JP2005306696A - Magnetic ferrite, and common mode noise filter and chip transformer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that a nonmagnetic material or low magnetic permeability material of a great magnetic loss is used, resulting in reduction of a coupling coefficient in a laminated common mode noise filter. <P>SOLUTION: The magnetic ferrite has a composition obtained by adding 8 to 14wt% copper oxide to 100 parts by weight to a composition enclosed by 39.5:53.0:7.5mol%. 39.5: 48.0:12.5mol%, 20.0:67.5.:12.5mol%, and 20.0:55.0:25.5mol% in terms of Fe<SB>2</SB>O<SB>3</SB>, CoO, and ZnO in the composition ratios of Fe, Co and Zn as essential components. As a result, the magnetic ferrite having the low temperature sinterability of low loss in a high-frequency band and the common mode noise filter and chip transformer using the same can be realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic ferrite used in various electronic devices, a common mode noise filter using the same, and a chip transformer.

  In recent years, with the miniaturization and high frequency of electronic devices, the demand for small electronic components used in the high frequency band has increased, and in order to meet this demand, laminated electronic components have been put into practical use. In particular, multilayer electronic components with a multilayer structure that incorporates a coil that is used in a high frequency band are also widely used in inductance components and noise countermeasure components. As an example of a multilayer electronic component with a multilayer structure that incorporates such a coil, a common There are laminated electronic components such as a mode noise filter and a chip transformer that incorporate two or more coils. This conventional laminated common mode noise filter is composed of a first insulator layer, which is a magnetic material, and a non-magnetic material or a low-permeability insulating material in order to link magnetic flux between two or more built-in coils. There is a configuration in which a second magnetic material layer having a property is combined (see, for example, Patent Document 1).

  The ZnCu ferrite or Ni—Zn—Cu—Co ferrite is insufficient from the viewpoint of loss characteristics as a magnetic material used in the high frequency band of GHz used for the coil component of such a laminated structure. Hexagonal ferrite is considered. However, the firing temperature of this hexagonal ferrite is higher than the melting point of silver, and as it is, simultaneous firing with the silver electrode is difficult, and it is difficult to realize a coil component having a laminated structure.

On the other hand, a magnetic material in which copper oxide and bismuth oxide are added as additives for realizing low-temperature sintering of this hexagonal ferrite is disclosed (for example, see Patent Document 2).
JP 2003-31416 A JP 2002-260911 A

  However, since the conventional configuration uses a non-magnetic material such as glass ceramic or ZnCu ferrite, a part of the magnetic flux generated from the coil is not linked between the two coils, so that the coupling coefficient of the laminated electronic component is lowered. Alternatively, when Ni—Zn—Cu—Co ferrite is used for the second insulator layer, the differential impedance of the laminated electronic component increases due to the magnetic loss of the magnetic material, resulting in a decrease in the coupling coefficient. Had.

  In addition, when hexagonal ferrite with additives added for low-temperature sintering and co-firing with a silver electrode, the silver electrode diffuses inside the hexagonal ferrite crystal, increasing conductor resistance and inducing migration. There was a problem. In particular, this problem becomes an important problem as the electrode pattern becomes finer.

  An object of the present invention is to solve the above-described conventional problems, and to provide a magnetic ferrite having a small magnetic loss in a high frequency band that can be simultaneously sintered with a silver electrode.

In order to solve the above-described conventional problems, the present invention has a composition ratio of Fe, Co, and Zn as main components of 39.5: 53.0: 7.5 mol% in terms of Fe ₂ O ₃ , CoO, ZnO, 39 5: 48.0: 12.5 mol%, 20.0: 67.5: 12.5 mol%, 20.0: 55.0: 25.0 mol% A magnetic ferrite having a composition to which ˜14 wt% is added is used.

  The magnetic ferrite of the present invention and the common mode noise filter and chip transformer using the magnetic ferrite realize a low-loss magnetic ferrite in a high frequency band that can be simultaneously sintered with a silver electrode, and use this for a laminated electronic component. A high-frequency common mode noise filter and a chip transformer having a large coupling coefficient between the coils can be realized.

(Embodiment 1)
Hereinafter, the magnetic ferrite according to Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a characteristic diagram showing the frequency characteristics of the magnetic ferrite according to the first embodiment of the present invention. FIG. 2 shows the relationship between the amount of copper oxide added to the magnetic ferrite and the firing shrinkage ratio according to the first embodiment of the present invention. FIG. FIG. 3 is a composition diagram showing the composition range of the magnetic ferrite of the present invention.

  The material composition of the magnetic ferrite having the above characteristics will be described in detail below while explaining the manufacturing method thereof.

First, commercially available iron oxide, cobalt carbonate and zinc oxide, which are starting materials for the magnetic ferrite of the present invention, are converted to Fe ₂ O ₃ , CoO, ZnO, Fe ₂ O ₃ = 30.0 mol%, CoO = 57.5. It mix | blends so that it may become a composition ratio of mol% and ZnO = 12.5 mol%, and after adding an appropriate amount of pure water to this and mixing using a ball mill, it dries and obtains mixed powder. This mixed powder is calcined at 800 ° C. and then pulverized using a planetary ball mill to obtain a magnetic powder (hereinafter referred to as calcined powder). The main crystal phase of the obtained calcined powder was a spinel crystal structure from the result of X-ray diffraction, and the average particle size was 0.8 μm.

  Next, 8 parts by weight of copper oxide powder is mixed with 100 parts by weight of the calcined powder, and an appropriate amount of PVA (polyvinyl alcohol) aqueous solution is added and kneaded to produce a granulated powder having an average particle diameter of about 300 μmφ. To do. Thereafter, the granulated powder is formed into a ring shape and fired at 900 ° C. to obtain a magnetic ferrite having a toroidal spinel crystal structure (Invention 1).

For comparison, commercially available iron oxide, nickel oxide, zinc oxide, copper oxide, and cobalt carbonate, which are starting materials, are converted to Fe ₂ O ₃ , NiO, ZnO, CuO, CoO, and Fe ₂ O ₃ = 46.0. Toroidal spinel crystals are blended so as to have a composition ratio of mol%, NiO = 38.5 mol%, CuO = 13.5 mol%, ZnO = 1 mol%, CoO = 1 mol%, and through the same process. A magnetic ferrite having a structure was produced (conventional product 1).

  Further, commercially available iron oxide, barium carbonate, cobalt carbonate, copper oxide, and bismuth oxide are 46.0 mol%, NiO = 38.5 mol%, CuO = 13.5 mol%, ZnO = 1 mol%, CoO = 1. A magnetic ferrite having a toroidal hexagonal crystal structure was prepared through a similar process by blending so as to have a composition ratio of mol% (conventional product 2).

  Inventive product 1 and conventional products 1 and 2 were both sintered at 900 ° C. and shrinkage was 15% or more, indicating that they were fully sintered.

  The frequency characteristics of the complex permeability of each toroidal magnetic ferrite thus obtained are shown in FIG. The complex magnetic permeability was determined by the coaxial tube method using a network analyzer HP8753C (manufactured by Agilent Technologies).

  As shown in FIG. 1, in the conventional product 1 and the conventional product 2, μ ″ increases at 600 MHz or more, while in the product of the present invention, μ ′ is approximately 2.5 up to 1 GHz, and μ ″ is approximately 0.00. 2 or less. That is, it can be seen that the product of the present invention is a magnetic ferrite having a loss as low as 1 GHz as compared with the conventional product 1 and the conventional product 2 and can be obtained at a firing temperature of about 900 ° C. at which simultaneous sintering with the silver electrode is possible.

  Next, FIG. 2 shows the relationship between the amount of copper oxide added to the magnetic ferrite shown in Invention 1 in Embodiment 1 of the present invention and the firing shrinkage rate.

  As shown in FIG. 2, it can be seen that the firing shrinkage ratio is 15% or more with the addition amount of copper oxide of 6 parts by weight or more, and the sintering is sufficiently advanced. Further, when the amount of copper oxide added is 16 parts by weight or more, μ ″ at 1 GHz is increased, and therefore the amount of copper oxide added is preferably in the range of 6 to 14 parts by weight.

Next, the composition of the calcined powder of magnetic ferrite in Embodiment 1 of the present invention is shown in Table 1 in terms of Fe ₂ O ₃ , CoO, and ZnO in terms of iron oxide powder, cobalt carbonate powder, and zinc oxide powder. By comparison, 8 parts by weight of copper oxide was added to these calcined powders, and a toroidal magnetic ferrite was prepared through the same process as described above (Examples 1 to 7).

  The complex permeability μ ′ and μ ″ at 1 GHz of the obtained toroidal magnetic ferrites are shown in Table 1 in comparison with Comparative Examples 1 to 8 which are outside the composition ratio of the present invention.

  From the results of (Table 1), if the Fe component decreases, μ ′ decreases as in Comparative Examples 7 and 8, so it is not desirable to decrease the Fe component more than necessary.

  Further, when the Zn component decreases, μ ′ decreases as in Comparative Examples 3 and 6, so it is not desirable to decrease the Zn component more than necessary. When the Zn content increases, μ ″ becomes large as in Comparative Examples 2, 4, and 5, which is inappropriate for applications requiring low loss.

  Further, when the Fe component was small as in Examples 5 and 7, μ ″ did not increase even when the Zn component was relatively large.

  Further, as in Comparative Example 1, a composition having a large amount of Fe component has a large change in the temperature of μ ′, and is inappropriate for applications requiring excellent temperature characteristics.

  From the above results, it is possible to realize a magnetic ferrite having effective characteristics in the GHz band in which μ ′ at 1 GHz is 1.5 or more and μ ″ is 0.1 or less in the composition range shown by hatching in FIG. It can be seen that practically useful effects do not appear even if the composition range is exceeded.

  The obtained magnetic ferrite of the present invention was found to have a spinel crystal structure as the main phase, although some foreign phases such as CoO were observed from the analysis results by X-ray diffraction. For identification of this crystal structure, an X-ray diffractometer RINT-2000 (manufactured by Rigaku Corporation) was used.

As described above, the obtained magnetic powder has a spinel crystal structure as the main phase, although some heterogeneous phases such as ZnFe ₂ O ₃ and ZnCo ₂ O ₄ are recognized from the analysis result by X-ray diffraction. The average particle size was 0.5 to 1.0 μm. When this average particle diameter is outside the above range, it is difficult to obtain dense magnetic ferrite. This average particle diameter was shown by the value of X ₅₀ measured with a laser diffraction particle size distribution analyzer SALD2100 (manufactured by Shimadzu Corporation).

Further, since cobalt carbonate used as a starting material changes to an oxide during the calcination process, the same effect can be obtained even when cobalt oxide having a different valence such as CoO or Co ₃ O ₄ is used as a starting material.

Further, it is desirable to select a calcining temperature of about 800 to 1000 ° C. and a temperature at which ZnFe ₂ O ₄ , ZnCo ₂ O _{4 and the} like are not contained in the calcined powder. When the calcined powder contains a large amount of ZnCo ₂ O ₄ , ZnFe ₂ O _4, etc. generated from iron oxide, cobalt carbonate and zinc oxide, which are starting materials in the course of calcining, the size of the compact is particularly large This is because cracks may occur during the firing process.

  Further, it is desirable to select a temperature at which the magnetic ferrite becomes dense at a firing temperature of 850 to 930 ° C. Since simultaneous firing with the silver electrode is performed, a firing temperature of 930 ° C. or higher is not preferable. Furthermore, since the progress of sintering depends on the composition of the magnetic ferrite and the particle size of the calcined powder, it is necessary to make some adjustments depending on the calcined powder used.

  The addition of copper oxide may be calcined in addition to the starting materials of iron oxide, zinc oxide and cobalt carbonate, and calcined powder obtained from iron oxide, zinc oxide and cobalt carbonate without adding copper oxide On the other hand, similar magnetic characteristics can be obtained at the same firing temperature as when copper oxide is added.

As described above, in the first embodiment, the main phase has a spinel crystal structure, and the composition ratio of Fe, Co, and Zn is 39.5: 53: 7.5 in terms of Fe ₂ O ₃ , CoO, and ZnO. To 100 parts by weight of the composition in the range surrounded by mol%, 39.5: 48: 12.5 mol%, 20: 67.5: 12.5 mol%, and 20:55:25 mol% It is a magnetic ferrite having a composition to which 6 to 14 parts by weight of copper oxide is added, and it is possible to realize a magnetic ferrite with a small magnetic loss up to 1 GHz that can be fired at 900 ° C. by adding copper oxide. In addition, since this magnetic ferrite exhibits optimum magnetic characteristics when fired at 900 ° C., it can be sintered simultaneously with an electrode material having a high conductivity such as silver or copper. Are also useful as magnetic ferrites.

(Embodiment 2)
Hereinafter, a common mode noise filter according to Embodiment 2 of the present invention will be described with reference to the drawings.

  FIG. 4A is an exploded perspective view for explaining the structure of the common mode noise filter according to the second embodiment of the present invention, and FIG. 4B is a circuit diagram showing an equivalent circuit thereof. FIG. 4C is an external perspective view.

  4 (a), 4 (b), and 4 (c), reference numeral 3 denotes a magnetic layer having insulating properties such as Ni-Zn-Cu ferrite. On the magnetic layer 3, a coil layer 7 composed of two coil patterns 2-1 and 2-2 is laminated. The coil patterns 2-1 and 2-2 used for the coil layer 7 are preferably electrode materials having high conductivity such as silver. Furthermore, an insulating magnetic layer 1 is laminated on the coil layer 7. The magnetic layer 1 is configured to use the magnetic ferrite of the present invention.

  Further, a coil layer 8 composed of two coil patterns 2-1 and 2-2 is laminated on the magnetic layer 1, and the two coil patterns 2-1 and 2-2 are formed on the magnetic layer 1. Are connected by vias 5 provided in The coil patterns 2-1 and 2-2 are formed as a spiral coil of two spirals in which two coils connected via a via 5 provided in the magnetic layer 1 are arranged in parallel. The connection circuit including these coils is arranged so as to constitute an equivalent circuit as shown in FIG. Further, extraction electrode portions 2-1a, 2-1b, 2-2a, 2-2b are connected to both ends of the coil patterns 2-1, 2-2.

  Next, the magnetic layer 3 having insulating properties is laminated on the coil layer 8.

  The common mode noise filter having such a laminated structure can be formed into a laminated molded body by a ceramic green sheet molding method and a printing technique, and fired at a temperature (around 900 ° C.) at which the coil patterns 2-1 and 2-2 do not melt. Thereafter, by forming the external electrode 6 electrically connected to any one of the extraction electrodes 2-1a, 2-1b, 2-2a, and 2-2b, as shown in FIG. A chip-like common mode noise filter 4 can be realized.

  As described above, in the common mode noise filter having a spiral configuration of two spirals in which the coil pattern 2-1 and the coil pattern 2-2 are arranged in parallel, between the coil layer 7 and the coil layer 8 By interposing the magnetic ferrite of the present invention, which is the magnetic layer 1 having low loss magnetic characteristics even in the high frequency band, the magnetic fluxes of the coil pattern 2-1 and the coil pattern 2-2 are efficiently linked. The magnetic coupling between the coil layer 7 and the coil layer 8 is strengthened, and the coupling coefficient as a common mode noise filter is improved.

  The magnetic layer 1 preferably has a lower magnetic permeability than the magnetic layer 3 in order to further increase the magnetic coupling between the coil pattern 2-1 and the coil pattern 2-2 arranged in parallel.

  Further, it is preferable that the magnetic layer 1 is in contact with only one side of the coil pattern 2-1 and the coil pattern 2-2. When the magnetic layer 1 is in contact with both surfaces of the coil pattern 2-1 and the coil pattern 2-2, the magnetic flux does not link between the coil patterns 2-1 and 2-2 arranged in parallel. This is because the magnetic coupling is deteriorated.

  Next, the laminated structure of the common mode noise filter will be described in detail while explaining the manufacturing method.

First, using iron oxide, cobalt oxide, and zinc oxide, which are starting materials for the magnetic ferrite of the present invention, a composition ratio of Fe ₂ O ₃ : CoO: ZnO = 38: 50: 12 mol% is obtained. Then, an appropriate amount of pure water is added to this and mixed using a ball mill, followed by drying at 120 ° C. to obtain a mixed powder.

  After calcining this mixed powder at 800 ° C., it is pulverized using a planetary ball mill until the maximum particle size becomes 8 μm or less to obtain a ferrite calcined powder. A 10% by weight CuO powder is added to the calcined ferrite powder, and an appropriate amount of butyral resin and butyl acetate are added and sufficiently dispersed using a ball mill to obtain a ceramic slurry. A ferrite green sheet using this ceramic slurry for the magnetic layer 1 of about 50 μm was obtained by the doctor blade method.

On the other hand, iron oxide, nickel oxide, zinc oxide and copper oxide, which are starting materials for ferrite to be the magnetic layer 3, have a composition ratio of Fe ₂ O ₃ : NiO: ZnO: CuO = 48: 21: 21: 10 mol%. The ferrite green sheet used for the magnetic layer 3 was obtained through the same process as the ferrite green sheet. Thereafter, each of the ferrite green sheets was cut into 5 cm □ to obtain a large number.

  Next, a plurality of ferrite green sheets used for the magnetic layer 3 cut to 5 cm □ are laminated to a thickness of 400 μm, and further, a line width of 30 μm mainly composed of Ag and a line width of 25 μm are arranged in parallel. Printed as coil patterns 2-1 and 2-2 composed of two electrode patterns.

  Thereafter, a ferrite green sheet used for the magnetic layer 1 in which the vias 5 connecting the coil patterns 2-1 and 2-2 between the layers were formed on the coil patterns 2-1 and 2-2 was laminated. After that, it is further printed and formed as an upper coil pattern 2-1 and a coil pattern 2-2 composed of two electrode patterns arranged in parallel with a line width of 30 μm mainly composed of Ag and a line width of 25 μm. Two spiral coils connected through the via 5 of the ferrite green sheet were formed.

  In the two spiral coils, the coil pattern 2-1 and the coil pattern 2-2 are provided in a spiral shape substantially parallel to the upper surface of the magnetic layer 3, and the magnetic layer 1 is further sandwiched between the magnetic layers 1. The coil pattern 2-1 and the coil pattern 2-2 provided on the upper part of the magnetic layer 1 are connected via vias 5 provided in the magnetic layer 1 and are provided in a substantially parallel spiral shape.

  Next, a plurality of ferrite green sheets used for the magnetic layer 3 were laminated thereon to obtain a laminated molded product having a thickness of about 1 mm.

  Thereafter, this multilayer molded product was cut into 128 pieces of common mode noise filters, fired at 930 ° C. for 2 hours, and extracted electrode portions 2-1a, 2-1b, 2- By forming external electrodes 6 of Ag or Cu on 2a and 2-2b by a thick film process or a plating process, 128 commons of 1.2 × 1.0 × 0.8 mm as shown in FIG. A mode noise filter could be obtained (Invention 2).

  For comparison, a common mode noise filter (conventional product 3) obtained through a similar process using Ni—Zn—Cu—Co ferrite as a magnetic layer was fabricated. The electrical characteristics of these common mode noise filters were evaluated.

  As a result, the common mode impedance of both the conventional product 3 and the invention product 2 was 90Ω, but the coupling coefficient of the conventional product 3 is 0.90, whereas the coupling coefficient of the invention product 2 is 0.93, which is good. Met.

  In addition, the thinner the ferrite green sheet used for the magnetic layer 1, the larger the common mode noise filter having a coupling coefficient can be obtained. In particular, the thickness after sintering is desirably 50 μm or less, and such a configuration is adopted. Thus, an excellent common mode noise filter having a coupling coefficient of 0.93 or more was obtained.

  The coil pattern 2-1 and the coil pattern 2-2 of the common mode noise filter can take various forms depending on desired inductance characteristics and crosstalk characteristics, but the coil formed by the magnetic layer 1 with two coils. As long as the pattern 2-1 and the coil pattern 2-2 are in contact with each other, the same effect can be obtained in any case. In particular, the effect becomes smaller as the distance between the two coil patterns 2-1 and 2-2 becomes narrower. growing.

  As a result of examining these, it has been found that by setting the distance between the electrode patterns to 30 μm or less, there is an effect of increasing the magnetic flux interlinking between the two coils.

  As described above, in the second embodiment, the magnetic layer 1 that is a magnetic ferrite having a low loss up to 1 GHz is provided at least in part between the coil pattern 2-1 and the coil pattern 2-2 that form two built-in coils. By intervening, the magnetic flux linked between the coils is increased without increasing the magnetic loss, thereby realizing a common mode noise filter with a large coupling coefficient and efficiently removing common mode noise as a common mode noise filter. It becomes possible to do.

  In addition, by using the common mode noise filter having such a configuration, a multilayer electronic component having a small size and excellent characteristics in the GHz band can be realized.

  Furthermore, by making a composite component with this common mode noise filter built-in, it is useful as a multilayer electronic component that is made into a composite component with a high-density multilayer ceramic electronic component, a multilayer module component, or other capacitor element or resistor element. is there.

(Embodiment 3)
Hereinafter, a chip transformer according to Embodiment 3 of the present invention will be described with reference to the drawings.

  FIG. 5A is an exploded perspective view for explaining the structure of the chip transformer according to the third embodiment of the present invention, FIG. 5B is a circuit diagram showing an equivalent circuit thereof, and FIG. Is an external perspective view thereof.

  FIG. 6 is a sectional structural view of a chip transformer which is another example in the third embodiment.

  Next, an example of a stacked chip transformer according to the third embodiment of the present invention will be described with reference to FIGS. 5 (a) to 5 (c).

  The laminated chip transformer according to the present invention shown in FIG. 5A includes a primary coil 21 (including an extraction electrode portion 21a and an extraction electrode portion 21b) and a secondary coil 22 sandwiched between magnetic layers 30 having an insulating property. A magnetic layer 10 having an insulating property is interposed between the coil layer 7 and the coil layer 8 on which the (extraction electrode portion 22 a and extraction electrode portion 22 b) are formed, and the coil layer 7 and the coil layer 8 are respectively connected via the via 5. It has an electrode structure connected as a primary coil 21 and a secondary coil 22, and in particular, a spiral primary coil 21 and a secondary coil 22 composed of two parallel electrode patterns mainly composed of silver. It is characterized by forming. As a result, the magnetic flux circulating around the primary coil 21 and the secondary coil 22 can be cut off, and the magnetic coupling between the two coils 21 and 22 can be strengthened.

  This exhibits the same effect as that of the second embodiment, and the only difference is that the combination of input / output terminals is different as shown in the equivalent circuit of FIG.

  FIG. 5C shows the appearance of the chip transformer having the configuration as described above. Reference numeral 11 denotes a chip transformer, and 12 denotes four external electrodes, which are electrically connected to any one of the extraction electrode portions 21a, 21b, 22a, and 22b shown in FIG.

  As a result of evaluating the characteristics of the chip transformer having the above configuration, the coupling coefficient of the chip transformer (conventional product 4) using Ni—Zn—Cu—Co ferrite, which is a conventional magnetic ferrite, is 0.9. The coupling coefficient of the chip transformer (Invention 3) using the Co—Zn—Cu ferrite of the present invention for the magnetic layer 10 was 0.93, which was good.

  As described above, in the third embodiment, magnetic ferrite having a low loss up to 1 GHz is interposed in at least a part between the primary coil 21 and the secondary coil 22 that form two built-in coils. By increasing the magnetic flux interlinking between the two coils without increasing the magnetic loss, a stacked chip transformer with a large coupling coefficient can be realized, and high-efficiency energy can be exchanged as a transformer.

  In addition, the electrode pattern formation method for all coils may be screen printing, and in order to form a fine pattern, plating transfer and intaglio transfer methods are effective. A chip transformer can be realized.

  Next, another example of the chip transformer in the third embodiment will be described.

  In FIG. 6, the cross-sectional structure of at least one surface is different in that the magnetic layer 3 having an insulating property covers the magnetic layer 1 having an insulating property. This configuration can realize a chip transformer with further improved magnetic characteristics by increasing the magnetic flux density by covering the outer periphery of the electrode pattern of the coil with the magnetic layer 3 having a high magnetic permeability.

  Such a configuration has confirmed the same effect in the configuration of the common mode noise filter.

  As described above, the magnetic ferrite, the common mode noise filter, and the chip transformer according to the present invention realize a low-loss magnetic ferrite in a high-frequency band that can be fired simultaneously with a low-resistance silver electrode. By using it as a magnetic material for noise filters and chip transformers, various common mode noise filters and chip transformers having a large coupling coefficient can be realized and useful for applications such as common mode noise filters and chip transformers used in various electronic devices. .

The characteristic view which shows the frequency characteristic of the magnetic ferrite in Embodiment 1 of this invention Characteristic diagram showing the relationship between the amount of copper oxide added to the magnetic ferrite and the firing shrinkage ratio after firing at 900 ° C Composition diagram showing composition range of magnetic ferrite (A) An exploded perspective view of a common mode noise filter according to Embodiment 2 of the present invention, (b) an equivalent circuit diagram, and (c) an external perspective view. (A) Exploded perspective view of chip transformer in Embodiment 3 of the present invention, (b) Equivalent circuit diagram, (c) External perspective view Cross-sectional view of the structure of another example chip transformer

Explanation of symbols

1 Magnetic layer (second)
2-1 Coil pattern 2-2 Coil pattern 2-1a, 2-1b Extraction electrode part 2-2a, 2-2b Extraction electrode part 3 Magnetic body layer (1st)
4 common mode noise filter 5 via 5a via electrode 6 external electrode 7 coil layer (first)
8 Coil layer (second)
10 Magnetic layer (second)
DESCRIPTION OF SYMBOLS 11 Chip transformer 12 External electrode 21 Primary coil 21a, 21b Extraction electrode part 22 Secondary coil 22a, 22b Extraction electrode part 30 Magnetic body layer (1st)

Claims (11)

The composition ratio of Fe, Co, and Zn as main components is 39.5: 53.0: 7.5 mol%, 39.5: 48.0: 12.5 mol% in terms of Fe ₂ O ₃ , CoO, ZnO, 6 to 14 parts by weight of copper oxide was added to 100 parts by weight of the composition surrounded by 20.0: 67.5: 12.5 mol% and 20.0: 55.0: 25.0 mol%. Magnetic ferrite consisting of composition. A spiral first coil layer composed of two electrode patterns arranged substantially in parallel is provided on the insulating first magnetic layer, and the first coil layer is formed on the first coil layer. Provided with two magnetic layers, a spiral second coil layer composed of two electrode patterns arranged substantially in parallel on the second magnetic layer, and the first coil layer And the second coil layer are connected to each other through a via provided in the second magnetic layer, so that two spiral coils are provided, and a third magnetic layer is formed on the second coil layer. 2. A common mode noise filter provided, wherein the second magnetic layer is made of the magnetic ferrite according to claim 1. The common mode noise filter according to claim 2, wherein the magnetic permeability of the second magnetic layer is smaller than the magnetic permeability of the first and third magnetic layers. The common mode noise filter according to claim 2, wherein the thickness of the second magnetic layer is 50 μm or less. The common mode noise filter according to claim 2, wherein an interval between the electrode patterns is 30 μm or less. The common mode noise filter according to claim 2, wherein the second magnetic layer is covered with the first or third magnetic layer in at least one cross section. A spiral first coil layer composed of two electrode patterns arranged substantially in parallel is provided on the insulating first magnetic layer, and the first coil layer is formed on the first coil layer. Provided with two magnetic layers, a spiral second coil layer composed of two electrode patterns arranged substantially in parallel on the second magnetic layer, and the first coil layer And the second coil layer are connected to each other through a via provided in the second magnetic layer, so that two spiral coils are provided, and a third magnetic layer is formed on the second coil layer. A chip transformer provided, wherein the second magnetic layer is formed of the magnetic ferrite according to claim 1. The chip transformer according to claim 7, wherein the magnetic permeability of the second magnetic layer is smaller than the magnetic permeability of the first magnetic layer. The chip transformer according to claim 7, wherein the thickness of the second magnetic layer is 50 μm or less. The chip transformer according to claim 7, wherein an interval between the electrode patterns is 30 μm or less. The chip transformer according to claim 7, wherein the second magnetic layer is covered with the first or third magnetic layer in at least one cross section.

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