Coaxial cable and device testing apparatus

Abstract

The invention provides a coaxial cable and a device testing apparatus which can be arranged at high density. The coaxial cable (40) is provided with a cylindrical outer conductor (45), an insulating part (44) covered by the outer conductor (45), and a plurality of inner conductors (41) arranged in the insulating part (44).

Description

Technical Field

[0001] The present invention relates to a coaxial cable and a device testing apparatus including the coaxial cable. Background Art

[0002] As a semiconductor device testing apparatus for testing the electrical characteristics of various semiconductor devices (DUTs) such as semiconductor integrated circuit elements, there is known an apparatus comprising a DSA, a test head, and a motherboard, wherein the DSA comprises a socket, the test head comprises a pin circuit card, and the motherboard comprises a coaxial cable electrically connecting the DSA and the test head (for example, see Patent Document 1).

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2008-078048 Summary of the Invention Technical problem to be solved by the invention In semiconductor device testing equipment, as the number of simultaneous measurements (the number of DUTs that can be tested simultaneously) increases, the number of coaxial cables included in the motherboard also increases. However, due to the limited space within the motherboard housing, increasing the number of coaxial cables can be difficult.

[0004] The technical problem to be solved by the present invention is to provide a coaxial cable that can be arranged at a high density and a device testing apparatus including the coaxial cable.

[0005] Technical solutions to technical problems [1] A first aspect of the present invention is a coaxial cable including a cylindrical outer conductor, an insulating portion covered by the outer conductor, and a plurality of inner conductors arranged in the insulating portion.

[0006] [2] A second aspect of the present invention may be a coaxial cable according to the first aspect, wherein the plurality of inner conductors are arranged in the insulating portion so as to be separated from each other.

[0007] [3] A third aspect of the present invention may be a coaxial cable according to the first or second aspect, wherein the insulating portion is interposed between the plurality of inner conductors.

[0008] [4] A fourth aspect of the present invention may be a coaxial cable according to any one of aspects 1 to 3, wherein the inner conductor has a cross-sectional shape extending in an arc shape.

[0009] [5] A fifth aspect of the present invention may be a coaxial cable according to any one of aspects 1 to 4, wherein the inner conductor has a cross-sectional shape extending substantially parallel to the inner peripheral surface of the outer conductor.

[0010] [6] Mode 6 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of Modes 1 to 5, the thickness of the inner conductor along the radial direction of the coaxial cable is smaller than the width of the inner conductor along the circumferential direction of the coaxial cable.

[0011] [7] A seventh aspect of the present invention may be a coaxial cable according to the sixth aspect, wherein the thickness of the inner conductor is not more than 1 / 5 of the width of the inner conductor.

[0012] [8] Aspect 8 of the present invention may be a coaxial cable according to any one of aspects 1 to 7, wherein the thickness of the inner conductor along the radial direction of the coaxial cable is substantially constant in the circumferential direction of the coaxial cable.

[0013] [9] A ninth aspect of the present invention may be a coaxial cable according to any one of aspects 1 to 8, wherein the plurality of inner conductors are arranged at intervals in the circumferential direction of the coaxial cable and are arranged concentrically with the outer conductor.

[0014]

[10] Aspect 10 of the present invention may be a coaxial cable according to aspect 9, wherein the plurality of inner conductors are arranged at substantially equal intervals in the circumferential direction of the coaxial cable.

[0015]

[11] Mode 11 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 1 to 10, the distance between the plurality of inner conductors is greater than the distance between the inner conductor and the outer conductor.

[0016]

[12] Mode 12 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 1 to 11, the inner conductor has a metal layer having an arc-shaped cross-section or a plurality of metal bare wires arranged in an arc shape.

[0017]

[13] A thirteenth aspect of the present invention may be a coaxial cable according to any one of aspects 1 to 12, wherein the insulating portion includes a first insulating portion made of a resin material.

[0018]

[14] A fourteenth aspect of the present invention may be a coaxial cable according to the thirteenth aspect, wherein the first insulating portion is a columnar or cylindrical resin body that holds the plurality of internal conductors, and the outer conductor covers the resin body.

[0019]

[15] A fifteenth aspect of the present invention may be a coaxial cable according to the fourteenth aspect, wherein the plurality of inner conductors are embedded in the resin body.

[0020]

[16] Mode 16 of the present invention may be a coaxial cable, wherein in the coaxial cable of mode 13, the first insulating portion includes a bare wire assembly for holding the plurality of internal conductors, the bare wire assembly includes a plurality of resin bare wires assembled together, and the outer conductor covers the bare wire assembly.

[0021]

[17] A seventeenth aspect of the present invention may be a coaxial cable according to the sixteenth aspect, wherein the inner conductor is arranged between the resin bare wires.

[0022]

[18] Aspect 18 of the present invention may be a coaxial cable according to any one of aspects 13 to 17, wherein the insulating portion includes a second insulating portion made of gas or vacuum.

[0023]

[19] A nineteenth aspect of the present invention may be a coaxial cable according to the eighteenth aspect, wherein the second insulating portion is interposed between the plurality of inner conductors.

[0024]

[20] Mode 20 of the present invention may be a coaxial cable, wherein in the coaxial cable of mode 18 or 19, the first insulating portion has a hole formed inside the first insulating portion, and the second insulating portion is gas or vacuum in the hole.

[0025]

[21] Mode 21 of the present invention may be a coaxial cable according to any one of modes 18 to 20, wherein the second insulating portion is interposed between the inner conductor and the outer conductor.

[0026]

[22] Mode 22 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 18 to 21, the first insulating portion has a groove formed on the outer peripheral surface of the first insulating portion, and the second insulating portion is gas or vacuum in the groove.

[0027]

[23] Aspect 23 of the present invention may be a coaxial cable according to any one of aspects 18 to 22, wherein the plurality of inner conductors are exposed in the second insulating portion.

[0028]

[24] Mode 24 of the present invention may be a coaxial cable, which is a coaxial cable of any one of modes 1 to 23, wherein the coaxial cable has a plurality of wall-shaped conductors, the plurality of wall-shaped conductors are located between the plurality of internal conductors in the circumferential direction of the coaxial cable, and the wall-shaped conductors are electrically connected to the external conductor.

[0029]

[25] Mode 25 of the present invention may be a coaxial cable, wherein in the coaxial cable of mode 24, the wall-shaped conductor is connected to the outer conductor and protrudes from the outer conductor toward the center of the coaxial cable.

[0030]

[26] Mode 26 of the present invention may be a coaxial cable, in which, in the coaxial cable of mode 24 or 25, the plurality of wall-shaped conductors are connected to each other at the center of the coaxial cable.

[0031]

[27] Mode 27 of the present invention may be a coaxial cable, which, in the coaxial cable of mode 26, comprises a central conductor, the central conductor being arranged at the center of the coaxial cable, and the plurality of wall-shaped conductors being connected to each other via the central conductor at the center of the coaxial cable.

[0032]

[28] Mode 28 of the present invention may be a coaxial cable, wherein in the coaxial cable of Mode 26, the plurality of wall-shaped conductors are directly connected to each other at the center of the coaxial cable.

[0033]

[29] Mode 29 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 24 to 28, the wall-shaped conductor has a metal layer extending in the radial direction of the coaxial cable or a plurality of metal bare wires arranged in the radial direction.

[0034]

[30] A 30th aspect of the present invention may be a coaxial cable according to any one of aspects 1 to 29, wherein the insulating portion is disposed in the outer conductor.

[0035]

[31] Mode 31 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 1 to 30, the outer conductor surrounds the plurality of inner conductors via the insulating portion.

[0036]

[32] Mode 32 of the present invention may be a coaxial cable, wherein in the coaxial cable of any one of modes 1 to 31, the coaxial cable includes a sheath covering the outer conductor.

[0037]

[33] Mode 33 of the present invention may be a coaxial cable, which is the coaxial cable of any one of Modes 1 to 32, and is used in a device test apparatus for testing a DUT.

[0038]

[34] A 34th aspect of the present invention is a device testing apparatus for testing a DUT, and is provided with the coaxial cable according to any one of the 1st to 33rd aspects.

[0039]

[35] Mode 35 of the present invention may be a device testing apparatus, wherein in the device testing apparatus of mode 34, the plurality of internal conductors transmit mutually different electrical signals.

[0040] Effects of the Invention According to the present invention, since the coaxial cable includes a plurality of inner conductors arranged in the insulating portion, the coaxial cables can be arranged at a high density. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic cross-sectional view showing the overall structure of the device testing apparatus in the first embodiment of the present invention.

[0042] Figure 2 This is an exploded cross-sectional view showing a DSA and a motherboard in the first embodiment of the present invention. Figure 1 The corresponding figure of Part II.

[0043] Figure 3 It is a cross-sectional view showing a coaxial cable according to the first embodiment of the present invention.

[0044] Figure 4 It is a cross-sectional view showing a modified example of the coaxial cable in the first embodiment of the present invention.

[0045] Figure 5 It is a cross-sectional view showing a coaxial cable according to a second embodiment of the present invention.

[0046] Figure 6 It is a cross-sectional view showing a coaxial cable according to a third embodiment of the present invention.

[0047] Figure 7 It is a cross-sectional view showing a first modified example of the coaxial cable in the third embodiment of the present invention.

[0048] Figure 8 It is a cross-sectional view showing a second modified example of the coaxial cable in the third embodiment of the present invention.

[0049] Figure 9 It is a cross-sectional view showing a coaxial cable according to a fourth embodiment of the present invention.

[0050] Figure 10 It is a cross-sectional view showing a coaxial cable according to a fifth embodiment of the present invention. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0052] (First embodiment) Figure 1 It is a schematic cross-sectional view showing the overall structure of a device testing apparatus 1 according to the first embodiment of the present invention. Figure 2 This is an exploded cross-sectional view showing the DSA 20 and the motherboard 30 in the first embodiment of the present invention. Figure 1 The corresponding figure of Part II.

[0053] The device test apparatus 1 in this embodiment is an apparatus for testing the electrical characteristics of a semiconductor device such as a semiconductor integrated circuit element (hereinafter also referred to as "DUT") 100. Specific examples of the DUT 100 as a test object are not particularly limited, and examples thereof include memory devices, logic devices, or SoCs (System on Chips). Figure 1 As shown, device testing apparatus 1 includes a tester 10 that performs a test on a DUT 100, and a handler 90 that handles DUT 100 and presses DUT 100 against a socket 21. Tester 10 also includes a DSA 20, a motherboard 30, a test head 70, and a main frame 80. The structure of tester 10 is not particularly limited to the following structure, as long as it includes a coaxial cable 40.

[0054] like Figure 1 and Figure 2 As shown, a DSA (Device Specific Adapter) 20 includes a socket 21, a socket board 23, and multiple connectors 24. The DSA 20 is electrically connected to a test head 70 via a motherboard 30. The DSA 20 is attachable to and detachable from the motherboard 30. The DSA 20 is designed based on the type of the DUT 100, and when the type of the DUT 100 changes, the DSA 20 is replaced with a corresponding type. There is no particular limit to the number of DSAs 20 mounted on the motherboard 30; multiple DSAs 20 may be mounted on the motherboard 30.

[0055] During testing of the DUT 100, the DUT 100 is pressed against the socket 21 by the handler 90, thereby electrically connecting the DUT 100 to the socket 21. The socket 21 includes a plurality of contactors 22 that contact the terminals 110 of the DUT 100. Although not particularly limited, specific examples of such contactors 22 include pogo pins, vertical probes, cantilever probes, anisotropic conductive rubber sheets, bumps provided on a membrane, and contactors manufactured using MEMS technology.

[0056] The socket board 23 is a wiring board with the sockets 21 mounted on its top surface. It should be noted that there is no particular limit to the number of sockets 21 mounted on the socket board 23; multiple sockets 21 may be mounted on the socket board 23. Furthermore, although not specifically shown, socket guides for positioning the DUT 100 relative to the sockets 21 may also be mounted on the top surface of the socket board 23. A coaxial connector 24 is mounted on the bottom surface of the socket board 23. The sockets 21 and coaxial connector 24 are electrically connected via conductive paths (not shown) such as wiring patterns and through-holes formed on the socket board 23.

[0057] The motherboard 30 is a repeater that electrically connects the DSA 20 and the test head 70. The motherboard 30 includes a housing 31, a plurality of coaxial connectors 32, and a plurality of coaxial cables 40. Although not particularly limited, for example, if the motherboard 30 includes more than 100 coaxial connectors 32 and 50 to 100 coaxial cables 40 are connected to one coaxial connector 32, the motherboard 30 may include thousands to tens of thousands of coaxial cables 40. The coaxial connector 32 is connected to one end of the coaxial cable 40 ( Figure 2 The coaxial connector 32 is connected to the coaxial connector 24 of the DSA 20 described above. The coaxial connector 32 is held in the upper portion of the housing 31 so as to correspond to the coaxial connector 24 of the DSA 20. When the DSA 20 is mounted on the motherboard 30, the coaxial connector 24 of the DSA 20 is mated with the coaxial connector 32 of the motherboard 30. The structure of the coaxial cable 40 will be described in detail later.

[0058] like Figure 1 As shown, the test head 70 houses a test module (pin circuit card) 71 for testing the DUT 100. This test module 71 is a wiring board mounted with electronic components, such as test devices, used to test the DUT 100. This test module 71 is electrically connected to the coaxial cable 40 on the motherboard 30 via a coaxial connector (not shown), etc., connected to the other end of the coaxial cable 40. This test module 71 transmits and receives test signals to and from the DUT 100 via the DSA 20 and the motherboard 30, thereby testing the DUT 100. The test head 70 is connected to the main frame 80 via a cable 72.

[0059] The main frame (tester body) 80 is, for example, a computer that executes a program. It communicates with each test module 71 within the test head 70 according to the program and controls each test module 71. Each test module 71 generates a test signal in response to instructions from the main frame 80 and outputs the test signal to the DUT 100.

[0060] Although not specifically shown in the figure, the processor 90 includes, for example: a conveying device that conveys the test tray carrying the DUT 100 to the top of the DSA 20; a pressing device that presses the DUT 100 against the socket 21 of the DSA 20; and a sorting device that takes out the DUT 100 from the test tray and sorts it according to the test results.

[0061] The handler 90 also includes a chamber 91 as a temperature adjustment device for applying high or low temperature thermal stress to the DUT 100. The chamber 91 is formed of a thermostatic chamber capable of maintaining the temperature within the chamber at a desired temperature. Therefore, the device test apparatus 1 can test the DUT 100 while applying thermal stress to the DUT 100, enabling the execution of so-called high-temperature and low-temperature tests.

[0062] The DSA 20 is inserted into the cavity 91 through the opening 92 formed in the handler 90, and the socket 21 of the DSA 20 is disposed in the cavity 91. The pressing device of the handler 90 presses the DUT 100 against the socket 21 of the DSA 20, thereby electrically connecting the DUT 100 and the socket 21.

[0063] It should be noted that the handler 90 may also be of a type that does not use a test tray but instead includes a contact arm that suction-holds and moves the DUT 100, and uses this contact arm to press the DUT 100. In this case, the handler 90 may include a heater or heat sink provided at the tip of the contact arm as a temperature control device, instead of the chamber 91. Alternatively, the handler 90 may include a heater or heat sink provided at the tip of the contact arm as a temperature control device in addition to the chamber 91.

[0064] Next, refer to Figure 3 The structure of the coaxial cable 40 included in the motherboard 30 will be described in detail. Figure 3 It is a cross-sectional view showing a coaxial cable 40 according to the first embodiment of the present invention.

[0065] like Figure 3 As shown, the coaxial cable 40 in this embodiment includes a plurality of inner conductors 41, a plurality of wall-shaped conductors 42, a center conductor 43, an insulating portion 44 for holding the conductors 41 to 43, an outer conductor 45 covering the insulating portion 44, and a sheath 46 covering the outer conductor 45. The coaxial cable 40 is a Figure 3 The cable extends in the direction normal to the paper surface, Figure 3 A cross section perpendicular to the longitudinal direction (axial direction) of the coaxial cable 40 is shown.

[0066] Each inner conductor 41 functions as a transmission path for transmitting an electrical signal between the test head 70 and the DUT 100. On the other hand, the outer conductor 45 is grounded and functions as an electromagnetic shielding layer for shielding against interference. In addition, the wall-shaped conductor 42 and the center conductor 43 have the function of suppressing crosstalk between the multiple inner conductors 41. In the above-mentioned device test apparatus 1, the electrical signal flowing through the inner conductor 41 is a high-frequency electrical signal, which is an electrical signal of 10 MHz or more, an electrical signal of 100 MHz or more, an electrical signal of 1 GHz or more, an electrical signal of 2.5 GHz or more, an electrical signal of 5 GHz or more, or an electrical signal of 10 GHz or more. In addition, by assigning different electrical signals to the multiple inner conductors 41, it is possible to transmit multiple (3 in this embodiment) electrical signals using a single coaxial cable 40.

[0067] The coaxial cable 40 of this embodiment includes three internal conductors 41. Each internal conductor 41 is a conductor layer that extends throughout the entire axial region of the coaxial cable 40. Each internal conductor 41 has an arcuate cross-sectional shape. Each internal conductor 41 extends substantially parallel to the inner peripheral surface 451 of the outer conductor 45, and a microstrip line structure is formed between the internal conductor 41 and the outer conductor 45. It should be noted that the number of internal conductors 41 included in the coaxial cable 40 only needs to be plural, and is not particularly limited to the above situation.

[0068] This internal conductor 41 has a strip-shaped cross-sectional shape. That is, the thickness t1 of this internal conductor 41 along the radial direction of the coaxial cable 40 is less than the width w1 of this internal conductor 41 along the circumferential direction of the coaxial cable 40 (t1 < w1). Although there is no particular limitation, the thickness t1 of the internal conductor 41 is preferably 1 / 5 or less of the width w1 of this internal conductor 41 (t1 < w1 × 1 / 5), and more preferably 1 / 10 or less of the width w1 of this internal conductor 41 (t1 < w1 × 1 / 10). In addition, the thickness t1 of this internal conductor 41 is substantially constant in the circumferential direction of the coaxial cable 40.

[0069] The thickness t1 of this internal conductor 41 is, for example, preferably 0.1 μ m or more and 20 μ m or less (0.1 μ m ≤ t1 ≤ 20 μ m), and more preferably 0.1 μ m or more and 10 μ m or less (0.1 μ m ≤ t1 ≤ 10 μ m). It should be noted that the thickness t1 of this internal conductor 41 can be set according to the frequency of the electrical signal flowing in the coaxial cable 40. Specifically, when the frequency of the electrical signal is high, the thickness t1 of the internal conductor 41 is set to be thin, and when the frequency of the electrical signal is low, the thickness t1 of the internal conductor 41 is set to be thick.

[0070] This internal conductor 41 is made of a conductive material. Although there is no particular limitation, specifically, this internal conductor 41 is made of a metal foil. As a specific example of the metal foil constituting the internal conductor 41, for example, copper foil and silver-plated copper foil can be exemplified. It should be noted that the internal conductor 41 can also be a thin film formed by plating methods such as electroplating and electroless plating. Alternatively, the internal conductor 41 can also be a thin film formed by physical vapor deposition (PVD) or chemical vapor deposition (CVD) methods such as vacuum evaporation and sputtering. Alternatively, the internal conductor 41 can also be a thin film formed by coating a paint containing metal particles and an adhesive material and curing it by heating.

[0071] The coaxial cable 40 of this embodiment includes three wall-shaped conductors 42. Each wall-shaped conductor 42 is a conductor layer extending over the entire axial area of ​​the coaxial cable 40. Each wall-shaped conductor 42 has a strip-shaped cross-sectional shape, and has a cross-sectional shape extending linearly along the radial direction of the coaxial cable 40. Each wall-shaped conductor 42 is connected to an outer conductor 45 at one end 421 of the wall-shaped conductor 42 and protrudes from the outer conductor 45 toward the center of the coaxial cable 40. Therefore, each wall-shaped conductor 42 is grounded via the outer conductor 45. It should be noted that the number of wall-shaped conductors 42 included in the coaxial cable 40 is not particularly limited to the number described above, and can be set according to the number of inner conductors 41 included in the coaxial cable 40.

[0072] The wall-shaped conductor 42 is made of a conductive material, similar to the internal conductor 41 described above. Although not particularly limited, specifically, the wall-shaped conductor 42 is made of metal foil. Specific examples of the metal foil constituting the wall-shaped conductor 42 include copper foil and silver-plated copper foil. It should be noted that the wall-shaped conductor 42 may also be a thin film formed by a plating method such as electrolytic plating or electroless plating. Alternatively, the wall-shaped conductor 42 may also be a thin film formed by a physical vapor deposition method (PVD) such as vacuum evaporation or sputtering, or a chemical vapor deposition method (CVD). Alternatively, the wall-shaped conductor 42 may also be a thin film formed by applying a coating containing metal particles and an adhesive and curing it by heating.

[0073] The center conductor 43 is a single wire extending throughout the entire axial direction of the coaxial cable 40. The center conductor 43 has a circular cross-sectional shape and is a solid wire made of a conductive material. A twisted wire may also be used as the center conductor 43.

[0074] The central conductor 43 is disposed at the center of the coaxial cable 40. Each wall-shaped conductor 42 is connected to the central conductor 43 at the other end 422 of the wall-shaped conductor 42, and all of the wall-shaped conductors 42 are electrically connected to each other via the central conductor 43. Therefore, the central conductor 43 is grounded via the wall-shaped conductor 42 and the outer conductor 45. Specific examples of the metal material constituting the central conductor 43 are not particularly limited as long as it is a metal material with good electrical conductivity, and examples thereof include silver, copper, and alloys thereof.

[0075] Should be explained, such as Figure 4 As shown, the coaxial cable 40 may not include the central conductor 43. In this case, all the wall-shaped conductors 42 are electrically connected to each other by directly connecting the wall-shaped conductors 42 to each other at the other ends 422 of the wall-shaped conductors 42. Figure 4 It is a cross-sectional view showing a modified example of the coaxial cable 40 according to the first embodiment of the present invention.

[0076] return Figure 3 The insulating portion 44 includes a cylindrical resin body 441 extending throughout the entire axial area of ​​the coaxial cable 40. The inner conductor 41, the wall-shaped conductor 42, and the center conductor 43 described above are embedded in the resin body 441. The resin body 441 is made of an electrically insulating resin material. While not particularly limited, specific examples of the resin material comprising the resin body 441 include imide-based resins such as polyimide, fluororesins such as polytetrafluoroethylene (PTFE), polyethylene (PE), and cross-linked foamed polyethylene.

[0077] The plurality of internal conductors 41 are arranged at substantially equal intervals in the circumferential direction of the coaxial cable 40. The plurality of internal conductors 41 are arranged concentrically with the external conductor 45. The resin body 441 is interposed between adjacent internal conductors 41.

[0078] The plurality of wall-shaped conductors 42 are arranged within the resin body 441 such that each wall-shaped conductor 42 is interposed between adjacent inner conductors 41 in the circumferential direction of the coaxial cable 40. Each wall-shaped conductor 42 is preferably arranged centered between adjacent inner conductors 41. The wall-shaped conductors 42 can suppress crosstalk between the plurality of inner conductors 41. The resin body 441 is interposed between the wall-shaped conductors 42 and the inner conductors 41.

[0079] Furthermore, a central conductor 43 is disposed at the center of the resin body 441, and the other ends 422 of the plurality of wall-shaped conductors 42 are connected to the central conductor 43. By connecting all the wall-shaped conductors 42 with the central conductor 43, crosstalk between the plurality of internal conductors 41 can be further suppressed. The resin body 441 is interposed between the central conductor 43 and the internal conductors 41.

[0080] When the internal conductor 41 and the wall-shaped conductor 42 are metal foils, for example, by extruding a resin material with the conductors 41 to 43 arranged as described above, a resin body 441 in which the conductors 41 to 43 are embedded can be formed. Alternatively, when the internal conductor 41 and the wall-shaped conductor 42 are thin films formed by plating or the like, for example, by repeatedly extruding a core material constituting a portion of the insulating portion 44 and forming a thin film on the core material, a resin body 441 in which the conductors 41 to 43 are embedded can be formed.

[0081] The outer conductor 45 is a cylindrical conductor layer that covers the entire circumference of the outer circumference 442 of the resin body 441 and extends over the entire axial area of ​​the coaxial cable 40. The resin body 441 is arranged in the outer conductor 45, and the outer conductor 45 surrounds all the inner conductors 41 through the resin body 441. The resin body 441 is interposed between the outer conductor 45 and each inner conductor 41. As described above, each wall-shaped conductor 42 is connected to the outer conductor 45 at one end 421 of the wall-shaped conductor 42 and is connected to the center conductor 43 at the other end 422 of the wall-shaped conductor 42. As a result, the internal space of the outer conductor 45 is divided into three chambers 453 by the wall-shaped conductor 42 and the center conductor 43, and each chamber 453 houses an inner conductor 41 separately.

[0082] The outer conductor 45 is a thin film formed on the outer peripheral surface 442 of the resin body 441. The thin film is made of a metal material. For example, the thin film is a plated layer formed by a plating method such as electrolytic plating or electroless plating. Specific examples of the metal material constituting the outer conductor 45 are not particularly limited as long as it has good electrical conductivity. Examples include silver, copper, and alloys thereof.

[0083] It should be noted that the method for forming the thin film of the outer conductor 45 is not limited to the aforementioned plating method. For example, the outer conductor 45 can also be formed by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Alternatively, the thin film of the outer conductor 45 can be a coating. Although not particularly limited, the coating can be formed, for example, by applying a coating containing metal particles and a binder to the outer peripheral surface 442 of the insulating portion 44 and curing it by heating.

[0084] Alternatively, the outer conductor 45 may be formed of a metal foil instead of the film. In this case, the outer conductor 45 is formed by winding the metal foil around the outer peripheral surface 442 of the resin body 441. Although not particularly limited, specific examples of the metal foil forming the outer conductor 45 include copper foil and silver-plated copper foil. Alternatively, a metal tube such as a copper tube may be used as the outer conductor 45 instead of the film. Alternatively, a braided shield comprising a plurality of braided bare metal wires may be used as the outer conductor 45 instead of the film.

[0085] The outer sheath 46 is a cylindrical member that covers the entire circumference of the outer circumferential surface 452 of the outer conductor 45, covering the entire axial region of the coaxial cable 40. The outer sheath 46 is made of a resin material having electrical insulating properties. While not particularly limited, specific examples of the resin material constituting the outer sheath 46 include polyvinyl chloride (PVC), polyethylene (PE), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and fluorinated ethylene propylene (FEP).

[0086] If the outer conductor of a coaxial cable is too thin, it can easily break. Furthermore, if the outer sheath of a coaxial cable is too thin, sufficient insulation may not be ensured. Due to these limitations on the thickness of the outer conductor and the outer sheath, there are limits to how thin the coaxial cable can be. Consequently, there are limits to how densely coaxial cables can be placed on a motherboard by thinning the coaxial cable.

[0087] In contrast, in this embodiment, the coaxial cable 40 includes multiple inner conductors 41, each of which shares a single outer conductor 45. Consequently, while the coaxial cable 40 has transmission characteristics comparable to conventional coaxial cables with a single inner conductor, it can have a smaller cross-sectional area than conventional coaxial cables having the same number of inner conductors 41 (three in this embodiment). Consequently, in this embodiment, the coaxial cables 40 can be densely arranged within the motherboard 30.

[0088] Furthermore, because the internal conductors of conventional coaxial cables are made of metal wires with a circular cross-section, they are relatively rigid, and multiple coaxial cables may be connected to a single connector. In this case, the greater the number of coaxial cables connected to a single connector, the greater the reaction force from the coaxial cables. Consequently, during motherboard assembly, forcible insertion of the coaxial cables can cause the coaxial cables to break, or cracks to form at the solder joints between the coaxial cable's internal conductors and the coaxial connector's terminals, leading to poor connections.

[0089] In contrast, in this embodiment, each inner conductor 41 has an arcuate cross-section, which reduces the rigidity of the coaxial cable 40 and reduces the reaction force of the coaxial cable 40. In this embodiment, the electrical signals used in the device testing apparatus have high frequencies, and due to the skin effect, the electrical signals are concentrated on the surface of the conductor as the frequency increases. Taking this into account, the cross-section of each inner conductor 41 is made thinner, thereby reducing the reaction force of the coaxial cable 40. This prevents breakage during assembly of the motherboard 30.

[0090] Furthermore, device testing equipment sometimes includes a sliding function that allows one connector (the connector to which the coaxial cable is connected) to slide laterally (in a direction perpendicular to the mating direction) relative to another connector (the connector mounted on the wiring board) to absorb mechanical errors during connector mating.

[0091] In this regard, in this embodiment, the reaction force of the coaxial cable 40 can be reduced as described above. Therefore, even if the connector 32 connected to the coaxial cable 40 has the above-mentioned sliding function, the contact pressure between the terminals of the connector 32 and the connector 24 can be fully ensured, and poor connection between the connectors 32 and 24 can be suppressed.

[0092] Furthermore, in device testing equipment, connectors are plugged and unplugged every time the DUT type is changed. If the number of coaxial cables connected to a single connector increases, the strong reaction force from the coaxial cables may cause the connector to fit in an inclined position. Consequently, sufficient connection reliability may no longer be guaranteed even after thousands of plugging and unplugging cycles.

[0093] In contrast, in this embodiment, the reaction force of the coaxial cable 40 can be reduced as described above, thereby preventing the connector 32 from being engaged with the mating connector 24 in an inclined state, and ensuring sufficient connection reliability during thousands of insertions and removals of the connectors 32 and 24.

[0094] Furthermore, when conducting low-temperature tests in device testing equipment (for example, testing a DUT at -50°C to -40°C), if the inner conductor of the coaxial cable is a metal wire with a circular cross-section, heat may be transferred to the motherboard through the inner conductor, causing the interior of the motherboard to cool and form condensation.

[0095] In contrast, in this embodiment, each internal conductor 41 has a thin cross-sectional shape extending in an arc shape, thereby suppressing heat transfer from the cavity 91 of the processor 90 to the inside of the motherboard 30 and suppressing condensation inside the motherboard 30 .

[0096] Furthermore, in this embodiment, each inner conductor 41 has a thin, arc-shaped cross-section, making it possible to reduce the weight of thousands to tens of thousands of coaxial cables 40. This reduces the strength of the housing 31 holding the coaxial cables 40, resulting in a reduction in the cost of the motherboard 30.

[0097] (Second embodiment) Figure 5 This is a cross-sectional view of a coaxial cable 40B according to a second embodiment of the present invention. In this embodiment, the structures of the inner conductor 41B, wall-shaped conductor 42B, center conductor 43B, and insulating portion 44B differ from those of the first embodiment; otherwise, the structure is the same as that of the first embodiment. Below, only the differences between the coaxial cable 40B in the second embodiment and the first embodiment will be described. Components identical to those in the first embodiment are designated with the same reference numerals, and their description will be omitted.

[0098] like Figure 5 As shown, each internal conductor 41B in this embodiment includes multiple bare metal wires 411 to replace a single conductor layer. Each bare metal wire 411 extends throughout the entire axial region of the coaxial cable 40B. These multiple bare metal wires 411 are arranged in an arc shape. As a result, each internal conductor 41B has a cross-sectional shape that extends in an arc shape. The multiple bare metal wires 411 are arranged substantially parallel to the inner peripheral surface 451 of the outer conductor 45, and a microstrip line structure is formed between the internal conductor 41B and the outer conductor 45. It should be noted that the number of bare metal wires 411 included in each internal conductor 41B may be multiple, and there is no particular limitation.

[0099] The thickness t2 of this internal conductor 41B along the radial direction of the coaxial cable 40B is less than the width w2 of this internal conductor 41B along the circumferential direction of the coaxial cable 40B (t2 < w2). Although there is no particular limitation, the thickness t2 of the internal conductor 41B is preferably 1 / 5 or less of the width w2 of this internal conductor 41B (t2 < w2 × 1 / 5), and more preferably 1 / 10 or less of the width w2 of this internal conductor 41B (t2 < w2 × 1 / 10). It should be noted that in this embodiment, as described later, since the cross-sectional shape of the bare metal wire 411 is circular, the thickness t2 of the internal conductor 41B is equal to the diameter of the bare metal wire 411.

[0100] In addition, each wall-shaped conductor 42B in this embodiment also includes multiple bare metal wires 423 to replace a single conductor layer. Each bare metal wire 423 extends throughout the entire axial region of the coaxial cable 40B. These multiple bare metal wires 423 are arranged linearly along the radial direction of the coaxial cable 40B. As a result, each wall-shaped conductor 42B has a cross-sectional shape that extends linearly. The bare metal wire 423a located at one end of each wall-shaped conductor 42B is connected to the outer conductor 45, and this wall-shaped conductor 42B protrudes from the outer conductor 45 toward the center of the coaxial cable 40B. Therefore, each wall-shaped conductor 42B is grounded via the outer conductor 45. It should be noted that the number of bare metal wires 423 included in each wall-shaped conductor 42B may be multiple, and there is no particular limitation.

[0101] The center conductor 43B in this embodiment also includes multiple bare metal wires 431. Each bare metal wire 431 extends throughout the entire axial region of the coaxial cable 40B. These multiple bare metal wires 431 are arranged in a circle at the center of the coaxial cable 40B. The bare metal wire 423b located at the other end of each wall-shaped conductor 42B is connected to this center conductor 43B, and all the above-mentioned wall-shaped conductors 42B are electrically connected to each other via the center conductor 43B. Therefore, this center conductor 43B is grounded via the wall-shaped conductor 42B and the outer conductor 45. It should be noted that the number of bare metal wires 431 included in the center conductor 43B is not particularly limited.

[0102] The aforementioned bare metal wires 411, 423, and 431 all have a circular cross-section and are solid wires made of a metal material with excellent electrical conductivity. While not particularly limited, specific examples of the metal material comprising the bare metal wires 411, 423, and 431 include copper, silver, or alloys thereof. While the bare metal wires 411, 423, and 431 have the same diameter in this embodiment, this is not a limitation; the diameters of the bare metal wires 411, 423, and 431 may differ.

[0103] The insulating portion 44B in this embodiment includes a bare wire assembly 446 that holds the inner conductor 41B, the wall-shaped conductor 42B, and the center conductor 43B. The bare wire assembly 446 includes a plurality of resin bare wires 447 assembled together. The outer conductor 45 covers the bare wire assembly 446.

[0104] Each resin bare wire 447 has a circular cross-section and is a solid wire made of an electrically insulating resin material. It extends throughout the entire axial region of the coaxial cable 40B. While not particularly limited, specific examples of the resin material comprising the resin bare wire 447 include imide-based resins such as polyimide, fluororesins such as polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkane (PFA), polyetheretherketone (PEEK), polyethylene (PE), and cross-linked foamed polyethylene. The plurality of resin bare wires 447 are arranged within the outer conductor 45 so as to fill the interior space of the outer conductor 45.

[0105] Similar to the first embodiment described above, in this embodiment, the plurality of inner conductors 41B are also arranged at substantially equal intervals in the circumferential direction of the coaxial cable 40B and are arranged concentrically with the outer conductor 45. Regarding the plurality of wall-shaped conductors 42B, each wall-shaped conductor 42B is interposed between adjacent inner conductors 41B. These wall-shaped conductors 42B can suppress crosstalk between the plurality of inner conductors 41B. Furthermore, a center conductor 43B, to which these plurality of wall-shaped conductors 42B are connected, is arranged at the center of the coaxial cable 40B. By connecting all the wall-shaped conductors 42B using the center conductor 43B, crosstalk between the plurality of inner conductors 41B can be further suppressed.

[0106] In this embodiment, the metal bare wires 411, 423, and 431 are arranged between the plurality of resin bare wires 447 so that the conductors 41B to 43B are arranged as described above. With the bare wires 411, 423, 431, and resin bare wires 447 thus arranged, these bare wires 411, 423, 431, and 447 are twisted together to form the inner conductor 41B, wall-shaped conductor 42B, center conductor 43B, and insulating portion 44B of this embodiment.

[0107] In this embodiment, similarly to the above-described first embodiment, the coaxial cable 40B includes a plurality of internal conductors 41B. Therefore, the coaxial cables 40B can be arranged at a high density within the motherboard 30 .

[0108] In addition, in this embodiment, similar to the first embodiment, each internal conductor 41B has a thin cross-sectional shape extending in an arc shape, thereby reducing the reaction force of the coaxial cable 40B and reducing the weight, and also suppressing condensation inside the motherboard 30.

[0109] (Third embodiment) Figure 6 This is a cross-sectional view of a coaxial cable 40C according to a third embodiment of the present invention. This embodiment differs from the first embodiment in that the coaxial cable 40C lacks a center conductor 43, but otherwise has the same structure as the first embodiment. Below, only the differences between the coaxial cable 40C in the third embodiment and the first embodiment will be described. Components identical to those in the first embodiment are designated with the same reference numerals, and their description will be omitted.

[0110] like Figure 6 As shown, the coaxial cable 40C of this embodiment does not include a center conductor 43. Furthermore, each wall-shaped conductor 42 is connected to an outer conductor 45 at one end 421 of the wall-shaped conductor 42, but the amount by which the wall-shaped conductor 42 protrudes from the outer conductor 45 is less than that of the first embodiment. It is sufficient for the wall-shaped conductor 42 to be interposed between the inner conductors 41 in the circumferential direction of the coaxial cable 40C. Since the wall-shaped conductor 42 is interposed between adjacent inner conductors 41 in the circumferential direction of the coaxial cable 40C, crosstalk between the inner conductors 41 can be suppressed.

[0111] In this embodiment, similar to the first embodiment described above, the inner conductor 41 has a cross-sectional shape extending substantially parallel to the inner circumferential surface 451 of the outer conductor 45. Therefore, a microstrip line structure is formed between the inner conductor 41 and the outer conductor 45. In this case, the shortest distance D1 between adjacent inner conductors 41 is preferably greater than the shortest distance D2 between the inner conductor 41 and the outer conductor 45 (D1>D2). This increases the distance between the inner conductors 41, further suppressing crosstalk between the inner conductors 41.

[0112] In this embodiment, similarly to the above-described first embodiment, the coaxial cable 40C includes a plurality of internal conductors 41 , and thus the coaxial cables 40B can be arranged at a high density within the motherboard 30 .

[0113] In addition, in this embodiment, similar to the first embodiment, each internal conductor 41 has a thin cross-sectional shape extending in an arc shape, thereby reducing the reaction force of the coaxial cable 40C and reducing the weight, and also suppressing condensation inside the motherboard 30.

[0114] Should be explained, such as Figure 7 As shown, the coaxial cable 40C may not include the wall-shaped conductor 42 . Figure 7 It is a cross-sectional view showing a first modified example of the coaxial cable according to the third embodiment of the present invention.

[0115] In addition, the number of the inner conductors 41 of the coaxial cable 40C is not particularly limited to the above number. Figure 8 As shown, the coaxial cable 40C may include two inner conductors 41 . Figure 8 2 is a cross-sectional view showing a second modified example of the coaxial cable according to the third embodiment of the present invention. Alternatively, although not particularly shown, the coaxial cable 40 may include four or more internal conductors 41 .

[0116] (Fourth embodiment) Figure 9 This is a cross-sectional view of a coaxial cable 40D according to a fourth embodiment of the present invention. This embodiment differs from the third embodiment in that an insulating portion 44D includes an air layer 445, but otherwise has the same structure as the third embodiment. The following description focuses solely on the differences between the coaxial cable 40D in the fourth embodiment and the third embodiment. Components identical to those in the third embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0117] like Figure 9As shown, the insulating portion 44D of this embodiment includes a resin body 441 and an air layer 445. The resin body 441 of this embodiment has a cylindrical shape and has a hole 443 at its center. This hole 443 penetrates the resin body 441 throughout the entire axial region of the coaxial cable 40D. The air in this hole 443 forms an air layer 445. This air layer 445 is interposed between the plurality of inner conductors 41.

[0118] It should be noted that a gas other than air may exist in the hole 443, or the hole 443 may be a vacuum, instead of the air layer 445. Figure 9 In the embodiment, the internal conductor 41 is completely buried in the resin body 441 , but the internal conductor 41 may be exposed from the resin body 441 to the air layer 445 .

[0119] In this embodiment, similarly to the third embodiment described above, the coaxial cable 40D includes a plurality of internal conductors 41 , and thus the coaxial cables 40D can be arranged at a high density within the motherboard 30 .

[0120] In addition, in this embodiment, similarly to the third embodiment, each inner conductor 41 has a thin cross-sectional shape extending in an arc shape, thereby reducing the reaction force of the coaxial cable 40D and reducing the weight, and also suppressing condensation inside the motherboard 30.

[0121] In this embodiment, similarly to the third embodiment, the inner conductor 41 has a cross-sectional shape extending substantially parallel to the inner peripheral surface 451 of the outer conductor 45 , so a microstrip line structure is formed between the inner conductor 41 and the outer conductor 45 .

[0122] In the present embodiment, similarly to the third embodiment, the wall-shaped conductor 42 is interposed between the inner conductors 41 adjacent to each other in the circumferential direction of the coaxial cable 40D. Therefore, crosstalk between the inner conductors 41 can be suppressed.

[0123] Furthermore, in this embodiment, air layers 445 are interposed between the plurality of internal conductors 41, and the dielectric constant of the portion between the internal conductors 41 in the insulating portion 44D is reduced, thereby increasing the electrical distance between the internal conductors 41. Furthermore, in this embodiment, the electrical distance between the internal conductors 41 can also be adjusted by adjusting the size of the holes 443 in the resin body 441.

[0124] (Fifth embodiment) Figure 10This is a cross-sectional view of a coaxial cable 40E according to a fifth embodiment of the present invention. This embodiment differs from the third embodiment in that an insulating portion 44E includes an air layer 445, but otherwise has the same structure as the third embodiment. Below, only the differences between the coaxial cable 40E in the fifth embodiment and the third embodiment will be described. Components identical to those in the third embodiment are denoted by the same reference numerals, and their description will be omitted.

[0125] like Figure 10 As shown, the insulating portion 44E of this embodiment includes a resin body 441 and an air layer 445. The resin body 441 of this embodiment has a cylindrical shape, but has a plurality of (three in this embodiment) grooves 444 on its outer peripheral surface 442. Each groove 444 is recessed toward the radial inner side of the coaxial cable 40E and extends over the entire axial area of ​​the coaxial cable 40E. The plurality of grooves 444 are arranged at substantially equal intervals in the circumferential direction of the coaxial cable 40E and are arranged concentrically with the outer conductor 45. The inner conductor 41 is arranged at the bottom of the groove 444. The outer conductor 45 covers the outer peripheral surface 442 of the resin body 441, and the air present in each groove 444 forms an air layer 445. Therefore, the air layer 445 is interposed between the inner conductor 41 and the outer conductor 45.

[0126] It should be noted that a gas other than air may be present in the groove 444, or the groove 444 may be a vacuum, instead of the air layer 445. Figure 10 In the embodiment, the internal conductor 41 is exposed from the resin body 441 to the air layer 445 , but the internal conductor 41 may be completely buried in the resin body 441 .

[0127] In this embodiment, similarly to the third embodiment described above, the coaxial cable 40E includes a plurality of internal conductors 41 , and thus the coaxial cables 40E can be arranged at a high density within the motherboard 30 .

[0128] In addition, in this embodiment, similarly to the third embodiment, each internal conductor 41 has a thin cross-sectional shape extending in an arc shape, thereby reducing the reaction force of the coaxial cable 40E and reducing the weight, and also suppressing condensation inside the motherboard 30.

[0129] In this embodiment, similarly to the third embodiment, the inner conductor 41 has a cross-sectional shape extending substantially parallel to the inner peripheral surface 451 of the outer conductor 45 , so a microstrip line structure is formed between the inner conductor 41 and the outer conductor 45 .

[0130] In the present embodiment, similarly to the third embodiment, the wall-shaped conductor 42 is interposed between the inner conductors 41 adjacent to each other in the circumferential direction of the coaxial cable 40E. Therefore, crosstalk between the inner conductors 41 can be suppressed.

[0131] Furthermore, in this embodiment, an air layer 445 is interposed between the inner conductor 41 and the outer conductor 45, thereby reducing the dielectric constant of the portion between the inner conductor 41 and the outer conductor 45 in the insulating portion 44E. Therefore, while the electrical distance between the inner conductor 41 and the outer conductor 45 can be maintained, the physical distance between the inner conductors 41 can be increased, thereby suppressing crosstalk between the inner conductors 41.

[0132] In this embodiment, in addition to the groove 444, the hole 443 described in the fourth embodiment may be formed in the resin body 441. The hole 443 can increase or adjust the electrical distance between the internal conductors 41.

[0133] It should be noted that the embodiments described above are described to facilitate understanding of the present invention and are not described to limit the present invention. Therefore, the elements disclosed in the embodiments described above also include all design changes and equivalents that fall within the technical scope of the present invention.

[0134] For example, in the third to fifth embodiments, the conductors 41 to 43 and the insulating portion 44 ( 44D, 44E) may be formed by twisting a plurality of bare wires as in the second embodiment.

[0135] Description of Reference Numerals 1: Device test equipment 10: Tester 20:DSA 21: Socket 22: Contactor 23: Socket board 24: Coaxial connector 30: Motherboard 31: Frame 32: Coaxial connector 40, 40B~40E: coaxial cable 41, 41B: Inner conductor 411: Bare metal wire 42, 42B: Wall conductor 421: One end 422: The other end 423, 423a, 423b: Bare metal wire 43, 43B: Center conductor 431: Bare metal wire 44, 44C ~ 44E: Insulation 441: Resin body 442: Outer surface 443: Hole 444: Slot 445: Air layer 446: Bare wire aggregate 447: Resin bare wire 45: External conductor 451: Inner circumference 452: Outer surface 453: Room 46: Skin 70: Test head 71: Experimental Module 72: Cable 80: Main frame 90: Processor 91: Chamber 92: Opening 100: DUT 110: Terminal.

Claims

1. A coaxial cable comprising: a cylindrical outer conductor; an insulating portion covered by the outer conductor; and A plurality of inner conductors are disposed in the insulating portion.

2. The coaxial cable according to claim 1, wherein The plurality of inner conductors are arranged in the insulating portion so as to be separated from each other.

3. The coaxial cable according to claim 1, wherein The inner conductor has a cross-sectional shape extending in an arc shape.

4. The coaxial cable according to claim 1, wherein The inner conductor has a cross-sectional shape extending substantially parallel to the inner peripheral surface of the outer conductor.

5. The coaxial cable according to claim 1, wherein A thickness of the inner conductor along a radial direction of the coaxial cable is smaller than a width of the inner conductor along a circumferential direction of the coaxial cable. The coaxial cable according to claim 1 , wherein: The plurality of inner conductors are arranged at intervals in a circumferential direction of the coaxial cable and are arranged concentrically with the outer conductor.

7. The coaxial cable according to claim 1, wherein The internal conductor includes a metal layer having an arc-shaped cross-section or a plurality of metal bare wires arranged in an arc shape.

8. The coaxial cable according to claim 1, wherein The insulating portion includes a first insulating portion, and the first insulating portion includes a resin material.

9. The coaxial cable according to claim 8, wherein The first insulating portion is a columnar or cylindrical resin body that holds the plurality of internal conductors, and the outer conductor covers the resin body.

10. The coaxial cable according to claim 8, wherein The first insulating portion includes a bare wire assembly for holding the plurality of internal conductors, wherein the bare wire assembly includes a plurality of resin bare wires assembled together. The outer conductor covers the bare wire assembly.

11. The coaxial cable according to claim 8, wherein The insulating portion includes a second insulating portion formed of gas or vacuum.

12. The coaxial cable according to claim 11, wherein The second insulating portion is interposed between the plurality of inner conductors.

13. The coaxial cable according to claim 11, wherein The second insulating portion is interposed between the inner conductor and the outer conductor.

14. The coaxial cable according to claim 1, wherein The coaxial cable includes a plurality of wall-shaped conductors, wherein the plurality of wall-shaped conductors are interposed between the plurality of inner conductors in a circumferential direction of the coaxial cable. The wall-shaped conductor is electrically connected to the external conductor.

15. The coaxial cable according to claim 14, wherein The plurality of wall-shaped conductors are connected to each other at the center of the coaxial cable.

16. The coaxial cable according to claim 14, wherein The wall-shaped conductor includes a metal layer extending in a radial direction of the coaxial cable or a plurality of bare metal wires arranged in the radial direction. 17 . A device testing apparatus for testing a device under test (DUT), comprising the coaxial cable according to claim 1 .

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