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"Ferrite Ceramic Composition, Ceramic Electronic Component, and Method for Manufacturing Ceramic Electronic Component" in Patent Application Approval...

July 15, 2014



"Ferrite Ceramic Composition, Ceramic Electronic Component, and Method for Manufacturing Ceramic Electronic Component" in Patent Application Approval Process

By a News Reporter-Staff News Editor at Life Science Weekly -- A patent application by the inventors NAKAMURA, Akihiro (Kyoto, JP); YAMAMOTO, Atsushi (Kyoto, JP), filed on February 27, 2014, was made available online on July 3, 2014, according to news reporting originating from Washington, D.C., by NewsRx correspondents (see also Murata Manufacturing Co., Ltd.).

This patent application is assigned to Murata Manufacturing Co., Ltd.

The following quote was obtained by the news editors from the background information supplied by the inventors: "In recent years, ceramic electronic components have been widely used which use ferrite ceramics with a spinel-type crystal structure such as Ni--Cu--Zn, and the development of ferrite materials has been also actively carried out.

"For example, JP 2002-193623 A proposes a magnetic ferrite material containing, as its main constituents, Fe.sub.2O.sub.3: 40.0 to 51.0 mol %, CuO: 5.0 to 30.0 mol %, ZnO: 0.5 to 35.0 mol %, and MgO+NiO: 5.0 to 50.0 mol % (MgO is essential), and containing, as its accessory constituents, Mn: 0.75 wt % or less (excluding 0) and Co: 0.75 wt % or less (excluding 0).

"JP 2002-193623 A is intended to reduce the magnetostriction constant by substituting some expensive NiO with relatively inexpensive MgO, and to achieve a magnetic ferrite material that is excellent in voltage resistance and durability by Mn and Co within predetermined ranges.

"In addition, JP 2002-193623 A also proposes a laminate-type ferrite component (laminated coil component) with the use of the magnetic ferrite material, and discloses, as internal electrode materials, low-resistance Ag, Ag alloys, Ag--Pd alloys, and the like which are preferably used, and Cu, Pd, etc. which can be also used, and discloses a laminated chip inductor array with the use of Ag for an internal electrode material."

In addition to the background information obtained for this patent application, NewsRx journalists also obtained the inventors' summary information for this patent application: "Problem to be Solved by the Disclosure

"Ni--Cu--Zn ferrite is commonly subjected to firing in an air atmosphere, and, for example, in the case of a laminated coil component as in JP 2002-193623 A, typically, Ag is used for an internal electrode material. A ferrite material and the internal electrode material are subjected to co-firing at a low temperature 930.degree. C. or lower.

"However, the use of Ag for the internal electrode material of the laminated coil component is likely to cause migrations, and the use for a long period of time under high humidity has the possibility of decreasing insulation properties, thereby leading to decreased reliability. In particular, in the case of high-density packaging such as the laminate-type chip inductor array described in JP 2002-193623 A, the interval between internal electrodes is also reduced, and the use for applications with a potential difference produced between coils thus makes an abnormality likely to be caused by the generation of migrations, thereby making it difficult to ensure sufficient reliability.

"In addition, in consideration of production cost, Pd and Ag--Pd are expensive, and inexpensive Cu is desirably used which is low in resistance and excellent in conductivity.

"However, it is known that from the relationship between the equilibrium oxygen partial pressure of Cu--Cu.sub.2O and the equilibrium oxygen partial pressure of Fe.sub.2O.sub.3--Fe.sub.3O.sub.4, there is no region where Cu and Fe.sub.2O.sub.3 coexist at high temperatures of 800.degree. C. or higher.

"More specifically, at temperatures of 800.degree. C. or higher, when firing is carried out with the oxygen partial pressure set in such an oxidizing atmosphere that maintains the state of Fe.sub.2O.sub.3, Cu is also oxidized to produce Cu.sub.2O. On the other hand, when firing is carried out with the oxygen partial pressure set in such a reducing atmosphere that maintains the state of the Cu metal, Fe.sub.2O.sub.3 is reduced to produce Fe.sub.3O.sub.4.

"As described above, there is no region where Cu and Fe.sub.2O.sub.3 coexist, and thus, firing in such a reducing atmosphere in which Cu is not oxidized reduces Fe.sub.2O.sub.3 to Fe.sub.3O.sub.4, thus decreasing the resistivity .rho., and for this reason, possibly leading to degradation of electrical properties.

"The present disclosure has been achieved in view of these circumstances, and an object of the present disclosure is to provide a ferrite ceramic composition capable of ensuring insulation properties and achieving favorable electrical properties even when the material is subjected to co-firing with a conductive material containing Cu as its main constituent, a ceramic electronic component such as an inexpensive highly-reliable laminated coil component with the use of the ferrite ceramic composition, and a method for manufacturing the ceramic electronic component.

"Means for Solving the Problem

"The inventors have carried out earnest studies on ferrite materials of spinel-type crystal structures represented by the general formula X.sub.2O.sub.3-MeO (X is Fe or Mn, and Me is Zn, Cu, Mg, or Ni), and found that when the molar contents of Fe and Mn in terms of Fe.sub.2O.sub.3 and Mn.sub.2O.sub.3 respectively meet specific ranges, and when the molar contents of Cu and Zn in terms of CuO and ZnO are respectively limited to predetermined ranges, desired favorable insulation properties can be achieved even when some of the NiO is substituted with MgO in a predetermined range, thereby making it possible to achieve a ceramic electronic component with favorable electric properties even when the Cu material and the ferrite material are subjected to co-firing.

"The present disclosure has been achieved on the basis of this finding, and a ferrite ceramic composition according to the present disclosure is a ferrite ceramic composition containing at least Fe, Mn, Cu, Zn, Mg, and Ni, which is characterized in that when the molar content x mol % of Fe in terms of Fe.sub.2O.sub.3 and the molar content y mol % of Mn in terms of Mn.sub.2O.sub.3 are represented by (x, y), (x, y) falls within the region surrounded by A (25, 1), B (47, 1), C (47, 7.5), D (46, 7.5), E (46, 10), F (30, 10), G (30, 7.5), and H (25, 7.5), the molar content of Cu is 0.5 to 10.0 mol % in terms of CuO, the content of Zn is 1.0 to 35.0 mol % in terms of ZnO, and the content of Mg is 5.0 to 35.0 mol % in terms of MgO.

"Thus, a ferrite ceramic composition can be achieved which is capable of improving the resistivity .rho. and ensuring desired insulation properties, even when the composition is subjected to co-firing with a Cu material.

"Furthermore, a ceramic electronic component according to the present disclosure includes a magnetic section composed of a ferrite material, and a conductive section containing Cu as its main constituent, and the component is characterized in that the magnetic section is formed from the ferrite ceramic composition mentioned above.

"Thus, even in the case of co-firing with the Cu material, a ceramic electronic component can be achieved at low cost, which has desired favorable electrical properties.

"In addition, the ceramic electronic component according to the present disclosure is preferably subjected to firing in an atmosphere at lower than or equal to the equilibrium oxygen partial pressure of Cu--Cu.sub.2O.

"Thus, a ceramic electronic component can be easily achieved which can be sintered without having Cu oxidized, and has favorable electrical properties, even when a conductive material containing Cu as its main constituent is used for a coil conductor, and subjected to co-firing with the magnetic section.

"In addition, the ceramic electronic component according to the present disclosure preferably has the magnetic section and conductive section co-fired.

"In addition, the ceramic electronic component according to the present disclosure preferably has the magnetic section and conductive section alternately stacked more than once.

"In addition, the ceramic electronic component according to the present disclosure is preferably a laminated coil component.

"Furthermore, a method for manufacturing a ceramic electronic component according to the present disclosure is characterized in that it includes a calcination step of weighing a Fe compound, a Mn compound, a Cu compound, a Mg compound, a Zn compound, and a Ni compound so that when the molar content x mol % of Fe in terms of Fe.sub.2O.sub.3 and the molar content y mol % of Mn in terms of Mn.sub.2O.sub.3 are represented by (x, y), (x, y) meets the region surrounded by A (25, 1), B (47, 1), C (47, 7.5), D (46, 7.5), E (46, 10), F (30, 10), G (30, 7.5), and H (25, 7.5), the molar content of Cu is 0.5 to 10.0 mol % in terms of CuO, the molar content of Zn is 1.0 to 35.0 mol % in terms of ZnO, and the molar content of Mg is 5.0 to 35.0 mol % in terms of MgO, and mixing and then calcining the weighed compounds to prepare a calcined powder. A ceramic thin-layer body preparation step includes preparing a ceramic thin-layer body from the calcined powder. A conductive film formation step includes forming, on the ceramic thin-layer body, a conductive film containing Cu as its main constituent in a predetermined pattern. A laminated body formation step includes forming a laminated body by stacking the ceramic thin-layer body with the conductive film formed in a predetermined order. A firing step includes firing the laminated body in a firing atmosphere at lower than or equal to the equilibrium oxygen partial pressure of Cu--Cu.sub.2O to co-fire the ceramic thin-layer body and the conductive film.

"Thus, even when the ceramic thin-layer body and the conductive film containing Cu as its main constituent are subjected to co-firing in a firing atmosphere at lower than or equal to the equilibrium oxygen partial pressure of Cu--Cu.sub.2O, a ceramic electronic component can be achieved which has favorable insulation properties and high reliability without having Fe reduced.

"Advantageous Effect of the Disclosure

"In the ferrite ceramic composition, when the molar content x mol % of Fe in terms of Fe.sub.2O.sub.3 and the molar content y mol % of Mn in terms of Mn.sub.2O.sub.3 are represented by (x, y), (x, y) falls within the specific range surrounded by the points A through H mentioned above, the molar content of Cu is 0.5 to 10.0 mol % in terms of CuO, the content of Mg is 5.0 to 35.0 mol % in terms of MgO, and the content of Zn is 1.0 to 35.0 mol % in terms of ZnO. Thus, even when the ferrite ceramic composition is subjected to co-firing with a Cu material, the resistivity .rho. can be improved, and desired insulation properties can be ensured.

"Specifically, favorable insulation properties can be achieved with the resistivity .rho. of 10.sup.7 .OMEGA.cm or more. Furthermore, this makes it possible to achieve a desired ceramic electronic component which has favorable electrical properties such as impedance characteristics.

"Moreover, the relatively inexpensive Mg contained can reduce the molar content of expensive Ni, thus allowing a reduction in cost.

"Furthermore, the ceramic electronic component according to the present disclosure includes the magnetic section composed of a ferrite material and the conductive section containing Cu as its main constituent, and the magnetic section is formed from the ferrite ceramic composition mentioned above. Thus, a ceramic electronic component can be achieved at low cost, which has desired favorable electrical properties even in the case of co-firing with the Cu material.

"Moreover, it becomes possible to avoid migrations as in the case of Ag materials. Therefore, a ceramic electronic component can be achieved, such as a highly reliable laminated coil component which is capable of ensuring favorable insulation properties even when the component is left for a long period of time under high humidity.

"Furthermore, the method for manufacturing a ceramic electronic component according to the present disclosure includes the calcination step of weighing a Fe compound, a Mn compound, a Cu compound, a Mg compound, a Zn compound, and a Ni compound so that when the molar content x mol % of Fe in terms of Fe.sub.2O.sub.3 and the molar content y mol % of Mn in terms of Mn.sub.2O.sub.3 are represented by (x, y), (x, y) meets the region surrounded by A (25, 1), B (47, 1), C (47, 7.5), D (46, 7.5), E (46, 10), F (30, 10), G (30, 7.5), and H (25, 7.5), the molar content of Cu is 0.5 to 10.0 mol % in terms of CuO, the molar content of Mg is 5.0 to 35.0 mol % in terms of MgO, and the molar content of Zn is 1.0 to 35.0 mol % in terms of ZnO, and mixing and then calcining the weighed compounds to prepare a calcined powder. The ceramic thin-layer body preparation step includes preparing a ceramic thin-layer body from the calcined powder. The conductive film formation step includes forming, on the ceramic thin-layer body, a conductive film containing Cu as its main constituent in a predetermined pattern. The laminated body formation step includes forming a laminated body by stacking the ceramic thin-layer body with the conductive film formed in a predetermined order. The firing step includes firing the laminated body in a firing atmosphere at lower than or equal to the equilibrium oxygen partial pressure of Cu--Cu.sub.2O to co-fire the ceramic thin-layer body and the conductive film. Thus, even when the ceramic thin-layer body and the conductive film containing Cu as its main constituent are subjected to co-firing in the firing atmosphere at lower than or equal to the equilibrium oxygen partial pressure of Cu--Cu.sub.2O, a highly-reliable ceramic electronic component with favorable insulation properties can be obtained without reducing Fe.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a diagram showing the composition range for Fe.sub.2O.sub.3 and Mn.sub.2O.sub.2 of a ferrite ceramic composition according to the present disclosure.

"FIG. 2 is a cross-sectional view illustrating an embodiment of a laminated coil component as a ceramic electronic component according to the present disclosure.

"FIG. 3 is an exploded perspective view illustrating a main section of the laminated coil component.

"FIG. 4 is a cross-sectional view of a sample for resistivity measurement, prepared in Example 1.

"FIG. 5 is a diagram showing impedance characteristics of a sample according to the present disclosure, prepared in Example 2.

"FIG. 6 is a diagram showing impedance characteristics of a sample according to a comparative example, prepared in Example 2."

URL and more information on this patent application, see: NAKAMURA, Akihiro; YAMAMOTO, Atsushi. Ferrite Ceramic Composition, Ceramic Electronic Component, and Method for Manufacturing Ceramic Electronic Component. Filed February 27, 2014 and posted July 3, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5752&p=116&f=G&l=50&d=PG01&S1=20140626.PD.&OS=PD/20140626&RS=PD/20140626

Keywords for this news article include: Chalcogens, Murata Manufacturing Co. Ltd.

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