JP2019175678A - Differential signal transmission cable, multicore cable, and method for manufacturing differential signal transmission cable - Google Patents

Abstract

To provide: a differential signal transmission cable capable of suppressing the amount of differential in-phase conversion and sack out; a multicore cable; and a method for manufacturing the differential signal transmission cable.SOLUTION: The differential signal transmission cable comprises: a pair of signal wires; an insulator layer covering the peripheries of the signal wires; a plating layer covering the insulator layer; and a metal foil tape wound around the outer peripheral surface of the plating layer and electrically connected with the plating layer. The method for manufacturing the differential signal transmission cable comprises: covering the peripheries of the pair of signal wires with the insulator layer; covering the outer peripheral surface of the insulator layer with the plating layer and winding the metal foil tape around the outer peripheral surface of the plating layer.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a differential signal transmission cable, a multicore cable, and a method for manufacturing a differential signal transmission cable.

  Conventionally, a differential signal transmission cable is used for signal transmission between electronic devices or signal transmission between substrates in an electronic device. Examples of electronic devices include servers, routers, and storage products that handle high-speed signals of several Gbps or more. The differential signal transmission cable includes a pair of signal lines (see Patent Document 1).

  Using the differential signal transmission cable, signal transmission using a differential signal can be performed on the receiving side. In signal transmission using differential signals, signals having opposite phases are input to a pair of signal lines provided in the differential signal transmission cable. The receiving side obtains an output by synthesizing the difference between the signals having opposite phases.

JP 2002-289047 A

  A conventional differential signal transmission cable includes an insulator layer covering the periphery of each signal line, and a metal foil tape wound around the outer peripheral surface of the insulator layer in a spiral shape. Due to the looseness of the metal foil tape, a gap may be generated between the outer peripheral surface of the insulator layer and the metal foil tape. When this gap is generated, there is a difference in propagation time between the pair of signal lines. This phenomenon is called inward skew. When the inward skew occurs, the differential component of the signal transmitted through the pair of signal lines is converted into the in-phase component, so that the output waveform obtained on the receiving side is significantly degraded.

  In addition, the metal foil tape wound in a spiral shape has a periodic structure in which the winding pitch of the metal foil tape is a period. Therefore, a minute suckout due to the periodic structure occurs.

  An object of one aspect of the present disclosure is to provide a differential signal transmission cable, a multicore cable, and a method for manufacturing a differential signal transmission cable that can suppress a differential common-mode conversion amount and suckout.

  One aspect of the present disclosure includes a pair of signal lines, an insulator layer that covers the periphery of the signal line, a plating layer that covers the insulator layer, and an outer peripheral surface of the plating layer, and the plating layer And a metal foil tape electrically connected to the differential signal transmission cable.

According to the differential signal transmission cable which is one aspect of the present disclosure, the differential common-mode conversion amount and the suckout can be reduced.
Another aspect of the present disclosure includes a plurality of differential signal transmission cables, a conductor layer that collectively covers the plurality of differential signal transmission cables, and a jacket that covers the conductor layer. Each of the plurality of differential signal transmission cables is a multi-core cable, and is configured by a differential signal transmission cable that is one aspect of the present disclosure and an outer insulating layer that covers the metal foil tape. This is a multicore cable.

According to the multicore cable which is another aspect of the present disclosure, it is possible to reduce the differential common-mode conversion amount and the suckout.
Another aspect of the present disclosure is a method for manufacturing a differential signal transmission cable, in which a pair of signal lines are covered with an insulator layer, and an outer peripheral surface of the insulator layer is covered with a plating layer, This is a method for manufacturing a differential signal transmission cable in which a metal foil tape is wound around the outer peripheral surface of a plating layer.

  According to the method for manufacturing a differential signal transmission cable according to another aspect of the present disclosure, a differential signal transmission cable with a small differential in-phase conversion amount and a suck-out can be manufactured.

1 is a perspective view illustrating a configuration of a differential signal transmission cable 1. FIG. FIG. 2A is an electron micrograph showing the result of the adhesion test in the comparative example, and FIG. 2B is an electron micrograph showing the result of the adhesion test in the example. FIG. 3A is an electron micrograph showing the surface state of the copper plating layer formed in the first comparative example, and FIG. 3B is an electron micrograph showing the surface state of the copper plating layer formed in the second comparative example. FIG. 3C is an electron micrograph showing the surface state of the copper plating layer formed after dry ice blasting and corona discharge exposure. It is a graph which shows the correlation with arithmetic mean roughness Ra of a polyethylene substrate after performing a specific surface modification process, and a contact angle. It is a graph which shows the correlation with arithmetic mean roughness Ra of the polyethylene substrate after performing a specific surface modification process, and adhesion wet surface free energy. It is an electron micrograph showing the recessed part formed in the outer peripheral surface of an insulator layer by the dry ice blast process. It is an X-ray-diffraction pattern in the sample of an insulator layer. It is an X-ray-diffraction pattern in the sample of an insulator layer. FIG. 9A is a graph showing the correlation between the crystallinity _Xc of the polyethylene substrate after the specific surface modification treatment and the contact angle, and FIG. 9B shows the crystal of the perfluoroethylene propene copolymer substrate after the specific surface modification treatment. It is a graph showing the correlation between the degree of conversion _Xc and the contact angle. It is an X-ray-diffraction pattern in the sample of an insulator layer. It is an X-ray-diffraction pattern in the sample of an insulator layer. It is a graph showing the correlation between the contact angle after the particular surface modification process (100) crystalline orientation degree O _100. FIG. 13A is a graph showing the correlation between the crystallite size D and the contact angle in the crystalline component of polyethylene after the specific surface modification treatment, and FIG. 13B shows the crystals of perfluoroethylene propene copolymer after the specific surface modification treatment. It is a graph showing the correlation with the crystallite size D in a component, and a contact angle. 2 is an explanatory diagram illustrating a configuration of a manufacturing system 101. FIG. 2 is an explanatory diagram illustrating a configuration of a manufacturing system 201. FIG. FIG. 5 is an explanatory diagram illustrating a configuration of a surface modification unit 203. It is explanatory drawing showing the other structure of the surface modification unit 203. FIG. It is explanatory drawing showing the other structure of the surface modification unit 203. FIG. 3 is a cross-sectional view illustrating a configuration of a multicore cable 301. FIG. 3 is a cross-sectional view illustrating a configuration of a differential signal transmission cable 302 included in a multicore cable 301. FIG. It is a graph showing the differential common-mode conversion amount of the differential signal transmission cable 1 and the comparative example. It is a graph showing the transmission loss of the cable 1 for differential signal transmission, and a comparative example. It is a graph showing the relationship between arithmetic mean roughness Ra and transmission loss Sdd21. It is explanatory drawing showing the structure of the cable 1 for differential signal transmission provided with the metal foil tape 9. FIG. It is a perspective view showing the structure of the cable 1 for differential signal transmission provided with the metal foil tape 9 and the insulation tape 11 for press winding. It is explanatory drawing showing the structure of the cable 1 for differential signal transmission provided with the metal foil tape 9, and the plating layer 7 having the crack 13. FIG.

Exemplary embodiments of the present disclosure will be described with reference to the drawings.
1. Differential Signal Transmission Cable (1-1) Basic Configuration of Differential Signal Transmission Cable A differential signal transmission cable according to the present disclosure includes a pair of signal lines and an insulator layer covering the periphery of the signal lines And a plating layer that covers the insulator layer.

  The differential signal transmission cable of the present disclosure has, for example, the configuration illustrated in FIG. As shown in FIG. 1, the differential signal transmission cable 1 includes a pair of signal lines 3, an insulator layer 5, and a plating layer 7. The insulator layer 5 covers the periphery of the signal line 3. In the example shown in FIG. 1, the insulator layer 5 covers a pair of signal lines 3 in a lump. The signal line 3 is composed of, for example, a strand. For example, the signal line 3 may be a stranded wire formed by twisting a plurality of strands. In the case of a stranded wire, the flexibility of the signal line 3 is improved.

  The differential signal transmission cable 1 according to the present disclosure may further include a metal foil tape 9 in addition to the pair of signal lines 3, the insulator layer 5, and the plating layer 7, for example, as illustrated in FIG. 24. Good. The metal foil tape 9 is wound around the outer peripheral surface of the plating layer 7. The plating layer 7 and the metal foil tape 9 are electrically connected. Since the plating layer 7 and the metal foil tape 9 are electrically connected, suck-out can be suppressed. The plating layer 7 and the metal foil tape 9 each function as a shield layer. As a method of winding the metal foil tape 9, for example, there is a method of winding in a spiral shape as shown in FIG.

  The differential signal transmission cable according to the present disclosure preferably has a maximum differential common-mode conversion amount of −26 dB or less in a frequency band of 50 GHz or less. The differential in-phase conversion amount is measured before winding the differential signal transmission cable around a drum or the like. In the differential signal transmission cable according to the present disclosure, a gap is hardly generated between the plating layer and the insulator layer. Therefore, the differential signal transmission cable of the present disclosure can suppress the differential common-mode conversion amount.

  The differential signal transmission cable of the present disclosure can be used, for example, for signal transmission between electronic devices or signal transmission between substrates in the electronic device. Examples of electronic devices include servers, routers, and storage products that handle high-speed signals of several Gbps or more. Moreover, the differential signal transmission cable of the present disclosure can be used as an acoustic cable, for example. The differential signal transmission cable of the present disclosure is, for example, a cable that transmits a high-speed signal of 25 GHz or more.

(1-2) Insulator layer The insulator layer preferably covers a pair of signal lines in a lump. Covering collectively means that both of a pair of signal lines are covered by an integral insulating layer. When the insulator layer covers a pair of signal lines at once, there is no gap between the insulator layers as in the case of covering each signal line. Therefore, variation in the dielectric constant in the longitudinal direction of the differential signal transmission cable can be suppressed. As a result, the differential common-mode conversion amount can be further suppressed.

  Further, when the insulator layer covers the pair of signal lines at once, the plating layer can be formed more uniformly on the outer peripheral surface of the insulator layer. Further, the insulator layer that covers one signal line of the pair of signal lines and the insulator layer that covers the other signal line may be separate.

  In the cross section orthogonal to the extending direction of the pair of signal lines, the shape of the outer edge of the insulator layer is preferably an oval or an ellipse. In this case, it becomes easy to form a plating layer uniformly over the entire outer peripheral surface of the insulator layer. Moreover, it becomes easy to perform surface roughening and surface modification uniformly over the entire outer peripheral surface of the insulator layer. An oval is a shape composed of two opposing parallel straight lines and an arc connecting ends of the straight lines.

  The arithmetic average roughness Ra on the outer peripheral surface of the insulator layer is preferably 0.6 μm or more. In this case, the adhesion between the plating layer and the insulator layer is high, and the plating layer is difficult to peel off from the insulator layer. Moreover, when arithmetic average roughness Ra is 0.6 micrometer or more, the adhesiveness of an insulator layer and a plating layer improves, and it is hard to produce a space | gap between an insulator layer and a plating layer. Therefore, the differential common-mode conversion amount can be further suppressed.

  As a method of setting the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer to 0.6 μm or more, for example, a method of performing surface roughening treatment such as blast treatment, acidic or alkaline solution immersion, chromic acid solution immersion, chelate solution immersion, etc. There is.

  Examples of the powder to be sprayed on the object to be treated in the blasting process include a powder composed of dry ice, metal particles, carbon particles, oxide particles, carbide particles, nitride particles, and the like. Dry ice powder is preferable because it hardly remains in the insulator layer after blasting.

  In the blast treatment, the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer can be increased as the speed at which the powder is ejected is increased. The longer the time for blasting, the greater the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer. The arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer can be increased as the distance between the tip of the nozzle that ejects the powder and the outer peripheral surface of the insulator layer is decreased.

  The arithmetic average roughness Ra on the outer peripheral surface of the insulator layer is preferably 10 μm or less, and more preferably 5 μm or less. When it is 10 μm or less, transmission loss can be suppressed.

  The arithmetic average roughness Ra is measured using a Keyence laser microscope VK8500. Specific measurement conditions are as follows. Of the outer peripheral surface of the insulator layer, two locations (hereinafter, referred to as a first measurement position and a second measurement position) that are located on opposite sides and have the smallest curvature are selected. At the first measurement position, a rectangular measurement region in which the length in the longitudinal direction of the cable is 150 μm and the length in the circumferential direction of the cable is 120 μm is set. In the measurement region, the arithmetic average roughness Ra is measured using the laser microscope. Similarly, the arithmetic average roughness Ra is measured at the second measurement position. Finally, an average value of the arithmetic average roughness Ra at the first measurement position and the arithmetic average roughness Ra at the second measurement position is calculated, and the average value is calculated as the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer. To do. The arithmetic average roughness Ra is a value at the time before forming the plating layer.

When the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer was 0.6 μm or more, it was confirmed by the following test (hereinafter referred to as the first test) that the plating layer was not easily peeled off from the insulator layer. A polyethylene substrate was prepared. This substrate corresponds to the insulator layer. The substrate was subjected to blasting using dry ice as powder (hereinafter referred to as dry ice blasting). Dry ice blasting corresponds to surface roughening. The arithmetic average roughness Ra of the surface of the substrate after the dry ice blast treatment was 0.6 μm or more. Thereafter, the substrate was subjected to corona discharge exposure treatment as a surface modification treatment. As the surface modification treatment, for example, treatments such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, and immersion in an ozone-containing liquid may be performed. The surface wetting surface free energy on the surface of the substrate after the corona discharge exposure treatment was 66 mJ / m ² or more, and the contact angle was 95 ° or more. A method for measuring the adhesion wetting surface free energy will be described later.

  After the corona discharge exposure treatment, a copper plating layer was formed on the surface of the substrate by electroless plating. Next, the copper plating layer was cut into a grid pattern. The cut penetrated the copper plating layer and reached the substrate. Next, after affixing the adhesive tape on the copper plating layer, the adhesive tape was peeled off. The state of the copper plating layer at that time is shown in FIG. 2B. In FIG. 2B, 181 represents a notch. The copper plating layer did not peel in any grid. That is, the adhesion between the copper plating layer and the substrate was high.

  The test of the comparative example was basically performed in the same manner. In the comparative example, the surface roughening treatment and the surface modification treatment were not performed on the substrate. The arithmetic average roughness Ra of the surface of the substrate was 0.13 μm. The state of the copper plating layer when the adhesive tape is peeled off in the comparative example is shown in FIG. 2A. Of the 20 grids, 17 had a copper plating layer peeled off, resulting in a portion 182 where the substrate was exposed. That is, in the comparative example, the adhesion between the copper plating layer and the substrate was low.

  The contact angle on the outer peripheral surface of the insulator layer is preferably 95 ° or less. In this case, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

  Examples of methods for setting the contact angle on the outer peripheral surface of the insulator layer to 95 ° or less include electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion in an ozone-containing liquid, etc. And a method of performing the surface modification treatment.

  In any process, the contact angle can be decreased as the intensity of the process is increased. Further, the longer the processing time, the smaller the contact angle. Examples of a method for enhancing the surface modification effect by corona discharge exposure include a method of increasing the voltage and a method of increasing the oxygen concentration in the atmosphere of corona discharge exposure. The measurement method of the contact angle is a method of reading the contact angle by dropping a water droplet having a diameter of 1.5 mm on the outer peripheral surface of the insulator layer. The contact angle is a value at the time before the plating layer is formed.

The absolute value of the adhesion wetting surface free energy on the outer peripheral surface of the insulator layer is preferably 66 mJ / m ² or more. In this case, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

As a method for setting the absolute value of the surface free energy on the outer surface of the insulator layer to 66 mJ / m ² or more, for example, electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ Examples of the method include surface modification treatment such as irradiation with a beam and immersion in an ozone-containing liquid.

  In any treatment, the absolute value of the adhesion wetting surface free energy can be increased as the strength of the treatment is increased. Further, the longer the treatment time, the larger the absolute value of the adhesion wetting surface free energy.

  The absolute value of the adhesion wetting surface free energy ΔG is calculated by the following equation (3).

Γ _LG in the formula (3) is a constant and is 72.75 mJ / m ² . θ is a contact angle on the outer peripheral surface of the insulator layer. The adhesion wetting surface free energy ΔG is a value before the plating layer is formed.

It was confirmed by the following test that the plating layer can be formed uniformly when the contact angle on the outer peripheral surface of the insulator layer is 95 ° or less or the absolute value of the adhesion wetting surface free energy is 66 mJ / m ² or more. .

A polyethylene substrate was prepared. This substrate corresponds to the insulator layer. The substrate was subjected to dry ice blasting, and then subjected to corona discharge exposure treatment. Dry ice blasting corresponds to surface roughening. Corona discharge exposure treatment corresponds to surface modification treatment. The arithmetic average roughness Ra of the surface of the substrate after the corona discharge exposure treatment was 0.6 μm or more. Further, the absolute value of the surface wetting surface free energy on the surface of the substrate after the corona discharge exposure treatment was 66 mJ / m ² or more, and the contact angle was 95 ° or less. Next, a copper plating layer was formed on the surface of the substrate by electrolytic plating. The thickness of the copper plating layer was three times the thickness of the copper plating layer formed in the first test. The formed copper plating layer is shown in FIG. 3C. The copper plating layer was uniformly formed. Moreover, the adhesiveness of a copper plating layer and a board | substrate was high, and the copper plating layer was not peeling.

Basically, the first comparative example was produced by the same method. However, in the first comparative example, the arithmetic average roughness Ra of the surface of the substrate after the surface roughening treatment was less than 0.6 μm. Further, the absolute value of the adhesion wetting surface free energy on the surface of the substrate after the surface modification treatment was 66 mJ / m ² or more, and the contact angle was 95 ° or less. The copper plating layer formed in the first comparative example is shown in FIG. 3A. The copper plating layer was significantly peeled off.

Further, a second comparative example was basically produced by the same method. However, in the second comparative example, the arithmetic average roughness Ra of the surface of the substrate after the surface roughening treatment was 0.6 μm or more. Further, the absolute value of the adhesion wetting surface free energy on the surface of the substrate after the surface modification treatment was less than 66 mJ / m ² , and the contact angle was larger than 95 °. The copper plating layer formed in the second comparative example is shown in FIG. 3B. A defective plating bulge 191 called blister was present on the surface of the copper plating layer, resulting in a heterogeneous plating state.
Arithmetic on the outer peripheral surface of the insulator layer by performing dry ice blasting on the outer peripheral surface of the insulator layer and then performing surface modification treatment (hereinafter referred to as specific surface modification treatment) that performs corona discharge exposure treatment It is possible to control the average roughness Ra and the absolute value of the contact angle or the adhesion wetting surface free energy. This was confirmed by the following test. Dry ice blasting corresponds to surface roughening. Corona discharge exposure treatment corresponds to surface modification treatment.

  A specific surface modification treatment was performed on a substrate made of polyethylene. The substrate corresponds to the insulator layer. There are a plurality of conditions for the specific reforming treatment. FIG. 4 shows the correlation between the arithmetic average roughness Ra and the contact angle after the specific surface modification treatment. By performing the specific surface modification treatment, the arithmetic average roughness Ra can be 0.6 μm or more and the contact angle can be 95 ° or less.

FIG. 5 shows the correlation between the arithmetic average roughness Ra and the adhesion wetting surface free energy after the specific surface modification treatment. By performing the specific surface modification treatment, the arithmetic average roughness Ra can be 0.6 μm or more, and the absolute value of the adhesion wetting surface free energy can be 66 mJ / m ² or more.

  The insulator layer preferably has a recess on its outer peripheral surface. In this case, the insulator layer and the plating layer are difficult to peel off. It is preferable that the recess has a portion that is wider than the opening in the recess on the back side in the depth direction. In this case, the following effects are produced. When forming the plating layer, the plating bath penetrates to the back side of the recess. Nucleation occurs on the back side of the recess, and the plating layer grows on the back side of the recess. Since the plating layer grown on the back side of the recess is larger than the opening, it is difficult to escape from the opening. As a result, an anchor effect occurs and the plating layer and the insulator layer are difficult to peel off.

  As a method of forming the recess in the insulator layer, a method of performing a blasting process can be given. Examples of the blast treatment include dry ice blast treatment. Dry ice blasting corresponds to surface roughening. An example of a recess formed on the outer peripheral surface of the insulator layer by dry ice blasting is shown in FIG. FIG. 6 is a cross-sectional view of the vicinity of the outer peripheral surface 72 of the insulator layer 71. A recess 73 is formed on the outer peripheral surface 72. The recess 73 has a portion that is wider than the opening 74 in the recess 73 on the back side in the depth direction. The form of the recess 73 is a Takotsubo-like form. In the example shown in FIG. 6, the material of the insulator layer 71 is polyethylene.

  Examples of the material for the insulator layer include polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene-perfluorodiode. Xol copolymer (TFE / PDD), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), silicone, polyethylene (PE) Etc.

  The material of the insulator layer may be a foamable resin. When the material of the insulator layer is a foamable resin, the dielectric constant and dielectric loss tangent of the insulator layer are reduced. As a method for producing an insulating layer made of a foamable resin, for example, there is a method in which a resin and a foaming agent are kneaded and foamed by controlling temperature and pressure when molding the insulating layer. In addition, as another method for manufacturing an insulating layer made of a foamable resin, for example, there is a method in which nitrogen gas or the like is injected when the insulating layer is subjected to high pressure molding, and then the pressure is reduced and foamed later.

  Moreover, you may manufacture the insulator layer which consists of a foamable resin as follows. An extrusion die having a desired shape is installed in the extruder. Using the extruder, the pair of signal lines and the foamable resin are extruded simultaneously. The foamable resin forms the insulator layer.

The insulator layer is preferably made of, for example, polyethylene and having a crystallinity _Xc represented by the following formula (1) of 0.744 or more. In this case, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

In the formula (1), I _c is the X-ray diffraction intensity of the crystal component, and I _a is the X-ray diffraction intensity of the amorphous component.

Examples of a method for setting the crystallinity _Xc of the insulator layer made of polyethylene to 0.744 or more include, for example, electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, ozone A method of performing a surface modification treatment such as immersion of the containing liquid is exemplified. In any treatment, the crystallinity _Xc can be increased as the strength of the treatment is increased. Further, the longer the treatment time, the larger the crystallinity _Xc .

I _c and I _a in the formula (1) are calculated as follows. An X-ray diffraction pattern of the sample of the insulator layer is obtained using RINT2500, which is an X-ray diffraction apparatus manufactured by Rigaku Corporation. Examples of X-ray diffraction patterns are shown in FIGS. The horizontal axis of the X-ray diffraction patterns shown in FIGS. 7 and 8 is the diffraction angle 2θ. The range of the diffraction angle 2θ in the X-ray diffraction pattern is 13 to 21 °.

  In the X-ray diffraction pattern, a broad halo (hereinafter referred to as an amorphous halo) having a diffraction peak near 16.4 to 16.5 ° corresponds to an amorphous component. In the X-ray diffraction pattern, a sharp spectrum having a peak at 17.7 ° (hereinafter referred to as a crystal component spectrum) corresponds to a crystal component.

To amorphous halo, it performs a spectrum fitting analysis using Lorentz function, to obtain a smooth curve F _a good agreement with the amorphous halo. The acquired curve _Fa is shown in FIGS. Based on this curve F _a , the intensity of the amorphous halo calculated by integral intensity calculation is defined as I _a .

Further, with respect to the crystal component spectra, it performs a spectrum fitting analysis using Lorentz function, to obtain a smooth curve F _c that matches well with the crystal component spectra. The acquired curve _Fc is shown in FIGS. Based on this curve F _c, the strength of the non-crystalline component spectrum calculated by integrated intensity calculation and I _c. The crystallinity _Xc is a value at the time before forming the plating layer.

The insulator layer is preferably made of, for example, a perfluoroethylene propene copolymer and having a crystallinity _Xc represented by the following formula (1) of 0.47 or less. In this case, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

In the formula (1), I _c is the X-ray diffraction intensity of the crystal component, and I _a is the X-ray diffraction intensity of the amorphous component. The calculation method of I _c and I _{a is} the method described above. The crystallinity _Xc is a value at the time before forming the plating layer.

As a method for setting the crystallinity _Xc of the insulator layer made of perfluoroethylene propene copolymer to 0.47 or less, for example, electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ Examples of the method include surface modification treatment such as irradiation with a beam and immersion in an ozone-containing liquid. In any treatment, the crystallinity _Xc can be increased as the strength of the treatment is increased. Further, the longer the treatment time, the larger the crystallinity _Xc .

The crystallinity _Xc has a correlation with the contact angle. This was confirmed by the following test. A specific surface modification treatment was performed on a substrate made of polyethylene. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. FIG. 9A shows the correlation between the crystallinity _Xc and the contact angle after the specific surface modification treatment. When the crystallinity _Xc was 0.744 or more, the contact angle was remarkably reduced.

Further, a specific surface modification treatment was performed on a substrate made of perfluoroethylene propene copolymer. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. FIG. 9B shows the correlation between the crystallinity _Xc and the contact angle after the specific surface modification treatment. When the crystallinity _Xc was 0.47 or less, the contact angle was remarkably reduced.

As the insulator layer, for example, the following are preferable. The insulator layer is made of polyethylene. The polyethylene has a triclinic crystal structure, an orthorhombic crystal structure, or a state in which at least one of them coexists, and is preferentially oriented to two or less specific axes of crystal axes. ing. The polyethylene has a (100) crystal orientation degree O ₁₀₀ represented by the following formula (2) of 0.26 or less. This insulator layer is hereinafter referred to as a specifically oriented polyethylene insulator layer.

In the above formula (2), I ₂₀₀ is the X-ray diffraction intensity of index 200, and I ₁₁₀ is the X-ray diffraction intensity of index 110.

  When the insulator layer is a specifically oriented polyethylene insulator layer, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

  As a method of making the insulator layer into a specific orientation polyethylene insulator layer, for example, surface modification such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion of ozone-containing liquid, etc. The method of performing quality processing is mentioned.

In any treatment, the degree of crystal orientation O ₁₀₀ can be reduced as the strength of the treatment is increased. Further, the longer the processing time, the smaller the crystal orientation degree O ₁₀₀ can be made.

I ₂₀₀ and I ₁₁₀ in the formula (2) are calculated as follows.
An X-ray diffraction pattern of the sample of the insulator layer is obtained using RINT2500, which is an X-ray diffraction apparatus manufactured by Rigaku Corporation. Examples of X-ray diffraction patterns are shown in FIGS. The horizontal axis of the X-ray diffraction patterns shown in FIGS. 10 and 11 is the diffraction angle 2θ. The range of the diffraction angle 2θ in the X-ray diffraction pattern is 19 to 26 °. 10 and 11 are X-ray diffraction patterns of a sample of an insulator layer made of polyethylene having an orthorhombic crystal structure. FIG. 10 is an X-ray diffraction pattern of polyethylene not subjected to surface modification treatment. FIG. 11 is an X-ray diffraction pattern of polyethylene subjected to corona discharge exposure treatment as a surface modification treatment.

  A diffraction spectrum having a peak near about 21.5 ° (hereinafter referred to as 110 diffraction spectrum) corresponds to the Miller index 110 and represents the direction of the (110) lattice plane. A diffraction spectrum having a peak near about 23.8 ° (hereinafter referred to as a 200 diffraction spectrum) corresponds to a Miller index of 200 and represents a (100) lattice plane.

A spectrum fitting analysis using a Lorentz function is performed on the 110 diffraction spectrum, and a smooth curve F ₁ that closely matches the 110 diffraction spectrum is obtained. The obtained curves _{F 1} are shown in FIGS. Based on this curve F ₁ , the intensity of the 110 diffraction spectrum calculated by the integral intensity calculation is I ₁₁₀ .

Further, with respect to 200 diffraction spectrum, performs a spectrum fitting analysis using Lorentz function, to obtain a smooth curve F ₂ that match well with 200 diffraction spectrum. The obtained curve _{F 2} are shown in FIGS. Based on this curve F ₂ , the intensity of the 200 diffraction spectrum calculated by the integral intensity calculation is defined as I ₂₀₀ .

In addition, when individual crystal particles included in a substance composed of a polycrystal are preferentially oriented in a certain direction, the X-ray diffraction intensity of a specific index plane is higher than other X-ray diffraction intensities. Relatively high. Therefore, the orientation of a predetermined lattice plane can be quantified by the intensity ratio of the X-ray diffraction intensity. The (100) crystal orientation degree O ₁₀₀ is the intensity ratio of the X-ray diffraction intensity and represents the preferential orientation of the (100) plane.

(100) The degree of crystal orientation O ₁₀₀ has a correlation with the contact angle. This was confirmed by the following test. A specific surface modification treatment was performed on a substrate made of polyethylene. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. FIG. 12 shows the correlation between the (100) crystal orientation degree O ₁₀₀ and the contact angle after the specific surface modification treatment. When the (100) crystal orientation degree O ₁₀₀ was 0.26 or less, the contact angle was remarkably reduced. (100) The degree of crystal orientation O ₁₀₀ is a value before the formation of the plating layer.

  As the insulator layer, for example, the following are preferable. The insulator layer is made of polyethylene. The crystallite size in the crystalline component of the polyethylene is 18 nm or more. When the insulator layer is as described above, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

  As a method of making the insulator layer as described above, for example, surface modification treatment such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion of ozone-containing liquid, etc. The method of performing is mentioned.

  In any treatment, the crystallite size in the crystalline component of polyethylene can be increased as the strength of the treatment is increased. In addition, the longer the treatment time, the larger the crystallite size in the polyethylene crystal component.

  The crystallite size in the crystal component of polyethylene is represented by the following formula (4).

In formula (4), D is the crystallite size in the crystalline component of polyethylene. K is the Scherrer constant. The value of K was 2 / π. λ is the X-ray wavelength. B is the breadth of the X-ray diffraction peak. θ is an X-ray diffraction angle. λ, B, and θ are values obtained from the X-ray diffraction pattern of the sample of the insulator layer. The crystallite size is a value before the plating layer is formed.

  The crystallite size D in the crystalline component of polyethylene has a correlation with the contact angle. This was confirmed by the following test. A specific surface modification treatment was performed on a substrate made of polyethylene. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. FIG. 13A shows the correlation between the crystallite size D and the contact angle in the polyethylene crystal component after the specific surface modification treatment. When the crystallite size D in the crystalline component of polyethylene was 18 nm or more, the contact angle was remarkably reduced.

  As the insulator layer, for example, the following are preferable. The insulator layer is made of perfluoroethylene propene copolymer. The crystallite size in the crystal component of the perfluoroethylene propene copolymer is 13.6 nm or less. When the insulator layer is as described above, it becomes easy to make the thickness of the plating layer uniform. If the thickness of the plating layer is made uniform, the transmission loss of the differential signal transmission cable can be suppressed.

  As a method of making the insulator layer as described above, for example, surface modification treatment such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion of ozone-containing liquid, etc. The method of performing is mentioned.

  In any treatment, the crystallite size in the crystal component of the perfluoroethylenepropene copolymer can be increased as the strength of the treatment is increased. In addition, the longer the treatment time, the larger the crystallite size in the crystal component of the perfluoroethylene propene copolymer. The calculation method of the crystallite size in the crystal component of the perfluoroethylene propene copolymer is the same as the calculation method of the crystallite size in the polyethylene crystal component. The crystallite size is a value before the plating layer is formed.

  The crystallite size D in the crystal component of the perfluoroethylene propene copolymer has a correlation with the contact angle. This was confirmed by the following test. A specific surface modification treatment was performed on a substrate made of perfluoroethylene propene copolymer. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. FIG. 13B shows the correlation between the crystallite size D and the contact angle in the crystal component of the perfluoroethylenepropene copolymer after the specific surface modification treatment. When the crystallite size D in the crystal component of the perfluoroethylene propene copolymer was 13.6 nm or less, the contact angle was remarkably reduced.

(1-3) Plating layer The thickness of the plating layer is preferably 1 μm or more and 5 μm or less. When the thickness of the plating layer is 1 μm or more, the inward skew can be further reduced and the differential common-mode conversion amount can be further suppressed. In particular, when a signal of 25 GHz or higher is transmitted, the differential common-mode conversion amount can be significantly suppressed.

  When the thickness of the plating layer is 5 μm or less, the time required for forming the plating layer can be reduced. Moreover, when the thickness of the plating layer is 5 μm or less, the flexibility of the differential signal transmission cable can be improved. Moreover, when the thickness of the plating layer is 5 μm or less, the outer diameter of the differential signal transmission cable is reduced. The thickness of the plating layer can be controlled by a known method. For example, the longer the electrolytic plating and / or electroless plating time, the thicker the plating layer. Moreover, the plating layer becomes thicker as the amount of current in electrolytic plating is increased.

  The standard deviation of the plating layer thickness is preferably 0.8 μm or less. In this case, transmission loss of the differential signal transmission cable can be suppressed. Moreover, since it is hard to produce the part whose thickness of a plating layer is too small, noise can be reduced further.

  The standard deviation of the thickness of the plating layer is calculated by the following method. Cross sections perpendicular to the longitudinal direction of the differential signal transmission cable are formed at four locations. The distance between each cross section is 3 m. Arbitrary four points are selected in each cross section. The thickness of the plating layer is measured at a total of 4 × 4 points. The measured standard deviation of the thickness of all the plating layers is adopted as the standard deviation of the thickness of the plating layer.

For example, the standard deviation of the thickness of the plating layer can be reduced by reducing the contact angle on the outer peripheral surface of the insulator layer or increasing the absolute value of the adhesion wetting surface energy.
Insulator layer is subjected to surface modification treatment such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion in ozone-containing liquid, etc. The contact angle at the outer peripheral surface of the layer can be reduced, and the absolute value of the wetting surface energy can be increased.

  The plating layer may be a laminate of a plurality of layers. The number of layers laminated in the plating layer can be, for example, 2, 3, or 4 or more. Of the plurality of layers, some layers may be magnetic layers made of ferrite or the like, and some other layers may be nonmagnetic layers made of copper or the like. In this case, the plating layer can exhibit a shielding effect against a strong magnetic field and a weak magnetic field. Moreover, the plating layer can exhibit a shielding effect against noise in a low frequency band of several tens to several hundreds of MHz and noise in a high frequency band of several tens of GHz.

  For example, the plating layer can be formed by a method in which electroless plating is first performed and then electrolytic plating is performed. In this case, the plating layer can be easily formed on the insulator layer. Further, the time required for forming the plating layer can be shortened as compared with a method in which the entire plating layer is formed by electroless plating.

(1-4) Metal Foil Tape When the differential signal transmission cable 1 according to the present disclosure includes the plating layer 7 and the metal foil tape 9, the shielding effect is higher than when only the plating layer 7 is provided. In addition, when the differential signal transmission cable 1 of the present disclosure includes the plating layer 7 and the metal foil tape 9, there is a gap between the insulator layer 5 and the shield layer as compared to the case where only the metal foil tape 9 is provided. Hard to occur. Therefore, the inward skew and the differential common-mode conversion amount can be suppressed.

  Moreover, when the differential signal transmission cable 1 of the present disclosure includes the plating layer 7 and the metal foil tape 9, the suck-out can be suppressed as compared with the case where only the metal foil tape 9 is provided. The reason is that the provision of the plating layer 7 continuous along the extending direction of the differential signal transmission cable 1 reduces the influence of the periodic structure having the winding pitch of the metal foil tape 9 as a period. Guessed.

  The material of the metal foil constituting the metal foil tape is, for example, copper, copper alloy, aluminum, or aluminum alloy. The metal foil is, for example, a rolled copper foil or an electrolytic copper foil. The rolled copper foil can be produced, for example, by rolling an annealed copper material to 10 μm or less, and thereafter annealing to remove internal strain. The electrolytic copper foil is, for example, a foil formed by electrodepositing copper on an electrodeposition drum. The thickness of the metal foil is preferably in the range of 7 to 10 μm. When the film thickness of the metal foil is 7 μm or more, the shielding effect for blocking electromagnetic waves is higher. When the thickness of the metal foil is 10 μm or less, the allowable elongation is even higher. The allowable elongation is an elongation representing a range in which elongation is possible without causing breakage.

  As shown in FIG. 25, for example, the differential signal transmission cable 1 according to the present disclosure includes a pair of signal lines 3, an insulator layer 5, a plating layer 7, and a metal foil tape 9, and a press-winding insulating tape. 11 may be further provided. The press-winding insulating tape 11 is wound around the outer peripheral surface of the metal foil tape 9. The press-winding insulating tape 11 may be composed of, for example, a first press-winding insulating tape 11A and a second press-winding insulating tape 11B.

  The first press-winding insulating tape 11 </ b> A is wound around the outer peripheral surface of the plating layer 7. The second pressing and winding insulating tape 11B is wound around the outer peripheral surface of the first pressing and winding insulating tape 11A.

  When the differential signal transmission cable 1 of the present disclosure includes the plating layer 7 and the metal foil tape 9, the plating layer 7 may have a crack 13 as illustrated in FIG. 26. The crack 13 penetrates the plating layer 7 in the thickness direction. The crack 13 may be singular or plural. The shape of the crack 13 may be a linear shape, a curved shape, or an irregular shape. When there are a plurality of cracks 13, the arrangement of the cracks 13 may be a regular arrangement or an irregular arrangement.

  When the plating layer 7 has the crack 13, the suck-out can be further suppressed. The reason is presumed as follows. When viewed alone, the metal foil tape 9 wound around the outer peripheral surface of the plating layer 7 has an electrical periodicity with the winding pitch of the metal foil tape 9 as a period. The shield layer composed of the plating layer 7 having the crack 13 and the metal foil tape 9 wound around the outer peripheral surface of the plating layer 7 has an electrical periodicity suppressed as a whole. Therefore, sack out can be suppressed.

  When the differential signal transmission cable 1 is bent, the plating layer 7 is stressed. When the plating layer 7 has the crack 13, the stress is relaxed by the crack 13. Therefore, the crack 13 is hard to extend any more. Moreover, it is hard to produce a new crack. As a result, even when the differential signal transmission cable 1 is bent, the electrical characteristics of the differential signal transmission cable 1 are unlikely to deteriorate.

2. Method for Producing Differential Signal Transmission Cable The differential signal transmission cable of the present disclosure can be produced, for example, by the following method. FIG. 14 shows a manufacturing system 101 used for manufacturing a differential signal transmission cable. The manufacturing system 101 includes a degreasing unit 103, a wet etching unit 105, a first activation unit 107, a second activation unit 109, an electroless plating unit 111, an electrolytic plating unit 113, a transport unit 115, Is provided.

  The degreasing unit 103 includes a degreasing tank 117 and a degreasing liquid 119. The degreasing liquid 119 is accommodated in the degreasing tank 117. The degreasing liquid 119 includes at least one of sodium borate, sodium phosphate, a surfactant, and the like, for example. The temperature of the degreasing liquid 119 is, for example, 40 to 60 ° C.

  The wet etching unit 105 for performing the surface roughening treatment includes an etching tank 121 and an etching solution 123. The etching solution 123 is stored in the etching tank 121. The etching solution 123 includes one or more of chromic acid, sulfuric acid, ozone, acid, alkali, chelate, and the like, for example. The temperature of the etching solution 123 is 65 to 70 ° C., for example.

  The first activation unit 107 includes a first activation tank 125 and a first activation liquid 127. The first activation liquid 127 is accommodated in the first activation tank 125. The first activation liquid 127 includes, for example, one or more of palladium chloride, stannous chloride, concentrated hydrochloric acid, and the like. The temperature of the 1st activation liquid 127 is 30-40 degreeC, for example.

  The second activation unit 109 includes a second activation tank 129 and a second activation liquid 131. The second activation liquid 131 is accommodated in the second activation tank 129. The second activation liquid 131 includes, for example, sulfuric acid. The temperature of the second activation liquid 131 is, for example, 0 to 50 ° C.

  The electroless plating unit 111 includes an electroless plating tank 133 and an electroless plating solution 135. The electroless plating solution 135 is accommodated in the electroless plating tank 133. The electroless plating solution 135 includes, for example, copper sulfate, Rossiel salt, formaldehyde, sodium hydroxide and the like. The temperature of the electroless plating solution 135 is, for example, 20 to 30 ° C.

  The electroplating unit 113 includes an electroplating tank 137, an electroplating solution 139, a pair of anodes 141, and a power supply unit 143. Electrolytic plating solution 139 is accommodated in electrolytic plating tank 137. The electrolytic plating solution 139 has a composition shown in Table 1 or Table 2, for example. The temperature of the electrolytic plating solution 139 is, for example, 20 to 25 ° C.

The anode 141 is immersed in the electrolytic plating solution 139. The anode 141 is obtained, for example, by rolling and casting molten copper made from copper water. Alternatively, the anode 141 may be manufactured as follows. Seed plate electrolysis is performed using crude copper as an anode and stainless steel or titanium as a cathode. The pure copper plate deposited on the cathode surface is peeled off to form the anode 141. The power supply unit 143 applies a DC voltage between the anode 141 and bobbins 165 and 169 described later.

  The transport unit 115 includes a plurality of bobbins 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, and 169. Hereinafter, these may be collectively referred to as a bobbin group. The bobbins 165 and 169 have conductivity. The bobbin 167 has an insulating property.

  The bobbin group is basically arranged in series along the conveyance direction D shown in FIG. The transport direction D is a direction from the degreasing unit 103 toward the electrolytic plating unit 113 through the wet etching unit 105, the first activation unit 107, the second activation unit 109, and the electroless plating unit 111 in order.

  A part of the bobbin 147 is immersed in the degreasing liquid 119. A part of the bobbin 151 is immersed in the etching solution 123. A part of the bobbin 155 is immersed in the first activation liquid 127. A part of the bobbin 159 is immersed in the second activation liquid 131. A part of the bobbin 163 is immersed in the electroless plating solution 135. The entire bobbin 167 is immersed in the electrolytic plating solution 139.

  The transport unit 115 continuously transports the differential signal transmission cable 171 along the transport direction D by the bobbin group. In the initial state, the differential signal transmission cable 171 to be conveyed is provided with a signal line and an insulator layer, but a plating layer is not yet formed. The insulator layer can be provided by, for example, known extrusion molding.

  The differential signal transmission cable 171 to be conveyed is first immersed in the degreasing liquid 119 in the degreasing unit 103 for 3 to 5 minutes. At this time, the oil and fat adhering to the surface of the insulator layer is removed.

  Next, the differential signal transmission cable 171 is immersed in the etching solution 123 for 8 to 15 minutes in the wet etching unit 105. At this time, an uneven shape is formed on the outer peripheral surface of the insulator layer. In addition, a functional group such as a carbonyl group or a hydroxy group is formed on the outer peripheral surface of the insulator layer. As a result, the outer peripheral surface of the insulator layer becomes hydrophilic and surface wettability is improved.

  Next, the differential signal transmission cable 171 is immersed in the first activation liquid 127 for 1 to 3 minutes in the first activation unit 107. At this time, a catalyst layer is formed on the outer peripheral surface of the insulator layer.

Next, the differential signal transmission cable 171 is immersed in the second activation liquid 131 in the second activation unit 109 for 3 to 6 minutes. At this time, the surface of the catalyst layer is washed.
Next, the differential signal transmission cable 171 is immersed in the electroless plating solution 135 in the electroless plating unit 111. The immersion time is, for example, 10 minutes or less. At this time, an electroless plating layer is formed on the outer peripheral surface of the insulator layer. The electroless plating layer corresponds to the plating layer. The longer the immersion time in the electroless plating solution 135, the greater the thickness of the electroless plating layer.

  Next, the differential signal transmission cable 171 is immersed in the electrolytic plating solution 139 in the electrolytic plating unit 113. The immersion time is, for example, 3 minutes or less. At this time, an electrolytic plating layer is formed on the outer peripheral surface of the electroless plating layer. The electrolytic plating layer corresponds to the plating layer. The longer the immersion time in the electrolytic plating solution 139, the greater the thickness of the electrolytic plating layer. Specific conditions for electrolytic plating in the electrolytic plating unit 113 are as shown in Table 3. Through the above steps, the differential signal transmission cable 171 is completed.

  After the plating step, a metal foil tape may be wound around the outer peripheral surface of the plating layer. The metal foil tape can be wound in a spiral shape, for example. For example, a crack may be formed in the plating layer before winding the metal foil tape.

Although omitted from FIG. 14, the differential signal transmission cable 171 is washed with pure water between the units. Cleaning methods include ultrasonic cleaning, rocking cleaning, and running water cleaning. By washing with pure water, it is possible to suppress the residual drug adhering to the previous unit from being brought into the subsequent unit.

The conveyance speed of the differential signal transmission cable 171 can be adjusted as appropriate. The conveyance speed may be changed during the conveyance, or a temporary stop may be performed.
A differential signal transmission cable may be manufactured using the manufacturing system 201 shown in FIG. The configuration of the manufacturing system 201 is basically the same as that of the manufacturing system 101, but is partially different. Below, it demonstrates centering around difference. The manufacturing system 201 does not include the degreasing unit 103 and the wet etching unit 105 but includes the surface modification unit 203. FIG. 16 shows a detailed configuration of the surface modification unit 203.

  The surface modification unit 203 includes a housing 204, a fine shape forming device 205, and a hydrophilic treatment device 207. The housing 204 accommodates each component of the surface modification unit 203. The housing 204 includes an inlet 204A on the upstream side in the direction D, and an outlet 204B on the downstream side in the direction D.

  The transport unit 115 includes four bobbins 209, 211, 213, and 215 in the housing 204. The differential signal transmission cable 171 is guided by the bobbin 145 and introduced into the housing 204 from the inlet 204A. The introduced differential signal transmission cable 171 is sent from the bobbin 209 to the bobbin 211 and is conveyed along an 8-shaped path returning to the bobbin 209 again. Next, the differential signal transmission cable 171 is sent from the bobbin 209 to the bobbin 213, further sent from the bobbin 213 to the bobbin 215, and conveyed along an 8-shaped path returning to the bobbin 213 again. Next, the differential signal transmission cable 171 is led out from the outlet 204B, guided to the bobbin 153, and sent to the first activation unit 107.

  The fine shape forming apparatus 205 injects dry ice powder from the nozzle 205 </ b> A onto the differential signal transmission cable 171 existing between the bobbin 209 and the bobbin 211. The driving force for injection is air pressure. The arithmetic average roughness Ra on the outer peripheral surface of the insulator layer is increased by colliding with the dry ice powder. Therefore, the fine shape forming apparatus 205 performs dry ice blasting. Dry ice blasting corresponds to surface roughening.

  When the bobbin 209 is sent to the bobbin 211 and when it returns from the bobbin 211 to the bobbin 209, the surface of the insulator layer facing the nozzle 205A is opposite. Therefore, the fine shape forming apparatus 205 can increase the arithmetic average roughness Ra over the entire outer peripheral surface of the insulator layer.

  The particle diameter of the dry ice powder, the distance from the tip of the nozzle 205A to the differential signal transmission cable 171 and the like can be appropriately set. The temperature of the differential signal transmission cable 171 is, for example, 20 ° C.

  The conditions in the dry ice blasting process can be changed as appropriate. Conditions for the dry ice blasting include, for example, the particle size of dry ice powder, the flow rate of dry ice, the air pressure, the distance from the tip of the nozzle 205A to the differential signal transmission cable 171 and the conveyance of the differential signal transmission cable 171. The speed, the temperature of the differential signal transmission cable 171 and the like can be mentioned. For example, the dry ice blast treatment may be performed at a temperature lower than the glass transition temperature of the material of the insulator layer. As temperature lower than the glass transition temperature of the material of an insulator layer, the temperature of -79 degreeC or more and 20 degrees C or less is mentioned, for example. The position of the nozzle 205A may be fixed, or may be swung or scanned.

  The hydrophilic treatment device 207 performs a hydrophilic treatment by corona discharge exposure. Corona discharge exposure corresponds to surface modification treatment. As shown in FIG. 16, the hydrophilic treatment apparatus 207 includes a total of four plate electrodes 208. The pair of plate electrodes 208 oppose each other with a differential signal transmission cable 171 sent from the bobbin 213 to the bobbin 215 interposed therebetween. The other pair of plate electrodes 208 oppose each other with the differential signal transmission cable 171 returning from the bobbin 215 to the bobbin 213 interposed therebetween. By applying a high frequency high voltage between the opposing flat plate electrodes 208, corona discharge is generated. By being exposed to corona discharge, the outer peripheral surface of the insulator layer becomes hydrophilic and wettability is improved. When the outer peripheral surface of the edge layer becomes hydrophilic and wettability is improved, the contact angle becomes smaller and the absolute value of the adhesion wetting surface free energy becomes larger.

The reason why the outer peripheral surface of the insulator layer is made hydrophilic by the corona discharge exposure and the wettability is improved is as follows. High energy electrons generated by corona discharge exposure ionize and dissociate oxygen molecules present in the air, generating oxygen radicals and ozone. At the same time, the high-energy electrons that have reached the vicinity of the outer peripheral surface of the insulator layer cut the main chain and side chains of the insulator layer, such as polyethylene and perfluoroethylene propene copolymer, and cleave them. The oxygen radicals and ozone generated by corona discharge recombine with the main chain and side chain cleaved as described above, and polar functional groups such as hydroxy groups and carbonyl groups are formed on the outer peripheral surface of the insulator layer. The As a result, the outer peripheral surface of the insulator layer becomes hydrophilic and wettability is improved.
The applied voltage in corona discharge exposure is, for example, 2 to 14 kV, and the frequency is 15 kV. The distance between the outer peripheral surface of the insulator layer and the plate electrode 208 is, for example, 0.1 to 3 mm. The atmosphere in the housing 204 is, for example, air.

  The conditions for corona discharge exposure can be changed as appropriate. Examples of the conditions in corona discharge exposure include the magnitude of the applied voltage, the frequency of the applied voltage, the distance between the outer peripheral surface of the insulator layer and the plate electrode 208, the atmosphere in the housing 204, and the like. The atmosphere in the housing 204 may contain oxygen, nitrogen, carbon dioxide, a rare gas, or the like. Further, a material such as silicone rubber may be sandwiched between the outer peripheral surface of the insulator layer and the flat plate electrode 208. In this case, when performing corona discharge, the plate electrode 208 indirectly contacts the insulator layer and slides against the silicone rubber. An exhaust mechanism that exhausts the air in the housing 204 or a drying device that dries the interior of the housing 204 may be provided. In this case, rust of the differential signal transmission cable 171 can be suppressed. In addition, a slow power device may be provided in the housing 204. In this case, static electricity in the housing 204 can be suppressed.

  As described above, in the method for manufacturing a differential signal transmission cable using the manufacturing system 201, the outer peripheral surface of the insulator layer is subjected to dry ice blasting, and then the outer peripheral surface of the insulator layer is subjected to corona discharge exposure processing. Thereafter, a permanganate treatment is performed, and then a plating layer is formed on the outer peripheral surface of the insulator layer. Dry ice blasting corresponds to surface roughening. Corona discharge exposure treatment corresponds to surface modification treatment. By performing the permanganic acid treatment, the insulator layer is easily plated. Further, by performing the permanganate treatment, the transmission characteristics of the differential signal transmission cable are improved. After the surface roughening treatment, permanganic acid treatment may be performed, and then corona discharge exposure treatment may be performed.

  Moreover, you may wind a metal foil tape around the outer peripheral surface of a plating layer after the process of plating. The metal foil tape can be wound in a spiral shape, for example. For example, a crack may be formed in the plating layer before winding the metal foil tape.

  The surface modification unit 203 may be as shown in FIG. The surface modification unit 203 includes a cylindrical hydrophilic treatment apparatus 207. The hydrophilic treatment device 207 includes a shaft hole 217. The differential signal transmission cable 171 conveyed by the bobbin 209 and the bobbin 213 passes through the shaft hole 217. The hydrophilic treatment device 207 generates a corona discharge in the shaft hole 217. By being exposed to the corona discharge, the outer peripheral surface of the insulator layer becomes hydrophilic and wettability is improved. When the outer peripheral surface of the edge layer becomes hydrophilic and wettability is improved, the contact angle becomes smaller and the absolute value of the adhesion wetting surface free energy becomes larger. Corona discharge exposure treatment corresponds to surface modification treatment.

  The surface modification unit 203 may be as shown in FIG. The hydrophilization treatment device 207 includes an arc-shaped electrode 219 at a portion facing the bobbin 213 and the bobbin 215. The bobbin 213 and the bobbin 215 are grounded. The hydrophilic treatment device 207 applies a voltage between the electrode 219, the bobbin 213, and the bobbin 215 to generate corona discharge. By being exposed to the corona discharge, the outer peripheral surface of the insulator layer becomes hydrophilic and wettability is improved. When the outer peripheral surface of the edge layer becomes hydrophilic and wettability is improved, the contact angle becomes smaller and the absolute value of the adhesion wetting surface free energy becomes larger. Corona discharge exposure treatment corresponds to surface modification treatment.

3. Multicore Cable The multicore cable of the present disclosure includes a plurality of differential signal transmission cables, a conductor layer, and a jacket. The conductor layer collectively covers a plurality of differential signal transmission cables. The jacket covers the conductor layer. Each of the plurality of differential signal transmission cables is basically the same as the differential signal transmission cable described in the section “1. Differential signal transmission cable”, and further includes an outer insulating layer. Prepare. When the differential signal transmission cable does not include the metal foil tape, the outer insulating layer covers the plating layer. When the metal foil tape is wound around the outer peripheral surface of the plating layer, the outer insulating layer covers the metal foil tape.

  The plurality of differential signal transmission cables may be twisted together or may not be twisted together. The number of differential signal transmission cables is not particularly limited, and may be, for example, 2, 8, 24, or the like. For example, a plurality of differential signal transmission cables may be divided into two or more groups, and an intervening space may be provided between the groups. Each group includes, for example, two or more differential signal transmission cables.

  A conductor layer can be comprised with a shield tape conductor, a braided wire, etc., for example. For example, the conductor layer may be a laminate of a shield tape conductor and a braided wire. As a material for the shield tape conductor and the braided wire, those generally used for cables can be used. As a material for the jacket, those generally used for cables can be used.

  Examples of the external insulating layer include an insulating tape, a laminate tape, and a film formed by spraying an insulator. As the laminate tape, for example, a tape generally used for a flat cable or the like can be used. The external insulating layer is preferably one that can be formed at room temperature or low temperature. In this case, it is possible to suppress the insulator layer from being deformed by heat when the external insulating layer is formed.

  Examples of the intervening material include paper, thread, and foam. Examples of the foam include foamed polyolefin such as foamed polypropylene and foamed ethylene. The multi-core cable of the present disclosure can suppress the differential in-phase conversion amount and suck-out.

  FIG. 19 shows an example of the multicore cable 301. The multicore cable 301 includes eight differential signal transmission cables 302, a shield tape conductor 303, a braided wire 305, and a jacket 307. The shield tape conductor 303 and the braided wire 305 collectively cover the eight differential signal transmission cables 302. The braided wire 305 is located on the outer peripheral side of the shield tape conductor 303. Jacket 307 covers braided wire 305.

The eight differential signal transmission cables 1 are divided into two groups at the center and six groups around them. An interposition 309 is provided between the two groups.
Each of the eight differential signal transmission cables 302 has the configuration shown in FIG. The differential signal transmission cable 302 includes a pair of signal lines 3, an insulator layer 5, a plating layer 7, and an outer insulating layer 311. A metal foil tape may be wound around the outer peripheral surface of the plating layer 7. The metal foil tape can be wound in a spiral shape, for example. For example, a crack may be formed in the plating layer 7 before winding the metal foil tape.

  The insulator layer 5 covers the pair of signal lines 3 at once. The plating layer 7 covers the insulator layer 5. When the differential signal transmission cable 1 does not include a metal foil tape, the outer insulating layer 311 covers the plating layer 7. When the metal foil tape is wound around the outer peripheral surface of the plating layer 7, the outer insulating layer 311 covers the metal foil tape. The differential signal transmission cable 302 has a maximum differential common-mode conversion amount of −26 dB or less in a frequency band of 50 GHz or less. The arithmetic average roughness Ra on the outer peripheral surface of the insulating layer 5 is 0.6 μm or more and 10 μm or less. The configurations of the signal line 3, the insulator layer 5, and the plating layer 7 are respectively those described in the section “1. Cable for differential signal transmission”, for example.

4). Example (4-1) Example 1
A differential signal transmission cable 1 of the example having the structure shown in FIG. 1 was manufactured. The material of the insulator layer 5 is polyethylene. The insulator layer 5 covers the pair of signal lines 3 at once. In the cross section orthogonal to the extending direction of the pair of signal lines 3, the shape of the outer edge of the insulator layer 5 is an ellipse. The thickness of the plating layer 7 is 4.56 μm. The standard deviation of the thickness of the plating layer 7 is 0.68 μm. The variation coefficient of the thickness of the plating layer 7 is 0.15.

As shown in FIG. 20, the outer diameter of the insulator layer 5 in the major axis direction L _1. The outer diameter of the insulator layer 5 in the minor axis and L _2. The distance between the centers of the pair of signal lines 3 and L _3. In the major axis direction, to the center of the signal line 3, the distance between the outer peripheral surface of the insulator layer 5 and L _4. In minor axis, and the center of the signal line 3, the distance between the outer peripheral surface of the insulator layer 5 and L _5.

In addition, even when the shape of the outer edge of the insulator layer 5 is oval, L _{1 to} L ₅ can be defined similarly. However, when the shape of the outer edge of the insulator layer 5 is an oval, the major axis direction is a direction parallel to two straight lines constituting the outer peripheral surface of the insulator layer 5. Moreover, when the shape of the outer edge of the insulator layer 5 is an oval, the minor axis direction is a direction orthogonal to the two straight lines.

In Example 1, _{L 1} is 2.03 mm. L ₂ is 1.04mm. L ₃ is 0.55mm. L ₄ is 0.74mm. L ₅ is 0.52mm.
Surface roughening treatment was performed on the outer peripheral surface of the insulator layer 5. The surface roughening treatment is chromic acid etching. At the time before the plating layer 7 is formed, the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer 5 is 0.6 μm. Before the plating layer 7 is formed, the contact angle on the outer peripheral surface of the insulator layer 5 is 95 °.

  The differential common-mode conversion amount of the differential signal transmission cable 1 was measured. The differential common-mode conversion amount was measured before the differential signal transmission cable was wound around a drum or the like. The measurement result is shown as “131” in FIG. The horizontal axis in FIG. 21 is the frequency expressed on a logarithmic scale. The vertical axis represents the differential in-phase conversion amount, and the unit is dB. The differential in-phase conversion amount on the vertical axis corresponds to the mixed mode S parameter Scd21. The larger the value on the vertical axis (that is, the smaller the absolute value of the negative measurement value), the greater the amount of noise in the differential common-mode conversion amount, indicating that the quality of the transmitted signal is significantly degraded. .

  Further, the differential common-mode conversion amount was also measured for the differential signal transmission cable R of the comparative example. The measurement result is shown as “132” in FIG. In the differential signal transmission cable R of the comparative example, the surface roughening treatment is not performed on the outer peripheral surface of the insulator layer. Therefore, the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer is 0.13 μm, and the contact angle on the outer peripheral surface of the insulator layer is 82 °. Moreover, the differential signal transmission cable R of the comparative example does not include a plating layer but includes a conductor layer wound with a metal tape.

  In the differential signal transmission cable 1 of the example, the differential common-mode conversion amount was smaller than that of the differential signal transmission cable R of the comparative example. In particular, in the high frequency region, the difference from the differential signal transmission cable R of the comparative example was significant.

  Further, the transmission characteristics of the differential signal transmission cable 1 of the example and the differential signal transmission cable R of the comparative example were measured. The transmission characteristics were measured before winding the differential signal transmission cable around a drum or the like. The measurement result of the differential signal transmission cable 1 of the example is shown as “51” in FIG. 22, and the measurement result of the differential signal transmission cable R of the comparative example is shown as “52”. The horizontal axis in FIG. 22 represents the frequency of the transmission signal. The vertical axis indicates transmission signal loss in dB. The transmission loss on the vertical axis corresponds to the mixed mode S parameter Sdd21. The smaller the value on the vertical axis (that is, the larger the absolute value of the negative measurement value), the greater the attenuation of the transmission signal, the greater the degradation associated with transmission of the outgoing signal, and the greater the transmission loss. Yes.

  In the differential signal transmission cable 1 of the example, the transmission loss was smaller than that of the differential signal transmission cable R of the comparative example. Further, no suck-out occurred in the differential signal transmission cable 1 of the example. Although not shown in FIG. 22, no suck-out occurred even in the region of 30 GHz or more and 50 GHz or less. Note that “suck out” means a rapid attenuation of a transmission signal.

On the other hand, sack out occurred in the differential signal transmission cable R of the comparative example. The reason why no sac-out occurs in the differential signal transmission cable 1 of the embodiment is that a plating layer is continuously formed over the entire differential signal transmission cable 1, such as a conductor layer wound with a metal tape. This is presumably because there is no overlap or seam.
(4-2) Example 2
Differential signal transmission cables S1 to S7 were manufactured under the conditions shown in Table 4.

Each of S1 to S7 includes an insulator layer made of polyethylene. In any of S1 to S7, the shape of the outer edge of the insulator layer is elliptical in the cross section orthogonal to the extending direction of the pair of signal lines 3. In Example 2, _{L 1} is 1.21 mm. L ₂ is 0.62mm. L ₃ is 0.35mm. L ₄ is 0.43mm. L ₅ is 0.31mm.

  S1 to S6 include a conductive layer made of a plating layer. In S7, a conductive layer was formed by horizontally winding a Cu tape. In S1 to S5, a dry ice blast process was performed on the outer peripheral surface of the insulator layer, and then a corona discharge exposure process was performed. The dry ice blast treatment corresponds to the surface roughening treatment, and the corona discharge exposure treatment corresponds to the surface modification treatment. In S1 to S3, permanganic acid treatment was performed after corona discharge exposure treatment. In S4 to S5, the permanganate treatment was not performed after the corona discharge exposure treatment. In S6, chromic acid treatment was performed on the outer peripheral surface of the insulator layer. In S7, the process before winding a Cu tape was not performed.

  About S1-S7, arithmetic mean roughness Ra and transmission loss Sdd21 were measured. The results are shown in Table 4 above. In Table 1, “first Ra” represents the arithmetic average roughness Ra at the first measurement position, “second Ra” represents the arithmetic average roughness Ra at the second measurement position, and “average Ra” is the average value thereof. Represents. FIG. 23 shows the relationship between the arithmetic average roughness Ra and the transmission loss Sdd21. The smaller the arithmetic average roughness Ra, the smaller the transmission loss Sdd21. S1-S3 which performed the permanganic acid process had a small transmission loss compared with S4-S5 which did not perform the permanganate process.

5. Other Embodiments Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and various modifications can be made.

  (1) In the first and second embodiments, the differential signal transmission cable may further include a metal foil tape in addition to the signal line 3, the insulator layer 5, and the plating layer 7. The metal foil tape is wound around the outer peripheral surface of the plating layer 7. The metal foil tape can be wound in a spiral shape, for example. For example, a crack may be formed in the plating layer before winding the metal foil tape.

  Even when the differential signal transmission cable includes a metal foil tape, the effects described in the first and second embodiments are exhibited. Furthermore, when the differential signal transmission cable includes a metal foil tape, the shielding effect is further enhanced.

  (2) A function of one component in each of the above embodiments may be shared by a plurality of components, or a function of a plurality of components may be exhibited by one component. Moreover, you may abbreviate | omit a part of structure of each said embodiment. In addition, at least a part of the configuration of each of the above embodiments may be added to or replaced with the configuration of the other above embodiments. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  (3) In addition to the above-described differential signal transmission cable or multicore cable, a system including at least one of them as a constituent element, a multicore cable manufacturing method, a signal transmission / reception method using a differential signal transmission cable, etc. The present disclosure can also be realized in various forms.

DESCRIPTION OF SYMBOLS 1 ... Cable for differential signal transmission, 3 ... Signal wire, 5 ... Insulator layer, 7 ... Plating layer, 9 ... Metal foil tape, 11 ... Insulating tape for press winding, 13 ... Crack, 71 ... Insulator layer, 72 DESCRIPTION OF SYMBOLS ... Outer peripheral surface, 73 ... Recessed part, 101, 201 ... Manufacturing system, 103 ... Degreasing unit, 105 ... Wet etching unit, 107 ... First activation unit, 109 ... Second activation unit, 111 ... Electroless plating unit, 113 ... Electrolytic plating unit, 115 ... conveying unit, 117 ... degreasing tank, 119 ... degreasing liquid, 121 ... etching tank, 123 ... etching liquid, 125 ... first activation tank, 127 ... first activation liquid, 129 ... second Activation tank, 131 ... second activation liquid, 133 ... electroless plating tank, 135 ... electroless plating liquid, 137 ... electrolytic plating tank, 139 ... electrolytic plating liquid, 141 ... anode, 1 3 ... power supply unit, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 209, 211, 213, 215 ... bobbin, 171 ... differential signal transmission cable, DESCRIPTION OF SYMBOLS 203 ... Surface modification unit, 204 ... Housing, 204A ... Inlet, 204B ... Outlet, 205 ... Fine shape forming device, 205A ... Nozzle, 207 ... Hydrophilization device, 208 ... Flat plate electrode, 217 ... Shaft hole, 219 ... Electrode 301 ... multi-core cable 302 ... differential signal transmission cable 303 ... shield tape conductor 305 ... braided wire 307 ... jacket 309 ... interposition 311 ... outer insulating layer

Claims (5)

A pair of signal lines;
An insulator layer covering the periphery of the signal line;
A plating layer covering the insulator layer;
A metal foil tape wound around the outer peripheral surface of the plating layer and electrically connected to the plating layer;
A differential signal transmission cable comprising: The differential signal transmission cable according to claim 1,
The metal foil tape is a differential signal transmission cable wound in a spiral shape. The differential signal transmission cable according to claim 1 or 2,
The plating layer has a crack for differential signal transmission. A plurality of differential signal transmission cables;
A conductor layer that collectively covers the plurality of differential signal transmission cables;
A jacket covering the conductor layer;
A multicore cable comprising:
Each of the plurality of differential signal transmission cables includes the differential signal transmission cable according to any one of claims 1 to 3 and an outer insulating layer covering the metal foil tape. Multi-core cable. A method of manufacturing a differential signal transmission cable,
Cover the periphery of a pair of signal lines with an insulator layer,
Coating the outer peripheral surface of the insulator layer with a plating layer;
A method of manufacturing a differential signal transmission cable in which a metal foil tape is wound around an outer peripheral surface of the plating layer.