Abstract:
A magnetic device comprises a magnetic element, a first magnetic field application device, and a second magnetic field application device. The first and second magnetic field applying means are disposed on mutually opposite sides of the magnetic element. The magnetic element is, for example, an element in which a soft magnetic film is formed in a meandering shape on a nonmagnetic substrate. The first and second magnetic field application device create a magnetic field in one direction from the first magnetic field application device toward the second magnetic field application device. The bias magnetic field in one direction is thereby applied to the entire soft magnetic film in the magnetic element disposed between the first and second magnetic field application device.

Description:
TECHNICAL FIELD 
   The present invention relates to a magnetic device that is provided with a magnetic sensor. 
   BACKGROUND ART 
   In recent years, in order to cut costs and reduce chip components, devices have been proposed in which induction elements such as magnetic impedance elements are integrated on substrates such as semiconductors. When magnetic impedance elements of this type are used for a magnetic sensor, it is necessary to apply a bias magnetic field to the magnetic impedance elements due to the characteristics of impedance change. 
   A method that may be considered in order to apply a bias magnetic field to the magnetic impedance elements is, for example, to place magnets adjacent to the magnetic impedance elements (See Japanese Patent Application Laid-Open (JP-A) No. 2002-43649). However, applying a bias magnetic field by means of magnets in this manner poses various problems when applied to magnetic sensors as the magnetic field strength of the individual magnets is not uniform, and it is difficult to consistently apply a bias magnetic field having a constant value. 
   In contrast, a method of consistently applying a bias magnetic field having a uniform strength to magnetic impedance elements is known in which a spiral-shape or coil-shape conductive layer is formed adjacent to the magnetic impedance elements, and a bias magnetic field is generated by energizing this conductive layer (Japanese Patent Application Laid-Open (JP-A) No.2001-221838). Because a magnetic sensor in which magnetic impedance elements are arranged along a coil center axis of a conductive layer formed in a coil shape, in particular, has the characteristic that it is possible to apply a strong bias magnetic field consistently to the magnetic impedance elements, this method is preferable as it enables highly accurate magnetic sensors to be obtained. 
   However, in order to apply a bias magnetic field to the magnetic impedance elements, when a coil-shape magnetic field application device is formed around the impedance elements so as to envelop the magnetic impedance elements, the outer configuration of the overall magnetic device is enlarged by this coil, so that the problem has arisen that this has prevented any size reduction or slenderization of any instrument in which this magnetic device is mounted. 
   SUMMARY OF INVENTION 
   Exemplary embodiments of the present invention were conceived in view of the above described circumstances, and to provide a magnetic device that is provided with magnetic elements that can be manufactured with a small size and weight and at low cost. However, exemplary embodiments of the present invention need not solve these or any other programs. 
   A first aspect of the present invention is a magnetic device that includes: a magnetic element; and a first magnetic field application device and a second magnetic field application device that are placed so as to sandwich the magnetic element, and that are used to apply a unidirectional bias magnetic field to the magnetic element. 
   A second aspect of the present invention is the magnetic device according to the first aspect in which the first magnetic field application device and the second magnetic field application device each include an independent magnetic field generating device and an independent magnetic field induction device. 
   A third aspect of the present invention is the magnetic device according to the first aspect in which the magnetic field induction devices of both the first magnetic field application device and the second magnetic field application device, and the magnetic element are placed on substantially the same plane. 
   A fourth aspect of the present invention is a magnetic device that includes: a first substrate having a first conductive layer and a second conductive layer; a second substrate having a third conductive layer and a fourth conductive layer; a magnetic element that is placed between the first substrate and the second substrate; a first connecting portion that electrically connects the first conductive layer and the third conductive layer; a second connecting portion that electrically connects the second conductive layer and the fourth conductive layer; a coil-shaped first magnetic field generating device that includes the first conductive layer, the third conductive layer, and the first connecting portion; a coil-shaped second magnetic field generating device that includes the second conductive layer, the fourth conductive layer, and the second connecting portion; a first magnetic field induction device that passes through the center of the coil shape of the first magnetic field generating device; and a second magnetic field induction device that passes through the center of the coil shape of the second magnetic field generating device. 
   A fifth aspect of the present invention is the magnetic device according to the fourth aspect in which there is further provided a third substrate that is placed between the first substrate and the second substrate, and the third substrate has a magnetic element housing portion that houses the magnetic element, a first housing portion that houses the first magnetic field induction device, and a second housing portion that houses the second magnetic field induction device, and the magnetic element housing portion is placed between the first housing portion and the second housing portion. 
   According to exemplary embodiments the magnetic device according to the present invention, as a result of the first magnetic field application device and the second magnetic field application device being placed on both sides of the magnetic element, it is possible to apply a strong bias magnetic field to the magnetic element that is efficient unidirectionally, and it is possible to achieve a highly accurate magnetic sensor. 
   In addition, a magnetic field generating device that is used to apply a bias magnetic field to a magnetic element can be located away from the magnetic element. Because of this, it is not necessary to form the magnetic field generating device in proximity to the magnetic element. As a result, it is possible to achieve reductions in the size, and particularly in the thickness of the overall magnetic device, and it is possible to improve the degree of freedom in the layout of the instrument on which the magnetic device is mounted. 
   Exemplary embodiments of the present invention may have the above discussed advantages. However, embodiments of the present invention need not have any advantages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     [ FIG. 1 ]  FIG. 1  is a perspective view showing an exemplary embodiment of the magnetic device according to the present invention. 
     [ FIG. 2 ]  FIG. 2  is a perspective view showing another exemplary embodiment of the magnetic device according to the present invention. 
     [ FIG. 3 ]  FIG. 3  is an exploded perspective view showing another exemplary embodiment of the magnetic device according to the present invention. 
     [ FIG. 4 ]  FIG. 4  is an explanatory view showing the magnetic field application device shown in  FIG. 3 . 
     [ FIG. 5 ]  FIG. 5  is an exploded perspective view showing another exemplary embodiment of the magnetic device according to the present invention. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   An embodiment of the magnetic device according to the present invention will now be described based on the drawings. Note that the present invention is not limited to this embodiment.  FIG. 1  is a perspective view showing an exemplary embodiment of the magnetic device (i.e., magnetic sensor) according to the present invention. A magnetic device  10  of the present invention is provided with a magnetic element  11 , and a first magnetic field application device  12  and second magnetic field application device  13  that are positioned so as to sandwich the magnetic element  11 . 
   The magnetic element  11  is obtained, for example, by forming a soft magnetic film  11   b  in a meandering pattern on a surface of a non-magnetic substrate  11   a . The first magnetic field application device  12  and second magnetic field application device  13  form a magnetic field M traveling in one direction S from the first magnetic field application device  12  towards the second magnetic field application device  13 . As a result, in the magnetic element  11  that is located between the first magnetic field application device  12  and the second magnetic field application device  13 , the bias magnetic field M traveling in the one direction is applied to the entire soft magnetic film  11   b.    
   According to the magnetic device  10  having this structure, as a result of the first magnetic field application device  12  and the second magnetic field application device  13  being placed on both sides of the magnetic element  11 , it is possible to apply a strong bias magnetic field to the magnetic element  11  that is efficient in the one direction, and it is possible to achieve a highly accurate magnetic sensor. 
   In addition, because a magnetic field generating device that is used to apply a bias magnetic field to the magnetic element  11  can be located away from the magnetic element  11 , it is not necessary to form the magnetic field generating device in proximity to the magnetic element. As a result, it is possible to achieve reductions in the size, and particularly in the thickness of the overall magnetic device  10 , and it is possible to improve the degree of freedom in the layout of the instrument on which the magnetic device  10  is mounted. 
   The first magnetic field application device  12  and the second magnetic field application device  13  may also each be formed from an independent magnetic field generating device and an independent magnetic field induction device. The first magnetic field application device  12  has a first magnetic field generating device  15  and a first magnetic field induction device  16 . The second magnetic field application device  13  has a second magnetic field generating device  17  and a second magnetic field induction device  18 . 
   Both ends of the first magnetic field generating device  15  and the second magnetic field generating device  17  are connected, for example, to a power supply  14 , and may be formed by an inductor that is wound in a coil shape. The first magnetic field induction device  16  and the second magnetic field induction device  18  may be formed, for example, by arranging a high permeability material which is formed in a ribbon shape (i.e., in a thin belt shape) such that it passes through a center axis P of the respective coil shapes of the first magnetic field generating device  15  and the second magnetic field generating device  17 . 
   Ends  16   a  and  18   a  on one side of the first magnetic field induction device  16  and the second magnetic field induction device  18  which are formed in this ribbon shape (i.e., a thin belt shape) extend to positions adjacent to the magnetic element  11 . Ends  16   b  and  18   b  on the other side of the first magnetic field induction device  16  and the second magnetic field induction device  18  are formed as open magnetic circuits in order to detect changes in the external magnetic field in the magnetic element  11 . 
   In this manner, by forming the first magnetic field application device  12  and the second magnetic field application device  13  each from an independent magnetic field generating device and an independent magnetic field induction device, when a solenoid coil, for example, is used for the magnetic field application device, it is sufficient for the first magnetic field generating device  15  and the second magnetic field generating device  17 , which are small-sized coils, to be formed so as to envelop the first magnetic field induction device  16  and the second magnetic field induction device  18 , which are formed from a thin, high permeability material in a ribbon shape, without having to form in the vicinity of the magnetic element a coil, which is a magnetic field generating device, such that it envelops the comparatively large-sized magnetic element  11 . Accordingly, it is possible to achieve a reduction in the thickness of the magnetic device  10 . 
   Moreover, by extending the one ends  16   a  and  18   a  of the first magnetic field induction device  16  and the second magnetic field induction device  18  to positions adjacent to the magnetic element  11 , even if the first magnetic field generating device  15  and the second magnetic field generating device  17  are formed at positions away from the magnetic element  11 , it is possible for a bias magnetic field generated by these magnetic field generating devices  15  and  17  to be applied to the magnetic element  11  without being attenuated by the first magnetic field induction device  16  and the second magnetic field induction device  18 . 
   For the high permeability material constituting the first magnetic field induction device  16  and the second magnetic field induction device  18 , it is possible to use, for example, a cobalt-based amorphous thin ribbon or a sintered ferrite thin film or the like. In particular, if a cobalt-based amorphous thin ribbon which has pliability is used for the first magnetic field induction device  16  and the second magnetic field induction device  18 , then because it is possible to place the first magnetic field generating device  15  and the second magnetic field generating device  17  in positions away from the magnetic element  11 , and induce a bias magnetic field in the magnetic element  11  by freely bending the first magnetic field induction device  16  and the second magnetic field induction device  18 , it becomes possible to arrange the magnetic device  10  in an unrestricted layout in accordance with the shape of the instrument in which the magnetic device  10  is incorporated. 
   The first magnetic field induction device  16  and second magnetic field induction device  18  and the magnetic element  11  may be placed on a substantially identical plane F. By placing the magnetic field induction devices  16  and  18  and the magnetic element  11  on substantially the same plane F, the bias magnetic field generated by the first magnetic field generating device  15  and the second magnetic field generating device  17  can be efficiently applied in the direction of the magnetic element  11  while any attenuation thereof is suppressed, thereby enabling a highly sensitive magnetic element  11  to be obtained. 
   In the above described embodiment, a coil-shaped inductor which is connected to a power supply, namely, an electromagnet is used for the magnetic field generating devices, however, in addition to this it is also possible to use permanent magnets or the like for the magnetic field generating devices. 
     FIG. 2  is a perspective view showing another exemplary embodiment of the magnetic device (i.e., magnetic sensor) according to the present invention. A magnetic device  20  of this embodiment is provided with a first magnetic field application device  22  and a second magnetic field application device  23  which are placed so as to sandwich a magnetic element  21 . The first magnetic field application device  22  is formed independently from a first magnetic field generating device  24  and a first magnetic field induction generating device  25 , while the second magnetic field application device  23  is formed independently from a second magnetic field generating device  26  and a second magnetic field induction generating device  27 . 
   The first magnetic field generating device  24  and the second magnetic field generating device  26  are formed by permanent magnets, for example, made of NdFeB or SmCo or the like. A bias magnetic field generated by these permanent magnets is inducted to the magnetic element  21  by means of the first magnetic field induction generating device  25  and the second magnetic field induction generating device  27 , so that a unidirectional bias magnetic field is applied to the magnetic element  21 . By using permanent magnets for the first magnetic field generating device  24  and the second magnetic field generating device  26 , it is possible to generate a bias magnetic field without having to supply electricity. Because of this, compared with a magnetic device which uses a solenoid coil or the like, it is possible to simplify the structure, and achieve reductions in both size and weight. 
   Next, a description will be given of an exemplary embodiment of the magnetic device according to the present invention is formed into a package having a multilayer structure.  FIG. 3  is an exploded perspective view showing another exemplary embodiment of the magnetic device according to the present invention. A magnetic device  30  has a first substrate  31 , a second substrate  32 , a magnetic element  34  which is sandwiched between the first substrate  31  and the second substrate  32 , and a first magnetic field induction device  48  and a second magnetic field induction device  49  which are placed so as to sandwich the magnetic element  34  from both sides thereof. It is also possible for a driver chip  35  to be placed between the first substrate  31  and the second substrate  32 , and for a third substrate  33  to be provided to house the magnetic element  34  and the driver chip  35 . 
   First conductive layers  41 , second conductive layers  42 , and extraction conductive layers  45  are formed on a surface  31   a  of the first substrate  31 . Third conductive layers  43  and fourth conductive layers  44  are formed on a surface  32   a  of the second substrate  32 . The magnetic element  34  is obtained, for example, by forming a soft magnetic film  34   b  in a meandering pattern on a surface of a non-magnetic substrate  34   a , and electrode pads  46   a  and  46   b  are formed on both ends of the soft magnetic film  34   b . When a bias magnetic field is applied to this magnetic element  34 , output signals therefrom are changed in accordance with the strength of the magnetic field. 
   Moreover, the driver chip  35  is an integrated circuit that controls the magnetic element  34 , and electrode pads  47   a  and  47   b  are formed on a surface thereof. A first non-conductive layer  54 , and a second non-conductive layer  55  that insulate the first magnetic field induction device  48  and the second magnetic field induction device  49  from the third conductive layers  43  and the fourth conductive layers  44  are formed respectively on the second substrate  32  side of the first magnetic field induction device  48  and the second magnetic field induction device  49 . 
   Third connecting portions  53  which are formed from conductive paste or copper plating or the like that penetrate from the one surface  31   a  to the other surface  31   b  of the first substrate  31  and electrically connect the extraction conductive layers  45  respectively to the electrode pads  46   a  and  46   b  of the magnetic element  34  and electrode pads  47   a  and  47   b  of the driver chip  35  are formed in the first substrate  31 . 
   In the third substrate  33 , there are provided (i) a magnetic element housing portion  36   a  that houses the magnetic element  34 , (ii) a chip housing portion  36   b  that houses the driver chip  35 , (iii) a first housing portion  36   c  that houses the first magnetic field induction device  48 , and (iv) a second housing portion  36   d  that houses the second magnetic field induction device  49 . 
   In addition, first connecting portions  51  which are formed from conductive paste that penetrate from one surface  33   a  to another surface  33   b  of the third substrate  33  and electrically connect the first conductive layers  41  to the second conductive layers  43  are formed in the third substrate  33 , and second connecting portions  52  which are formed from conductive paste that penetrate from one surface  33   a  to another surface  33   b  of the third substrate  33  and electrically connect the second conductive layers  42  to the fourth conductive layers  44  are formed in the third substrate  33 . 
   As a result of the first conductive layers  41  and the third conductive layers  43  being electrically connected by the first connecting portions  51 , and the second conductive layers  42  and the fourth conductive layers  44  being electrically connected by the second connecting portions  52  in this manner, as is shown in typical view in  FIG. 4 , a coil-shaped first magnetic field generating device  57  that envelops the periphery of the first magnetic field induction device  48 , and a coil-shaped second magnetic field generating device  58  that envelops the periphery of the second magnetic field induction device  49  are formed respectively. A first magnetic field application device  61  is formed by the first magnetic field generating device  57  and the first magnetic field induction device  48 , and a second magnetic field application device  62  is formed by the second magnetic field generating device  58  and the second magnetic field induction device  49 . 
   Furthermore, by respectively energizing the electrode pads  57   a  and  57   b  at both ends of the first magnetic field generating device  57  and the electrode pads  58   a  and  58   b  at both ends of the second magnetic field generating device  58 , magnetic fields are generated in the first magnetic field generating device  57  and the second magnetic field generating device  58 . The magnetic fields which are generated in the first magnetic field generating device  57  and the second magnetic field generating device  58  are inducted to the magnetic element  34  respectively by the first magnetic field induction device  48  and the second magnetic field induction device  49 . As a result, a unidirectional, strong bias magnetic field M is applied to the magnetic element  34 . 
   According to the magnetic device  30  having the above described structure, the first magnetic field generating device  57  and the second magnetic field generating device  58  are formed respectively in a compact coil shape so as to sandwich the magnetic element  34  from both sides while being isolated therefrom, and the bias magnetic fields which are generated by this first magnetic field generating device  57  and second magnetic field generating device  58  can be inducted by the first magnetic field induction device  48  and the second magnetic field induction device  49  without being attenuated thereby, and applied to the magnetic element  34 . Accordingly, it is possible to achieve a small, lightweight magnetic device that can be manufactured at low cost. 
   The first substrate  31  may be formed from a nonconductive resin such as, for example polyimide. The first conductive layer  41 , the second conductive layers  42 , and the extraction conductive layers  45  which are formed on the first substrate  31  may also be formed on the other surface  31   b  on the opposite side from the one surface  31   a  of the first substrate  31 . The first conductive layers  41 , the second conductive layers  42 , and the extraction conductive layers  45  may be formed from a material having superior conductivity such as, for example, copper, aluminum, gold, or the like. 
   It is sufficient if the soft magnetic film  34   b  that makes up the magnetic element  34  is, for example, an amorphous soft magnetic material. Moreover, provided that the shape of the soft magnetic film  34   b  is one that makes it possible to detect magnetism with a high degree of accuracy, then any type of shape may be used in addition to a meandering shape. The first connecting portions  51 , the second connecting portions  52 , and the third connecting portions  53  may be a conductive paste which is formed by dispersing a fine powder of conductive metal in an adhesive medium. For the first magnetic field induction device  48  and the second magnetic field induction device  49 , it is possible to use, for example, a cobalt-based amorphous thin ribbon or a sintered ferrite thin film or the like. 
   In the above described embodiment, the first substrate  31  and the second substrate  32  are joined so as to sandwich the third substrate  33  using the first connecting portions  51  and the second connecting portions  52  which are formed from the aforementioned adhesive conductive paste, however, in addition to this it is also possible to employ a structure in which the respective layers are joined together by forming adhesive layers using an adhesive agent or the like between the first substrate  31  and the third substrate  33 , and between the third substrate  33  and the second substrate  32 . 
   The second substrate  32  may be formed from a nonconductive resin such as, for example, polyimide. The third conductive layers  43  and the fourth conductive layers  44  which are formed on the second substrate  32  may also be formed on the other surface  32   b  on the opposite side from the one surface  32   a  of the second substrate  32 . The third conductive layers  43  and the fourth conductive layers  44  may be formed from a material having superior conductivity such as, for example, copper, aluminum, gold, or the like. 
   In an example in which the above described magnetic device is formed into a package having a multilayer structure as well, it is also possible to use magnets as the magnetic field generating device.  FIG. 5  is an exploded perspective view showing another exemplary embodiment of the magnetic device according to the present invention. In this embodiment, a magnetic device  70  has a first substrate  71 , a second substrate  72 , a magnetic element  73  which is sandwiched between the first substrate  71  and the second substrate  72 , and a first magnetic field application device  74  and a second magnetic field application device  75  which are placed so as to sandwich the magnetic element  73  from both sides thereof. 
   The first magnetic field application device  74  is formed by the first magnetic field generating device  76  and the first magnetic field induction device  77 . The second magnetic field application device  75  is formed by the second magnetic field generating device  78  and the second magnetic field induction device  79 . In addition, permanent magnets are used for the first magnetic field generating device  76  and the second magnetic field generating device  78 . 
   As a result, the bias magnetic fields which are generated by the first magnetic field generating device  76  and second magnetic field generating device  78 , which are permanent magnets, can be applied to the magnetic element  73  by the first magnetic field induction device  77  and the second magnetic field induction device  79  without being attenuated thereby. By using magnets as magnetic field generating devices in this manner, it is possible to generate a bias magnetic field without having to supply electricity. Because of this, compared with a magnetic device which uses a solenoid coil or the like, it is possible to simplify the structure, and achieve reductions in both size and weight of the magnetic device  70 . 
   EXAMPLES 
   The effects of the magnetic field induction device constructed from a high permeability magnetic material of the present invention were tested. In a magnetic device such as that shown in  FIG. 1 , a film of CoZrNb was formed in a meandering pattern on a Si substrate having a chip size of 2.5 mm×1.2 mm×625 μm so as to provide a magnetic element. The bias magnetic field of this magnetic element was 8 (Oe). A ribbon-shaped cobalt-based amorphous alloy having a width of approximately 1 mm and a thickness of 20 μm was used for the magnetic field induction devices. 0.2 A of current was supplied to coil-shaped magnetic field application devices having 120 turns in the coil. The spacing between end portions of the magnetic field induction devices and the magnetic element was 1 mm. The strengths of the bias magnetic fields applied to the magnetic element when one magnetic field induction device in the form of a ribbon-shaped cobalt-based amorphous alloy was used, and when three magnetic field induction devices in the form of ribbon-shaped cobalt-based amorphous alloys were stacked, and when no magnetic field induction device was formed (in order to provide a comparative example) were measured. The results of this test are shown in Table 1. 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               Number of ribbons 
               Magnetic field strength (Oe) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               0 (Comparative example) 
               2.5 
             
             
                 
               1 
               6 
             
             
                 
               3 
               12 
             
             
                 
                 
             
           
        
       
     
   
   According to the results shown in Table 1, it was confirmed that it is possible to increase the strength of the bias magnetic field that is applied to a magnetic element by forming a magnetic field induction device. It was also confirmed that it is possible to increase the strength of the bias magnetic field by increasing the number of magnetic field induction devices.