JP2013042040A - Manufacturing method of common mode choke coil and common mode choke coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a common mode choke coil which inhibits silver from being diffused over glass ceramic while using the silver as material of a conductor coil and the glass ceramic as material of a non-magnetic layer, and therefore can manufacture a highly reliable common mode choke coil.SOLUTION: A manufacturing method of a common mode choke coil (10) laminating a non-magnetic layer (3) and a second magnetic layer (5) on a first magnetic layer (1), and including two conductor coils (2, 4) opposed to each other in the non-magnetic layer (3) comprises the steps of: forming the conductor coils (2, 4) by a conductor including silver; and burning glass ceramic with the conductor including silver in the atmosphere where an oxygen concentration is 0.1 vol.% or less so that the non-magnetic layer (3) is at least partly formed.

Description

  The present invention relates to a method for manufacturing a common mode choke coil. More specifically, a nonmagnetic layer and a second magnetic layer are stacked on a first magnetic layer, and two opposing conductor coils are included in the nonmagnetic layer. The present invention relates to a method for manufacturing a common mode choke coil. The present invention also relates to a common mode choke coil obtained by such a manufacturing method.

  The common mode choke coil is also referred to as a common mode noise filter, and is used for reducing, preferably removing, common mode noise that may be generated when using various electronic devices. In particular, common mode noise is a problem in high-speed data communication using a differential transmission method, and common mode choke coils are widely used for such applications.

  Conventionally, as a common mode choke coil, a configuration in which a nonmagnetic layer and a second magnetic layer are stacked on a first magnetic layer, and two opposing conductor coils are included in the nonmagnetic layer is known. As a material for the nonmagnetic layer, a resin such as a polyimide resin or an epoxy resin is used from the viewpoints of electrical insulation and workability (see Patent Document 1). Further, glass ceramics are also used as the material for the nonmagnetic layer, thereby improving the moisture resistance of the nonmagnetic layer and the connection strength between the laminate including the nonmagnetic layer and the external end face electrode ( (See Patent Document 2).

JP 2004-260017 A JP 2006-319209 A

  When glass ceramic is used as the material of the nonmagnetic layer, it is necessary to fire (sinter) the glass ceramic (for example, in Patent Document 2, the green sheet laminate is integrally fired). Since two opposing conductor coils are embedded in the nonmagnetic layer, when the glass ceramic is fired, the conductor coil material is also exposed to a high temperature during firing. According to the knowledge of the present inventors, when silver is used for the conductor coil material, it has been recognized that silver diffusion occurs during firing of the glass ceramic. For this reason, there is a problem that the insulation resistance between the conductor coils in the obtained nonmagnetic layer is lowered, and as a result, the reliability of the common mode choke coil is lowered. In order to cope with such a problem, it is conceivable to increase the distance between the two opposing conductor coils. In this case, however, the magnetic coupling between the coils decreases, and so on. This creates a new difficulty that performance is degraded. In addition, there is another problem that the wiring resistance of the conductor coil increases due to the diffusion of silver, and the insertion loss increases when the common mode choke call is inserted into the signal line.

  When a resin is used as the material of the nonmagnetic layer, the nonmagnetic layer can be formed at a relatively low temperature, and has already been fired as the first magnetic layer and the second magnetic layer that sandwich the nonmagnetic layer. Since a sintered ferrite material can be used, the conductor coil material is not exposed to a high temperature necessary for firing, and it is considered that the above-described problems did not occur.

  The object of the present invention is to suppress silver diffusion into glass ceramics while using silver as the material of the conductor coil and glass ceramics as the material of the non-magnetic layer, and thus reliability. It is an object to provide a method capable of manufacturing a common mode choke coil having a high height. A further object of the present invention is to provide a common mode choke coil itself obtained by such a manufacturing method.

According to one aspect of the present invention, there is provided a method of manufacturing a common mode choke coil in which a nonmagnetic layer and a second magnetic layer are stacked on a first magnetic layer, and the two non-magnetic layers include two opposing conductor coils. There,
Forming the conductor coil with a conductor containing silver;
There is provided a production method including at least partially forming the nonmagnetic layer by firing glass ceramics in an atmosphere having an oxygen concentration of 0.1% by volume or less in the presence of a conductor containing silver.

  According to the study by the present inventors, it was found that by calcination of glass ceramics in an atmosphere having an oxygen concentration of 0.1% by volume or less, silver diffusion into the glass ceramics is suppressed as compared with the case of firing in air. It was issued. Therefore, according to the method of the present invention, when silver is used as the material of the conductor coil and glass ceramics is used as the material of the nonmagnetic layer, the glass ceramic is used when a conductor containing silver is present. Since the firing is performed in an atmosphere having an oxygen concentration of 0.1% by volume or less, the diffusion of silver into the glass ceramics can be suppressed during the firing, and as a result, the insulation resistance between the conductor coils in the nonmagnetic layer It is possible to effectively prevent the decrease in the resistance and the increase in the wiring resistance of the conductor coil. Thereby, a highly reliable common mode choke coil can be manufactured.

In one embodiment of the present invention, the above method of the present invention uses a ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less. It further includes forming the second magnetic layer by firing in an atmosphere having a concentration of 0.1% by volume or less.

According to the study by the present inventors, a ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and containing CuO of 5 mol% or less is used. It was found that by firing in this atmosphere, it was possible to sinter at a lower temperature than when firing the ferrite material in air while ensuring a high specific resistance. When a ferrite material is baked to form a second magnetic layer, a conductor including silver that forms a conductor coil and a glass that forms a nonmagnetic layer exist between the first magnetic layer and the ferrite material that forms the second magnetic layer. Ceramics are also exposed to the high temperature during firing. However, according to the above aspect of the present invention, since the firing of the ferrite material for forming the second magnetic layer can be realized at a low temperature, the heat load on the silver in the glass ceramic can be reduced during the firing. Thus, diffusion of silver into the glass ceramic can be suppressed, and as a result, a decrease in insulation resistance between conductor coils in the nonmagnetic layer and an increase in wiring resistance of the conductor coils can be more effectively prevented. Moreover, according to the said aspect of this invention, since the specific resistance and sintering density of a 2nd magnetic layer can be maintained high, the insulation resistance and reliability of the obtained common mode choke coil can be improved.

  In one embodiment of the present invention, a sintered ferrite material may be used as the first magnetic layer. In such an embodiment, the sintered ferrite material may be pre-fired under any suitable conditions using any ferrite material.

In another aspect of the present invention, the above method of the present invention uses a ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less. Further comprising forming the first magnetic layer by firing in an atmosphere having an oxygen concentration of 0.1% by volume or less;
The firing for forming the nonmagnetic layer, the firing for forming the second magnetic layer, and the firing for forming the first magnetic layer may be performed simultaneously. According to this aspect, from the above-mentioned knowledge of the present inventors, both the firing of the ferrite material for forming the second magnetic layer and the firing for forming the first magnetic layer can be realized at a low temperature. Moreover, in such an embodiment, since these firings are performed simultaneously with the firing for forming the nonmagnetic layer, the thermal load on the silver in the glass ceramics can be minimized, and the glass ceramics can be obtained. As a result, a decrease in insulation resistance between conductor coils in the nonmagnetic layer and an increase in wiring resistance of the conductor coils can be more effectively prevented. Further, according to the above aspect of the present invention, since the specific resistance and sintered density of the second magnetic layer and the first magnetic layer can be maintained high, the insulation resistance and reliability of the obtained common mode choke coil can be increased. .

According to another aspect of the present invention, a non-magnetic layer and a second magnetic layer are stacked on a first magnetic layer, and the common magnetic choke coil includes two opposing conductor coils in the non-magnetic layer,
A common mode choke coil in which the conductor coil is made of a conductor containing silver and the non-magnetic layer is made of sintered glass ceramic fired in an atmosphere having an oxygen concentration of 0.1% by volume or less in the presence of the conductor containing silver. Also provided.

  Such a common mode choke coil of the present invention can be obtained by the manufacturing method of the present invention described above. The common mode choke coil of the present invention is characterized by reduced silver diffusion in the nonmagnetic layer.

In one embodiment of the present invention, the second magnetic layer may be made of a sintered ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO equivalent content of 5 mol% or less. The component of the second magnetic layer can be confirmed by breaking the common mode choke coil and quantitatively analyzing the fracture surface of the second magnetic layer by wavelength dispersion X-ray analysis (WDX method). The CuO equivalent content means the CuO content when Cu is converted to CuO on the assumption that all of the Cu in the second magnetic layer is in the form of CuO, specifically, the second magnetic layer. It is investigated by quantitatively analyzing the Cu in the above by the WDX method.

  In one aspect of the present invention, the first magnetic layer and the second magnetic layer may be connected through the insides of the two conductor coils arranged in the nonmagnetic layer. According to this aspect, it is possible to improve the magnetic coupling between the coils and provide a common mode choke coil having a higher common mode impedance.

  According to the present invention, when silver is used as the material of the conductor coil and glass ceramics is used as the material of the non-magnetic layer, the glass ceramics has an oxygen concentration of 0.1 when a conductor containing silver is present. By firing in an atmosphere of less than or equal to volume%, it is possible to suppress the diffusion of silver into the glass ceramics compared to firing in air, and as a result, a highly reliable common mode choke coil can be manufactured. it can.

It is a figure which shows the common mode choke coil in one embodiment of this invention, Comprising: (a) is a schematic perspective view of a common mode choke coil, (b) is seen along the XX 'line of (a). It is a schematic sectional drawing of a common mode choke coil. FIG. 2 is a schematic exploded perspective view of a common mode choke coil in the embodiment of FIG. 1, with an external electrode omitted. It is a figure which shows the common mode choke coil in the modification of embodiment of FIG. 1, Comprising: It is a figure corresponding to FIG.1 (b). The figure which shows the result of having investigated the in-plane distribution of Ag element in the conductor coil and its vicinity about the common mode choke coil in Examples 1-2 of this invention, and the comparative example 1 by wavelength dispersion type | mold X-ray analysis (WDX) (A) shows the analysis result of Comparative Example 1, (b) shows the analysis result of Example 1, and (c) shows the analysis result of Example 2.

  A method for manufacturing a common mode choke coil of the present invention and a common mode choke coil obtained thereby will be described in detail below with reference to the drawings.

(Embodiment 1)
As shown in FIGS. 1 and 2, the common mode choke coil 10 of this embodiment includes a laminated body 7 including a first magnetic layer 1 and a nonmagnetic layer 3 and a second magnetic layer 5 sequentially laminated thereon. Comprising. Two conductor coils 2 and 4 are embedded in the nonmagnetic layer 3 so as to face each other. External electrodes 9a to 9d can be provided around the laminated body 7, both ends of the conductor coil 2 can be connected to the external electrodes 9a and 9c, and both ends of the conductor coil 4 can be connected to the external electrodes 9b and 9d, respectively.

  More specifically, the nonmagnetic layer 3 can be composed of non-magnetic sublayers 3a to 3e made of glass ceramics (FIG. 1 (b)). The conductor coil 2 is composed of a lead portion 2a and a main body portion 2b, and the lead portion 2a and the main body portion 2b are integrally formed through the via 6a of the nonmagnetic sublayer 3b. The conductor coil 4 is composed of a lead portion 4a and a main body portion 4b, and the lead portion 4a and the main body portion 4b are integrally formed through a via 6b of the nonmagnetic sublayer 3d. Each of the main body portions 2b and 4b has a spiral shape (FIG. 2), and is disposed so as to face the nonmagnetic sublayer 3c therebetween. The lead portion 2a is formed by the nonmagnetic sublayer 3a by the first magnetic layer. The lead portion 4a is spaced apart from the second magnetic layer 5 by the nonmagnetic sublayer 3e (FIG. 1B). However, it should be noted that the configuration, shape, number of turns, arrangement, and the like of the conductor coils 2 and 4 of the present embodiment are not limited to the illustrated example.

  In the present embodiment, the common mode choke coil 10 is manufactured as follows. In the manufacturing method of this embodiment, a sintered ferrite material is generally used for the first magnetic layer 1, and the nonmagnetic sublayers 3a to 3e are formed by firing for each layer to obtain the nonmagnetic layer 3. Thereafter, the second magnetic layer 5 is formed thereon by firing (separate firing of the nonmagnetic layer and the second magnetic layer).

(A) Preparation of First Magnetic Layer First, a magnetic substrate made of a sintered ferrite material is prepared as the first magnetic layer 1. The magnetic substrate made of the sintered ferrite material may be obtained by sintering any appropriate ferrite material as long as a predetermined inductance can be obtained. Examples of the ferrite material include a Ni-based ferrite material containing Fe ₂ O ₃ and NiO as main components, a Ni—Zn-based ferrite material containing Fe ₂ O ₃ , NiO and ZnO as main components, Fe ₂ O ₃ , NiO, A Ni—Zn—Cu based ferrite material containing ZnO and CuO as main components may be used. Such a magnetic substrate may be one obtained by cutting a ferrite material into a desired shape, but is not limited thereto.

(B) Formation of Nonmagnetic Sublayer 3a Next, glass ceramics are laminated on the first magnetic layer 1, the obtained laminate is subjected to heat treatment, and the glass ceramics is baked to form the nonmagnetic sublayer 3a. Form. Although photosensitive or non-photosensitive glass ceramics may be used as the raw glass ceramics, it is preferable to use the same (photosensitive) glass ceramics as the nonmagnetic sublayer 3b. For example, glass ceramics include borosilicate glass (glass containing silicon dioxide as a main component and further containing boric acid and other compounds as required), borosilicate glass (containing silicon dioxide as a main component, boric acid And glass containing other compounds as needed) may be used. The glass ceramics are laminated on the first magnetic layer 1 by a method such as printing a paste of glass ceramics together with any other appropriate insulating component (hereinafter simply referred to as glass paste). The first magnetic layer 1 is formed by applying a coating on the magnetic layer 1 or by forming a glass ceramic together with any other appropriate insulating component into a green sheet (hereinafter simply referred to as a glass ceramic green sheet). This can be done by overlaying on top. The firing (heat treatment) for forming the nonmagnetic sublayer 3a is not particularly limited as long as the glass ceramic can be sintered. In this step, since no conductor containing silver is present in the laminate, the glass ceramic may be fired by heat-treating the laminate in the air. Although a calcination temperature will not be specifically limited if it is the temperature more than the softening point of glass, For example, it can be set as 820-870 degreeC.

(C) Formation of the lead portion 2a of the conductor coil 2 Next, the lead portion 2a is formed by patterning a conductor containing silver on the non-magnetic sublayer (sintered glass ceramic layer) 3a. The conductor containing silver may contain silver as a main component and may optionally contain other conductive components. Pattern formation of a conductor containing silver is performed by forming a paste of silver (and other conductive components if necessary) in the form of a paste together with glass or the like on the nonmagnetic sublayer 3a. Screen printing, silver film formation on the nonmagnetic sublayer 3a by sputtering, etching into a predetermined pattern by photolithography, or silver selective plating to a predetermined pattern. Selective plating can be performed by, for example, a full additive method (resist pattern formation, electroless plating, and resist peeling method) or a semi-additive method (seed layer formation by electroless plating, resist pattern formation, electroplating, resist peeling, seeding). A method by layer removal) can be used.

(D) Formation of Nonmagnetic Sublayer 3b Thereafter, a glass ceramic is laminated on the nonmagnetic sublayer (sintered glass ceramic layer) 3a and the lead portion 2a in the same manner as in the step (b). However, in this step, photosensitive glass ceramics are used as the raw glass ceramics, and vias 6a are formed in this layer by photolithography to partially expose the drawn portions 2a. Then, the obtained laminate is subjected to heat treatment, and the glass ceramic is fired to form the nonmagnetic sublayer 3b. Firing (heat treatment) for forming the nonmagnetic sublayer 3b is performed by heat-treating the laminate in an atmosphere having an oxygen concentration of 0.1% by volume or less and firing the glass ceramic in the atmosphere. In this step, a conductor containing silver is present in the laminate, and the diffusion of silver can be prevented by firing the glass ceramic in an atmosphere having an oxygen concentration of 0.1% by volume or less. Although the present invention is not bound by any theory, it is considered that when silver is oxidized, diffusion into glass ceramics is promoted. By firing in a low oxygen concentration atmosphere, the oxidation of silver can be suppressed, thereby preventing the diffusion of silver. It is considered to be suppressed. The oxygen concentration in the firing atmosphere may be 0.1% by volume or less, but is preferably 0.0001% by volume or more from the viewpoint of securing the sinterability of the glass ceramic. Although a calcination temperature will not be specifically limited if it is the temperature more than the softening point of glass, For example, it can be set as 820-870 degreeC.

(E) Formation of Main Body 2b of Conductor Coil 2 Next, a conductor containing silver is patterned on the inside of the via 6a and the nonmagnetic sublayer (sintered glass ceramic layer) 3b to form the main body 2b in a spiral shape. To form. The pattern formation of the conductor containing silver can be performed in the same manner as in the above step (c), but the conductor containing silver is embedded in the via 6a to connect the main body 2b and the lead-out part 2a, and these are integrated. Thus, the conductor coil 2 is configured.

(F) Formation of Nonmagnetic Sublayer 3c Thereafter, glass ceramics are laminated on the nonmagnetic sublayer (sintered glass ceramic layer) 3b and the main body 2b in the same manner as in the above step (b), and the resulting laminate is obtained. The body is subjected to heat treatment, and the glass ceramic is fired to form the nonmagnetic sublayer 3c. In the firing (heat treatment) for forming the nonmagnetic sub-layer 3c, the laminated body is heat-treated in an atmosphere having an oxygen concentration of 0.1% by volume or less, and the glass ceramic is fired in the atmosphere as in the step (d). To implement.

(G) Formation of Main Body 4b of Conductor Coil 4 Next, a conductor containing silver is patterned on the nonmagnetic sublayer (sintered glass ceramic layer) 3c to form the main body 4b in a spiral shape. The pattern formation of the conductor containing silver can be performed in the same manner as in the above step (c).

(H) Formation of Nonmagnetic Sublayer 3d Thereafter, a glass ceramic is laminated on the nonmagnetic sublayer (sintered glass ceramic layer) 3c and the main body 4b in the same manner as in the step (b). However, in this step, photosensitive glass ceramic is used as the raw glass ceramic, and vias 6b are formed in this layer by photolithography to partially expose the main body 4b. Then, the obtained laminate is subjected to heat treatment, and the glass ceramic is fired to form the nonmagnetic sublayer 3d. In the firing (heat treatment) for forming the nonmagnetic sub-layer 3d, the laminated body is heat-treated in an atmosphere having an oxygen concentration of 0.1% by volume or less and the glass ceramic is fired in the atmosphere as in the step (d). To implement.

(I) Formation of the lead portion 4a of the conductor coil 4 Next, a conductor containing silver is patterned on the inside of the via 6b and on the nonmagnetic sublayer (sintered glass ceramic layer) 3d to form the lead portion 4a. . The pattern formation of the conductor containing silver can be performed in the same manner as in the above step (c), but the conductor containing silver is embedded in the via 6b to connect the main body portion 4b and the lead portion 4a. Thus, the conductor coil 4 is configured.

(J) Formation of Nonmagnetic Sublayer 3e Thereafter, glass ceramics are laminated on the nonmagnetic sublayer (sintered glass ceramic layer) 3d and the lead portion 4a in the same manner as in the above step (b), and the resulting laminate is obtained. The body is subjected to heat treatment, and the glass ceramic is fired to form the nonmagnetic sublayer 3e. In the firing (heat treatment) for forming the nonmagnetic sublayer 3e, the glass ceramic is fired in the atmosphere by heat-treating the laminate in an atmosphere having an oxygen concentration of 0.1% by volume or less, as in the step (d). To implement. By forming the nonmagnetic sub-layer 3e, the non-magnetic sub-layers 3a to 3e are all sintered, and these constitute the non-magnetic layer 3 (sintered glass ceramic layer) as a whole.

(K) Formation of the second magnetic layer 5 A predetermined ferrite material is laminated on the nonmagnetic layer 3 of the laminated body obtained as described above, and the obtained laminated body is subjected to heat treatment, and the ferrite material is fired. Thus, the second magnetic layer 5 is formed. As this ferrite material, a Ni—Zn—Cu based ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less is used. The ferrite material is laminated on the nonmagnetic layer 3 by coating the ferrite material together with any other suitable components on the nonmagnetic layer 3 by a method such as printing. It can be carried out by superimposing a material in the form of a green sheet together with any appropriate other components on the nonmagnetic layer 3. Firing (heat treatment) for forming the second magnetic layer 5 is performed by heat-treating the laminate in an atmosphere having an oxygen concentration of 0.1% by volume or less and firing the ferrite material in the atmosphere. By firing the ferrite material in an atmosphere having an oxygen concentration of 0.1% by volume or less, sintering can be performed at a lower temperature than when the ferrite material is fired in air. The present invention is not bound by any theory, but when fired in a low oxygen concentration atmosphere, oxygen defects are formed in the crystal structure, and interdiffusion of Fe, Ni, Cu, Zn present in the crystal is promoted, and the low temperature It is considered that the sinterability can be improved. In this step, a conductor containing silver is present in the laminate, but diffusion of silver can be prevented by firing the ferrite material at a low temperature in an atmosphere having an oxygen concentration of 0.1% by volume or less. In addition, by using a Ni—Zn—Cu ferrite material having a CuO content of 5 mol% or less, the second magnetic layer 5 is high even when fired in an atmosphere with an oxygen concentration of 0.1 volume% or less. Specific resistance can be secured. The present invention is not bound by any theory, but when fired in a low oxygen concentration atmosphere, CuO is reduced to Cu ₂ O by the reducing action of the heat treatment atmosphere, and the specific resistance of the second magnetic layer 5 is reduced (impedance is reduced). It is considered that the formation of Cu ₂ O due to the reduction of CuO can be suppressed by reducing the content of CuO, and the decrease in specific resistance is thereby suppressed. The content of CuO in the ferrite material may be 5 mol% or less, but is preferably 0.2 mol% or more in order to obtain sufficient sinterability. Such a ferrite material may contain other components such as Bi ₂ O ₃ as necessary with respect to a total of 100 parts by weight of the main components Fe ₂ O ₃ , ZnO, NiO, and CuO, for example, 0.1 to 1. It may further be contained in parts by weight. The oxygen concentration in the firing atmosphere may be 0.1% by volume or less, but is preferably 0.001% by volume or more in order to ensure the specific resistance of the second magnetic layer. Although the present invention is not bound by any theory, if the oxygen concentration is too low, oxygen defects may be generated more than necessary, and the specific resistance of the second magnetic layer 5 may be reduced. Therefore, it is considered that the generation of oxygen defects can be avoided and thereby a high specific resistance can be secured.

  Thereby, the nonmagnetic layer 3 and the second magnetic layer 5 are laminated on the first magnetic layer 1, and a laminate 7 including two opposing conductor coils 2, 4 is obtained in the nonmagnetic layer 3. The laminated body 7 may be manufactured individually. However, after the plurality of the stacked bodies 7 are manufactured in a matrix at once, they are individually divided by dicing or the like (elements are separated) into individual pieces. There may be.

(L) Formation of External Electrodes 9a to 9d External electrodes 9a to 9d are formed on opposite sides of the multilayer body 7. The external electrodes 9a to 9d are formed, for example, by applying a paste made of silver powder together with glass or the like to a predetermined region, and placing the obtained structure in an atmosphere having an oxygen concentration of 0.1% by volume or less. For example, it can be carried out by baking silver at a temperature of 750 to 780 ° C.

  As described above, the common mode choke coil 10 of the present embodiment is manufactured. According to the present embodiment, silver diffusion in the glass ceramic constituting the nonmagnetic layer 3 is suppressed, and a highly reliable common mode choke coil can be obtained. The insulation resistance between the conductor coils 2 and 4 of the nonmagnetic layer 3 can be secured, and the wiring resistance of the conductor coils 2 and 4 can be lowered. Further, the low temperature sinterability of the second magnetic layer 5 is good, and the specific resistance of the second magnetic layer 5 can be kept high.

In the common mode choke coil 10 of the present embodiment, the second magnetic layer 5 is made of a sintered ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO equivalent content of 5 mol% or less. The composition may be different from that of the Ni—Zn—Cu-based ferrite material before sintering. For example, CuO may be partially changed to Cu ₂ O by firing.

(Embodiment 2)
In the present embodiment, the common mode choke coil 10 described in the first embodiment is manufactured by another method. Hereinafter, the same members as those in the first embodiment will be described with the same reference numerals. In the manufacturing method of the present embodiment, the material of the first magnetic layer 1 is laminated on the holding layer and the material of the nonmagnetic layer 3 (while forming the conductor coils 2 and 4) by a substrate-less method. ) After laminating and laminating the material of the second magnetic layer 5 thereon, the obtained laminated body is baked at one time to form the first magnetic layer 1, the nonmagnetic layer 3, and the second magnetic layer 5. (Co-firing of the first magnetic layer, the nonmagnetic layer and the second magnetic layer).

(M) Formation of Material Layer of First Magnetic Layer 1 A predetermined ferrite material is laminated on any appropriate holding layer (not shown) to form a material layer of the first magnetic layer 1. As this ferrite material, a Ni—Zn—Cu based ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less is used. Lamination of the ferrite material on the holding layer can be done by applying a paste of ferrite material together with any other suitable components onto the holding layer using a method such as printing and drying. Can be carried out by laminating a green sheet together with any other suitable component on the holding layer.

(N) Stacking of Nonmagnetic Sublayers 3a to 3e and Formation of Conductor Coils 2 and 4 On the material layer (unsintered Ni—Zn—Cu ferrite material layer) of the first magnetic layer 1, nonmagnetic The nonmagnetic sublayers 3a to 3j are the same as the steps (b) to (j) described in the first embodiment except that the firing is not performed in each step to form the sublayers 3a to 3e. The material layer 3e (unsintered glass ceramic material layer) is laminated while forming the conductor coils 2 and 4. Thereby, the material layer of the nonmagnetic layer 3 is formed with the conductor coils 2 and 4 embedded therein.

(O) Formation of Material Layer of Second Magnetic Layer 5 Thereafter, a predetermined ferrite material is laminated on the material layer of the nonmagnetic layer 3 in the same manner as in the above step (m). A material layer is formed. Also for this ferrite material, a Ni—Zn—Cu based ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less is used. As long as these conditions are satisfied, the material of the first magnetic layer 1 and the material of the second magnetic layer 5 may be the same or different.

  Thereby, an unbaked laminated body is obtained. The unfired laminate may be produced individually, but after several pieces are produced in a matrix at a time, they are divided into individual pieces by dicing or the like (element separation) and separated into pieces. It may be.

(P) Formation of the first magnetic layer 1, the nonmagnetic layer 3, and the second magnetic layer 5 The unfired laminate obtained as described above is subjected to a heat treatment, and the glass ceramic is fired to form the nonmagnetic layer. 3 and the ferrite material is fired to form the first magnetic layer 1 and the second magnetic layer. Firing (heat treatment) for forming the first magnetic layer 1, the nonmagnetic layer 3, and the second magnetic layer 5 is performed by heat-treating the laminate in an atmosphere having an oxygen concentration of 0.1% by volume or less to produce glass ceramics and ferrite. This is done by firing the material simultaneously in the atmosphere.

  Thereby, the nonmagnetic layer 3 and the second magnetic layer 5 are laminated on the first magnetic layer 1, and a laminate 7 including two opposing conductor coils 2, 4 is obtained in the nonmagnetic layer 3.

(Q) Formation of External Electrodes 9a to 9d Thereafter, external electrodes 9a to 9d are formed on opposite sides of the multilayer body 7 in the same manner as in the step (l) described in the first embodiment.

  As described above, the common mode choke coil 10 of the present embodiment is manufactured. According to the present embodiment, unlike the manufacturing method of the first embodiment, the firing (heat treatment) for forming the nonmagnetic layer 3 and the second magnetic layer is completed once, so that the glass ceramic forming the nonmagnetic layer is formed. The diffusion of silver into the inside can be effectively suppressed, and a more reliable common mode choke coil can be obtained. Since the diffusion of silver can be more effectively suppressed, the nonmagnetic layer 3 can be made thinner than in the manufacturing method according to the first embodiment. Accordingly, the characteristics of the common mode choke coil can be improved and the size can be reduced.・ Low profile is possible. In addition, the same effects as those of the first embodiment can be obtained.

Although two embodiments of the present invention have been described above, various modifications can be made to these embodiments. For example, in the common mode choke coils of the first and second embodiments, as shown in FIG. 3, the through-holes 11 that penetrate the nonmagnetic layer 3 are sandblasted so that the conductor coils 2 and 4 are not exposed from the nonmagnetic layer 3. The through hole may be embedded with a Ni—Zn—Cu ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less. The ferrite material may be the same as or different from the material of the second magnetic layer 5 (and the material of the first magnetic layer 1 in the case of Embodiment 2). According to this configuration, the magnetic coupling between the conductor coils 2 and 4 can be strengthened, and a common mode choke coil with higher common mode impedance can be obtained.

(Experiment)
In order to investigate a ferrite material suitable for use as the material of the second magnetic layer, the following experiment was conducted.

As raw materials for the ferrite material, Fe ₂ O ₃ , ZnO, NiO, CuO, and Bi ₂ O ₃ powders were prepared. The compositions of the main components Fe ₂ O ₃ , ZnO, NiO, and CuO are No. 1 in Table 1. These powders were weighed so as to have the ratios shown in 1 to 7, and Bi ₂ O ₃ was weighed and added at 0.25 parts by weight with respect to 100 parts by weight of the main components.

  Next, sample No. Each of the 1 to 7 weighed products was put in a ball mill together with pure water and cobblestone, and was sufficiently mixed and pulverized by a wet method. PSB (Partial Stabilized Zirconia) balls were used as the cobblestones. The pulverized product was evaporated to dryness and calcined at a temperature of 700 to 800 ° C. for 2 hours. The calcined product thus obtained was again placed in a ball mill and wet pulverized for about 10 hours to produce a magnetic powder adjusted to a particle size of about 0.5 to 1.5 μm.

  Each magnetic powder obtained as described above was mixed with an organic vehicle composed of a binder resin (ethylcellulose resin) and an organic solvent (α-terpineol), and kneaded with a three-roll mill, thereby producing a magnetic paste.

  The produced magnetic paste was subjected to screen printing on a polyethylene terephthalate (PET) film by screen printing, drying, and film formation were repeated to produce a 1 mm thick coating film. Two of the produced coating films were punched into a disk shape having a diameter of 10 mm to produce an unfired sample.

Sample No. Two unsintered samples prepared for each of 1 to 7 are under flow of air, and the other is under flow of N ₂ —O ₂ mixed gas with oxygen concentration adjusted to 0.1% by volume. And baked at a temperature of 900 ° C. for 1 hour. Note that the temperature of 900 ° C. applied as an index of the firing temperature is a temperature at which simultaneous firing with silver is possible.

The sintered density (g / cm ³ ) was determined by the Archimedes method for each of the fired samples thus obtained. For each of the samples after firing, a silver paste was applied to both main surfaces, and heat treated at 770 ° C. for 5 minutes in the same atmosphere as the gas used for the firing, so that the silver was baked to form a pair of electrodes. The insulation resistance (IR) was measured by applying a DC voltage of 50 V between these electrodes, and the specific resistance log ρ (Ω · cm) was determined from the measured value and the sample dimensions. The results are summarized in Table 1.

As understood from Table 1, when sintered in air (900 ° C.), a high sintered density could not be obtained unless the CuO content was 7 mol% or more. CuO is a component having a relatively low melting point among the main components. This result shows that when firing in air, it is necessary to fire at a higher temperature, for example, higher than 1000 ° C., in order to obtain a high sintered density. On the other hand, when sintered (900 ° C.) in a low oxygen concentration atmosphere (oxygen concentration of 0.1% by volume or less), a high sintered density was obtained even if the CuO content was 7 mol% or less. This is thought to be possible even when sintered at a low temperature because, when fired in a low oxygen concentration atmosphere, oxygen defects were formed in the crystal structure and the interdiffusion of Fe, Ni, Cu, Zn present in the crystal was promoted. It is done. However, among these, when the content of CuO exceeded 5 mol%, it was recognized that the specific resistance decreased. This is presumably because when the firing was performed in a low oxygen concentration atmosphere, the specific resistance was lowered because CuO was largely reduced by Cu ₂ O. To sum up the above, when firing (900 ° C.) in a low oxygen concentration atmosphere (oxygen concentration of 0.1% by volume or less), the CuO content is set to 5 mol% or less, whereby a sample after firing (this is a specific magnetic layer) It was confirmed that low temperature sintering is possible while maintaining a high specific resistance.

Example 1
According to the manufacturing method of the first embodiment, the common mode choke coil 10 shown in FIGS. In the present example, the following conditions were applied.

In the above-described step (a), as the first magnetic layer 1, a substrate made of a sintered Ni—Zn—Cu based ferrite material (Fe ₂ O ₃ 49.0 mol%, ZnO 30.0 mol%, NiO 19.0 mol). %, CuO 2.0 mol%, and Bi ₂ O ₃ 0.25 parts by weight based on 100 parts by weight of these main components).

In the above-described step (b), a glass paste using photosensitive borosilicate glass (SiO ₂ —B ₂ O ₃ —CaO—K ₂ O, the same applies hereinafter) is applied by a printing method, and then 840 ° C. The non-magnetic sub-layer 3a was formed by baking the glass ceramics for 30 minutes.

  In the above-described step (c), the lead-out portion 2a was formed by selective plating by a semi-additive method. Specifically, a seed layer (Ag in this embodiment is Ag, but Ag / Ti may be used) is formed over the entire main surface of the nonmagnetic layer 3a by sputtering, and a photosensitive photoresist is formed on the seed layer by photolithography. After pattern formation by the method, using the seed layer that is exposed without being covered with the resist, silver is formed in the opening of the resist pattern by electrolytic plating, the resist is peeled off, and the exposed seed layer portion Was removed by etching. The formation of the main body 2b in the above-described step (e), the formation of the main body 4b in the step (g), and the formation of the lead-out portion 4a in the step (i) were the same as this.

In the above-mentioned step (d), a glass paste using photosensitive borosilicate glass was coated by a printing method, a via 6a was formed by a photolithography method, and then the oxygen concentration was adjusted to 0.1% by volume. In a N ₂ —O ₂ mixed gas atmosphere, heat treatment was performed at 840 ° C. for 30 minutes, and the glass ceramic was fired to form the nonmagnetic sublayer 3b. The formation of the nonmagnetic sublayer 3c in the step (f), the formation of the nonmagnetic sublayer 3d and the via 6b in the step (h), and the formation of the nonmagnetic sublayer 3e in the step (j) are the same as this. .

In the step (k), a Ni—Zn—Cu based ferrite material (Fe ₂ O ₃ 49.0 mol%, ZnO 30.0 mol%, NiO 19.0 mol%, CuO 2.0 mol%, And a magnetic paste using Bi ₂ O ₃ 0.25 parts by weight based on 100 parts by weight of the total of these main components) was applied by a printing method, and then the oxygen concentration was adjusted to 0.1% by volume. In a N ₂ —O ₂ mixed gas atmosphere, the second magnetic layer 5 was formed by subjecting to a heat treatment at 900 ° C. for 35 minutes and firing the ferrite material. The Ni—Zn—Cu ferrite material used here is No. 1 shown in Table 1. This corresponds to the composition of 4.

  The laminated body 7 thus obtained was diced into individual pieces. The dimensions of one element were 0.5 mm in length, 0.65 mm in width, and 0.3 mm in height.

  In the above-mentioned step (l), a silver paste is applied, and the resulting structure is subjected to a heat treatment at 770 ° C. for 5 minutes in an atmosphere having an oxygen concentration of 0.1% by volume or less, thereby baking silver. Thus, external electrodes 9a to 9d were formed. As described above, the common mode choke coil 10 of this example was manufactured.

(Example 2)
Each firing for forming the nonmagnetic layers 3b to 3e and firing for forming the external electrodes 9a to 9d were performed using an N ₂ —O ₂ mixed gas atmosphere in which the oxygen concentration was adjusted to 0.001% by volume. A common mode choke coil was manufactured in the same manner as in Example 1 except for the above (see Table 2).

(Comparative Example 1)
Each firing for forming the nonmagnetic layers 3b to 3e, firing for forming the second magnetic layer 5 and firing for forming the external electrodes 9a to 9d were performed in air, and the second magnetic layer 5 as a Ni—Zn—Cu ferrite material (Fe ₂ O ₃ 49.0 mol%, ZnO 30 mol%, NiO 12.0 mol%, CuO 9.0 mol%, and a total of 100 parts by weight of these main components) A common mode choke coil was fabricated in the same manner as in Example 1 except that the magnetic paste using 0.25 parts by weight of Bi ₂ O ₃ was added (see Table 2). The Ni—Zn—Cu ferrite material used here is No. 1 shown in Table 1. 7. It corresponds to the composition of 7.

  The common mode choke coils of Examples 1 and 2 and Comparative Example 1 manufactured as described above were cut along the line XX ′ in FIG. 1A, the cut surface was mirror-polished, and wavelength dispersion X-ray analysis The in-plane distribution of Ag element was examined using the method (WDX). The analysis result of Comparative Example 1 is shown in FIG. 4 (a), the analysis result of Example 1 is shown in FIG. 4 (b), and the analysis result of Example 2 is shown in FIG. 4 (c). Note that the Ag level shown in FIG. 4 means a relative value where the highest value of Ag concentration (corresponding to the coil portion) in the measurement range is 100. As understood from FIG. 4, in Comparative Example 1, it was recognized that Ag element was diffused in the glass ceramic (Ag level of about 50 to 80). In Examples 1 and 2, the Ag element glass ceramic was observed. There was almost no diffusion into it (Ag level of about 22 or less). This is considered to be because the oxidation of Ag can be suppressed by firing in a low oxygen concentration atmosphere, and the diffusion into the glass ceramic, which is also an oxide, is suppressed.

  Regarding the common mode choke coils of Examples 1 and 2 and Comparative Example 1, the insulation resistance value (IR) between the conductor coils 2 and 4 was measured using an electrometer R8340A manufactured by Advantest Corporation. ) = 8.1, log (IR) = 9.2 in Example 2, and log (IR) = 5.3 in Comparative Example 1. In Examples 1 and 2, a sufficient insulation resistance as a common mode choke coil was obtained, but in Comparative Example 1, the insulation resistance was low.

(Example 3)
According to the manufacturing method of the second embodiment, the common mode choke coil 10 shown in FIGS. In the present example, the following conditions were applied.

In the above-mentioned step (m), a paste formed by combining alumina powder with a binder and a solvent on an alumina substrate is applied by a printing method, and then the solvent is dried and coated to form a holding layer (not shown). Used as. On this holding layer, Ni—Zn—Cu ferrite material (Fe ₂ O ₃ 49.0 mol%, ZnO 30.0 mol%, NiO 19.0 mol%, CuO 2.0 mol%, and a total of 100 parts by weight of these main components) A magnetic paste using 0.25 part by weight of Bi ₂ O ₃ was added to the coating film by a printing method and dried. The Ni—Zn—Cu ferrite material used here is No. 1 shown in Table 1. This corresponds to the composition of 4.

In the above-mentioned step (n), a glass paste using photosensitive borosilicate glass (SiO ₂ —B ₂ O ₃ —CaO—K ₂ O, the same applies below) is applied by a printing method, and dried. A material layer of the nonmagnetic sublayer 3a was formed. On top of this, a silver paste was coated by a printing method and dried to form a drawer portion 2a. A glass paste using photosensitive borosilicate glass was coated thereon by a printing method, vias 6a were formed by a photolithography method, and dried to form a material layer of the nonmagnetic sublayer 3b. On top of this, a silver paste was coated by a printing method and dried to form the main body 2b. A glass paste using photosensitive borosilicate glass was coated thereon by a printing method and dried to form a material layer of the nonmagnetic sublayer 3c. On top of this, a silver paste was applied by a printing method and dried to form the main body 4b. A glass paste using photosensitive borosilicate glass was coated thereon by a printing method, vias 6b were formed by a photolithography method, and dried to form a material layer of the nonmagnetic sublayer 3d. On top of this, a silver paste was coated by a printing method and dried to form a drawer portion 4a.

  In the above-described step (o), a magnetic paste using the same Ni—Zn—Cu-based ferrite material as used in the above step (m) is applied onto the material layer of the nonmagnetic layer 3 by a printing method. And dried.

  The green laminate thus obtained was diced into individual pieces. The dimensions of one element were 0.5 mm in length, 0.65 mm in width, and 0.3 mm in height.

In the above-mentioned step (p), the glass ceramic and the ferrite material are subjected to a heat treatment at 900 ° C. for 35 minutes in an N ₂ —O ₂ mixed gas atmosphere in which the oxygen concentration is adjusted to 0.1% by volume. The first magnetic layer 1, the nonmagnetic layer 3 and the second magnetic layer 5 were formed by simultaneous firing in an atmosphere.

  In the above-mentioned step (q), a silver paste is applied, and the obtained structure is subjected to a heat treatment at 770 ° C. for 5 minutes in an atmosphere having an oxygen concentration of 0.1% by volume or less, thereby baking silver. Thus, the external electrodes 9a to 9e were formed. As described above, the common mode choke coil 10 of this example was manufactured.

  The common mode choke coil of Example 3 manufactured as described above was subjected to the in-plane distribution of Ag element using wavelength dispersion X-ray analysis (WDX) in the same manner as the common mode choke coil of Examples 1 and 2. When examined, even in Example 3, almost no diffusion of Ag element into the glass ceramic was observed.

  The common mode choke coil obtained by the manufacturing method of the present invention can be used for various applications that require reduction and elimination of common mode noise, such as high-speed data communication using a differential transmission method.

DESCRIPTION OF SYMBOLS 1 1st magnetic layer 2 Conductor coil 2a Lead part 2b Main body part 3 Nonmagnetic layer 3a-3e Nonmagnetic sublayer 4 Conductor coil 4a Leader part 4b Main body part 5 2nd magnetic layer 6a, 6b Via 7 Laminate body 9a-9d External Electrode 10 Common mode choke coil 11 Through hole

Claims (7)

A method of manufacturing a common mode choke coil, in which a nonmagnetic layer and a second magnetic layer are stacked on a first magnetic layer, and two opposing conductor coils are included in the nonmagnetic layer,
Forming the conductor coil with a conductor containing silver;
A manufacturing method comprising forming the nonmagnetic layer at least partially by firing glass ceramics in an atmosphere having an oxygen concentration of 0.1% by volume or less in the presence of a conductor containing silver. By firing the ferrite material in an atmosphere having an oxygen concentration of 0.1% by volume or less using a ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less, The method of manufacturing a common mode choke coil according to claim 1, further comprising forming the second magnetic layer.   The method for manufacturing a common mode choke coil according to claim 1, wherein a sintered ferrite material is used as the first magnetic layer. By firing the ferrite material in an atmosphere having an oxygen concentration of 0.1% by volume or less using a ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO content of 5 mol% or less, Forming the first magnetic layer;
The common mode choke coil according to claim 2, wherein firing for forming the nonmagnetic layer, firing for forming the second magnetic layer, and firing for forming the first magnetic layer are simultaneously performed. Manufacturing method. A non-magnetic layer and a second magnetic layer are laminated on the first magnetic layer, and the nonmagnetic layer includes two opposing conductor coils,
The conductor coil is made of a conductor containing silver,
A common mode choke coil in which a nonmagnetic layer is made of sintered glass ceramics fired in an atmosphere having an oxygen concentration of 0.1% by volume or less in the presence of a conductor containing silver. The common mode choke coil according to claim 5, wherein the second magnetic layer is made of a sintered ferrite material containing Fe ₂ O ₃ , NiO, ZnO, CuO and having a CuO equivalent content of 5 mol% or less.   The common mode choke coil according to claim 5 or 6, wherein the first magnetic layer and the second magnetic layer are connected through the insides of the two conductor coils arranged in the nonmagnetic layer.