Differential signal transmission cable

Abstract

This differential signal transmission cable comprises: an insulating layer extending in the longitudinal direction of the differential signal transmission cable; a pair of signal lines extending in the longitudinal direction and embedded inside the insulating layer; and a shield layer that covers the outer peripheral surface of the insulating layer. The shield layer has an electroless plating layer containing copper and an alloy element. The type and content of the alloy element are selected so that tensile stress acts on the shield layer.

Description

[Technical Field]

[0001] The present disclosure relates to a cable for transmitting differential signals. [Background technology]

[0002] Patent Document 1 (JP 2019-16451 A) describes a differential signal transmission cable. The differential signal transmission cable described in Patent Document 1 has an insulating layer, a pair of signal wires, and an electroless plating layer. The pair of signal wires are embedded inside the insulating layer. The electroless plating layer is formed on the outer peripheral surface of the insulating layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-16451 Summary of the Invention

[0004] The differential signal transmission cable of the present disclosure includes an insulating layer extending along the longitudinal direction of the differential signal transmission cable, a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer, and a shielding layer covering the outer surface of the insulating layer. The shielding layer has an electroless plating layer containing copper and an alloying element. The type and content of the alloying element are selected so that a tensile stress acts on the shielding layer. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view of a cable 100. [Figure 2] FIG. 2 is a cross-sectional view of the cable 100. [Figure 3] FIG. 3 is a partially enlarged view of the vicinity of the outer peripheral surface 10a of FIG. [Figure 4] FIG. 4 is a process diagram showing a method for manufacturing the cable 100. [Figure 5]FIG. 5 is a cross-sectional view of the processing target member 100A prepared in the preparation step S1. [Figure 6] FIG. 6 is a cross-sectional view of the processing target member 100A after the intermediate layer forming step S2 has been performed. [Figure 7] FIG. 7 is a cross-sectional view of the treatment target member 100A after the catalyst particle arrangement step S3 has been performed. [Figure 8] FIG. 8 is a cross-sectional view of the treatment target member 100A after the oxide layer forming step S4 and the electroless plating step S5 have been performed. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] When the differential signal transmission cable described in Patent Document 1 is bent, the electroless plating layer may peel off from the outer peripheral surface of the insulating layer. If the electroless plating layer peels off from the outer peripheral surface of the insulating layer due to bending, the transmission characteristics of the differential signal transmission cable will deteriorate in the area where the peeling occurs.

[0007] The present disclosure has been made in consideration of the above-mentioned problems of the conventional art. More specifically, the present disclosure provides a method for preventing a shield layer from peeling off from an outer peripheral surface of an insulating layer. difference The present invention provides a cable for transmitting dynamic signals.

[0008] [Effects of this disclosure] The differential signal transmission cable according to the present disclosure can prevent the shield layer from peeling off from the outer peripheral surface of the insulating layer.

[0009] [Outline of the embodiment] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A differential signal transmission cable according to a first aspect includes an insulating layer extending along the longitudinal direction of the differential signal transmission cable, a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer, and a shielding layer covering the outer surface of the insulating layer. The shielding layer has an electroless plating layer containing copper and an alloying element. The type and content of the alloying element are selected so that a tensile stress acts on the shielding layer.

[0011] According to the differential signal transmission cable (1), it is possible to prevent the shield layer from peeling off from the outer peripheral surface of the insulating layer.

[0012] (2) In the differential signal transmission cable of (1), the copper content in the shield layer may be 90 mass percent or more. The alloying element may be at least one of nickel, iron, and cobalt. At least one of the following may be satisfied: the nickel content in the shield layer is 0.10 mass percent or more and 3.0 mass percent or less, the iron content in the shield layer is 0.0010 mass percent or more and 0.0050 mass percent or less, and the cobalt content in the shield layer is 0.0010 mass percent or more and 0.0050 mass percent or less.

[0013] According to the differential signal transmission cable (2), it is possible to stabilize the plating solution used to form the electroless plating layer.

[0014] (3) The differential signal transmission cable of (1) or (2) may further include a metal oxide layer between the insulating layer and the shielding layer. In the metal oxide layer, the value obtained by dividing the atomic ratio of iron by the atomic ratio of copper may be 0.000010 or more and 0.00010 or less. In the metal oxide layer, the value obtained by dividing the atomic ratio of nickel by the atomic ratio of copper may be 0.000050 or more and 0.00080 or less. In the metal oxide layer, the value obtained by dividing the atomic ratio of cobalt by the atomic ratio of copper may be 0.000010 or more and 0.00010 or less.

[0015] According to the differential signal transmission cable (3), it is possible to improve the adhesion of the shield layer.

[0016] (4) The differential signal transmission cable of (1) to (3) may further include catalyst particles between the insulating layer and the shielding layer. The catalyst particles may be particles containing palladium.

[0017] (5) The differential signal transmission cables of (1) to (4) may further include an intermediate layer covering the outer circumferential surface of the insulating layer. A shielding layer may cover the outer circumferential surface of the intermediate layer.

[0018] (6) A differential signal transmission cable according to a second aspect of the present disclosure includes an insulating layer extending along the longitudinal direction of the differential signal transmission cable, a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer, and a shielding layer covering the outer surface of the insulating layer. The hardness of the insulating layer is 0.020 GPa or more. The hardness of the shielding layer is 4.0 GPa or less.

[0019] According to the differential signal transmission cable (6), it is possible to prevent the shield layer from peeling off from the outer peripheral surface of the insulating layer.

[0020] (7) In the differential signal transmission cable of (6), the value obtained by dividing the hardness of the shield by the hardness of the insulating layer may be 20 or more and 100 or less.

[0021] (8) In the differential signal transmission cable of (6) or (7), in a cross section perpendicular to the longitudinal direction, the insulating layer may have a first portion that is a portion that is a portion that is a distance of up to 50 μm from the outer peripheral surface of each of the pair of signal lines, and a second portion that is a portion that is a portion that is a distance of up to 50 μm from the outer peripheral surface of the insulating layer. The value obtained by dividing the hardness of the first portion by the hardness of the second portion may be 1.05 or more and 1.50 or less.

[0022] According to the differential signal transmission cable of (8), the differential signal transmission cable can be made easier to bend.

[0023] (9) A differential signal transmission cable according to a third aspect of the present disclosure includes an insulating layer extending along the longitudinal direction of the differential signal transmission cable, a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer, and a shielding layer covering the outer surface of the insulating layer. The shielding layer contains copper. The crystallite size of the copper in the shielding layer is 20 nm or more and 75 nm or less.

[0024] According to the differential signal transmission cable (10), it is possible to prevent the shield layer from peeling off from the outer peripheral surface of the insulating layer.

[0025] [Details of the embodiment] Next, details of embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated.

[0026] (Configuration of differential signal transmission cable according to embodiment) The configuration of a differential signal transmission cable according to an embodiment will be described below. The differential signal transmission cable according to an embodiment will be referred to as a cable 100.

[0027] FIG. 1 is a perspective view of cable 100. FIG. 2 is a cross-sectional view of cable 100. FIG. 2 shows a cross-section perpendicular to the longitudinal direction of cable 100. FIG. 3 is an enlarged partial view of FIG. 2 in the vicinity of outer peripheral surface 10a. As shown in FIGS. 1, 2, and 3, cable 100 has an insulating layer 10, signal lines 20a and 20b, an intermediate layer 30, a metal oxide layer 40, a shielding layer 50, and catalyst particles 60.

[0028] The insulating layer 10 extends along the longitudinal direction of the cable 100. The insulating layer 10 is made of an electrically insulating material. The insulating layer 10 is made of, for example, polyethylene (PE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene (PP), cyclic olefin polymer, or polymethylpentene. The insulating layer 10 may be a layer containing one or more of these materials. The hardness of the insulating layer 10 is preferably 0.020 GPa or more. The hardness of the insulating layer 10 may be 0.0035 GPa or more.

[0029] The directions perpendicular to the longitudinal direction of the cable 100 are defined as a first direction DR1 and a second direction DR2. The first direction DR1 and the second direction DR2 are perpendicular to each other. In a cross-sectional view perpendicular to the longitudinal direction of the cable 100, the insulating layer 10 has, for example, an elliptical shape with its major axis aligned with the first direction DR1.

[0030] The insulating layer 10 has an outer peripheral surface 10a. The insulating layer 10 has a first portion 11 and a second portion 12. The first portion 11 is a portion that is up to 50 μm away from the outer peripheral surface of the signal line 20a (signal line 20b). The second portion 12 is a portion that is up to 50 μm away from the outer peripheral surface 10a. The hardness of the second portion 12 is preferably smaller than that of the first portion 11. 12 The value obtained by dividing this by the hardness is preferably 1.05 or more and 1.50 or less.

[0031] The hardness of the insulating layer 10 (first portion 11, second portion 12) was measured using a Bruker Tri Bo Measurements are made using a Hysitron TI980 indenter. A Berkovich indenter is used in this measurement. The maximum load is 8 mN. The loading time is 5 seconds. The maximum load holding time is 0 seconds. This measurement is performed in air at 25°C. Analysis using the TI980 is performed using TribScan, the dedicated software for the TI980. This measurement is performed on samples that have been embedded in epoxy resin and mirror-polished.

[0032] The signal line 20a and the signal line 20b form a pair. A signal of opposite phase to the signal applied to the signal line 20a is applied to the signal line 20b. This allows the cable 100 to transmit differential signals.

[0033] The signal lines 20a and 20b are embedded inside the insulating layer 10. The signal lines 20a and 20b extend along the longitudinal direction of the cable 100. The signal lines 20a and 20b are made of a conductive material. For example, the signal lines 20a and 20b are made of copper (Cu). However, the material of the signal lines 20a and 20b is not limited to copper. The signal lines 20a and 20b are arranged side by side along, for example, a first direction DR1.

[0034] The intermediate layer 30 covers the outer peripheral surface 10a. The intermediate layer 30 has an outer peripheral surface 30a. The intermediate layer 30 is made of an electrically insulating material. The intermediate layer 30 is made of, for example, polyolefin. The intermediate layer 30 may also be made of acrylonitrile butadiene styrene resin (ABS resin).

[0035] The metal oxide layer 40 is a layer of metal oxide. The metal oxide layer 40 mainly contains copper oxide (CuO). However, the metal oxide layer 40 may contain elements other than copper and oxygen. The metal oxide layer 40 may further contain at least one of nickel (Ni), iron (Fe), and cobalt (Co), for example.

[0036] The atomic ratio of copper in the metal oxide layer 40 is A (unit: atomic percent), and the metal oxide layer 40The atomic ratio of iron in the metal oxide layer 40 is defined as B (unit: atomic percent). The atomic ratio of nickel in the metal oxide layer 40 is defined as C (unit: atomic percent). The atomic ratio of cobalt in the metal oxide layer 40 is defined as D (unit: atomic percent). The value obtained by dividing B by A is preferably 0.000010 or more and 0.00010 or less. The value obtained by dividing C by A is preferably 0.000050 or more and 0.00080 or less. The value obtained by dividing D by A is preferably 0.000010 or more and 0.00010 or less. The values ​​of A, B, C, and D are measured using EDX (Energy Dispersive X-ray spectroscopy).

[0037] The metal oxide layer 40 covers the outer peripheral surface 30a. It is preferable that the metal oxide layer 40 covers the entire outer peripheral surface 30a. However, the metal oxide layer 40 may not cover a portion of the outer peripheral surface 30a. In this case, the portion of the outer peripheral surface 30a that is not covered by the metal oxide layer 40 is in contact with the shield layer 50.

[0038] The metal oxide layer 40 has a first surface 40a and a second surface 40b. The first surface 40a faces the intermediate layer 30. The second surface 40b is the surface opposite the first surface 40a. The second surface 40b faces the shield layer 50. The metal oxide layer 40 is in contact with the intermediate layer 30 at the first surface 40a, and in contact with the shield layer 50 at the second surface 40b.

[0039] The shield layer 50 covers the second surface 40b. That is, the shield layer 50 covers the outer peripheral surface 10a with the intermediate layer 30 and the metal oxide layer 40 interposed therebetween. The shield layer 50 is electrically conductive.

[0040] The shield layer 50 has, for example, an electroless plated layer 51 and an electrolytic plated layer 52. The electroless plated layer 51 covers the metal oxide layer 40. The electrolytic plated layer 52 covers the electroless plated layer 51.

[0041] The electroless plated layer 51 is a layer formed by electroless plating. The electroless plated layer 51 contains copper. The electroless plated layer 51 further contains an alloying element. The type and content of the alloying element are selected so as to generate tensile stress in the shielding layer 50. The alloying element is, for example, an element that forms a solid solution in copper. More specifically, the alloying element is at least one of iron, nickel, and cobalt. However, the alloying element is not limited to iron, nickel, and cobalt. The electrolytic plated layer 52 is a layer formed by electrolytic plating. The electrolytic plated layer 52 contains, for example, copper.

[0042] When electroless plated layer 51 contains the above alloying elements, the alloying elements dissolve in the copper in electroless plated layer 51, causing distortion in the copper crystals in electroless plated layer 51. Furthermore, since the crystallinity of electroless plated layer 52 reflects the crystallinity of electroless plated layer 51, the inclusion of the above alloying elements in electroless plated layer 51 also causes distortion in electrolytic plated layer 52. Such distortion causes residual tensile stress in shielding layer 50.

[0043] The copper content in the shield layer 50 is, for example, 90 mass percent or more. The iron content in the shield layer 50 is preferably 0.0010 mass percent or more and 0.0050 mass percent or less. The nickel content in the shield layer 50 is preferably 0.10 mass percent or more and 3.0 mass percent or less. The cobalt content in the shield layer 50 is preferably 0.0010 mass percent or more and 0.0050 mass percent or less. Preferably, at least one of the following is satisfied: the nickel content in the shield layer 50 is 0.10 mass percent or more and 3.0 mass percent or less, the iron content in the shield layer 50 is 0.0010 mass percent or more and 0.0050 mass percent or less, and the cobalt content in the shield layer 50 is 0.0010 mass percent or more and 0.0050 mass percent or less. The contents of copper, iron, nickel, and cobalt in the shield layer 50 are measured by dissolving the shield layer 50 in a solution and performing ICP (Inductive Coupled Plasma) emission spectroscopy on the solution.

[0044] The hardness of the shield layer 50 is preferably 4.0 GPa or less. The value obtained by dividing the hardness of the shield layer 50 by the hardness of the insulating layer 10 is preferably 20 or more and 100 or less.

[0045] The hardness of the shield layer 50 is measured using a Bruker tripo-indenter, Hysitron TI980. In this measurement, a Berkovich indenter is used as the indenter. The maximum load is 30 μN. The load time is 2 seconds. The maximum load holding time is 2 seconds. This measurement is performed in air at 25°C. Analysis using the TI980 is performed using TribScan, the dedicated software for the TI980. This measurement is performed on a sample that is embedded in epoxy resin and mirror-polished.

[0046] The crystallite size of the copper in the shield layer 50 is preferably 20 nm or more and 75 nm or less. End It is more preferable that the thickness is 60 nm or less. The shield layer 50 contains copper crystal grains. The portion of the crystal grain that can be considered to be a single crystal is called a crystallite. Therefore, the size of the copper crystallite in the shield layer 50 is equal to or smaller than the grain size of the copper crystal grains contained in the shield layer 50.

[0047] The copper crystallite size in the shield layer 50 can be measured using X-ray diffraction. More specifically, X-ray diffraction is performed using a Rigaku SmartLab. In this measurement, the X-ray source is CuKα, the incident light source is CBO-f, and the detector is Hypix-3000. X-ray diffraction is performed over a diffraction angle 2θ range of 20° to 80°, with the diffraction angle 2θ being changed in steps of 0.03°.

[0048] The line profile obtained by X-ray diffraction of a sample has a shape that includes both the true broadening due to the physical quantity of the sample's crystallite size and the broadening due to the measurement instrument. To determine the crystallite size, the components due to the instrument are removed from the line profile obtained by X-ray diffraction of the sample, and the integral width of the true line profile (the value obtained by dividing the integrated intensity of the peak by the peak height) is calculated. The crystallite size of the sample can be obtained by substituting the integral width of the true line profile into the Scherrer equation.

[0049] LaB6 manufactured by NIST is used as a standard sample to remove components caused by the instrument from the line profile obtained by X-ray diffraction of the sample. The integral width of the true line profile is β, the integral width of the line profile obtained by X-ray diffraction of the sample is β1, and the integral width of the line profile obtained by X-ray diffraction of the standard sample is β2. The relationship between β, β1, and β2 is as follows: 2 =β1 2 -β2 2This is shown in (Equation 1). The Scherrer equation is expressed as D = Kλ / β cos θ (Equation 2). Here, D is the crystallite size of the sample, K is the Scherrer constant (K = 1.33), λ is the wavelength of the X-rays, and θ is the Bragg angle of the Cu200 diffraction line. By substituting β obtained from Equation 1 into Equation 2, the value of D, i.e., the crystallite size of the sample, can be obtained.

[0050] The catalyst particles 60 are located between the insulating layer 10 and the shield layer 50. More specifically, the shield layer 50 is located in the metal oxide layer 40. The catalyst particles 60 are also located at the interface between the metal oxide layer 40 and the intermediate layer 30. The catalyst particles 60 are, for example, particles containing palladium (Pd).

[0051] (Method of manufacturing a differential signal transmission cable according to an embodiment) The following describes a method for manufacturing cable 100. Fig. 4 is a process diagram showing the method for manufacturing cable 100. As shown in Fig. 4, the method for manufacturing cable 100 includes a preparation step S1, an intermediate layer formation step S2, a catalyst particle arrangement step S3, an oxide layer formation step S4, an electroless plating step S5, an electrolytic plating step S6, and a heat treatment step S7.

[0052] After the preparation step S1, an intermediate layer forming step S2 is performed. After the intermediate layer forming step S2, a catalyst particle arranging step S3 is performed. After the catalyst particle arranging step S3, an oxide layer forming step S4 is performed. After the oxide layer forming step S4, an electroless plating step S5 is performed. After the electroless plating step S5, an electrolytic plating step S6 is performed. After the electrolytic plating step S6, a heat treatment step S7 is performed.

[0053] In the preparation step S1, a processing target member 100A is prepared. Fig. 5 is a cross-sectional view of the processing target member 100A prepared in the preparation step S1. As shown in Fig. 5, the processing target member 100A has an insulating layer 10, a signal line 20a, and a signal line 20b.

[0054] Fig. 6 is a cross-sectional view of the treatment target member 100A after the intermediate layer forming step S2 has been performed. As shown in Fig. 6, in the intermediate layer forming step S2, an intermediate layer 30 is formed so as to cover the outer peripheral surface 10a. In the intermediate layer forming step S2, a material constituting the intermediate layer 30 is applied to the outer peripheral surface 10a, and the applied material is cured to form the intermediate layer 30 so as to cover the outer peripheral surface 10a.

[0055] Fig. 7 is a cross-sectional view of the treatment target member 100A after the catalyst particle arrangement step S3 has been performed. As shown in Fig. 7, in the catalyst particle arrangement step S3, catalyst particles 60 are dispersed and arranged on the outer peripheral surface 30a. In the catalyst particle arrangement step S3, a solution containing the catalyst particles 60 is applied to the outer peripheral surface 30a, and the solution is volatilized, thereby dispersing and arranging the catalyst particles 60 on the outer peripheral surface 30a.

[0056] 8 is a cross-sectional view of the treatment target member 100A after the oxide layer forming step S4 and the electroless plating step S5 have been performed. As shown in Fig. 8, a metal oxide layer 40 is formed in the oxide layer forming step S4, and an electroless plated layer 51 is formed on the metal oxide layer 40 in the electroless plating step S5.

[0057] In the oxide layer forming step S4, the treatment target member 100A is immersed in a plating solution in which the material contained in the electroless plated layer 51 is dissolved and in which an oxygen-containing gas (e.g., air) is bubbled. As a result, a metal oxide layer 40 is formed so as to cover the outer peripheral surface 30a, with the catalyst particles 60 as nuclei. Some of the catalyst particles 60 that serve as nuclei for the growth of the metal oxide layer 40 are present in the metal oxide layer 40, and the rest are present at the interface between the intermediate layer 30 and the metal oxide layer 40. Note that by adding alloying elements such as iron, nickel, or cobalt to the plating solution, the metal oxide layer 40 contains these alloying elements.

[0058] In the electroless plating step S5, the bubbling is stopped, and as a result, an electroless plating layer 51 is plated on the metal oxide layer 40.

[0059] In the electrolytic plating step S6, an electrolytic plated layer 52 is formed to cover the electroless plated layer 51. In the electrolytic plating step S6, the processing target member 100A is immersed in a plating solution in which the material contained in the electrolytic plated layer 52 is dissolved, and a current is passed through the electroless plated layer 51. As a result, the electrolytic plated layer 52 is plated onto the electroless plated layer 51, and the cable 100 having the structure shown in FIGS. 1 to 3 is manufactured.

[0060] In the heat treatment step S7, the cable 100 is subjected to a heat treatment. This heat treatment causes the copper crystal grains contained in the shield layer 50 to grow, and as a result, the crystallite size in the shield layer 50 also increases. Since the hardness of the shield layer 50 decreases as the grain size of the copper crystal grains contained in the shield layer 50 increases (Hall-Petch law), this heat treatment reduces the hardness of the shield layer 50. Furthermore, this heat treatment promotes crystallization of the resin material that constitutes the insulating layer 10, so the hardness of the insulating layer 10 increases as a result of this heat treatment.

[0061] (Effects of the differential signal transmission cable according to the embodiment) The effects of the cable 100 will be described below.

[0062] The cable 100 may be used in a bent state. A compressive bending stress acts on the shielding layer 50 located on the inside of the bent cable 100. This compressive bending stress may cause the shielding layer 50 to buckle and peel off from the insulating layer 10 located on the inside of the bent cable 100. When this peeling occurs, the transmission characteristics of the cable 100 deteriorate.

[0063] However, in cable 100, electroless plating layer 51 contains alloying elements, which causes tensile stress to act on shielding layer 50. In this way, cable 100 reduces the compressive stress acting on shielding layer 50 on the inside of bent cable 100, thereby suppressing peeling due to buckling of shielding layer 50, thereby making it possible to suppress deterioration in the transmission characteristics of cable 100 when bent.

[0064] The plating solution used to form electroless plated layer 51 is chemically unstable and therefore difficult to handle. As described above, when electroless plated layer 51 contains at least one of iron and nickel, these elements are added to the plating solution used to form electroless plated layer 51. The addition of iron, nickel, and cobalt chemically stabilizes the plating solution used to form electroless plated layer 51. Therefore, when electroless plated layer 51 contains at least one of iron, nickel, and cobalt, the manufacturing process of cable 100 can be stabilized.

[0065] In order to ensure adhesion of shield layer 50 to insulating layer 10, it is conceivable to roughen outer surface 10a to enhance the anchoring effect between shield layer 50 and insulating layer 10. However, roughening outer surface 10a deteriorates the transmission characteristics of cable 100 in the high frequency range.

[0066] Cable 100 has metal oxide layer 40, and hydrogen bonding occurs between shielding layer 50 (electroless plating layer 51) and metal oxide layer 40. This hydrogen bonding ensures adhesion between metal oxide layer 40 and shielding layer 50, thereby ensuring adhesion between insulating layer 10 and shielding layer 50 without roughening outer circumferential surface 10a. In this way, when cable 100 has metal oxide layer 40, it is possible to ensure adhesion of shielding layer 50 to insulating layer 10 while maintaining the transmission characteristics of cable 100 in the high-frequency range.

[0067] If the hardness of the insulating layer 10 is low, the insulating layer 10 on the inside of the bent cable 100 will bend toward the inside of the cable 100. If the hardness of the shielding layer 50 is high, the shielding layer 50 on the inside of the bent cable 100 will bend toward the inside of the cable 100. In this way, if the difference in hardness between the insulating layer 10 and the shielding layer 50 becomes large, wrinkles will occur on the inside of the cable 100 when the cable 100 is bent, and the transmission characteristics will deteriorate.

[0068] In cable 100, the hardness of insulating layer 10 is 0.020 GPa or more and the hardness of shielding layer 50 is 4.0 GPa or less, so the difference between the hardness of insulating layer 10 and the hardness of shielding layer 50 is small, making it possible to suppress deterioration of transmission characteristics when cable 100 is bent. If the value obtained by dividing the hardness of shielding layer 50 by the hardness of insulating layer 10 is 20 or more and 100 or less, it is possible to further suppress deterioration of transmission characteristics when cable 100 is bent.

[0069] When the copper crystallite size in the shielding layer 50 is 20 nm or more and 75 nm or less, the hardness of the shielding layer 50 can be reduced, and similarly, deterioration of the transmission characteristics when the cable 100 is bent can be further suppressed.

[0070] When the value obtained by dividing the hardness of the first portion 11 by the hardness of the second portion 12 of the cable 100 is 1.05 or more and 1.50 or less, the second moment of area of ​​the insulating layer 10 becomes small, and the deformation of the insulating layer 10 easily follows the deformation of the cable 100. Therefore, in this case, the insulating layer 10 is less likely to peel off from the signal line 20a (signal line 20b) when the cable 100 is bent.

[0071] (First loss evaluation test) In the first loss evaluation test, the relationship between the content of alloy elements in the shielding layer 50 (electroless plated layer 51) and the transmission characteristics of the cable 100 was evaluated. In the first loss evaluation test, Samples 1-1 to 1-9 were used as samples of the cable 100. As shown in Table 1, the contents of nickel, iron, and cobalt in the shielding layer 50 were changed in Samples 1-1 to 1-9. Although not shown in Table 1, the copper content in the shielding layer 50 was set to 90 mass percent or more in Samples 1-1 to 1-9.

[0072] [Table 1]

[0073] In the first loss evaluation test, the transmission characteristics were evaluated by measuring the insertion loss in differential mode of each sample while it was wrapped around a cylinder with a diameter of 50 mm. If there was no difference in the insertion loss in differential mode before and after wrapping, or if the insertion loss in differential mode after wrapping was -25 dB / m or more, it was evaluated as OK, and if the insertion loss in differential mode after wrapping was less than -25 dB / m, it was evaluated as NG.

[0074] Condition 1 is that the nickel content in the shield layer 50 is 0.10 mass percent or more and 3.0 mass percent or less, condition 2 is that the iron content in the shield layer 50 is 0.0010 mass percent or more and 0.0050 mass percent or less, and condition 3 is that the cobalt content in the shield layer 50 is 0.0010 mass percent or more and 0.0050 mass percent or less.

[0075] Samples 1-1 to 1-7 satisfied at least one of conditions 1 to 3. On the other hand, Samples 1-8 and 1-9 did not satisfy any of conditions 1 to 3. The transmission characteristics of Samples 1-1 to 1-7 were all evaluated as OK. On the other hand, the transmission characteristics of Samples 1-8 and 1-9 were all evaluated as NG. From this comparison, it was experimentally revealed that by satisfying at least one of conditions 1 to 3, it is possible to suppress deterioration in the transmission characteristics of cable 100 due to bending.

[0076] (Second loss evaluation test) In the second loss evaluation test, the relationship between the hardness of the shielding layer 50 and the hardness of the insulating layer 10 and the transmission characteristics of the cable 100 was evaluated. In the second loss evaluation test, Samples 2-1 to 2-3 were used as samples of the cable 100. As shown in Table 2, the atomic ratios of copper, nickel, iron, and cobalt in the shielding layer 50 were changed in Samples 2-1 to 2-3. Accordingly, the values ​​obtained by dividing B by A, C by A, and D by A were changed in Samples 2-1 to 2-3.

[0077] [Table 2]

[0078] In the second loss evaluation test, the transmission characteristics of each sample were evaluated using the same method as in the first loss evaluation test. Condition 4 was that the value obtained by dividing B by A was between 0.000010 and 0.00010, condition 5 was that the value obtained by dividing C by A was between 0.000010 and 0.00080, and condition 6 was that the value obtained by dividing D by A was between 0.000010 and 0.00010. below Condition 6 is that

[0079] In Sample 2-1 and Sample 2-2, all of Conditions 4 to 6 were satisfied. On the other hand, in Sample 2-3, Condition 5 was not satisfied. In Sample 2-1 and Sample 2-2, the transmission characteristics were both evaluated as OK. On the other hand, in Sample 2-3, the transmission characteristics were evaluated as NG. From this comparison, it was experimentally revealed that by satisfying all of Conditions 4 to 6, it is possible to suppress deterioration in the transmission characteristics due to bending of cable 100.

[0080] (Third loss evaluation test) In the third loss evaluation test, the relationship between the hardness of the shield layer 50 and the hardness of the insulating layer 10 and the transmission characteristics of the cable 100 was evaluated. Samples 3-1 to 3-11 were used as cable 100 samples in the third loss evaluation test. As shown in Table 3, the type of material constituting the insulating layer 10, the hardness of the insulating layer 10, and the hardness of the shield layer 50 were changed in Samples 3-1 to 3-11. The hardness of the shield layer 50 was adjusted by performing the heat treatment shown in Table 3.

[0081] [Table 3]

[0082] In the third loss evaluation test, the transmission characteristics of each sample were evaluated using the same method as in the first loss evaluation test. For Samples 3-1 to 3-10, the value obtained by dividing the hardness of the shield layer 50 by the hardness of the insulating layer 10 was within the range of 20 to 100. On the other hand, for Sample 3-11, the value obtained by dividing the hardness of the shield layer 50 by the hardness of the insulating layer 10 was not within the range of 20 to 100. For Samples 3-1 to 3-10, the transmission characteristics were all evaluated as "OK." On the other hand, for Sample 3-11, the transmission characteristics were evaluated as "NG." From this comparison, it was experimentally demonstrated that deterioration of the transmission characteristics due to bending of the cable 100 can be suppressed by setting the value obtained by dividing the hardness of the shield layer 50 by the hardness of the insulating layer 10 to be within the range of 20 to 100.

[0083] (Fourth loss evaluation test) In the fourth loss evaluation test, the relationship between the hardness of the shielding layer 50 and the hardness of the insulating layer 10 and the transmission characteristics of the cable 100 was evaluated. Samples 4-1 to 4-3 were used as samples of the cable 100. As shown in Table 4, the type of material constituting the insulating layer 10, the hardness of the first portion 11, and the hardness of the second portion 12 were changed in Samples 4-1 to 4-3.

[0084] [Table 4]

[0085] In the fourth loss evaluation test, the transmission characteristics of each sample were evaluated using the same method as in the first loss evaluation test. In Samples 4-1 and 4-2, the value obtained by dividing the hardness of the first portion 11 by the hardness of the second portion 12 was within the range of 1.05 to 1.50. On the other hand, in Sample 4-3, the value obtained by dividing the hardness of the first portion 11 by the hardness of the second portion 12 was not within the range of 1.05 to 1.50. In Samples 4-1 and 4-2, the transmission characteristics were evaluated as "OK." On the other hand, in Sample 4-3, the transmission characteristics were evaluated as "NG." From this comparison, it was experimentally demonstrated that deterioration of the transmission characteristics due to bending of the cable 100 can be suppressed by setting the value obtained by dividing the hardness of the first portion 11 by the hardness of the second portion 12 to be within the range of 1.05 to 1.50.

[0086] (5th loss evaluation test) In the fifth loss evaluation test, the relationship between the copper crystallite size in the shielding layer 50 and the transmission characteristics of the cable 100 was evaluated. In the fourth loss evaluation test, Samples 5-1 to 5-5 were used as samples of the cable 100. As shown in Table 5, the copper crystallite size in the shielding layer 50 was changed in Samples 5-1 to 5-5.

[0087] [Table 5]

[0088] In the fifth loss evaluation test, the transmission characteristics of each sample were evaluated using the same method as in the first loss evaluation test. In samples 5-1 to 5-4, the crystallite size in the shielding layer 50 was within the range of 20 nm to 75 nm. On the other hand, in sample 5-5, the crystallite size in the shielding layer 50 was outside the range of 20 nm to 75 nm.

[0089] The transmission characteristics of Samples 5-1 to 5-4 were all evaluated as "OK." On the other hand, the transmission characteristics of Sample 5-5 were evaluated as "NG." From this comparison, it was experimentally revealed that by setting the crystallite size in the shielding layer 50 to be 20 nm or more and 75 nm or less, deterioration of the transmission characteristics due to bending of the cable 100 can be suppressed.

[0090] In Samples 5-1 to 5-3, the crystallite size in the shielding layer 50 was within the range of 20 nm to 60 nm. On the other hand, in Sample 5-4, the crystallite size in the shielding layer 50 was not within the range of 20 nm to 60 nm. The transmission characteristics of Samples 5-1 to 5-3 were superior to the transmission characteristics of Sample 5-4. From this comparison, it was experimentally revealed that by setting the crystallite size in the shielding layer 50 to 20 nm to 60 nm, it is possible to further suppress deterioration in the transmission characteristics due to bending of the cable 100.

[0091] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0092] 10 insulating layer, 10a outer peripheral surface, 11 first portion, 12 second portion, 20a, 20b signal line, 30 intermediate layer, 30a outer peripheral surface, 40 metal oxide layer, 40a first surface, 40b second surface, 50 shielding layer, 51 electroless plating layer, 52 electrolytic plating layer, 53 third portion, 54 fourth portion, 60 catalyst particle, 100 cable, 100A treatment target member, DR1 first direction, DR2 second direction, S1 preparation process, S2 intermediate layer formation process, S3 catalyst particle arrangement process, S4 oxide layer formation process, S5 electroless plating process, S6 electrolytic plating process, S7 heat treatment process.

Claims

1. A differential signal transmission cable, an insulating layer extending along the longitudinal direction of the differential signal transmission cable; a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer; a shield layer covering an outer peripheral surface of the insulating layer, the shield layer has an electroless plating layer containing copper and an alloy element, A differential signal transmission cable, wherein the type and content of the alloying elements are selected so that tensile stress acts on the shielding layer.

2. The copper content in the shielding layer is 90 mass percent or more, the alloying element is at least one of nickel, iron, and cobalt, 2. The differential signal transmission cable according to claim 1, wherein at least one of the following is satisfied: the nickel content in the shielding layer is 0.10 mass percent or more and 3.0 mass percent or less, the iron content in the shielding layer is 0.0010 mass percent or more and 0.0050 mass percent or less, and the cobalt content in the shielding layer is 0.0010 mass percent or more and 0.0050 mass percent or less.

3. a metal oxide layer between the insulating layer and the shielding layer; In the metal oxide layer, the value obtained by dividing the atomic ratio of iron by the atomic ratio of copper is 0.000010 or more and 0.00010 or less, In the metal oxide layer, the value obtained by dividing the atomic ratio of nickel by the atomic ratio of copper is 0.000010 or more and 0.00080 or less, 3. The differential signal transmission cable according to claim 1, wherein the atomic ratio of cobalt divided by the atomic ratio of copper in the metal oxide layer is equal to or greater than 0.000010 and equal to or less than 0.00010.

4. further comprising catalytic particles between the insulating layer and the shielding layer; 4. The differential signal transmission cable according to claim 1, wherein the catalyst particles are particles containing palladium.

5. An intermediate layer covering an outer peripheral surface of the insulating layer is further provided, The differential signal transmission cable according to claim 1 , wherein the shielding layer covers an outer peripheral surface of the intermediate layer.

6. A differential signal transmission cable, an insulating layer extending along the longitudinal direction of the differential signal transmission cable; a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer; a shield layer covering an outer peripheral surface of the insulating layer, the hardness of the insulating layer is 0.020 GPa or more; A differential signal transmission cable, wherein the hardness of the shielding layer is 4.0 GPa or less.

7. 7. The differential signal transmission cable according to claim 6, wherein a value obtained by dividing the hardness of the shielding layer by the hardness of the insulating layer is 20 or more and 100 or less.

8. In a cross section perpendicular to the longitudinal direction, the insulating layer has a first portion that is a portion that is a portion that is a distance from an outer peripheral surface of each of the pair of signal lines up to 50 μm, and a second portion that is a portion that is a distance from an outer peripheral surface of the insulating layer up to 50 μm, 8. The differential signal transmission cable according to claim 6, wherein a value obtained by dividing the hardness of the first portion by the hardness of the second portion is equal to or greater than 1.05 and equal to or less than 1.

50.

9. A differential signal transmission cable, an insulating layer extending along the longitudinal direction of the differential signal transmission cable; a pair of signal lines extending along the longitudinal direction and embedded inside the insulating layer; a shield layer covering an outer peripheral surface of the insulating layer, the shielding layer contains copper; A differential signal transmission cable, wherein the crystallite size of the copper in the shielding layer is 20 nm or more and 75 nm or less.

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