JP6963723B2 - Manufacturing method of differential signal transmission cable, multi-core cable, and differential signal transmission cable - Google Patents

Description

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

Conventionally, a differential signal transmission cable is used for signal transmission between electronic devices or between substrates in an electronic device. Examples of electronic devices include servers, routers, storage products, etc. 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).

A differential signal transmission cable can be used to transmit a differential signal signal to the receiving side. In signal transmission using a differential signal, signals having opposite phases are input to a pair of signal lines included in the differential signal transmission cable. The receiving side obtains an output by synthesizing the differences between signals having opposite phases.

JP-A-2002-289047

A conventional cable for differential signal transmission includes an insulator layer that covers the periphery of each signal line, and a metal foil tape that is wound around the outer peripheral surface of the insulator layer. A gap may be generated between the outer peripheral surface of the insulator layer and the metal foil tape due to looseness of the metal foil tape or the like. 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 by the pair of signal lines is converted into the in-phase component, so that the waveform deterioration of the output obtained on the receiving side becomes remarkable.

One aspect of the present disclosure is to provide a method for manufacturing a differential signal transmission cable, a multi-core cable, and a differential signal transmission cable capable of suppressing a differential in-phase conversion amount.

One aspect of the present disclosure includes a pair of signal lines, an insulator layer that covers the periphery of the signal lines, and a plating layer that covers the insulator layer, and is differentially in phase in a frequency band of 50 GHz or less. This is a differential signal transmission cable having a maximum conversion amount of −26 dB or less.

According to the differential signal transmission cable, which is one aspect of the present disclosure, the amount of differential common mode conversion 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 layers. Each of the plurality of differential signal transmission cables is a multi-core cable, and each of the plurality of differential signal transmission cables is composed of a differential signal transmission cable according to one aspect of the present disclosure and an outer insulating layer covering the plating layer. It is a core cable.

According to the multi-core cable, which is another aspect of the present disclosure, the differential common mode conversion amount can be reduced.
Another aspect of the present disclosure is a method of manufacturing a differential signal transmission cable comprising a pair of signal lines, an insulator layer covering the periphery of the signal lines, and a plating layer covering the insulator layer. Therefore, the outer peripheral surface of the insulator layer is subjected to a dry ice blast treatment, then the outer peripheral surface is subjected to a corona discharge exposure treatment, and then the plating layer is formed on the outer peripheral surface of the differential signal transmission cable. It is a manufacturing method. The dry ice blast treatment corresponds to the surface roughening treatment. The corona discharge exposure treatment corresponds to the surface modification treatment.

According to the method for manufacturing a differential signal transmission cable, which is another aspect of the present disclosure, it is possible to manufacture a differential signal transmission cable having a small amount of differential in-phase conversion.

It is a perspective view which shows the structure of the differential signal transmission cable 1. 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. Yes, FIG. 3C is an electron micrograph showing the surface condition of the copper plating layer formed after dry ice blasting and corona discharge exposure. It is a graph which shows the correlation between the arithmetic mean roughness Ra of a polyethylene substrate after a specific surface modification treatment, and a contact angle. It is a graph which shows the correlation between the arithmetic mean roughness Ra of a polyethylene substrate after the specific surface modification treatment, and the adhesion wet surface free energy. It is an electron micrograph which shows the recess formed on the outer peripheral surface of an insulator layer by the dry ice blasting 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 X c} of the polyethylene substrate after the specific surface modification treatment and the contact angle, and FIG. 9B is the crystal of the perfluoroethylene propene copolymer substrate after the specific surface modification treatment. It is a graph which shows the correlation between the crystallizationlinity X _{c 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 which shows the correlation between (100) crystal orientation degree O _{100 and contact angle after a specific surface modification treatment.} FIG. 13A is a graph showing the correlation between the crystallite size D and the contact angle in the crystal component of polyethylene after the specific surface modification treatment, and FIG. 13B is a crystal of the perfluoroethylene propene copolymer after the specific surface modification treatment. It is a graph which shows the correlation between the crystallite size D and the contact angle in a component. It is explanatory drawing which shows the structure of the manufacturing system 101. It is explanatory drawing which shows the structure of the manufacturing system 201. It is explanatory drawing which shows the structure of the surface modification unit 203. It is explanatory drawing which shows the other structure of the surface modification unit 203. It is explanatory drawing which shows the other structure of the surface modification unit 203. It is sectional drawing which shows the structure of the multi-core cable 301. It is sectional drawing which shows the structure of the differential signal transmission cable 302 included in the multi-core cable 301. It is a graph which shows the differential common mode conversion amount of a differential signal transmission cable 1 and a comparative example. It is a graph which shows the transmission loss of the differential signal transmission cable 1 and the comparative example. It is a graph which shows the relationship between the arithmetic mean roughness Ra and the transmission loss Sdd21.

An embodiment of the present disclosure will be described.
1. 1. Cable for differential signal transmission (1-1) Basic configuration of cable for differential signal transmission The cable for differential signal transmission of the present disclosure includes a pair of signal lines and an insulator layer that covers 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 shown 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 collectively covers a pair of signal lines 3. The signal line 3 is composed of, for example, a strand. The signal line 3 may be, for example, a stranded wire formed by twisting a plurality of strands. In the case of stranded wire, the flexibility of the signal wire 3 is improved.

The differential signal transmission cable of the present disclosure has a maximum differential in-phase conversion amount of −26 dB or less in a frequency band of 50 GHz or less. The differential common mode conversion amount is measured before the differential signal transmission cable is wound around a drum or the like. In the differential signal transmission cable of the present disclosure, a gap is unlikely to occur 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, signal transmission between substrates in electronic devices, and the like. Examples of electronic devices include servers, routers, storage products, etc. that handle high-speed signals of several Gbps or more. Further, the differential signal transmission cable of the present disclosure can be used as, for example, an acoustic cable. The differential signal transmission cable of the present disclosure is, for example, a cable that transmits a high-speed signal of 25 GHz or higher.

(1-2) Insulator layer The insulator layer preferably covers a pair of signal lines collectively. Covering all at once means covering both of the pair of signal lines with 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 where each signal line is covered. Therefore, it is possible to suppress variations in the dielectric constant in the longitudinal direction of the differential signal transmission cable. As a result, the amount of differential common mode conversion can be further suppressed.

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

In a 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 oval or elliptical. In this case, it becomes easy to form the plating layer uniformly over the entire outer peripheral surface of the insulator layer. In addition, it becomes easy to uniformly roughen and modify the surface of the outer peripheral surface of the insulator layer. The oval shape is a shape composed of two parallel straight lines facing each other and an arc connecting the ends of the straight lines.

The arithmetic mean 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. Further, when the arithmetic average roughness Ra is 0.6 μm or more, the adhesion between the insulator layer and the plating layer is improved, and voids are less likely to occur between the insulator layer and the plating layer. Therefore, the differential common mode conversion amount can be further suppressed.

As a method for setting the arithmetic mean 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 blasting treatment, immersion in an acidic or alkaline solution, immersion in a chromic acid solution, or immersion in a chelate solution. There is.

Examples of the powder to be sprayed on the object to be treated in the blasting treatment include powders composed of dry ice, metal particles, carbon particles, oxide particles, carbide particles, nitride particles and the like. The powder made of dry ice is preferable because it does not easily remain in the insulator layer after the blasting treatment.

In the blasting process, the higher the speed at which the powder is ejected, the larger the arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer can be increased. The longer the blasting time, the larger the arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer. The smaller the distance between the tip of the nozzle that ejects the powder and the outer peripheral surface of the insulator layer, the larger the arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer can be increased.

The arithmetic mean 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 method for measuring the arithmetic mean roughness Ra is a measuring method using a laser microscope VK8500 manufactured by KEYENCE. The specific measurement conditions are as follows. Of the outer peripheral surfaces of the insulator layer, two locations that are located on opposite sides of each other and are flat or have the smallest curvature (hereinafter referred to as the first measurement position and the second measurement position) are selected. At the first measurement position, a rectangular measurement area is set in which the length of the cable in the longitudinal direction is 150 μm and the length of the cable in the circumferential direction is 120 μm. In the measurement area, the arithmetic mean roughness Ra is measured using the above laser microscope. Similarly, at the second measurement position, the arithmetic mean roughness Ra is measured in the same manner. Finally, the average value of the arithmetic mean roughness Ra at the first measurement position and the arithmetic mean roughness Ra at the second measurement position is calculated, and the average value is taken as the arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer. do. The arithmetic mean roughness Ra is a value at a time before forming the plating layer.

When the arithmetic mean 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 difficult to peel off from the insulator layer. A polyethylene substrate was prepared. This substrate corresponds to the insulator layer. The substrate was subjected to a blast treatment using dry ice as a powder (hereinafter referred to as a dry ice blast treatment). The dry ice blast treatment corresponds to the surface roughening treatment. The arithmetic mean roughness Ra of the surface of the substrate after the dry ice blasting treatment was 0.6 μm or more. Then, the substrate was subjected to a 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 ozone-containing liquid immersion may be performed. The free energy of the wetted 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. The method for measuring the free energy on the wetted surface will be described later.

After the corona discharge exposure treatment, a copper plating layer was formed on the surface of the substrate by an electroless plating method. Next, cuts were made in the copper plating layer in a grid pattern. The notch penetrated the copper plating layer and reached the substrate. Next, the adhesive tape was attached to the copper plating layer, and then 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-plated layer did not peel off on any of the grids. That is, the adhesion between the copper plating layer and the substrate was high.

Comparative examples were tested in basically the same way. In the comparative example, the substrate was not subjected to surface roughening treatment or surface modification treatment. The arithmetic mean roughness Ra of the surface of the substrate was 0.13 μm. FIG. 2A shows the state of the copper plating layer when the adhesive tape is peeled off in the comparative example. Of the 20 grids, 17 had the 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. When 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 reducing the contact angle on the outer peripheral surface of the insulator layer to 95 ° or less, for example, electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, immersion in ozone-containing liquid, etc. A method of performing the surface modification treatment of the above can be mentioned.

In any of the treatments, the higher the strength of the treatment, the smaller the contact angle can be. Further, the longer the processing time is, the smaller the contact angle can be. Examples of the method of enhancing the surface modification effect by the corona discharge exposure include a method of increasing the voltage, a method of increasing the oxygen concentration in the atmosphere of the corona discharge exposure, and the like. The contact angle is measured by dropping a water droplet having a diameter of 1.5 mm onto the outer peripheral surface of the insulator layer and reading the contact angle. The contact angle is a value at a time before forming the plating layer.

It is preferable that the absolute value of the free energy of the adhered wet surface on the outer peripheral surface of the insulator layer is 66 mJ / m ^{2 or more.} In this case, it becomes easy to make the thickness of the plating layer uniform. When 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 setting the absolute value of the free energy of the adhered wet surface on the outer peripheral 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 thereof include a method of performing surface modification treatment such as beam irradiation and immersion in an ozone-containing liquid.

In any of the treatments, the higher the treatment intensity, the larger the absolute value of the adhesion wet surface free energy. Further, the longer the treatment time, the larger the absolute value of the free energy of the adhered wet surface can be increased.

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

式（３）におけるγ_LGは定数であり、７２．７５ｍＪ／ｍ²である。θは、絶縁体層の外周面における接触角である。付着ぬれ表面自由エネルギーΔＧは、めっき層を形成する前の時点における値である。

_{Γ LG} in the formula (3) is a constant and is 72.75 mJ / m ² . θ is the contact angle on the outer peripheral surface of the insulator layer. The adhesion wet surface free energy ΔG is a value at a time before forming the plating layer.

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 when the absolute value of the free energy of the adhered wet surface is 66 mJ / m ^{2 or more.} ..

A polyethylene substrate was prepared. This substrate corresponds to the insulator layer. The substrate was subjected to a dry ice blast treatment and then a corona discharge exposure treatment. The dry ice blast treatment corresponds to the surface roughening treatment. The corona discharge exposure treatment corresponds to the surface modification treatment. The arithmetic mean 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 free energy of the adhered wet surface of 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 an electrolytic plating method. The thickness of the copper plating layer was set to 3 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. Further, the adhesion between the copper plating layer and the substrate was high, and the copper plating layer was not peeled off.

Basically, the first comparative example was prepared by the same method. However, in the first comparative example, the arithmetic mean 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 free energy of the adhered wet surface of 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.

In addition, a second comparative example was prepared by basically the same method. However, in the second comparative example, the arithmetic mean 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 free energy of the adhered wet surface of 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 plating defect swelling 191 called a blister was present on the surface of the copper plating layer, resulting in an inhomogeneous plating state.
Arithmetic on the outer peripheral surface of the insulator layer by performing a dry ice blast treatment on the outer peripheral surface of the insulator layer and then performing a surface modification treatment (hereinafter referred to as a specific surface modification treatment) in which a corona discharge exposure treatment is performed. The average roughness Ra and the absolute value of the contact angle or the adhesion wet surface free energy can be controlled. This was confirmed by the following test. The dry ice blast treatment corresponds to the surface roughening treatment. The corona discharge exposure treatment corresponds to the 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 multiple conditions for the specific reforming process. FIG. 4 shows the correlation between the arithmetic mean roughness Ra and the contact angle after the specific surface modification treatment is performed. By performing the specific surface modification treatment, the arithmetic mean roughness Ra can be set to 0.6 μm or more, and the contact angle can be set to 95 ° or less.

FIG. 5 shows the correlation between the arithmetic mean roughness Ra after the specific surface modification treatment and the free energy of the adhered wet surface. By performing the specific surface modification treatment, the arithmetic mean roughness Ra can be set to 0.6 μm or more, and the absolute value of the adhesion wet surface free energy ^{can be set to 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 wider than the opening in the recess on the inner side in the depth direction. In this case, the following effects are obtained. When forming the plating layer, the plating bath penetrates deep into the recess. Nucleation occurs on the inner side of the recess, and the plating layer grows on the inner side of the recess. Since the plating layer grown on the inner side of the recess is larger than the opening, it is difficult to pull out from the opening. As a result, an anchor effect is generated, and the plating layer and the insulator layer are less likely to be peeled off.

As a method of forming a recess in the insulator layer, a method of performing a blast treatment can be mentioned. Examples of the blasting treatment include dry ice blasting treatment. The dry ice blast treatment corresponds to the surface roughening treatment. FIG. 6 shows an example of the recess formed on the outer peripheral surface of the insulator layer by the dry ice blasting treatment. FIG. 6 is a cross-sectional view of the insulator layer 71 near the outer peripheral surface 72. A recess 73 is formed on the outer peripheral surface 72. The recess 73 has a portion wider than the opening 74 in the recess 73 on the inner side in the depth direction. The shape of the recess 73 is a takotsubo-like shape. In the example shown in FIG. 6, the material of the insulator layer 71 is polyethylene.

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

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 the dielectric loss tangent of the insulator layer become small. As a method for producing an insulator 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 the temperature and pressure when molding the insulator layer. Further, as another method for producing an insulator layer made of a foamable resin, for example, there is a method in which nitrogen gas or the like is injected at the time of high-pressure molding of the insulator layer, and then the pressure is reduced to foam the insulator layer.

Further, an insulator layer made of a foamable resin may be produced as follows. An extruder having a desired shape is installed in the extruder. Using the extruder, a pair of signal lines and a foamable resin are extruded at the same time. The foamable resin forms an insulator layer.

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

前記式（１）におけるＩ_cは結晶成分のＸ線回折強度であり、Ｉ_aは非晶質成分のＸ線回折強度である。

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.

_{As a method for increasing the crystallinity X c} of the insulator layer made of polyethylene to 0.744 or more, for example, electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, ozone. Examples thereof include a method of performing a surface modification treatment such as immersion in a containing liquid. In any of the treatments, the higher the treatment intensity, the higher the crystallinity X _c . Further, the longer the treatment time, the _{larger the crystallinity X c} can be.

_{I c} and I _a in the equation (1) are calculated as follows. The X-ray diffraction pattern of the sample of the insulator layer is acquired by using RINT2500 which is an X-ray diffractometer manufactured by Rigaku. Examples of the X-ray diffraction pattern are shown in FIGS. 7 and 8. The horizontal axis of the X-ray diffraction pattern shown in FIGS. 7 and 8 is a 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 having a diffraction peak near 16.4 to 16.5 ° (hereinafter referred to as an amorphous halo) 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.

Spectral fitting analysis using the Lorentz function is performed on the amorphous halo to obtain _{a smooth curve Fa that matches well with the amorphous halo.} The acquired curve _Fa is shown in FIGS. 7 and 8. _{Let I a} be the intensity of the amorphous halo calculated by the integral intensity calculation based on this curve F a.

Further, the spectrum fitting analysis using the Lorentz function is performed on the crystal component spectrum to obtain a _{smooth curve F c that matches well with the crystal component spectrum.} The acquired curves F _c are shown in FIGS. 7 and 8. Based on this curve F _c , the intensity of the amorphous component spectrum calculated by the integral intensity calculation is defined as I _c . The crystallinity X _c is a value at a time before forming the plating layer.

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

前記式（１）におけるＩ_cは結晶成分のＸ線回折強度であり、Ｉ_aは非晶質成分のＸ線回折強度である。Ｉ_c、Ｉ_aの算出方法は上述した方法である。結晶化度Ｘ_cは、めっき層を形成する前の時点における値である。

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 above-mentioned method. The crystallinity X _c is a value at a time before forming the plating layer.

_{As a method for reducing the crystallinity X c} of the insulator layer made of the 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 thereof include a method of performing surface modification treatment such as beam irradiation and immersion in an ozone-containing liquid. In any of the treatments, the higher the treatment intensity, the higher the crystallinity X _c . Further, the longer the treatment time, the _{larger the crystallinity X c} can be.

The crystallinity X _c correlates 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. _{The correlation between the crystallinity X c} and the contact angle after the specific surface modification treatment is shown in FIG. 9A. When the crystallinity X _c was 0.744 or more, the contact angle became remarkably small.

In addition, a substrate made of a perfluoroethylene propene copolymer was subjected to a specific surface modification treatment. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. _{The correlation between the crystallinity X c} and the contact angle after the specific surface modification treatment is shown in FIG. 9B. When the crystallinity X _c was 0.47 or less, the contact angle became remarkably small.

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 a specific axis of two or less axes among the crystal axes. ing. Further, the polyethylene has a (100) crystal orientation degree O ₁₀₀ represented by the following formula (2) of 0.26 or less. In the following, this insulator layer will be referred to as a specific orientation polyethylene insulator layer.

前記式（２）においてＩ₂₀₀は指数２００のＸ線回折強度であり、Ｉ₁₁₀は指数１１０のＸ線回折強度である。

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

When the insulator layer is a polyethylene insulator layer having a specific orientation, it becomes easy to make the thickness of the plating layer uniform. When 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 forming 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, and ozone-containing liquid immersion. A method of performing quality treatment can be mentioned.

In any of the treatments, the higher the treatment intensity, the smaller the _{crystal orientation degree O 100.} Further, the longer the treatment time, the smaller the _{crystal orientation degree O 100.
I 200} and I ₁₁₀ in the above formula (2) are calculated as follows.

The X-ray diffraction pattern of the sample of the insulator layer is acquired by using RINT2500 which is an X-ray diffractometer manufactured by Rigaku. Examples of the X-ray diffraction pattern are shown in FIGS. 10 and 11. The horizontal axis of the X-ray diffraction pattern shown in FIGS. 10 and 11 is a 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 that has not been surface-modified. FIG. 11 is an X-ray diffraction pattern of polyethylene subjected to a corona discharge exposure treatment as a surface modification treatment.

The diffraction spectrum having a peak in the vicinity of about 21.5 ° (hereinafter referred to as 110 diffraction spectrum) corresponds to the Miller index 110 and represents the orientation 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 the Lorentz function is performed on the 110 diffraction spectrum, and a smooth curve F ₁ that matches well with the 110 diffraction spectrum is obtained. The acquired curve F ₁ is shown in FIGS. 10 and 11. Based on this curve F ₁ , the intensity of the 110 diffraction spectrum calculated by the integrated intensity calculation is defined as I ₁₁₀ .

Further, the spectrum fitting analysis using the Lorentz function is performed on the 200 diffraction spectrum, and a smooth curve F ₂ that matches well with the 200 diffraction spectrum is obtained. The acquired curve F ₂ is shown in FIGS. 10 and 11. Based on this curve F ₂ , the intensity of the 200 diffraction spectrum calculated by the integrated intensity calculation is defined as I ₂₀₀ .

When individual crystal particles contained in a substance composed of polycrystalline materials are in a state of preferential orientation in a certain direction, the X-ray diffraction intensity of a specific exponential plane is higher than that of other X-ray diffraction intensities. It will be relatively high. Therefore, the orientation of a predetermined lattice plane can be quantified by the intensity ratio of the X-ray diffraction intensity. (100) Crystal orientation degree O ₁₀₀ is an intensity ratio of X-ray diffraction intensity and represents 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.} (100) When the crystal orientation degree O ₁₀₀ was 0.26 or less, the contact angle became remarkably small. (100) The degree of crystal orientation O ₁₀₀ is a value at a time before forming 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 crystal component of the polyethylene is 18 nm or more. When the insulator layer is the above, it becomes easy to make the thickness of the plating layer uniform. When 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 forming the insulator layer as described above, for example, surface modification treatments such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, and ozone-containing liquid immersion are performed. There is a way to do it.

In any of the treatments, the higher the strength of the treatment, the larger the crystallite size in the crystal component of polyethylene. Further, the longer the treatment time, the larger the crystallite size in the crystal component of polyethylene can be increased.

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

式（４）においてＤはポリエチレンの結晶成分における結晶子サイズである。Ｋはシェラー定数である。Ｋの値は２／πとした。λはＸ線波長である。ＢはＸ線回折ピークの広がり幅である。θはＸ線回折角である。λ、Ｂ、θは、絶縁体層の試料のＸ線回折パターンから得られる値である。結晶子サイズは、めっき層を形成する前の時点における値である。

In formula (4), D is the crystallite size in the crystal component of polyethylene. K is a Scheller constant. The value of K was 2 / π. λ is the X-ray wavelength. B is the spread width of the X-ray diffraction peak. θ is the 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 at a time before forming the plating layer.

The crystallite size D in the crystal 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 crystal component of polyethylene after the specific surface modification treatment. When the crystallite size D in the crystal component of polyethylene was 18 nm or more, the contact angle became remarkably small.

As the insulator layer, for example, the following are preferable. The insulator layer consists of a 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 the above, it becomes easy to make the thickness of the plating layer uniform. When 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 forming the insulator layer as described above, for example, surface modification treatments such as electron beam irradiation, ion irradiation, corona discharge exposure, plasma exposure, ultraviolet irradiation, X-ray irradiation, γ-ray irradiation, and ozone-containing liquid immersion are performed. There is a way to do it.

In any of the treatments, the higher the treatment intensity, the larger the crystallite size in the crystal component of the perfluoroethylene propene copolymer. In addition, the longer the treatment time, the larger the crystallite size in the crystal component of the perfluoroethylene propene copolymer. The method for calculating the crystallite size in the crystal component of the perfluoroethylene propene copolymer is the same as the method for calculating the crystallite size in the crystal component of polyethylene. The crystallite size is a value at a time before forming the plating layer.

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 a perfluoroethylene propene copolymer. The substrate corresponds to the insulator layer. There are multiple conditions for the specific surface modification treatment. The correlation between the crystallite size D and the contact angle in the crystal component of the perfluoroethylene propene copolymer after the specific surface modification treatment is shown in FIG. 13B. When the crystallite size D in the crystal component of the perfluoroethylene propene copolymer was 13.6 nm or less, the contact angle was significantly 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 transmitting a signal of 25 GHz or higher, the differential common mode conversion amount can be remarkably suppressed.

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

The standard deviation of the thickness of the plating layer is preferably 0.8 μm or less. In this case, the transmission loss of the differential signal transmission cable can be suppressed. Further, since a portion where the thickness of the plating layer is excessively small is unlikely to occur, noise can be further reduced.

The standard deviation of the thickness of the plating layer is calculated by the following method. A cross section orthogonal to the longitudinal direction of the differential signal transmission cable is formed at four points. The distance between each cross section is 3 m. Select any 4 points in each cross section. The thickness of the plating layer is measured at a total of 4 × 4 points. The standard deviation of the thickness of all the measured 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 adhered wet surface energy.
The 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, and immersion in an ozone-containing liquid. The contact angle on the outer peripheral surface of the layer can be reduced, and the absolute value of the adhered wet surface energy can be increased.

The plating layer may be a stack of a plurality of layers. The number of laminated layers 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 non-magnetic layers made of copper or the like. In this case, the plating layer can exert a shielding effect against a strong magnetic field and a weak magnetic field. Further, the plating layer can exert 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 first performing electroless plating and then performing electrolytic plating. 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 the method of forming the entire plating layer by electroless plating.

2. Method for Manufacturing Cable for Differential Signal Transmission The cable for differential signal transmission of the present disclosure can be manufactured by, for example, the following method. FIG. 14 shows a manufacturing system 101 used for manufacturing a cable for differential signal transmission. 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 transfer unit 115, and the like. To be equipped.

The degreasing unit 103 includes a degreasing tank 117 and a degreasing liquid 119. The degreasing liquid 119 is housed in the degreasing tank 117. The degreasing liquid 119 contains, for example, one or more of soda borate, sodium phosphate, surfactant and the like. 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 housed in the etching tank 121. The etching solution 123 contains, for example, one or more of chromic acid, sulfuric acid, ozone, acid, alkali, chelate and the like. The temperature of the etching solution 123 is, for example, 65 to 70 ° C.

The first activation unit 107 includes a first activation tank 125 and a first activation liquid 127. The first activation liquid 127 is housed in the first activation tank 125. The first activation liquid 127 contains, for example, one or more of palladium chloride, stannous chloride, concentrated hydrochloric acid and the like. The temperature of the first activation liquid 127 is, for example, 30 to 40 ° C.

The second activation unit 109 includes a second activation tank 129 and a second activation liquid 131. The second activation liquid 131 is housed in the second activation tank 129. The second activation liquid 131 contains, for example, sulfuric acid or the like. The temperature of the second activating 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 housed in the electroless plating tank 133. The electroless plating solution 135 contains, 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 liquid 139, a pair of anodes 141, and a power supply unit 143. The electrolytic plating solution 139 is housed in the electrolytic plating tank 137. The electrolytic plating solution 139 has, for example, the composition shown in Table 1 or Table 2. The temperature of the electrolytic plating solution 139 is, for example, 20 to 25 ° C.

アノード１４１は電解めっき液１３９の中に浸漬されている。アノード１４１は、例えば、銅湯から作製した溶融銅を圧延鋳造したものである。あるいは、アノード１４１は、以下のように製造されたものであってもよい。粗銅をアノードとし、ステンレス又はチタンをカソードとして種板電解を行う。カソード表面に析出した純銅板を剥ぎ取って、アノード１４１とする。電源ユニット１４３は、アノード１４１と、後述するボビン１６５、１６９との間に直流電圧を印加する。

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

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

The bobbin groups are basically arranged in series along the transport direction D shown in FIG. The transport direction D is a direction from the degreasing unit 103 to 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 this 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 conveyed differential signal transmission cable 171 includes a signal line and an insulator layer, but a plating layer has not yet been formed. The insulator layer can be provided, for example, by known extrusion molding.

The conveyed differential signal transmission cable 171 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. Further, 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 the 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 for 3 to 6 minutes in the second activation unit 109. 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 larger 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, the 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 larger the thickness of the electrolytic plating layer. The specific conditions for electroplating in the electroplating unit 113 are as shown in Table 3. Through the above steps, the differential signal transmission cable 171 is completed.

なお、図１４では記載を省略しているが、各ユニットの間では、差動信号伝送用ケーブル１７１を純水で洗浄する。洗浄の方法として、超音波洗浄、揺動洗浄、流水洗浄等がある。純水で洗浄することにより、前のユニットで付着した残留薬剤が後のユニットに持ち込まれることを抑制できる。

Although the description is omitted in FIG. 14, the differential signal transmission cable 171 is washed with pure water between the units. Cleaning methods include ultrasonic cleaning, rocking cleaning, running water cleaning, and the like. By cleaning with pure water, it is possible to prevent the residual chemicals adhering from the previous unit from being carried into the later unit.

The transport speed of the differential signal transmission cable 171 can be adjusted as appropriate. The transport speed may be changed during the transport, or the transport may be paused.
A cable for differential signal transmission 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 there are some differences. The differences will be mainly described below. The manufacturing system 201 does not include the degreasing unit 103 and the wet etching unit 105, but includes a surface modification unit 203. FIG. 16 shows the 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 configuration 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 bobbin 209 to bobbin 211, and is conveyed along a figure-eight path returning to 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 carried along the figure-eight 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 205A into the differential signal transmission cable 171 existing between the bobbin 209 and the bobbin 211. The driving force of the injection is air pressure. The arithmetic mean 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 the dry ice blasting process. The dry ice blast treatment corresponds to the surface roughening treatment.

The surface of the outer peripheral surface of the insulator layer facing the nozzle 205A is opposite between the time of sending from the bobbin 209 to the bobbin 211 and the time of returning from the bobbin 211 to the bobbin 209. Therefore, the fine shape forming apparatus 205 can increase the arithmetic mean roughness Ra over the entire outer peripheral surface of the insulator layer.

The particle size 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 for the dry ice blasting process can be changed as appropriate. Conditions in the dry ice blasting process include, for example, the particle size of the dry ice powder, the dry ice flow rate, the air pressure, the distance from the tip of the nozzle 205A to the differential signal transmission cable 171 and the transport of the differential signal transmission cable 171. Examples include the speed and the temperature of the differential signal transmission cable 171. For example, the dry ice blasting treatment may be performed at a temperature lower than the glass transition temperature of the material of the insulator layer. Examples of the temperature lower than the glass transition temperature of the material of the insulator layer include temperatures of −79 ° C. and higher and 20 ° C. and lower. The position of nozzle 205A may be fixed, rocked or scanned.

The hydrophilization treatment device 207 performs a hydrophilization treatment by exposure to corona discharge. Corona discharge exposure corresponds to a surface modification process. As shown in FIG. 16, the hydrophilization treatment device 207 includes a total of four plate electrodes 208. The pair of flat plate electrodes 208 face each other with the differential signal transmission cable 171 sent from the bobbin 213 to the bobbin 215. The other pair of plate electrodes 208 face each other with the differential signal transmission cable 171 returning from the bobbin 215 to the bobbin 213. Corona discharge occurs by applying a high frequency high voltage between the opposing plate electrodes 208. By being exposed to the corona discharge, the outer peripheral surface of the insulator layer becomes hydrophilic and the wettability is improved. When the outer peripheral surface of the rim layer becomes hydrophilic and the wettability is improved, the contact angle becomes small and the absolute value of the free energy of the adhered wet surface becomes large.

It is presumed that the reason why the outer peripheral surface of the insulator layer becomes hydrophilic and the wettability is improved by the corona discharge exposure is as follows. High-energy electrons generated by corona discharge exposure ionize and dissociate oxygen molecules existing in the air, and oxygen radicals, ozone, and the like are generated. At the same time, the high-energy electrons that reach the vicinity of the outer peripheral surface of the insulator layer cut and cleave the main chain and side chains of, for example, polyethylene and perfluoroethylene propene copolymer contained in the insulator layer. The oxygen radicals, ozone, etc. generated by the corona discharge recombine with the main chain and side chains 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. NS. As a result, the outer peripheral surface of the insulator layer becomes hydrophilic and the wettability is improved.
The applied voltage in the 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 flat plate electrode 208 is, for example, 0.1 to 3 mm. The atmosphere inside the housing 204 is, for example, the atmosphere.

The conditions for exposure to corona discharge can be changed as appropriate. Conditions for corona discharge exposure include, for example, 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 flat plate electrode 208, the atmosphere inside the housing 204, and the like. The atmosphere inside the housing 204 may contain oxygen, nitrogen, carbon dioxide, a rare gas, and 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 the corona discharge is performed, the flat plate electrode 208 indirectly contacts the insulator layer and slides against the silicone rubber.
An exhaust mechanism for exhausting the air inside the housing 204 and a drying device for drying the inside of the housing 204 may be provided. In this case, rust on the differential signal transmission cable 171 can be suppressed. Further, a power reducing 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 cable for differential signal transmission using the manufacturing system 201, a dry ice blast treatment is performed on the outer peripheral surface of the insulator layer, and then a corona discharge exposure treatment is performed on the outer peripheral surface of the insulator layer. Then, a permanganic acid treatment is performed, and then a plating layer is formed on the outer peripheral surface of the insulator layer. The dry ice blast treatment corresponds to the surface roughening treatment. The corona discharge exposure treatment corresponds to the surface modification treatment. By performing the permanganate treatment, the insulator layer is easily plated. Further, by performing the permanganate treatment, the transmission characteristics of the differential signal transmission cable are improved. Permanganate treatment may be performed after the surface roughening treatment, and then corona discharge exposure treatment may be performed.

The surface modification unit 203 may be the one shown in FIG. The surface modification unit 203 includes a cylindrical hydrophilization treatment device 207. The hydrophilization treatment device 207 includes a shaft hole 217. The differential signal transmission cable 171 carried by the bobbin 209 and the bobbin 213 passes through the shaft hole 217. The hydrophilization 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 the wettability is improved. When the outer peripheral surface of the rim layer becomes hydrophilic and the wettability is improved, the contact angle becomes small and the absolute value of the free energy of the adhered wet surface becomes large. The corona discharge exposure treatment corresponds to the surface modification treatment.

The surface modification unit 203 may be the one 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 bobbin 215 are grounded to the ground. The hydrophilization treatment device 207 applies a voltage between the electrode 219 and the bobbins 213 and 215 to generate a corona discharge. By being exposed to the corona discharge, the outer peripheral surface of the insulator layer becomes hydrophilic and the wettability is improved. When the outer peripheral surface of the rim layer becomes hydrophilic and the wettability is improved, the contact angle becomes small and the absolute value of the free energy of the adhered wet surface becomes large. The corona discharge exposure treatment corresponds to the surface modification treatment.

3. 3. Multi-core cable The multi-core 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" above, and covers the plating layer. Further provided with an outer insulating layer.

The plurality of differential signal transmission cables may or may not be twisted. 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 interposition may be provided between the groups. Each group includes, for example, two or more differential signal transmission cables.

The conductor layer can be composed of, for example, a shield tape conductor, a braided wire, or the like. The conductor layer may be, for example, a laminate of a shield tape conductor and a braided wire. Shielding tape As the material for conductors and braided wires, those commonly used for cables can be used. As the material of the jacket, those commonly used for cables can be used.

Examples of the external insulating layer include an insulating tape, a laminated tape, a film formed by spray-coating an insulator, and the like. 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 prevent the insulator layer from being deformed by heat when the external insulating layer is formed.

Examples of the intervening material include paper, thread, foam, and the like. Examples of the foam include expanded polyolefins such as expanded polypropylene and expanded ethylene. The multi-core cable of the present disclosure can suppress the differential common mode conversion amount.

FIG. 19 shows an example of the multi-core cable 301. The multi-core 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. The jacket 307 covers the braided wire 305.

The eight differential signal transmission cables 1 are divided into two groups in the center and six groups around the cables 1. 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.

The insulator layer 5 collectively covers a pair of signal lines 3. The plating layer 7 covers the insulator layer 5. The outer insulating layer 311 covers the plating layer 7. 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 mean roughness Ra on the outer peripheral surface of the insulator 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 each described in, for example, the section “1. Differential signal transmission cable”.

4. Example (4-1) Example 1
The differential signal transmission cable 1 of the embodiment having the structure shown in FIG. 1 was manufactured. The material of the insulator layer 5 is polyethylene. The insulator layer 5 collectively covers a pair of signal lines 3. 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 elliptical. 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 coefficient of variation 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 is L ₁ . _{Let L 2 be} the outer diameter of the insulator layer 5 in the minor axis direction. _{Let L 3} be the distance between the centers of the pair of signal lines 3. In the major axis direction, the distance between the center of the signal line 3 and the outer peripheral surface of the insulator layer 5 is L ₄ . In the minor axis direction, the distance between the center of the signal line 3 and the outer peripheral surface of the insulator layer 5 is L ₅ .
Even when the shape of the outer edge of the insulator layer 5 is oval, L _{1 to} L ₅ can be defined in the same manner. However, when the shape of the outer edge of the insulator layer 5 is oval, the major axis direction is a direction parallel to the two straight lines forming the outer peripheral surface of the insulator layer 5. When the shape of the outer edge of the insulator layer 5 is oval, the minor axis direction is a direction orthogonal to the above two straight lines.
In Example 1, L ₁ is 2.03 mm. L ₂ is 1.04 mm. L ₃ is 0.55 mm. L ₄ is 0.74 mm. L ₅ is 0.52 mm.

The outer peripheral surface of the insulator layer 5 was subjected to a surface roughening treatment. The surface roughening treatment is chromic acid etching. The arithmetic mean roughness Ra on the outer peripheral surface of the insulator layer 5 is 0.6 μm before the plating layer 7 is formed. Before forming the plating layer 7, the contact angle on the outer peripheral surface of the insulator layer 5 is 95 °.

The amount of differential common mode conversion 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 a frequency represented by a logarithmic scale. The vertical axis is the differential common mode conversion amount, and the unit is dB. The differential common mode conversion amount on the vertical axis corresponds to Scd21 of the mixed mode S parameter. The larger the value on the vertical axis (that is, the smaller the absolute value of the negative measured value), the larger the amount of noise in the differential in-phase conversion amount, indicating that the quality of the transmitted signal deteriorates significantly. ..

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 outer peripheral surface of the insulator layer is not surface-roughened. Therefore, the arithmetic mean 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 °. Further, the differential signal transmission cable R of the comparative example does not have a plating layer, but includes a conductor layer around which a metal tape is wound.

In the differential signal transmission cable 1 of the embodiment, the amount of differential in-phase conversion 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 remarkable.

Further, the transmission characteristics of the differential signal transmission cable 1 of the embodiment and the differential signal transmission cable R of the comparative example were measured. The transmission characteristics were measured before the differential signal transmission cable was wound around a drum or the like. The measurement result of the differential signal transmission cable 1 of the embodiment 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 is the frequency of the transmission signal. The vertical axis shows the transmission signal loss in dB. The transmission loss on the vertical axis corresponds to the mixed mode S parameter Sdd21. It is shown that the smaller the value on the vertical axis (that is, the larger the absolute value of the negative measured value), the larger the attenuation of the transmitted signal, the larger the deterioration due to the transmission of the transmitted signal, and the more remarkable the transmission loss. There is.

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

On the other hand, in the differential signal transmission cable R of the comparative example, a suckout occurred. The reason why the suckout does not occur 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 and is like a conductor layer around which a metal tape is wound. It is presumed that this is because there are no overlaps or seams.
(4-2) Example 2
Cables S1 to S7 for differential signal transmission were manufactured under the conditions shown in Table 4.

Ｓ１〜Ｓ７はいずれも、ポリエチレンから成る絶縁体層を備える。Ｓ１〜Ｓ７のいずれにおいても、一対の信号線３の延在方向に直交する断面において、絶縁体層の外縁の形状は楕円形である。実施例２において、Ｌ₁は１．２１ｍｍである。Ｌ₂は０．６２ｍｍである。Ｌ₃は０．３５ｍｍである。Ｌ₄は０．４３ｍｍである。Ｌ₅は０．３１ｍｍである。
Ｓ１〜Ｓ６は、めっき層から成る導電層を備える。Ｓ７は、Ｃｕテープを横巻きすることで導電層を形成した。Ｓ１〜Ｓ５では、絶縁体層の外周面に、ドライアイスブラスト処理を行い、その後、コロナ放電暴露処理を行った。ドライアイスブラスト処理は表面粗化処理に対応し、コロナ放電暴露処理は表面改質処理に対応する。Ｓ１〜Ｓ３では、コロナ放電暴露処理の後、過マンガン酸処理を行った。Ｓ４〜Ｓ５では、コロナ放電暴露処理の後、過マンガン酸処理を行わなかった。Ｓ６では、絶縁体層の外周面にクロム酸処理を行った。Ｓ７では、Ｃｕテープを巻く前の処理は行わなかった。

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 0.62 mm. L ₃ is 0.35 mm. L ₄ is 0.43 mm. L ₅ is 0.31 mm.
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, the outer peripheral surface of the insulator layer was subjected to a dry ice blast treatment, and then a corona discharge exposure treatment 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, permanganate treatment was performed after the corona discharge exposure treatment. In S4 to S5, the permanganate treatment was not performed after the corona discharge exposure treatment. In S6, the outer peripheral surface of the insulator layer was treated with chromic acid. In S7, the treatment before winding the Cu tape was not performed.

For S1 to S7, the arithmetic mean roughness Ra and the transmission loss Sdd21 were measured. The results are shown in Table 4 above. In Table 1, "1st Ra" represents the arithmetic mean roughness Ra at the 1st measurement position, "2nd Ra" represents the arithmetic mean roughness Ra at the 2nd measurement position, and "average Ra" represents their average value. Represents. Further, FIG. 23 shows the relationship between the arithmetic mean roughness Ra and the transmission loss Sdd21. The smaller the arithmetic mean roughness Ra, the smaller the transmission loss Sdd21. S1 to S3 treated with permanganate had a smaller transmission loss than S4 to S5 not treated with permanganate.

5. Other Embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented in various modifications.

(1) The function of one component in each of the above embodiments may be shared by a plurality of components, or the function of the plurality of components may be exerted by one component. Further, a part of the configuration of each of the above embodiments may be omitted. In addition, at least a part of the configuration of each of the above embodiments may be added or replaced with respect to the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

(2) In addition to the above-mentioned differential signal transmission cable or multi-core cable, a system having at least one of them as a component, a method for manufacturing a multi-core cable, a signal transmission / reception method using a differential signal transmission cable, etc. The present disclosure can also be realized in various forms.

1 ... Differential signal transmission cable, 3 ... Signal line, 5 ... Insulation layer, 7 ... Plating layer, 71 ... Insulation layer, 72 ... Outer surface, 73 ... Recession, 101, 201 ... Manufacturing system, 103 ... Degreasing Unit, 105 ... Wet etching unit, 107 ... 1st activation unit, 109 ... 2nd activation unit, 111 ... Electroplating unit, 113 ... Electroplating unit, 115 ... Transfer 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 ... Electroplating tank , 135 ... Electroplating solution, 137 ... Electroplating tank, 139 ... Electroplating solution, 141 ... Anode, 143 ... 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, 203 ... Surface modification unit, 204 ... Housing, 204A ... Inlet, 204B ... Outlet, 205 ... Fine shape forming device , 205A ... nozzle, 207 ... hydrophilization treatment device, 208 ... flat plate electrode, 217 ... shaft hole, 219 ... electrode, 301 ... multi-core cable, 302 ... differential signal transmission cable, 303 ... shield tape conductor, 305 ... braid Wire, 307 ... jacket, 309 ... intervening, 311 ... outer insulating layer

Claims (18)

A pair of signal lines and
An insulator layer that covers the periphery of the signal line and
The plating layer that covers the insulator layer and
With
A recess is provided on the outer peripheral surface of the insulator layer.
The recess, on the back side in the depth direction, have a widened portion than the opening,
The insulator layer is made of polyethylene.
A cable for differential signal transmission in which the crystallite size in the crystal component of polyethylene is 18 nm or more. The differential signal transmission cable according to claim 1.
The insulator layer is a differential signal transmission cable that collectively covers the pair of signal lines. The differential signal transmission cable according to claim 1 or 2.
A cable for differential signal transmission in which the shape of the outer edge of the insulator layer is oval or elliptical in a cross section orthogonal to the extending direction of the pair of signal lines. The differential signal transmission cable according to any one of claims 1 to 3.
A cable for differential signal transmission in which the thickness of the plating layer is 1 μm or more and 5 μm or less. The differential signal transmission cable according to any one of claims 1 to 4.
A cable for differential signal transmission in which the standard deviation of the thickness of the plating layer acquired at four points in each of the four cross sections orthogonal to the extending direction of the pair of signal lines is 0.8 μm or less. The differential signal transmission cable according to any one of claims 1 to 5.
A cable for differential signal transmission in which the arithmetic average roughness Ra on the outer peripheral surface of the insulator layer is 0.6 μm or more. The differential signal transmission cable according to any one of claims 1 to 6.
A cable for differential signal transmission having a contact angle of 95 ° or less on the outer peripheral surface of the insulator layer. The differential signal transmission cable according to any one of claims 1 to 7.
A cable for differential signal transmission in which the absolute value of the adhered wet surface energy on the outer peripheral surface of the insulator layer is 66 mJ / m ^{2 or more.} The differential signal transmission cable according to any one of claims 1 to 8.
A cable for differential signal transmission in which the maximum value of the differential common mode conversion amount is −26 dB or less in the frequency band of 50 GHz or less. The cable for differential signal transmission according to any one of claims 1 to 9.
The plating layer is continuously formed over the entire cable for differential signal transmission.
A differential signal transmission cable that does not cause suckout in the frequency band of 50 GHz or less. The differential signal transmission cable according to any one of claims 1 to 10.
The insulator layer is made of polyethylene.
A cable for differential signal transmission having _{a crystallinity X c} of 0.744 or more represented by the following formula (1).

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 differential signal transmission cable according to claim 14.
The insulator layer is made of a perfluoroethylene propene copolymer.
A cable for differential signal transmission having _{a crystallinity X c} of 0.47 or less represented by the following formula (1).

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 differential signal transmission cable according to any one of claims 1 to 11.
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 a specific axis of two or less axes among the crystal axes. And
A cable for differential signal transmission having a _{crystal orientation degree O 100} of 0.26 or less, which is represented by the following formula (2).

In the above formula (2), I ₂₀₀ is the X-ray diffraction intensity of the index 200, and I ₁₁₀ is the X-ray diffraction intensity of the index 110. A pair of signal lines and
An insulator layer that covers the periphery of the signal line and
The plating layer that covers the insulator layer and
With
A recess is provided on the outer peripheral surface of the insulator layer.
The recess has a portion wider than the opening on the inner side in the depth direction.
The insulator layer is made of a perfluoroethylene propene copolymer.
A cable for differential signal transmission in which the crystallite size in the crystal component of the perfluoroethylene propene copolymer is 13.6 nm or less. Multiple differential signal transmission cables and
A conductor layer that collectively covers the plurality of differential signal transmission cables, and
A jacket that covers the conductor layer and
It is a multi-core cable equipped with
Each of the plurality of differential signal transmission cables is composed of the differential signal transmission cable according to any one of claims 1 to 14 and an outer insulating layer covering the plating layer. Core cable. A method for manufacturing a differential signal transmission cable, comprising a pair of signal lines, an insulator layer that covers the periphery of the signal lines, and a plating layer that covers the insulator layer.
The outer peripheral surface of the insulator layer is subjected to a dry ice blast treatment, then the outer peripheral surface is subjected to a corona discharge exposure treatment, and then the plating layer is formed on the outer peripheral surface.
A method for manufacturing a differential signal transmission cable in which a suckout does not occur in a frequency band of 50 GHz or less. The method for manufacturing a differential signal transmission cable according to claim 16.
The differential signal transmission cable is a method for manufacturing a differential signal transmission cable in which the maximum value of the differential in-phase conversion amount is −26 dB or less in a frequency band of 50 GHz or less. The method for manufacturing a cable for differential signal transmission according to claim 16 or 17.
A method for manufacturing a differential signal transmission cable that forms the plating layer after performing the corona discharge exposure treatment on the outer peripheral surface of the insulator layer and then performing the permanganic acid treatment.

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