High-temperature-resistant special high-frequency flexible cable and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant special high-frequency flexible cable and a preparation method thereof. Relates to the technical field of special high-frequency cables for high-end equipment manufacturing. The special high-frequency cable comprises a conductor, an insulating layer, an inner shielding layer, an outer shielding layer and a sheath layer which are sequentially arranged from inside to outside, the conductor is of a single-wire structure or a multi-wire stranded structure; a wire forming the conductor is composed of a copper wire core and a chromium plating layer or a chromium alloy plating layer plated outside the copper wire core. The insulating layer is of an extruded structure formed by foaming type modified polyimide materials outside the conductor; the inner shielding layer is an overlapped wrapping structure of a chromium-plated alloy temperature-resistant metal belt outside the insulating layer; and the outer shielding layer is a braided structure with silver-plated nickel-silicon alloy wires outside the inner shielding layer. The flexible cable has excellent electrical signal transmission stability, high temperature resistance and flexible bendability, can be effectively applied to aerospace working conditions, can be repeatedly used for a long time in the working conditions, and is safe and reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of special high-frequency cables for high-end equipment manufacturing, and in particular to a high-temperature resistant special high-frequency soft cable and a preparation method thereof. Background Art

[0002] High-frequency cables are widely used in the aerospace field, covering rocket engines, avionics equipment, space probes and other aspects, and are used as airborne temperature control antennas, engine cabin compensation wires, emergency communication wires, etc. Due to the particularity of aerospace equipment, high-frequency cables are required to have excellent high temperature resistance, especially in the application scenario of rocket engines.

[0003] For a long time, the main technical measure to improve the heat resistance of high-frequency cables is to form a heat-resistant layer in the protective structure outside the conductor with heat-resistant materials. Although this technical measure has a certain heat-resistant effect, on the one hand, it will increase the structural size of the formed high-frequency cable, which is not conducive to forming a compact and easy-to-lay soft cable; on the other hand, due to the relative independence of each structural layer, it cannot form a good synergy, which makes the improvement of heat resistance limited.

[0004] In order to solve the technical problems of large structural dimensions and poor heat resistance of the high-frequency cable with a heat-resistant layer, the industry has tried to manufacture conductors with heat-resistant performance, such as adding chromium and nickel with good heat resistance to the constituent materials of the conductor. Please refer to the technology disclosed in the Chinese patent document entitled "A High-temperature Resistant Shielded Compensating Cable", with a publication number of CN201307443Y and a publication date of September 9, 2009. Although such addition of heat-resistant metal elements to the constituent materials of the conductor is beneficial to improving the heat resistance of the conductor and reducing the external protective structure layer, the softness and electrical conductivity of the formed conductor are not as good as those of the traditional copper conductor due to the hard texture and poor electrical conductivity of the heat-resistant metal elements. As a result, the laying convenience and signal transmission stability of the formed high-frequency cable in the working environment are poor, and the technical requirements of the working environment cannot be effectively met. Summary of the invention

[0005] The technical purpose of the present invention is to provide a high temperature resistant special high frequency soft cable and a preparation method thereof which is high temperature resistant, soft and has good transmission performance in view of the above-mentioned deficiencies in the prior art.

[0006] The technical solution adopted by the present invention is as follows: A high temperature resistant special high frequency flexible cable, comprising a conductor, an insulating layer, an inner shielding layer, an outer shielding layer and a sheath layer arranged in sequence from the inside to the outside; The conductor is a single-conductor structure or a multi-conductor twisted structure; the conductor is composed of a copper wire core and a chromium coating or a chromium alloy coating coated on the outside; The insulating layer is an extruded structure of a foamed modified polyimide material outside the conductor; The inner shielding layer is an overlapping and wrapped structure of a chrome-plated heat-resistant metal belt outside the insulating layer; The outer shielding layer is a braided structure of silver-plated nickel-silicon alloy wires outside the inner shielding layer.

[0007] The conductor wire in the above technical measures is composed of a copper wire core and a chromium coating or chromium alloy coating coated on the outside. The copper wire core with good flexibility is used as the substrate for reliable signal transmission. Under the premise of basically not affecting the flexibility of the conductor and the stability of signal transmission, the excellent temperature resistance of the chromium / chromium alloy coating is used to improve the high temperature resistance of the conductor; the insulating layer composed of the foamed modified polyimide material extruded on the outside of the conductor effectively ensures that the internal conductor has excellent electrical signal transmission stability and temperature resistance; the inner shielding layer structure with the chrome-plated alloy heat-resistant metal belt overlapping and wrapped on the outside of the insulating layer basically does not hinder the soft bending of the cable, and at the same time can enhance the impact mechanical strength and electromagnetic shielding capability of the cable inside, and has reliable high temperature resistance; the outer shielding layer structure woven with silver-plated nickel-silicon alloy wire on the outside of the inner shielding layer has excellent shielding effect, good high temperature resistance and softness, so as to reliably ensure the stability of electrical signal transmission of the internal conductor. Therefore, the high-frequency cable of the above structure has excellent electrical signal transmission stability, high temperature resistance, and soft bending properties with a compact structure, effectively meeting the technical requirements of aerospace working environments.

[0008] Furthermore, the sheath layer is composed of an inner sheath layer and an outer sheath layer. The inner sheath layer is an overlapping wrapped structure of a self-adhesive polyimide composite film outside the outer shielding layer, and the adhesive surface layer of the self-adhesive polyimide composite film faces outward; The outer sheath layer is a braided structure of at least one layer of graphite fiber filaments outside the inner sheath layer.

[0009] The above technical measures, by combining the inner sheath layer and the outer sheath layer in a specific way to form a sheath layer, can not only effectively isolate the influence of external high temperature on the cable and obtain excellent high temperature resistance, but also enable the cable to operate sustainably in a low-loss manner in the high frequency band, and can also obtain good radiation resistance and dielectric resistance. In addition, the composite structure of the aforementioned sheath layer has good integrity, good softness during the bending process of cable laying, and the outer sheath layer can maintain good stability outside the inner sheath layer without displacement.

[0010] Furthermore, the self-adhesive polyimide composite film of the inner sheath layer is a polyimide aluminum composite film; The self-adhesive polyimide composite film has a thickness of 0.045 mm to 0.076 mm and a width of 5 mm to 9 mm; The overlapping wrapping rate of the inner sheath layer is 48% to 50%.

[0011] The above technical measures can effectively isolate external heat and radiation and strengthen the protection of the inside of the cable; at the same time, they can form a reliable bond with the graphite fiber filaments constituting the outer sheath layer, and the composite has high integrity.

[0012] Furthermore, the diameter of the graphite fiber filaments of the outer sheath layer is 5um to 8um, and the graphite content is ≥99%; The braiding density of each layer of the outer sheath layer is ≥90%.

[0013] The above technical measures can effectively isolate external heat and make the cable have excellent environmental resistance. It can be used for a long time within the temperature range of 300°C and work normally for about 10 minutes at a temperature of 600°C.

[0014] Furthermore, the coating thickness on the outside of the wire is ≥2 um.

[0015] The above technical measures can achieve stable high temperature resistance by controlling the coating on the outside of the conductor without substantially hindering the function of the copper wire core.

[0016] Furthermore, the dielectric constant of the foamed modified polyimide material of the insulating layer is 1.45-1.48, and the foam density is 0.05 g / cm 3 , the foam particle size is 20um~30um.

[0017] Furthermore, the foamable modified polyimide material is composed of the following raw materials in the following weight ratio: 65 to 80 parts of polyimide resin, 10 to 20 parts of filler, 6 to 12 parts of modifier, 1 to 10 parts of promoter, 8 to 15 parts of foaming agent, and 10 to 20 parts of stabilizer; The filler is at least one of polyester amine salt powder, nano zinc oxide, and nano SIO2 particles; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins; The accelerator is a mixture of at least two of zinc powder, lead powder and nitroguanidine; The foaming agent is at least one of nano-silicon dioxide, azodicarbonamide, and polyhedral oligomeric silsesquioxane; The stabilizer is tetrahydrofuran.

[0018] The above technical measures can enable the polyimide which is difficult to extrude to obtain good extrusion performance, and effectively meet the technical requirements of extrusion molding as an insulating material on the outside of the conductor.

[0019] The insulating layer formed by the materials with the above technical measures has good electrical performance indicators. Its dielectric constant and dielectric loss are almost unaffected by temperature changes. It can provide reliable insulation performance for the internal conductor, and at the same time provide reliable protection for the high temperature resistance and transmission stability of the internal conductor, so that the cable can transmit signals normally at extremely high temperatures.

[0020] Furthermore, the chrome-plated alloy heat-resistant metal strip of the inner shielding layer is a chrome-plated alloy copper strip; The thickness of the chrome alloy copper strip is 0.05 mm to 0.07 mm, and the thickness of the chrome alloy coating is ≥ 3 um; The overlapping wrapping rate of the inner shielding layer is 44% to 46%.

[0021] The above technical measures can further strengthen the protection of the inside of the cable, while improving the cable's high temperature resistance and electromagnetic shielding capabilities.

[0022] Furthermore, the braiding density of the outer shielding layer is ≥90%.

[0023] The above technical measures can further improve the high temperature resistance and electromagnetic shielding capability of the cable, minimize signal attenuation, and ensure the transmission performance of the cable.

[0024] A method for preparing the above-mentioned high temperature resistant special high frequency flexible cable, the preparation method comprising the following process steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium coating or a chromium alloy coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare a foamable modified polyimide material for standby use; Step 2. Install the copper-based conductor that meets the design requirements in the extruder through a constant tension system, and extrude the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and a chrome-plated alloy heat-resistant metal strip that meets the design requirements is wrapped around the outside of the insulating structure in step 2 with an overlap rate of 44% to 46% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire that meets the design requirements is braided on the outside of the inner shielding structure in step 3 with a braiding density of ≥90% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and a self-adhesive polyimide composite film that meets the design requirements is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of 48% to 50% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is installed in a braiding machine, and the graphite fiber filaments that meet the design requirements are braided on the outside of the inner sheath structure in step 5 with a braiding density of ≥90% by the braiding machine to obtain an outer sheath structure.

[0025] The above technical measures can produce special cables that are resistant to high temperatures, have good transmission performance and good flexibility. The prepared special cables can be effectively applied to aerospace working environments, and can be used repeatedly for a long time in such working environments, safely and reliably.

[0026] One or more technical solutions provided by the present invention have at least the following technical effects or advantages: The conductor of the present invention is composed of a copper wire core and a chromium coating or a chromium alloy coating coated on the outside. The copper wire core with good flexibility is used as a substrate for reliable signal transmission. Under the premise of basically not affecting the flexibility of the conductor and the stability of signal transmission, the excellent temperature resistance of the chromium / chromium alloy coating is used to improve the high temperature resistance of the conductor; the insulating layer formed by extruding the foamed modified polyimide material on the outside of the conductor effectively ensures that the internal conductor has excellent electrical signal transmission stability and temperature resistance; the inner shielding layer structure with the chromium-plated alloy heat-resistant metal belt overlapping and wrapping on the outside of the insulating layer basically does not hinder the soft bending of the cable, and at the same time can enhance the impact resistance of the cable The mechanical strength and electromagnetic shielding ability of the cable are enhanced, and it has reliable high temperature resistance; the outer shielding layer structure woven with silver-plated nickel-silicon alloy wire on the outside of the inner shielding layer has an excellent shielding effect, and good high temperature resistance and flexibility, thereby reliably ensuring the stability of the electrical signal transmission of the internal conductor. Therefore, the high-frequency cable of the above structure has excellent electrical signal transmission stability, high temperature resistance, and soft bending properties with a compact structure, effectively meeting the technical requirements of aerospace working environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of the present invention, and do not constitute a limitation on the embodiments of the present invention; Figure 1 It is a structural schematic diagram of the high temperature resistant special high frequency soft cable in the present invention; Figure 2 It is a cross-sectional schematic diagram of the high temperature resistant special high frequency flexible cable in the present invention; Among them, 1-conductor; 2-insulating layer; 3-inner shielding layer; 4-outer shielding layer; 5-inner sheath layer; 6-outer sheath layer. DETAILED DESCRIPTION

[0028] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those within the scope of this description. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below. Example

[0030] Reference Figure 1 and Figure 2 This embodiment provides a high temperature resistant special high frequency flexible cable, comprising a conductor 1, an insulating layer 2, an inner shielding layer 3, an outer shielding layer 4 and a sheath layer arranged in sequence from the inside to the outside.

[0031] The conductor 1 is a single-conductor structure. The conductor 1 is composed of a copper wire core and a chromium coating on the outside. The coating thickness on the outside of the conductor is about 2 um.

[0032] The insulating layer 2 is an extruded structure of a foamed modified polyimide material on the outside of the conductor 1. The dielectric constant of the foamed modified polyimide material is about 1.45 and the foam density is about 0.05g / cm 3 , the foam particle size is about 20um.

[0033] The inner shielding layer 3 is an overlapping and wrapped structure of a chrome-plated heat-resistant alloy metal belt outside the insulating layer 2; The chrome-plated alloy heat-resistant metal strip of the inner shielding layer 3 is a chrome-plated alloy copper strip; The thickness of the chrome-plated copper strip is about 0.05 mm, and the thickness of the chrome-plated layer is about 3 um; The overlapping wrapping ratio of the inner shielding layer 3 is about 44%.

[0034] The outer shielding layer 4 is a braided structure of silver-plated nickel-silicon alloy wires outside the inner shielding layer 3; The braiding density of the outer shielding layer 4 is about 90%.

[0035] The sheath layer is composed of an inner sheath layer 5 and an outer sheath layer 6.

[0036] The inner sheath layer 5 is an overlapping wrapped structure of a self-adhesive polyimide composite film outside the outer shielding layer 4, and the adhesive surface layer of the self-adhesive polyimide composite film faces outwards; The self-adhesive polyimide composite film of the inner sheath layer 5 is a polyimide aluminum composite film, and is coated with high temperature resistant insulating glue on one side; The thickness of the self-adhesive polyimide composite film is about 0.045 mm and the width is about 5 mm; The overlapping wrapping ratio of the inner sheath layer 5 is about 48%.

[0037] The outer sheath layer 6 is a woven structure of graphite fiber filaments outside the inner sheath layer 5; The diameter of the graphite fiber filaments of the outer sheath layer 6 is about 5um and the graphite content is about 99%; The braiding density of each layer of the outer sheath layer 6 is about 90%.

[0038] The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 65 parts of polyimide resin, 10 parts of filler, 6 parts of modifier, 1 part of accelerator, 8 parts of foaming agent, and 10 parts of stabilizer; Wherein, the filler is polyester amine salt powder; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins, with a mixing ratio of 1:0.8; The accelerator is a mixture of zinc powder and lead powder in a ratio of 1:0.9; The foaming agent is nano silicon dioxide; The stabilizer is tetrahydrofuran, which can provide reliable stabilization performance for the foaming structure.

[0039] The foamable modified polyimide material in this embodiment is obtained by the following preparation method: Step 1. Put the polyimide resin and filler in the above formula into a reaction kettle and mix them at a temperature of about 351°C for about 2 hours; Step 2. Put the mixture of step 1 into a stirrer, stir at a speed of about 100 r / min for about 60 min, and stir evenly to obtain a mixed colloid; Step 3. Put the mixed colloid in step 2 into a reactor, add the above-mentioned formula amount of modifier into the reactor, and perform low-temperature modification at a temperature of about -5°C to obtain a low-temperature modified polyimide resin; Step 4. Put the low-temperature modified polyimide resin of step 3 into an internal mixer, and mix it at a temperature of about 380° C. for about 40 minutes to obtain a high-temperature modified polyimide resin; Step 5. Place the high temperature modified polyimide resin of step 4 into a reaction kettle, add the above formula amount of accelerator into the reaction kettle, and promote the reaction for about 120 minutes; Step 6. Add the foaming agent and stabilizer in the above formula into the reactor in step 5, and perform a mixing and foaming reaction at a temperature of about 380° C.; After being mixed evenly, the mixture was allowed to stand for about 3.5 hours to obtain a modified polyimide with a porous structure; Step 7. Drying the foamed polyimide in step 6 at a temperature of about 150° C. for about 6 hours; The dried foamed modified polyimide plastic is extruded at high temperature by a screw extruder and the material is cut into particles by a particle cutter to obtain a foamed modified polyimide material.

[0040] The high temperature resistant special high frequency flexible cable in this embodiment is obtained by the preparation method according to the following steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare a foamable modified polyimide material for standby use; Step 2. inserting the copper-based conductor into the extruder through the constant tension system, and extruding the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and the chrome-plated alloy heat-resistant copper tape is wrapped around the outside of the insulating structure in step 2 with an overlap rate of about 44% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire is braided on the outside of the inner shielding structure in step 3 at a braiding density of about 90% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and the self-adhesive polyimide composite film is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of about 48% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is put into a braiding machine, and the graphite fiber filaments are braided on the outside of the inner sheath structure in step 5 at a braiding density of about 90% by the braiding machine to obtain an outer sheath structure. Example

[0041] This embodiment provides a high-temperature resistant special high-frequency flexible cable, including a conductor, an insulating layer, an inner shielding layer, an outer shielding layer and a sheath layer arranged in sequence from the inside to the outside.

[0042] The conductor is a multi-wire twisted structure. The wires constituting the conductor are composed of a copper wire core and a chromium alloy coating coated on the outside. The coating thickness on the outside of the wire is about 3um.

[0043] The insulating layer is a foamed modified polyimide material extruded outside the conductor. The dielectric constant of the foamed modified polyimide material is about 1.48 and the foam density is about 0.05g / cm 3 , the foam particle size is about 30um.

[0044] The inner shielding layer is an overlapping wrapping structure of a chrome-plated heat-resistant alloy metal belt outside the insulating layer; The chrome-plated alloy heat-resistant metal strip of the inner shielding layer is a chrome-plated alloy copper strip; The thickness of the chrome-plated copper strip is about 0.07 mm, and the thickness of the chrome-plated layer is about 4 μm. The overlapping coverage of the inner shielding layer is about 46%.

[0045] The outer shielding layer is a braided structure of silver-plated nickel-silicon alloy wire outside the inner shielding layer; The braiding density of the outer shield is approximately 91%.

[0046] The sheath layer is composed of an inner sheath layer and an outer sheath layer.

[0047] The inner sheath layer is an overlapping wrapped structure of a self-adhesive polyimide composite film outside the outer shielding layer, and the adhesive surface layer of the self-adhesive polyimide composite film faces outwards; The self-adhesive polyimide composite film of the inner sheath layer is a polyimide aluminum composite film; The thickness of the self-adhesive polyimide composite film is about 0.076 mm and the width is about 9 mm; The overlapping rate of the inner sheath layer is about 50%.

[0048] The outer sheath layer is a two-layer braided structure with graphite fiber filaments outside the inner sheath layer; The diameter of the graphite fiber filaments in the outer sheath layer is about 8um, and the graphite content is about 99.2%; The braiding density of each layer of the outer sheath layer is about 92%.

[0049] The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 80 parts of polyimide resin, 20 parts of filler, 12 parts of modifier, 10 parts of promoter, 15 parts of foaming agent, and 20 parts of stabilizer; Wherein, the filler is nano zinc oxide; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins in a mixing ratio of 1:0.9; The accelerator is a mixture of zinc powder and nitroguanidine in a 1:1 ratio; The blowing agent is azodicarbonamide; The stabilizer is tetrahydrofuran.

[0050] The foamable modified polyimide material in this embodiment is obtained by the following preparation method: Step 1. Put the polyimide resin and filler in the above formula into a reaction kettle and mix them at a temperature of about 355°C for about 3 hours; Step 2. Put the mixture of step 1 into a stirrer, stir at a speed of about 300 r / min for about 30 minutes, and stir evenly to obtain a mixed colloid; Step 3. Put the mixed colloid in step 2 into a reactor, add the above-mentioned formula amount of modifier into the reactor, and perform low-temperature modification at a temperature of about -15°C to obtain a low-temperature modified polyimide resin; Step 4. Put the low-temperature modified polyimide resin of step 3 into an internal mixer, and mix it at a temperature of about 430° C. for about 30 minutes to obtain a high-temperature modified polyimide resin; Step 5. Place the high temperature modified polyimide resin of step 4 into a reaction kettle, add the above formula amount of accelerator into the reaction kettle, and promote the reaction for about 180 minutes; Step 6. Add the foaming agent and stabilizer in the above formula into the reactor in step 5, and perform a mixing and foaming reaction at a temperature of about 430° C.; After being mixed evenly, the mixture was allowed to stand for about 4 hours to obtain a modified polyimide with a porous structure; Step 7. Drying the foamed polyimide in step 6 at a temperature of about 200° C. for about 4 hours; The dried foamed modified polyimide plastic is extruded at high temperature by a screw extruder and the material is cut into particles by a particle cutter to obtain a foamed modified polyimide material.

[0051] The high temperature resistant special high frequency flexible cable in this embodiment is obtained by the preparation method according to the following steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium alloy coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare a foamable modified polyimide material for standby use; Step 2. inserting the copper-based conductor into the extruder through the constant tension system, and extruding the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and the chrome-plated alloy copper tape is wrapped around the outside of the insulating structure in step 2 with an overlap rate of about 46% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire is braided on the outside of the inner shielding structure in step 3 at a braiding density of about 91% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and the self-adhesive polyimide composite film is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of about 50% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is put into a braiding machine, and the graphite fiber filaments are braided on the outside of the inner sheath structure in step 5 at a braiding density of about 92% by the braiding machine to obtain an outer sheath structure. Example

[0052] This embodiment provides a high-temperature resistant special high-frequency flexible cable, including a conductor, an insulating layer, an inner shielding layer, an outer shielding layer and a sheath layer arranged in sequence from the inside to the outside.

[0053] The conductor is a single-wire structure. The wire constituting the conductor is composed of a copper wire core and a chromium alloy coating coated on the outside. The coating thickness on the outside of the wire is about 2.5um.

[0054] The insulating layer is an extruded structure of a foamed modified polyimide material on the outside of the conductor. The dielectric constant of the foamed modified polyimide material is about 1.46 and the foam density is about 0.05g / cm 3 , the foam particle size is about 21um.

[0055] The inner shielding layer is an overlapping wrapping structure of a chrome-plated heat-resistant alloy metal belt outside the insulating layer; The chrome-plated alloy heat-resistant metal strip of the inner shielding layer is a chrome-plated alloy copper strip; The thickness of the chrome-plated copper strip is about 0.06 mm, and the thickness of the chrome-plated layer is about 3.2 um; The overlapping coverage of the inner shielding layer is about 45%.

[0056] The outer shielding layer is a braided structure of silver-plated nickel-silicon alloy wire outside the inner shielding layer; The braid density of the outer shield is approximately 95%.

[0057] The sheath layer is composed of an inner sheath layer and an outer sheath layer.

[0058] The inner sheath layer is an overlapping wrapped structure of a self-adhesive polyimide composite film outside the outer shielding layer, and the adhesive surface layer of the self-adhesive polyimide composite film faces outwards; The self-adhesive polyimide composite film of the inner sheath layer is a polyimide aluminum composite film; The thickness of the self-adhesive polyimide composite film is about 0.056 mm and the width is about 6 mm; The overlapping rate of the inner sheath layer is about 49%.

[0059] The outer sheath layer is a woven structure of graphite fiber filaments outside the inner sheath layer; The diameter of the graphite fiber filaments in the outer sheath layer is about 6um, and the graphite content is about 99.3%; The braiding density of each layer of the outer sheath layer is about 93%.

[0060] The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 70 parts of polyimide resin, 15 parts of filler, 8 parts of modifier, 5 parts of promoter, 10 parts of foaming agent, and 15 parts of stabilizer; Wherein, the filler is nano-SIO2 particles; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins in a mixing ratio of 1:1.2; The accelerator is a mixture of lead powder and nitroguanidine in a ratio of 1:1.1; The blowing agent is polyhedral oligomeric silsesquioxane; The stabilizer is tetrahydrofuran.

[0061] The foamable modified polyimide material in this embodiment is obtained by the following preparation method: Step 1. Put the polyimide resin and filler in the above formula into a reaction kettle, and mix them at a temperature of about 360° C. for about 2.5 hours; Step 2. Put the mixture of step 1 into a stirrer, stir at a speed of about 150 r / min for about 40 minutes, and stir evenly to obtain a mixed colloid; Step 3. Put the mixed colloid in step 2 into a reactor, add the above-mentioned formula amount of modifier into the reactor, and perform low-temperature modification at a temperature of about -10°C to obtain a low-temperature modified polyimide resin; Step 4. Put the low-temperature modified polyimide resin of step 3 into an internal mixer, and mix it at a temperature of about 390° C. for about 35 minutes to obtain a high-temperature modified polyimide resin; Step 5. Place the high temperature modified polyimide resin of step 4 into a reaction kettle, add the above formula amount of accelerator into the reaction kettle, and promote the reaction for about 150 minutes; Step 6. Add the foaming agent and stabilizer in the above formula into the reactor in step 5, and perform a mixing and foaming reaction at a temperature of about 390° C.; After being mixed evenly, the mixture was allowed to stand for about 3.6 hours to obtain a modified polyimide with a porous structure; Step 7. Drying the foamed polyimide in step 6 at a temperature of about 160° C. for about 5 hours; The dried foamed modified polyimide plastic is extruded at high temperature by a screw extruder and the material is cut into particles by a particle cutter to obtain a foamed modified polyimide material.

[0062] The high temperature resistant special high frequency flexible cable in this embodiment is obtained by the preparation method according to the following steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium alloy coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare a foamable modified polyimide material for standby use; Step 2. inserting the copper-based conductor into the extruder through the constant tension system, and extruding the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and the chrome-plated alloy copper tape is wrapped around the outside of the insulating structure in step 2 with an overlap rate of about 45% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire is braided on the outside of the inner shielding structure in step 3 at a braiding density of about 95% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and the self-adhesive polyimide composite film is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of about 49% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is put into a braiding machine, and the graphite fiber filaments are braided on the outside of the inner sheath structure in step 5 at a braiding density of about 93% by the braiding machine to obtain an outer sheath structure. Example

[0063] This embodiment provides a high-temperature resistant special high-frequency flexible cable, including a conductor, an insulating layer, an inner shielding layer, an outer shielding layer and a sheath layer arranged in sequence from the inside to the outside.

[0064] The conductor is a multi-conductor twisted structure. The conductor consists of a copper wire core and a chromium coating on the outside. The coating thickness on the outside of the conductor is about 3.5um.

[0065] The insulating layer is a foamed modified polyimide material extruded outside the conductor. The dielectric constant of the foamed modified polyimide material is about 1.47 and the foam density is about 0.05g / cm 3 , the foam particle size is about 23um.

[0066] The inner shielding layer is an overlapping wrapping structure of a chrome-plated heat-resistant alloy metal belt outside the insulating layer; The chrome-plated alloy heat-resistant metal strip of the inner shielding layer is a chrome-plated alloy copper strip; The thickness of the chrome-plated copper strip is about 0.055 mm, and the thickness of the chrome-plated layer is about 4.2 um; The overlapping coverage rate of the inner shielding layer is about 44.5%.

[0067] The outer shielding layer is a braided structure of silver-plated nickel-silicon alloy wire outside the inner shielding layer; The braiding density of the outer shield is approximately 97%.

[0068] The sheath layer is composed of an inner sheath layer and an outer sheath layer.

[0069] The inner sheath layer is an overlapping wrapped structure of a self-adhesive polyimide composite film outside the outer shielding layer, and the adhesive surface layer of the self-adhesive polyimide composite film faces outwards; The self-adhesive polyimide composite film of the inner sheath layer is a polyimide aluminum composite film; The thickness of the self-adhesive polyimide composite film is about 0.062 mm and the width is about 7 mm; The overlapping wrapping rate of the inner sheath layer is about 48.5%.

[0070] The outer sheath layer is a two-layer braided structure in which graphite fiber filaments are outside the inner sheath layer.

[0071] The diameter of the graphite fiber filaments in the outer sheath layer is about 7um, and the graphite content is about 99.6%; The braiding density of each layer of the outer sheath layer is about 94%.

[0072] The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 75 parts of polyimide resin, 13 parts of filler, 9 parts of modifier, 4 parts of accelerator, 12 parts of foaming agent, and 16 parts of stabilizer; The filler is a mixture of polyester amine salt powder and nano zinc oxide, with a mixing ratio of 1:0.8; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins in a mixing ratio of 1:0.9; The accelerator is a mixture of zinc powder, lead powder and nitroguanidine in a ratio of 1:0.5:0.8; The foaming agent is a mixture of nano-silicon dioxide and azodicarbonamide, with a mixing ratio of 1:1; The stabilizer is tetrahydrofuran.

[0073] The foamable modified polyimide material in this embodiment is obtained by the following preparation method: Step 1. Put the polyimide resin and filler in the above formula into a reaction kettle, and mix them at a temperature of about 370° C. for about 2.2 hours; Step 2. Put the mixture of step 1 into a stirrer, stir at a speed of about 130 r / min for about 45 minutes, and stir evenly to obtain a mixed colloid; Step 3. Put the mixed colloid in step 2 into a reactor, add the above-mentioned formula amount of modifier into the reactor, and perform low-temperature modification at a temperature of about -9°C to obtain a low-temperature modified polyimide resin; Step 4. Put the low-temperature modified polyimide resin of step 3 into an internal mixer, and internally mix at a temperature of about 410° C. for about 36 minutes to obtain a high-temperature modified polyimide resin; Step 5. Place the high temperature modified polyimide resin of step 4 into a reaction kettle, add the above formula amount of accelerator into the reaction kettle, and promote the reaction for about 145 minutes; Step 6. Add the foaming agent and stabilizer in the above formula into the reactor in step 5, and perform a mixing and foaming reaction at a temperature of about 395° C.; After being mixed evenly, the mixture was allowed to stand for about 3.2 hours to obtain a modified polyimide with a porous structure; Step 7. Drying the foamed polyimide in step 6 at a temperature of about 185° C. for about 5.2 hours; The dried foamed modified polyimide plastic is extruded at high temperature by a screw extruder and the material is cut into particles by a particle cutter to obtain a foamed modified polyimide material.

[0074] The high temperature resistant special high frequency flexible cable in this embodiment is obtained by the preparation method according to the following steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare the above-mentioned foamable modified polyimide material for standby use; Step 2. inserting the copper-based conductor into the extruder through the constant tension system, and extruding the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and the chrome-plated alloy copper tape is wrapped around the outside of the insulating structure in step 2 with an overlap rate of about 44.5% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire is braided on the outside of the inner shielding structure in step 3 at a braiding density of about 97% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and the self-adhesive polyimide composite film is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of about 48.5% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is put into a braiding machine, and the graphite fiber filaments are braided on the outside of the inner sheath structure in step 5 at a braiding density of about 94% by the braiding machine to obtain an outer sheath structure. Example

[0075] The other contents of this embodiment are the same as those of Embodiment 1, except that: The dielectric constant of the foamed modified polyimide material of the insulation layer is about 1.455 and the foam density is about 0.05g / cm 3 , the foam particle size is about 24um; The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 66 parts of polyimide resin, 11 parts of filler, 7 parts of modifier, 3 parts of promoter, 11 parts of foaming agent, and 12 parts of stabilizer; The filler is a mixture of polyester amine salt powder and nano-SIO2 particles, with a mixing ratio of 1:1.2; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins in a mixing ratio of 1:0.9; The accelerator is a mixture of zinc powder, lead powder and nitroguanidine in a ratio of 1:0.5:0.8; The foaming agent is a mixture of nano-silica and polyhedral oligomeric silsesquioxane, with a mixing ratio of 1:1; The stabilizer is tetrahydrofuran. Example

[0076] The other contents of this embodiment are the same as those of Embodiment 1, except that: The dielectric constant of the foamed modified polyimide material of the insulation layer is about 1.456 and the foam density is about 0.05g / cm 3 , the foam particle size is about 25um; The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 75 parts of polyimide resin, 18 parts of filler, 9 parts of modifier, 7 parts of promoter, 13 parts of foaming agent, and 15 parts of stabilizer; The filler is a mixture of nano zinc oxide and nano SIO2 particles, with a mixing ratio of 1:0.9; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins in a mixing ratio of 1:1.1; The accelerator is a mixture of zinc powder, lead powder and nitroguanidine in a ratio of 1:0.5:0.8; The foaming agent is a mixture of azodicarbonamide and polyhedral oligomeric silsesquioxane, with a mixing ratio of 1:1.2; The stabilizer is tetrahydrofuran. Example

[0077] The other contents of this embodiment are the same as those of Embodiment 1, except that: The dielectric constant of the foamed modified polyimide material of the insulation layer is about 1.457 and the foam density is about 0.05g / cm 3 , the foam particle size is about 26um; The above-mentioned foamable modified polyimide material in this embodiment is composed of the following raw materials in the following weight ratio: 76 parts of polyimide resin, 19 parts of filler, 7 parts of modifier, 8 parts of promoter, 11 parts of foaming agent, and 16 parts of stabilizer; The filler is a mixture of polyester amine salt powder, nano zinc oxide and nano SIO2 particles, with a mixing ratio of 1:0.5:0.8; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins, with a mixing ratio of 1:0.8; The accelerator is a mixture of zinc powder, lead powder and nitroguanidine in a ratio of 1:0.5:0.8; The foaming agent is a mixture of nano-silicon dioxide, azodicarbonamide and polyhedral oligomeric silsesquioxane, with a mixing ratio of 1:0.8:0.5; The stabilizer is tetrahydrofuran.

[0078] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0079] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A high temperature resistant special high frequency flexible cable, comprising a conductor (1), an insulating layer (2), an inner shielding layer (3), an outer shielding layer (4) and a sheath layer arranged in sequence from the inside to the outside; Features: The conductor (1) is a single-conductor structure or a multi-conductor twisted structure; the conductor (1) is composed of a copper wire core and a chromium coating or a chromium alloy coating coated on the outside; The insulating layer (2) is an extruded structure of a foamed modified polyimide material on the outside of the conductor (1); The inner shielding layer (3) is a structure in which a chrome-plated heat-resistant alloy metal strip is wrapped around the outside of the insulating layer (2) in an overlapping manner; The outer shielding layer (4) is a braided structure of silver-plated nickel-silicon alloy wires outside the inner shielding layer (3).

2. The high temperature resistant special high frequency flexible cable according to claim 1, characterized in that: The sheath layer is composed of an inner sheath layer (5) and an outer sheath layer (6); The inner sheath layer (5) is a self-adhesive polyimide composite film that is wrapped around the outer shielding layer (4) in an overlapping manner, and the adhesive surface layer of the self-adhesive polyimide composite film faces outwards; The outer sheath layer (6) is a braided structure of at least one layer of graphite fiber filaments outside the inner sheath layer (5).

3. The high temperature resistant special high frequency flexible cable according to claim 2, characterized in that: The self-adhesive polyimide composite film of the inner sheath layer (5) is a polyimide aluminum composite film; The self-adhesive polyimide composite film has a thickness of 0.045 mm to 0.076 mm and a width of 5 mm to 9 mm; The overlapping wrapping rate of the inner sheath layer (5) is 48% to 50%.

4. The high temperature resistant special high frequency flexible cable according to claim 2, characterized in that: The graphite fiber filaments of the outer sheath layer (6) have a diameter of 5 um to 8 um and a graphite content of ≥ 99%; The braiding density of each layer of the outer sheath layer (6) is ≥90%.

5. The high temperature resistant special high frequency flexible cable according to claim 1, characterized in that: The coating thickness on the outside of the wire is ≥2um.

6. The high temperature resistant special high frequency flexible cable according to claim 1, characterized in that: The dielectric constant of the foamed modified polyimide material of the insulating layer (2) is 1.45 to 1.48, and the foam density is 0.05 g / cm 3 , the foam particle size is 20um~30um.

7. The high temperature resistant special high frequency flexible cable according to claim 1 or 6, characterized in that: The foamable modified polyimide material is composed of the following raw materials in the following weight ratio: 65 to 80 parts of polyimide resin, 10 to 20 parts of filler, 6 to 12 parts of modifier, 1 to 10 parts of promoter, 8 to 15 parts of foaming agent, and 10 to 20 parts of stabilizer; The filler is at least one of polyester amine salt powder, nano zinc oxide, and nano SIO2 particles; The modifier is a mixture of methacrylic acid-based and epoxy-based acrylic resins; The accelerator is a mixture of at least two of zinc powder, lead powder and nitroguanidine; The foaming agent is at least one of nano-silicon dioxide, azodicarbonamide, and polyhedral oligomeric silsesquioxane; The stabilizer is tetrahydrofuran.

8. The high temperature resistant special high frequency flexible cable according to claim 1, characterized in that: The chrome-plated alloy heat-resistant metal strip of the inner shielding layer (3) is a chrome-plated alloy copper strip; The thickness of the chrome alloy copper strip is 0.05 mm to 0.07 mm, and the thickness of the chrome alloy coating is ≥ 3 um; The overlapping wrapping rate of the inner shielding layer (3) is 44% to 46%.

9. The high temperature resistant special high frequency flexible cable according to claim 1, characterized in that: The braiding density of the outer shielding layer (4) is ≥90%.

10. A method for preparing the high temperature resistant special high frequency flexible cable according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following process steps: Step 1. According to the design transmission requirements, select a copper wire core of corresponding diameter, plate a chromium coating or a chromium alloy coating on the copper wire core to obtain a copper-based conductor for standby use; Prepare a foamable modified polyimide material for standby use; Step 2. Install the copper-based conductor that meets the design requirements in the extruder through a constant tension system, and extrude the foamed modified polyimide material onto the outside of the copper-based conductor through the extruder to obtain an insulating structure; Step 3. The insulating structure obtained in step 2 is installed in a constant tension wrapping machine, and a chrome-plated alloy heat-resistant metal strip that meets the design requirements is wrapped around the outside of the insulating structure in step 2 with an overlap rate of 44% to 46% by the wrapping machine to obtain an inner shielding structure; Step 4. The inner shielding structure obtained in step 3 is installed in a braiding machine, and the silver-plated nickel-silicon alloy wire that meets the design requirements is braided on the outside of the inner shielding structure in step 3 with a braiding density of ≥90% by the braiding machine to obtain an outer shielding structure; Step 5. The outer shielding structure obtained in step 4 is installed in a constant tension wrapping machine, and a self-adhesive polyimide composite film that meets the design requirements is wrapped around the outer surface of the outer shielding structure in step 4 with the adhesive surface layer facing outward and an overlap rate of 48% to 50% by the wrapping machine to obtain an inner sheath structure; Step 6. The inner sheath structure obtained in step 5 is installed in a braiding machine, and the graphite fiber filaments that meet the design requirements are braided on the outside of the inner sheath structure in step 5 with a braiding density of ≥90% by the braiding machine to obtain an outer sheath structure.

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