JP2004022620A - Superconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductor device having excellent high-frequency characteristics, small sized and lightweight. <P>SOLUTION: The device compromises a superconductor component 901 for a high frequency with superconductor layer formed on an insulation substrate, and a supporting body 900 for securing the superconductor component. The supporting body 900 is formed with the sidewalls of a rectangular column, and the superconductor component 901 is arranged inside the rectangular column. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a superconductor device capable of selectively transmitting only a signal of a predetermined frequency with a small loss of a high frequency signal of MHz or higher.
[0002]
[Prior art]
Oxide superconductors are considered promising because they have almost no loss even when a large current is applied, and their electrical resistance to high-frequency current is very small. In this member, a superconducting film formed on the substrate surface is processed by lithography to resonate and transmit only a desired frequency.
[0003]
In order to efficiently transmit a high frequency, the superconducting film must face a grounded surface with a dielectric interposed therebetween. Normally, a superconductor film is also formed on the back surface of the substrate on which the superconductor is formed, and this surface is brought into contact with a grounded metal or other conductive holder.
[0004]
The holder is cooled via the cold head of the refrigerator or a cooling member attached thereto. Furthermore, in order to prevent emission of a high-frequency signal, the element made of a superconducting film is encased in a case made of a grounded conductor.
[0005]
[Problems to be solved by the invention]
In particular, when the above-described superconducting member is used in a base station of a mobile phone, it is desired that the superconducting member be placed very close to the antenna. For that purpose, it is desirable to be small and lightweight, but if it is made small and lightweight together with the cooling device, the cooling capacity is reduced. As a result, heat transmitted through the transmission cable, heat radiation from the outside, and the like cannot be ignored, and there has been a problem that the element is not sufficiently cooled.
[0006]
[Means for Solving the Problems]
The present invention includes a high-frequency superconductor element having a superconductor layer formed on an insulating substrate, and a support for fixing the high-frequency superconductor element, wherein the support forms a prismatic side wall, A superconductor device is provided, wherein the body element is disposed inside the prism.
[0007]
In the prism, the high-frequency superconductor element may be separated by a partition, and at least one surface of the partition may have a conductor layer or a superconductor layer.
[0008]
The prism may be a triangular prism.
[0009]
A plurality of said prisms may arrange outer side surfaces close to each other.
[0010]
A high-frequency superconductor element having a superconductor layer formed on an insulating substrate; a support for fixing the high-frequency superconductor element to the front and back surfaces; And a member having a lower thermal conductivity than other portions is provided below the connector of the support.
[0011]
The connector may be shifted on the front and back surfaces of the support.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples.
(Embodiment 1)
1 and 2 are views for explaining an element 100 using a superconductor film according to the present embodiment. FIG. 1 is a plan view, and FIG. 2 is a cross-sectional view.
[0013]
As shown in the figure, a superconductor film is formed on the upper and lower surfaces of the substrate 101 by a method such as CVD, vacuum evaporation, sputtering, or laser ablation. Here, since the substrate 101 has a relatively small dielectric loss, a single crystal of LaAlO ₃ , MgO or sapphire is used. Further, for the superconductor film, Re ₁ Ba ₂ Cu ₃ O _x (Re = a rare earth element such as Y, Ho, and Yb) and other oxide superconductors such as Bi-based and Tl-based can be used. The sapphire substrate can use a single crystal R-plane.
[0014]
Next, as shown in FIG. 1, the superconductor film 102 on the surface is processed by lithography or the like so as to have a desired resonance frequency. On the other hand, on the superconducting film 102 on the back surface, Ag is formed as a contact resistance reducing layer 103 with a thickness of about 100 nm or more and about 5 μm or less.
[0015]
Thereafter, annealing is performed in an oxygen atmosphere of at least 10 Pa at a temperature of about 400 ° C. to about 900 ° C., preferably at a temperature of about 400 ° C. to about 700 ° C. Although the contact resistance between Ag and the oxide superconductor is small, this treatment further reduces the contact resistance so that it is difficult to detect.
[0016]
Next, the contact resistance reducing layer 103 and the support 105 are fixed via the bonding material 104. Here, as the support 105, a 3 mm-thick copper plate whose surface is coated with Au of 1 μm or more and 5 μm or less can be used. When Ag is used as the contact resistance reducing layer 103, Ag also has an effect of suppressing a reaction. Therefore, in the case of using the bonding material 104 having high reactivity, it is better that the thickness of the Ag film is large, and it is desired that the thickness be 100 nm or more, preferably 500 nm or more. In practice, it may be 5 μm or less.
[0017]
The fixing method may be mechanical attachment using a jig. However, when Au is provided on the superconducting film on the back surface and the outermost surface of the support, they are brought into contact with each other in a vacuum, an inert gas or an oxygen atmosphere. In this case, the bonding may be performed by heating to about 200 ° C. to 400 ° C.
[0018]
In general, heat intrusion occurs when heat transmitted through a power cable is transmitted through a connector to a support on which an element is fixed. Therefore, it is important to take measures to prevent heat from entering from the connector.
[0019]
Therefore, as shown in FIG. 3, the support 701 for fixing the element 700 is not formed by a single member, but a member 702 having a low thermal conductivity is used for a portion for supporting the connector 703. Is good. Further, a member 702 having a low thermal conductivity is coated with Au so that the outer skin 704 of the connector 703 has the same potential as the ground surface 705 of the element 700, and a part thereof is brought into contact with the ground surface 705 of the element 700.
[0020]
At this time, the contact area S between the ground plane 705 and the member 702 having low thermal conductivity is preferably wider for the input high frequency, but the heat insulating effect is reduced. On the other hand, if it is narrow, the ground level of the passage characteristic increases.
[0021]
The experimental results on this point are shown in FIG. Here, S1 is the area of the member 702 having a low thermal conductivity.
[0022]
Therefore, the contact area S is preferably 1% or more and 30% or less with respect to the area of the member 702 having low thermal conductivity. More preferably, it is desired to be 5% or more and 20% or less.
[0023]
When the support 701 was attached to the cold head and cooled, it could be cooled to 50K.
[0024]
In many cases, the element 100 and the low noise amplifier (LNA) 201 are fixed to the element substrate 200 as shown in FIG. It is preferable that the element substrate 200 be as thin as possible and have a small surface area in order to reduce heat penetration due to radiation. Reducing the thickness of the element substrate 200 is also effective for reducing the weight. The element substrate 200 does not necessarily need to be made of metal, and sapphire or the like having a good thermal conductivity at a low temperature of around 50K can be used. However, when sapphire is used, it is necessary to provide a metal film having a low specific resistance, such as Au, Ag, Al, or Cu, having a thickness of at least 300 nm on the surface, and ground this film. Since sapphire is strong, it can be made thinner and is also effective in reducing the weight.
[0025]
A signal that has entered the element 100 from the antenna through the connector 208 enters the low noise amplifier (LNA) 201 from the output electrode 204 and is amplified. The connection between the element 100 and the LNA 201 is preferably made using a thin metal wire or foil 206. In the present embodiment, the LNA 201 is formed on a substrate 202 made of alumina or quartz having a low thermal conductivity and provided between the element 100 and a connector 203 for connecting an output cable. With such an arrangement, heat intrusion from the connector 203 side can be reduced.
[0026]
Generally, a transmission / reception device of three sectors is installed in a base station of a mobile phone. This is because three antennas are shared by 120 degrees each and a transmission / reception device is provided for enabling communication with a user who is within a circle having a radius of 1 to several km around the base station. Furthermore, a method called diversity is used, in which case two reception filters are required per sector.
[0027]
FIG. 6 shows an example in which three superconducting elements 901 are fixed on a support 900. FIG. 6A is a perspective view, and FIG. 6B is a top view.
[0028]
Here, the elements 901 are mounted on three surfaces inside the support 900. Accordingly, a hollow structure in which the back surface of the support 900 is a rectangular surface of a triangular prism is obtained. Inside, each element 901 is separated by a partition 910 having one of a conductor or a superconductor disposed on the surface so as to be placed in a separated space.
[0029]
FIG. 7 shows a case where a pulse tube refrigerator is used to cool this structure.
[0030]
Generally, a pulse tube refrigerator connects a cold head, a compressor, and a buffer tank with two pipes. Here, the first pipe 1001 connected to the buffer tank often becomes an obstacle when attaching the superconducting member to the cold head. Therefore, in the present invention, a cylindrical shield 1002 is provided in a triangular prism, and a first pipe 1001 connecting the cold head 1203 and the buffer tank is passed through the inside. Thereby, radiant heat from the first pipe 1001 can be blocked, and the element can be compactly stored. Further, a partition 1003 for separating each element may be connected to the shield 1002.
[0031]
Note that the triangular prism here may be a triangular prism as shown in FIG. 8 in order to secure a sufficient distance between each element and a partition for separating the elements and reduce the surface area.
[0032]
FIG. 9 is a diagram showing the cooling member 1204 attached to the bottom surface on the side in contact with the cold head 1203 in FIG. The connector 1201 provided on each element 901 needs to be provided with a hole 1200 in the cooling member 1204 provided on the bottom surface of the triangular prism so as not to directly contact the cold head 1203 or the cooling member 1204 attached thereto. .
[0033]
FIG. 10 is a diagram showing a case where six elements are used. One unit is a hollow triangular prism having three elements mounted on the inner surface, and one surface of each is brought into contact with or close to the back surface. At this time, two cold heads 1303 may be attached to each of them, or two cold heads 1303 may be attached to two cooling members attached to one cold head.
[0034]
FIG. 11 is a block diagram of a device when two cold heads are used.
[0035]
He gas compressed by the compressor 1410 is sent to two cold heads 1412 through two pipes 1411. At this time, it is preferable to provide a flow control valve 1413 so that the respective gas flow rates are the same. Also, it is desirable that the two pipes at the branch point 1414 have a symmetrical shape, and have the same length and shape from there to the cold head. Further, it is desirable that the pipes from the cold head to the buffer tank 1415 have the same length and shape.
[0036]
Thereby, two units of superconducting members can be efficiently cooled by one compressor.
[0037]
FIG. 12 shows an example in which two compressors 1510 are provided to one cold head 1512 via a switching valve 1513. The usage method is (1) normally, move only one unit and switch to the other unit when an abnormality occurs. (2) Normally, move both units at half output and one unit when an abnormality occurs in one of them. It is conceivable to switch to only driving at full power.
[0038]
By doing so, even if one compressor fails, communication is not disabled and reliability is improved.
[0039]
More specifically, a low-thermal-conductivity member made of quartz coated with 300 nm or more of Au on the surface (both surfaces) of a part of the copper support is incorporated, and a superconducting element is arranged on the copper part. A connector for input and output is placed on a member with low efficiency.
[0040]
These three members are assembled so that the element faces inward, and the outer periphery is covered with a heat insulating sheet called super insulation. In addition, a separation jig having three plates attached to a cylinder was provided inside. This partition also makes it possible to suppress interference between the elements.
[0041]
When a pulse tube refrigerator is used, it can be made compact by passing a pipe through a cylinder. Also, the cylinder can block radiant heat from the pipe. According to the present invention, the surface area can be significantly reduced as compared with the case where the element is mounted on the outside as in the related art, so that heat penetration due to radiation can be reduced. As a result, a small refrigerator can be used, and a small and lightweight superconducting member can be obtained.
(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIG.
[0042]
In the same manner as in the first embodiment, a superconductor is formed on both surfaces of a sapphire single-crystal R-plane substrate by a laser ablation method, and then a single-sided superconducting film is processed by lithography so as to have a desired resonance frequency. On the other hand, Ag is formed as a contact resistance reducing layer on the back surface of the superconducting film in a thickness of 100 nm or more and 5 μm or less. Thereafter, annealing is performed at a temperature of 400 ° C. or more and 900 ° C. or less, preferably 400 ° C. or more and 700 ° C. or less in an oxygen atmosphere of at least 10 Pa, and further, Au is formed on the back surface to a thickness of 100 nm or more and 5 μm or less. Formed.
[0043]
In addition, a 3 mm-thick copper plate whose surface is coated with Au of 1 μm or more and 5 μm or less can be used as the support 300.
[0044]
The element 301 is fixed to both surfaces of the support 300. The fixing method may be mechanical attachment using a jig. However, when Au is provided on the superconducting film on the back surface and the outermost surface of the support, they are brought into contact with each other in a vacuum, an inert gas or an oxygen atmosphere. In this case, the bonding may be performed by heating to about 200 ° C. to 400 ° C.
[0045]
On the other hand, a cooling member 302 having an outer dimension of 30 mm × 60 mm is installed on the cold head. The cooling member 302 is provided with a recess having an inner dimension of 25 mm × 55 mm and a depth of 10 mm.
[0046]
A member in which the support 300 and the element 301 are integrated is set on the housing 302.
[0047]
Further, it is covered with a cover 303 having an outer dimension of 30 mm x 60 mm provided with a recess having a depth of 10 mm and an inner dimension of 25 mm x 55 mm.
[0048]
At this time, the larger the area S and the depth L of the cover 303 and the cooling member 302 are, the better the high-frequency transmission characteristics are. It is desired that the area S is at least 60% or more, preferably 80% or more, more preferably 100% or more of the element area. On the other hand, it is desired that the depth L is 2 mm or more, preferably 5 mm or more, and more preferably 10 mm or more. However, increasing this dimension increases the surface area and heat penetration, so it is appropriate to set the area to 120% or less and the depth to 20 mm or less.
[0049]
The superconducting member thus obtained was placed in a vacuum insulated container, depressurized by a vacuum pump (not shown), and then cooled by operating a refrigerator. When two elements were arranged in a plane, cooling could only be performed up to 80K. However, according to the present invention, even if the same refrigerator was used, the surface area of the member could be reduced, and cooling could be performed up to 60K. .
[0050]
In this way, the surface area of the member can be made smaller than when the two elements 301 are arranged on one plane, and a superconducting member with less heat intrusion due to radiation can be obtained.
[0051]
In this case, since the area of the support 300 that contacts the cooling member 302 is small, a metal film having a low specific resistance such as Au, Ag, Al, or Cu having a thickness of at least 300 nm is formed on the surface of the support 300. Sapphire provided may be used.
[0052]
When the support 300 is thin, the input / output electrodes connected to the connector 305 are preferably not on a line passing through the center of the substrate provided with the superconductor so that the connectors 305 do not come into contact with each other. For example, as shown in FIG. 14, when the input / output electrodes 1401 are on both sides of the substrate, they may be in the same direction or the opposite direction from the line passing through the center of the substrate 1402, but if they are at least 2 mm or more away, Even if the element is attached to both sides of the support having a thickness of about 2 mm, no problem occurs in the connection of the connector. When the input / output electrode 1401 is on one side of the substrate as shown in FIG. 15, one of the electrodes may be on a line passing through the center of the substrate, and the connectors may be provided on both sides of the support 300. What is necessary is just to attach an element.
[0053]
The cover 303 does not need to be cooled to the same temperature as the element 301. Therefore, it is preferable to be made of a material having poor heat conductivity. However, high-frequency power requires low surface resistance. For example, Al, Ni, Ta, Mo, SUS, etc. may be used, but it is desirable to coat Au on the surface, at least on the side facing the element. Au has a high infrared reflectance, so that if it is coated on the outside, a heat insulating effect can be obtained.
[0054]
Specifically, a superconducting element is fixed on both sides of a support made of sapphire having a thickness of 1 mm and coated on the surface thereof with a thickness of 300 nm or more and 5 μm or less so that the connector does not come into contact with the superconducting element. After the pressure was reduced by a vacuum pump, the refrigerator was operated and cooled. When the two elements were arranged in a plane, it could only be cooled down to 80K, but even when the same refrigerator was used, the surface area of the member was reduced. By using sapphire having higher thermal conductivity than copper, the entire device could be cooled down to 55K with good uniformity.
[0055]
When the cover 303 is made of a material having good heat conductivity such as Cu, as shown in FIG. 16, the heat conductivity in a temperature range of 50K to 100K is 250 k / W. m ^-1 . It is preferable to attach via a connection member 610 made of a material having a specific resistance of 0.01 Ωcm or less, for example, Al, which is not more than K− ¹ .
[0056]
Note that a member having a superconductor disposed on the inner surface of a cover made of Al may be used for weight reduction. However, the superconductor must be grounded. When a superconductor is used, the cover must be lowered to a temperature lower than the superconducting transition temperature. The use of such a cover improves the high-frequency transmission characteristics of the element.
[0057]
As a result of measurement using an Al cover whose surface is coated with Au of 300 nm or more and 5 μm or less, it was possible to cool down to 60 K with lower power without deteriorating high-frequency transmission characteristics.
[0058]
It is more effective to coat Au not only on the inner periphery but also on the outer periphery of the cover.
(Embodiment 3)
In the present embodiment, two elements are arranged on the front and back of one support, but each element is provided on a substrate formed of members having different thermal conductivity.
[0059]
Each element 700 is formed on a substrate as shown in FIG. In addition, a member 702 having low thermal conductivity is incorporated in a part of the support 701.
[0060]
When the element 700 is provided also on the back surface side of the member in which the element 700 and the support 701 thus formed are integrated, the result is as shown in FIG.
[0061]
For example, copper having high thermal conductivity can be used for the support 701 and Al can be used for the member 702 having low thermal conductivity. More preferably, if the surface (both surfaces) of quartz coated with Au of 300 nm or more is used as the member 702 having low thermal conductivity, the thermal conductivity of quartz is low, so that the heat insulating effect is greater. Here, it is necessary to provide conductive films on both surfaces of the support 701 and the support 702 of the low thermal conductivity member.
(Embodiment 4)
As described above, generally, a base station of a mobile phone is equipped with a transmitting and receiving device of three sectors, and when a system called diversity is used, two receiving filters are required for one sector. become.
[0062]
In such a case, it is preferable to load six elements 801 into one cooling member 800 as in the present embodiment. (FIG. 18)
Here, the individual elements 801 are provided on a support 802. At this time, the support 802 may be made of a single material, or a member having a low thermal conductivity may be used for a portion where the connector is provided.
[0063]
It is also desirable to provide a partition 810 having a conductor or superconductor disposed on the surface between the facing elements. It is desired that the distance L between the element and the partition is 2 mm or more, preferably 5 mm or more, and more preferably 10 mm or more. However, increasing this dimension increases the surface area and increases heat penetration, so it is appropriate to set the dimension to 20 mm or less. In this way, the surface area of the member can be made smaller than when the six elements are arranged on one plane, and a superconducting member with less heat penetration by radiation can be obtained.
[0064]
【The invention's effect】
As described above, according to the present invention, a small and lightweight superconducting member having excellent high-frequency characteristics can be provided.
[Brief description of the drawings]
1 is a plan view of a superconducting element according to the present invention. FIG. 2 is a cross-sectional view of a superconducting element according to the present invention. FIG. 3 is a perspective view of a superconducting element according to the present invention. FIG. 5 is a perspective view of a superconducting element according to the present invention. FIG. 6 is a perspective view of a structure according to the first embodiment. FIG. 7 is a perspective view of a structure according to the first embodiment. FIG. 9 is a bottom view of the structure according to the first embodiment. FIG. 10 is a modification of the first embodiment. FIG. 11 is a block diagram of a refrigerator and equipment. 12 is a block diagram of a refrigerator and equipment. FIG. 13 is a view for explaining a second embodiment. FIG. 14 is a plan view of an element according to a second embodiment. FIG. 15 is an illustration of an element according to a second embodiment. FIG. 16 is a plan view. FIG. 16 is a modified example of the second embodiment. FIG. 17 is a diagram illustrating a third embodiment. FIG. Diagram for explaining a state DESCRIPTION OF SYMBOLS
100 element 900 support 901 element 910 partition 1203 cold head

Claims (6)

A high-frequency superconductor element having a superconductor layer formed on an insulating substrate,
A support for fixing the high-frequency superconductor element,
The superconductor device is characterized in that the support has a prismatic side wall, and the superconductor element is arranged inside the prism. In the prism, the high-frequency superconductor element is separated by a partition,
The superconductor device according to claim 1, wherein at least one surface of the partition has a conductor layer or a superconductor layer. The superconductor device according to claim 1, wherein the prism is a triangular prism. The superconductor device according to claim 1, wherein the plurality of prisms have outer surfaces arranged close to each other. A high-frequency superconductor element having a superconductor layer formed on an insulating substrate,
A support for fixing the high-frequency superconductor element to the front and back surfaces,
An input / output connector is provided at an end of the high-frequency superconductor element,
A member having lower thermal conductivity than other portions is provided below the connector of the support. The superconductor device according to claim 5, wherein the connector is shifted on the front and back surfaces of the support.

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