 is formed outside the integrated shielding core. A 64-spindle braiding machine is used with 0.08mm diameter silver-plated soft copper wire, braided at an 86.5° braiding angle with a braiding density of 92%. After braiding, the cable is passed through a pair of smooth calendering rollers at 80°C for calendering, flattening the braided strands and ensuring they adhere tightly to the surface of the composite shielding layer 40. Finally, a low-smoke halogen-free flame-retardant polyolefin sheath 60 is extruded over the outer shielding layer 50, with a sheath layer 60 thickness of 0.5mm, completing the cable fabrication.

[0079] Comparative Example

[0080] To verify the technical effect of the present invention, the following comparative tests were conducted.

[0081] Comparative Example A: A multi-layer shielding structure is used, which is a traditional tin-plated copper wire braided layer (braiding density 90%) + single-sided aluminum-plastic composite tape wrapping structure. There is no molten blending interface. The rest of the cable structure, materials and preparation method are the same as those in the embodiments of the present invention.

[0082] Comparative Example B: A double-layer aluminum-plastic composite tape wrapping structure is used as a multi-layer shielding structure. The layers are in physical contact with each other and there is no melt-blending interface. The rest of the cable structure, materials and preparation method are the same as those in the embodiments of the present invention.

[0083] Comparative Example C: A comparative cable bonded with high-performance conductive adhesive. This cable's multi-layer shielding structure includes an inner shielding layer, a middle shielding layer, and an outer shielding layer. The inner shielding layer is the same as in the embodiment of this invention (iron-based soft magnetic amorphous alloy foil strip, coated on one side with a thermoplastic polyurethane self-adhesive layer). The middle shielding layer is a single-layer metal foil strip (electrolytic aluminum foil, 30 μm thick), with a high-performance conductive adhesive (epoxy resin-based conductive adhesive, filled with silver powder, approximately 15 μm thick) coated on the side facing the inner shielding layer. The outer shielding layer is the same as in the embodiment of this invention.

[0084] In the preparation process, after the inner shielding layer is wrapped around the insulating layer, a metal foil strip coated with high-performance conductive adhesive is wrapped around the inner shielding layer, with an overlap rate of 35%. The conductive adhesive is partially cured by heating to form an adhesive interface. The remaining structure, materials, and preparation method of Comparative Example C are consistent with the embodiments of the present invention.

[0085] Performance testing

[0086] The cables prepared in the examples and comparative examples were subjected to performance tests, and the test methods are as follows:

[0087] (1) Interlayer peel strength test

[0088] Tests were conducted according to ASTM D903-98. Strip specimens containing insulation layers and multi-layered shielding structures were prepared from the cable, with a specimen width of 10 mm and a length of not less than 100 mm. A 180° peel test was performed using a universal testing machine at a peel speed of 100 mm / min. The maximum and average forces during the peel process were recorded, and the peel failure modes were observed, distinguishing between interfacial peeling (failure occurring at the interlayer interface) and cohesive failure (failure occurring within the material).

[0089] (2) Shielding effectiveness test after dynamic bending cycle

[0090] The dynamic bending cycle was performed according to Section 8.3 of IEC 61196-1. The cable was wound around a cylinder with a bending radius eight times its outer diameter and bent back and forth at a rate of 10-15 times per minute, with a bending angle of 90°, for a total of 5000 cycles. Before and after bending, the shielding effectiveness of the cable at a frequency of 3 GHz was tested according to ASTM D4935-18, and the attenuation value ΔSE of the shielding effectiveness after bending was calculated.

[0091] (3) Initial shielding effectiveness test

[0092] The test was conducted according to IEC 62153-4-7 standard. The triaxial sleeve method was used, with a vector network analyzer and triaxial fixtures as the testing equipment. The initial shielding effectiveness of the cable was measured at a frequency of 3 GHz. The system was calibrated before testing, and the sample length was determined according to the fixture requirements. The shielding effectiveness values ​​were recorded.

[0093] (4) Low-frequency shielding effectiveness test

[0094] The test was conducted according to IEC 62153-4-7 standard. The triaxial method was used to measure the cable's transfer impedance at a frequency of 100kHz, which was then converted to shielding effectiveness (SE). The test equipment consisted of a network analyzer with a triaxial fixture, and the sample length was 1m.

[0095] (5) Signal transmission attenuation test

[0096] The test was conducted according to IEC 61196-1 standard. A network analyzer was used in conjunction with a phase-stabilized test cable to measure the insertion loss of the cable at a frequency of 2 GHz, and the attenuation value was recorded in dB / 100m. The sample length was 10m, with both ends connected to the test ports of the network analyzer.

[0097] (6) Temperature cycling reliability test

[0098] The cable was placed in a temperature cycling test chamber and subjected to cyclic testing within a range of -25°C to 85°C. Each cycle consisted of: cooling from room temperature to -25°C (holding for 30 minutes), heating to 85°C (holding for 30 minutes), and then cooling back to room temperature. The number of cycles was 1000. After the test, the 3GHz shielding effectiveness and interlayer peel strength were retested to evaluate performance changes.

[0099] (7) Interface energy dissipation performance test

[0100] Dynamic mechanical properties of the interface region between the cable shielding layers were tested using a dynamic mechanical analyzer (DMA) in both Example 1 and Comparative Example C. A sample containing the interface between the inner shielding layer and the composite shielding layer was peeled from the cable. The sample was taken along the cable axis, with a width of 5 mm and a clamp spacing of 10 mm. The test used a temperature scan mode at a frequency of 1 Hz, a temperature range of -40℃ to 120℃, and a heating rate of 3℃ / min. The loss factor (tanδ) was recorded as a function of temperature, and the morphology and width of the tanδ peak in the interface region within the range of -20℃ to 80℃ were observed.

[0101] The performance test results are shown in Table 1.

[0102] Table 1

[0103]

[0104] As shown in Table 1, the cable of this embodiment exhibits a shielding effectiveness attenuation of only 1.5 dB after 5000 dynamic bending cycles, significantly better than Comparative Example A (18.7 dB), Comparative Example B (12.3 dB), and Comparative Example C (8.5 dB). The interlayer peel strength reaches 3.8 N / mm and is characterized by cohesive failure, demonstrating that the interfacial bonding strength is higher than that of the material bulk. The shielding effectiveness at 100 kHz is 45 dB, and the transmission attenuation at 2 GHz is 15.2 dB / 100m. The performance remains stable after 1000 temperature cycles. DMA testing shows that the interface exhibits a broad and gentle tanδ peak, indicating excellent energy dissipation capability. These results verify that the molten blend interface formed by the stepwise melting process of this invention has comprehensive advantages in terms of dynamic stability, interfacial bonding strength, full-band shielding performance, and environmental reliability.

[0105] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0106] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method of making a dynamically stabilized shielded signal cable, characterized by, The dynamically stabilized shielded signal cable includes a conductor, an insulation layer covering the conductor, and a multi-layer shielding structure covering the insulation layer. The multi-layer shielding structure includes an inner shielding layer and a composite shielding layer; The composite shielding layer is a multi-layer composite strip, comprising a metal conductive layer and at least two polymer adhesive layers located inside the metal conductive layer; of the at least two polymer adhesive layers, the polymer adhesive layer located in the outer region has a first melting point Tm1, and the polymer adhesive layer located in the inner region and facing the inner shielding layer has a second melting point Tm2, ​​and Tm1 <Tm2; The inner shielding layer and the composite shielding layer have a melt-blended interface, which is formed by the polymer adhesive layer located in the inner region bonding with the back of the inner shielding layer in a molten state and then solidifying. The inner shielding layer, the melt-blended interface, and the composite shielding layer constitute an integrated shielding core. The process of forming the melt blend interface includes: after wrapping the composite shielding layer around the inner shielding layer, first placing the composite shielding layer in a temperature range lower than Tm2 but higher than Tm1, and then placing the composite shielding layer in a temperature range not lower than Tm2. The preparation method includes the step of forming the integrated shielding core in-line, which includes: An inner shielding layer is formed outside the conductor covered with an insulating layer; The multilayer composite tape is wrapped around the inner shielding layer, and the resulting wire core is sequentially passed through at least two heating zones at different temperatures, wherein: The temperature of the first heating zone is controlled to be lower than Tm2 but higher than Tm1; The temperature of the second heating zone is controlled to be no lower than Tm2, ​​so that the polymer adhesive layer located in the inner region melts and contacts the back of the inner shielding layer. The wire core after passing through the second heating zone is cooled to solidify the molten polymer adhesive layer, forming the molten blend interface.

2. The method of making a dynamically stable shielded signal cable of claim 1, wherein, The inner shielding layer is a soft magnetic alloy foil or metal foil, and a thermoplastic adhesive layer is provided on the side facing the insulating layer, and the thermoplastic adhesive layer is bonded to the surface of the insulating layer.

3. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The multilayer composite tape also includes a polymer carrier film, which is located between the polymer adhesive layer in the outer region and the polymer adhesive layer in the inner region.

4. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The difference between the second melting point Tm2 and the first melting point Tm1 is not less than 15℃.

5. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The polymer adhesive layer in the outer region is an ethylene-vinyl acetate copolymer or an ethylene-acrylate copolymer; the polymer adhesive layer in the inner region is a copolyamide or a modified polyolefin.

6. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The 180° peel strength of the melt blend interface, as tested according to ASTM D903, is not less than 2.5 N / mm.

7. The dynamically stable shielded signal cable according to claim 1, characterized in that, After undergoing 5000 dynamic bending cycles as specified in the IEC 61196-1 standard, the shielding effectiveness of the integrated shielding core at a frequency of 3GHz does not decrease by more than 3dB.

8. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The insulating layer is composed of a low dielectric loss composite material, comprising, by weight: 40-60 parts of metallocene polyethylene, 20-30 parts of styrene-based thermoplastic elastomer, and 10-20 parts of spherical silica modified with a coupling agent.

9. The method for preparing a dynamically stable shielded signal cable according to claim 1, characterized in that, The multi-layer shielding structure also includes an outer shielding layer located outside the composite shielding layer. The outer shielding layer is a metal wire braided layer, and the outer surface of the metal wire braided layer has been rolled.

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