Abstract:
A laminated-type electronic component including: plural magnetic material layers; plural conductive patterns; a laminated layer body formed by laminating the plural magnetic material layers and the plural conductive patterns; a coil formed in the laminated layer body by connecting the conductive patterns between the magnetic material layers; and at least one magnetic gap formed in the laminated layer body, wherein the magnetic gaps are formed of a compound of Ni and Cu.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2012-91657 filed on Apr. 13, 2012 and No. 2012-262071 filed on Nov. 30, 2012, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a laminated-type electronic component in which magnetic material layers and conductive patterns are laminated, the conductive patterns disposed between the magnetic material layers are connected to form a coil in a laminated layer body, and at least one magnetic gap is also formed in this laminated layer body. 
     2. Related Art 
     One of conventional laminated-type electronic components is configured to laminate magnetic material layers and conductive patterns, and spirally connect the conductive patterns disposed between the magnetic material layers to form a coil in its laminated layer body. 
     Recently, laminated-type electronic components of this type have been increasingly used in power supply circuits where large currents flow and in inductors or transformers for DC-DC converter circuits, and others. The laminated-type electronic components of this type are desired to be small-sized, and have a large DC superimposed allowable current value. In order to increase the DC superimposed allowable current value, such a solution has been used that increases line widths of the conductive patterns so as to reduce a DC resistance of the coil, or that laminates magnetic material layers and conductive patterns  61 A to  61 E to form a laminated layer body, and also forms magnetic gaps  62  in the laminated layer body so as to prevent magnetic saturation of the magnetic material used in the laminated layer body, as shown in  FIG. 6 , (see Japanese Patent Laid-Open No. 02-165607). 
     In such a conventional laminated-type electronic component having magnetic material layers of Ni-based ferrite, Zn-based or Cu—Zn-based ferrite is used in the magnetic gaps for the purpose of securing preferable junctions between the magnetic material layers and the magnetic gaps. In this laminated-type electronic component, elements of the magnetic material layers and elements of the magnetic gaps are dispersed mutually during burning the laminated layer body, and ferrite layers having compositions graded toward opposite elements are formed at the junctions between the magnetic material layers and the magnetic gaps. Such ferrite layers cause a problem of ununiform compositions and unstable magnetic characteristics. Particularly, Ni ferrite is dispersed from the magnetic material layers toward the magnetic gaps, which forms a composition of mixture of Zn ferrite with slight amount of Ni ferrite. It has been known that such a composition has the Curie point in vicinity of a room temperature (25° C.), and if the temperature increases greater than the room temperature, its magnetic property is rapidly lost. 
     Hence, in the conventional laminated-type electronic component, its magnetic property is lost at the interfaces between the magnetic material layers and the magnetic gaps if the temperature is equal to or more than the Curie point. Consequently, the laminated-type electronic component has a negative temperature property, which causes a problem such as deterioration of the temperature characteristics of the coil. 
     In such a situation, laminated-type electronic components for use in power supply circuits or DC/DC converter circuits are disposed in a usage environment having a high temperature, and their coils generate heat due to large currents flowing in the coils, so that the laminated-type electronic components have great variation in temperature during operating. Consequently, in the conventional laminated-type electronic components, increase in temperature may cause an abrupt decrease in the inductance value. 
     In order to solve such a problem, it has been considered that the magnetic gaps are formed by using a mixed material of SiO 2  and oxide. This solution, however, has a problem that SiO 2  used in the magnetic gaps is dispersed in the magnetic material layers, which causes deterioration of magnetic permeability of ferrite included in the magnetic material layers. 
     It may be considered to use such a solution that cancels the negative temperature characteristics with positive temperature characteristics of the ferrite in the magnetic material layers. Unfortunately, this solution also has a problem that a variation range of the inductance value depends on an area of the interfaces between the magnetic material layers and the magnetic gaps, so that flexibility of structural design may become lowered, or it may be necessary to provide ferrite having different temperature characteristics in accordance with the structure. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-described problems, an object of the present invention is to provide a small-sized laminated-type electronic component capable of obtaining a large DC superimposed allowable current value without deteriorating temperature characteristics. 
     The present invention provides a laminated-type electronic component includes plural magnetic material layers and plural conductive patterns; a laminated layer body formed by laminating the plural magnetic material layers and the plural conductive patterns; a coil formed in the laminated layer body by connecting the conductive patterns disposed between the magnetic material layers; and at least one magnetic gap formed in the laminated layer body, and in this laminated-type electronic component, the magnetic gaps are formed of a compound of Ni and Cu. 
     The laminated-type electronic component of the present invention includes plural magnetic material layers; plural conductive patterns; a laminated layer body formed by laminating the plural magnetic material layers and the plural conductive patterns; a coil formed in the laminated layer body by connecting the conductive patterns between the magnetic material layers; and at least one magnetic gap formed in the laminated layer body, and in this laminated-type electronic component, the magnetic gaps are formed of a compound of Ni and Cu; therefore, it is possible to increase a DC superimposed allowable current value without deteriorating the temperature characteristics even if the laminated-type electronic component is small-sized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view showing a first embodiment of a laminated-type electronic component of the present invention; 
         FIG. 2  is a characteristic diagram of the first embodiment of the laminated-type electronic component of the present invention; 
         FIG. 3  is a cross sectional view showing a second embodiment of the laminated-type electronic component of the present invention; 
         FIG. 4  is a cross sectional view showing a third embodiment of the laminated-type electronic component of the present invention; 
         FIG. 5  is a characteristic diagram of the third embodiment of the laminated-type electronic component of the present invention; and 
         FIG. 6  is a cross sectional view of a conventional laminated-type electronic component. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The laminated-type electronic component of the present invention is configured such that magnetic material layers formed of ferrite containing Ni and conductive patterns made of conductors are laminated to form a laminated layer body, and the conductive patterns disposed between the magnetic material layers are spirally connected to form a coil in the laminated layer body. Magnetic gaps made of a compound of Ni and Cu containing no Zn are formed in the laminated layer body. 
     Hence, the laminated-type electronic component of the present invention uses no Zn in the magnetic gap, and thus no composition having the Curie point in vicinity of a room temperature is generated at interfaces between the magnetic material layers and the magnetic gaps, thereby enhancing temperature characteristics. The laminated layer body has no portion where magnetic property significantly varies depending on the temperature; accordingly a correlation between structural design of a product and properties of the product becomes preferable, thereby enhancing accuracy of the design. Embodiments 
     Hereinafter, description will be provided on embodiments of the laminated-type electronic component of the present invention with reference to  FIG. 1  to  FIG. 5 . 
       FIG. 1  is a cross sectional view showing a first embodiment of the laminated-type electronic component of the present invention. In  FIG. 1 , numeral references  11 A to  11 E denote the conductive patterns, and numeral references  12 A and  12 B denotes the magnetic gaps. 
     Magnetic material layers are formed of Ni—Cu—Zn-based ferrite. The conductive patterns are formed of conductive paste made of a silver, silver-based, gold, gold-based or platinum metallic material in a paste form. The conductive pattern  11 A is formed on a surface of a non-magnetic material layer  12 A constituting the magnetic gap formed on the magnetic material layer. One end of the conductive pattern  11 A extends to an end surface of the magnetic material layer. The non-magnetic material layer  12 A constituting the magnetic gap is formed of a compound of Ni and Cu, and formed to be smaller in size than the magnetic material layer. 
     The conductive pattern  11 B is formed on a surface of the magnetic material layer laminated on the conductive pattern  11 A. One end of the conductive pattern  11 B is connected to the other end of the conductive pattern  11 A. 
     The conductive pattern  11 C is formed on a surface of the magnetic material layer laminated on the conductive pattern  11 B. One end of the conductive pattern  11 C is connected to the other end of the conductive pattern  11 B. The conductive pattern  11 D is formed on a surface of the magnetic material layer laminated on the conductive pattern  11 C. One end of the conductive pattern  11 D is connected to the other end of the conductive pattern  11 C. 
     The conductive pattern  11 E is formed on a surface of the magnetic material layer laminated on the conductive pattern  11 D. One end of the conductive pattern  11 E is connected to the other end of the conductive pattern  11 D. The other end of the conductive pattern  11 E extends to an end surface of the magnetic material layer. In addition, the magnetic material layer is laminated on the conductive pattern  11 E through a non-magnetic material layer  12 B constituting the magnetic gap. The non-magnetic material layer  12 B constituting the magnetic gap is formed of a compound of Ni and Cu, and formed to be smaller in size than the magnetic material layer. In this manner, the magnetic material layers and the conductive patterns  11 A to  11 E are laminated, and the conductive patterns  11 A to  11 E between the magnetic material layers are spirally connected to one another so as to form a coil in the laminated layer body, and the magnetic gaps are also formed in the laminated layer body. An external terminal is formed at an end surface of this laminated layer body, and the conductive pattern extending to the end surface of the laminated layer body is connected to the external terminal. 
     In the laminated-type electronic component of the present invention configured in this manner, the magnetic material layers were formed of Ni—Cu—Zn-based ferrite containing NiO: 19 mol %, ZnO: 25 mol %, CuO: 9 mol %, and Fe 2 O 3 : 47 mol %, and the magnetic gaps were formed of a compound of Ni and Cu in a ratio of 8:2; and as a result of this, a rate of change of the inductance value relative to the temperature became approximately zero, as shown by a solid line of  FIG. 2 . 
     Specifically, a conventional laminated-type electronic component having magnetic material layers formed of Ni—Cu—Zn-based ferrite containing NiO: 19 mol %, ZnO: 25 mol %, CuO: 9 mol %, and Fe 2 O 3 : 47 mol %, and having the magnetic gaps formed of Cu—Zn-based ferrite had a rate of change of the inductance value relative to the temperature of 8% at maximum, as shown by a dotted line of  FIG. 2 ; and compared to this conventional component, the electronic component of the present invention could greatly enhance the temperature characteristics. 
     In the laminated-type electronic component of the present invention configured in this manner, the ratio of Ni and Cu used in the magnetic gaps was variously changed; and as a result of this, an open circuit was generated in the conductive pattern in contact with the magnetic gap whose ratio of Ni was 1 or less; to the contrary, no sintering was generated in the magnetic gap whose ratio of Ni was 9 or more after burned at a temperature of 900° C. 
     The laminated layer body using various ratios of Ni to Cu of 2:8, 5:5, 8:2 attained magnetic permeability at 1 MHz of 118, 119, and 120, respectively. Increase in ratio of Ni contributed to increase in the magnetic permeability of the laminated layer body, thereby increasing the inductance value of the coil formed in the laminated layer body. 
       FIG. 3  is a cross sectional view showing a second embodiment of the laminated-type electronic component of the present invention. In the second embodiment, the magnetic material layers are formed of Ni—Cu—Zn-based ferrite. The conductive patterns are formed of conductive paste made of a silver, silver-based, gold, gold-based or platinum metallic material in a paste form. 
     A conductive pattern  31 A is formed on a surface of the magnetic material layer, and one end thereof extends to an end surface of the magnetic material layer. A conductive pattern  31 B is formed on a surface of the magnetic material layer laminated on the conductive pattern  31 A. One end of the conductive pattern  31 B is connected to the other end of the conductive pattern  31 A. 
     A conductive pattern  31 C is formed on a surface of the magnetic material layer laminated on the conductive pattern  31 B. A non-magnetic material layer  32  constituting the magnetic gap is formed in an inner circumference of the conductive pattern  31 C. The non-magnetic material layer  32  constituting this magnetic gap is formed of a compound of Ni and Cu. One end of the conductive pattern  31 C is connected to the other end of the conductive pattern  31 B. 
     A conductive pattern  31 D is formed on a surface of the magnetic material layer laminated on the conductive pattern  31 C. One end of the conductive pattern  31 D is connected to the other end of the conductive pattern  31 C. 
     A conductive pattern  31 E is formed on a surface of the magnetic material layer laminated on the conductive pattern  31 D. One end of the conductive pattern  31 E is connected to the other end of the conductive pattern  31 D. The other end of the conductive pattern  31 E extends to an end surface of the magnetic material layer. 
     In this manner, the magnetic material layers and the conductive patterns  31 A to  31 E are laminated, and the conductive patterns  31 A to  31 E between the magnetic material layers are spirally connected to one another so as to form a coil in the laminated layer body, and the magnetic gap is also formed in the laminated layer body. An external terminal is formed at an end surface of this laminated layer body, and the conductive pattern extending to the end surface of the laminated layer body is connected to the external terminal. 
       FIG. 4  is a cross sectional view showing a third embodiment of the laminated-type electronic component of the present invention. In the third embodiment, the magnetic material layers are formed of Ni—Cu—Zn-based ferrite. The conductive patterns are formed of conductive paste made of a silver, silver-based, gold, gold-based or platinum metallic material in a paste form. 
     A conductive pattern  41 A is formed on a surface of a non-magnetic material layer  42 A constituting the magnetic gap formed on the magnetic material layer. One end of the conductive pattern  41 A extends to an end surface of the magnetic material layer. The non-magnetic material layer  42 A constituting the magnetic gap is formed of a compound of Ni and Cu, and formed to be smaller in size than the magnetic material layer. A conductive pattern  41 B is formed on a surface of a non-magnetic material portion  43 A that constitutes the magnetic gap, and vertically extends through the magnetic material layer laminated on the conductive pattern  41 A. One end of the conductive pattern  41 B is connected to the other end of the conductive pattern  41 A. 
     A conductive pattern  41 C is formed on a surface of a non-magnetic material portion  43 B that constitutes the magnetic gap, and vertically extends through the magnetic material layer laminated on the conductive pattern  41 B. One end of the conductive pattern  41 C is connected to the other end of the conductive pattern  41 B. 
     A conductive pattern  41 D is formed on a surface of a non-magnetic material portion  43 C that constitutes the magnetic gap, and vertically extends through the magnetic material layer laminated on the conductive pattern  41 C. One end of the conductive pattern  41 D is connected to the other end of the conductive pattern  41 C. 
     A conductive pattern  41 E is formed on a surface of a non-magnetic material portion  43 D that constitutes the magnetic gap, and vertically extends through the magnetic material layer laminated on the conductive pattern  41 D. One end of the conductive pattern  41 E is connected to the other end of the conductive pattern  41 D. The other end of the conductive pattern  41 E extends to an end surface of the magnetic material layer. The magnetic material layer is further laminated on the conductive pattern  41 E through a non-magnetic material layer  42 B constituting the magnetic gap. The non-magnetic material layer  42 B constituting the magnetic gap is formed of a compound of Ni and Cu, and formed to be smaller in size than the magnetic material layer. In this manner, the magnetic material layers and the conductive patterns  41 A to  41 E are laminated, and the conductive patterns  41 A to  41 E between the magnetic material layers are spirally connected to one another so as to form a coil in the laminated layer body, and the magnetic gaps are also formed in the laminated layer body. An external terminal is formed at an end surface of this laminated layer body, and the conductive pattern extending to the end surface of the laminated layer body is connected to the external terminal. 
     In the laminated-type electronic component of the present invention configured in this manner, the magnetic material layers were formed of Ni—Cu—Zn-based ferrite made by adding SnO 2  of 0.6 to 1.5 wt % to a ferrite material containing NiO: 19 to 45 mol %, ZnO: 1 to 25 mol %, CuO: 6 to 10 mol %, and Fe 2 O 3 : 47 to 49 mol %, and the magnetic gaps were formed of a compound of Ni and Cu in a ratio of 0:10 to 10:0; and as a result of this, the rate of change of the inductance value became as shown in  FIG. 5 . Note that each specimen No. marked with an asterisk (*) in a table of  FIG. 5  represents that this specimen deviated from the scope of the present invention (Comparative Examples). 
     All the compositions used in the laminated-type electronic component of the present invention attained a smaller rate of change of the inductance value than that of the conventional laminated-type electronic component using Cu—Zn-based ferrite in the magnetic gaps. 
     In the magnetic material layers formed of Ni—Cu—Zn-based ferrite made by adding SnO 2  of 1.5 wt % to a ferrite material containing NiO: 19 mol %, ZnO: 25 mol %, CuO: 9 mol %, and Fe 2 O 3 : 47 mol %, the magnetic gaps whose ratio of Ni to Cu was other than 2:8 to 8:2 resulted in cracking, or an open circuit in the conductive pattern in contact with this magnetic gap. 
     In addition, in the magnetic material layers formed of Ni—Cu—Zn-based ferrite made by adding SnO 2  of 1.5 wt % to a ferrite material containing NiO: 27 mol %, ZnO: 14 mol %, CuO: 10 mol %, and Fe 2 O 3 : 49 mol %, the magnetic gap formed of a compound of Ni and Cu whose ratio of Ni to Cu was 8:2 attained a smaller rate of change of the inductance value, compared to the conventional laminated-type electronic component having the magnetic material layers formed of Ni—Cu—Zn-based ferrite containing no SnO 2 , and having no magnetic gap. The electronic component of the present invention also attained a rate of change of the inductance value equal to that of the conventional laminated-type electronic component having magnetic material layers formed of Ni—Cu—Zn-based ferrite made by adding SnO 2  of 1.5 wt % to a ferrite material containing NiO: 27 mol %, ZnO: 14 mol %, CuO: 10 mol %, and Fe 2 O 3 : 49 mol %, and having no magnetic gap. 
     The embodiments of the laminated-type electronic component of the present invention have been described above, but the present invention is not limited to them. For example, the magnetic material layers may be formed of Ni—Zn-based ferrite or Ni ferrite. The ferrite constituting the magnetic material layers may contain slight amount of elements derived from its material such as MnO 2 , SiO 2 , and the like. The compound of Ni and Cu included in the magnetic gaps may contain slight amount of elements derived from its material, or may contain SnO 2  to prevent dispersion of SnO 2  contained in the ferrite constituting the magnetic material layers. In addition, the non-magnetic material layers constituting the magnetic gaps may be formed in the same size as that of the magnetic material layers. Metallic foils may be used in the conductive patterns. The non-magnetic material layers constituting the magnetic gaps may be formed in three or more layers. In the second embodiment, the non-magnetic material portions constituting the magnetic gaps may be disposed between the conductive patterns.