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Patent Application Titled "Multilayer Electronic Component and Method for Manufacturing the Same" Published Online

July 3, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors MOTOKI, Akihiro (Fukui-shi, JP); OGAWA, Makoto (Fukui-shi, JP); KAWASAKI, Kenichi (Echizen-shi, JP); TAKEUCHI, Shunsuke (Echizen-shi, JP); KURODA, Shigeyuki (Sabae-shi, JP), filed on February 11, 2014, was made available online on June 19, 2014.

The assignee for this patent application is Murata Manufacturing Co., Ltd.

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to a multilayer electronic component and a method for manufacturing the same, and more particularly to a multilayer electronic component formed by plating external electrodes directly on external surfaces of a laminate and to a method for manufacturing the multilayer electronic component.

"As shown in FIG. 4, a multilayer electronic component 101, which is represented by a multilayer ceramic capacitor, generally includes a laminate 105 including a plurality of insulating layers 102 laminated to each other and a plurality of layer-shaped internal electrodes 103 and 104 provided along interfaces between the insulating layers 102. At end surfaces 106 and 107 of the laminate 105, edges of the internal electrodes 103 and 104 are exposed, respectively, and external electrodes 108 and 109 are provided to electrically connect the edges of the internal electrodes 103 and 104, respectively.

"When the external electrodes 108 and 109 are formed, in general, paste electrode films 110 are first formed by applying a metal paste containing a metal component and a glass component on the end surfaces 106 and 107 of the laminate 105, followed by firing. Next, on the paste electrode films 110, first plating layers 111 containing Ni or other suitable material as a primary component are formed, and furthermore, on the first plating films, second plating films 112 containing Sn or other suitable material as a primary component are formed. That is, each of the external electrodes 108 and 109 have a three-layer structure including the paste electrode film 110, the first plating film 111, and the second plating film 112.

"The external electrodes 108 and 109 must have superior wettability to solder when the multilayer electronic component 101 is mounted on a substrate using solder. At the same time, the external electrode 108 must electrically connect the internal electrodes 103 which are in an electrically insulated state, and the external electrode 109 must electrically connect the internal electrodes 104 which are in an electrically insulated state. The second plating film 112 ensures the solder wettability, and the paste electrode films 110 electrically connect the respective internal electrodes 103 and 104. The first plating film 111 prevents solder leaching during solder bonding.

"However, the paste electrode film 110 has a relatively large thickness, such as several tens to several hundreds micrometers. Thus, when the dimensions of this multilayer electronic component 101 are set within a predetermined standard value, an effective volume to ensure an electrostatic capacity must be decreased by an amount corresponding to that required to ensure the volume of the paste electrodes 110. On the other hand, since the thickness of each of the plating films 111 and 112 is approximately several micrometers, if each of the external electrodes 108 and 109 can be only with the first plating film 111 and the second plating film 112, a larger effective volume for the electrostatic capacity can be provided.

"For example, Japanese Unexamined Patent Application Publication No. 63-169014 disclose a method for depositing a conductive metal layer by electroless plating so that internal electrodes exposed at one side wall surface of a laminate are short-circuited to the entire side wall surface at which the internal electrodes are exposed.

"However, in the method disclosed in Japanese Unexamined Patent Application Publication No. 63-169014, since the bonding between the internal electrodes and the plating film is insufficient, moisture and other contaminants are disadvantageously likely to enter the laminate. Thus, when a loading test is performed under high-temperature and high-humidity conditions, the life of a multilayer electronic component is likely to be reduced."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "To overcome the problems described above, preferred embodiments of the present invention provide a method for manufacturing a multilayer electronic component, and a multilayer electronic component manufactured thereby.

"A preferred embodiment of the present invention is directed to a method for manufacturing a multilayer electronic component, including the steps of preparing a laminate which includes a plurality of insulating layers laminated to each other and a plurality of internal electrodes formed along interfaces between the insulating layers, edges of the internal electrodes being exposed at a predetermined surface of the laminate, and forming an external electrode on the predetermined surface so as to electrically connect the edges of the internal electrodes, which are exposed at the predetermined surface of the laminate.

"Preferably, the step of forming an external electrode includes the steps of a plating step of forming a continuous plating film by depositing plating deposits on the edges of the internal electrodes exposed at the predetermined surface of the laminate which is prepared in the step of preparing a laminate and by performing plating growth of the plating deposits so as to be connected to each other, and a heat treatment step of performing a heat treatment on the laminate provided with the plating film at an oxygen partial pressure of about 5 ppm or less and at a temperature of about 600.degree. C. or more.

"In the above-described heat treatment step, the temperature to be applied is preferably about 800.degree. C. or more.

"A metal defining a primary component of the internal electrodes and a metal defining a primary component of the plating film are preferably different from each other.

"The metal which is a primary component of the internal electrodes may be, for example, Ni, Cu, Pd, or Ag. In the preferred embodiment described above, for the metal which is a primary component of the internal electrodes and the metal which is a primary component of the plating film, when the former is Ni, the latter is preferably at least one of Ag, Au, Co, Cr, Cu, Fe, Sn, Pt, and Pd; when the former is Cu, the latter is preferably at least one of Ag, Au, Co, Cr, Fe, In, Ir, Ni, Pd, Pt, Rh, Sn, and Zn; when the former is Pd, the latter is preferably at least one of Cu, Fe, Ni, Rh, and Sn; and when the former is Ag, the latter is preferably at least one of Au, Co, Cu, Fe, In, Ni, Pd, Sn, and Zn.

"More preferably, the metal which is a primary component of the internal electrodes is Ni, Cu, Pd, or Ag. In the preferred embodiment described above, for the metal which is a primary component of the internal electrodes and the metal which is a primary component of the plating film, when the former is Ni, the latter is Cu; when the former is Cu, the latter is Ni; and when the former is Pd or Ag, the latter is Cu or Ni.

"The step of forming an external electrode may further include a step of forming a second plating film on the plating film. The heating treatment step is preferably performed before the step of forming a second plating film.

"A multilayer electronic component obtained by the manufacturing method according to preferred embodiments of the present invention has the following structural features.

"A multilayer electronic component according to a preferred embodiment of the present invention includes a laminate which includes a plurality of insulating layers laminated to each other and a plurality of internal electrodes provided along interfaces between the insulating layers, edges of the internal electrodes being exposed at a predetermined surface of the laminate, and an external electrode provided on the predetermined surface. The external electrode includes a plating film which is directly provided on the predetermined surface of the laminate so as to electrically connect the edges of the internal electrodes exposed at the predetermined surface of the laminate. In addition, at boundary portions between each of the internal electrodes and the plating film, a counter diffusion layer is provided, in which a metal component in the plating film and a metal component in the internal electrodes are both detectable, so as to extend to both sides of the internal electrodes and the plating film, and at the side of the internal electrodes, the counter diffusion layer extends to a location spaced from the predetermined surface of the laminate by about 2 .mu.m or more.

"According to preferred embodiments of the present invention, after the plating film is formed which defines the external electrode, a heat treatment under specific conditions is performed, and counter diffusion occurs at the boundary portions between the internal electrodes and the plating film. This counter diffusion causes volume expansion at locations at which it occurs. That is, at the boundary portions between the internal electrodes and the plating film, volume expansion occurs. As a result, voids which may be generated at individual interfaces of the insulating layers with the internal electrodes and the external electrode are filled, and as a result, sealing properties are provided to the laminate. Thus, moisture, a plating solution, and other contaminants are prevented from entering the laminate, and as a result, a reduction in life, which is caused when a loading test is performed under high-temperature and high-humidity conditions, is prevented.

"When the temperature to be applied in the heat treatment step is increased to about 800.degree. C. or more, at the location at which the counter diffusion occurs, uniform dispersion between a plating film component and an internal electrode component is provided. This phenomenon rapidly occurs when the heat treatment temperature reaches about 800.degree. C. or more, and as a result, the above sealing properties are significantly improved.

"In addition, when the metal which is a primary component of the internal electrode and the metal which is a primary component of the plating film are different from each other, the counter diffusion is improved as compared to that obtained when the metals are the same.

"In a preferred embodiment in which the second plating film is formed on the plating film, which is to be processed by the heat treatment as described above to form the external electrode, when the heat treatment step is performed before the step of forming a second plating film, a plating solution used for forming the second plating film is prevented from entering the laminate.

"Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

"FIG. 1 is a cross-sectional view showing a multilayer electronic component 1 according to a first preferred embodiment of the present invention.

"FIG. 2 is a partly enlarged cross-sectional view of a laminate 5 shown in FIG. 1.

"FIG. 3 is a cross-sectional view of a multilayer electronic component 1a according to a second preferred embodiment of the present invention.

"FIG. 4 is a cross-sectional view of a conventional multilayer electronic component 101."

For more information, see this patent application: MOTOKI, Akihiro; OGAWA, Makoto; KAWASAKI, Kenichi; TAKEUCHI, Shunsuke; KURODA, Shigeyuki. Multilayer Electronic Component and Method for Manufacturing the Same. Filed February 11, 2014 and posted June 19, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=6957&p=140&f=G&l=50&d=PG01&S1=20140612.PD.&OS=PD/20140612&RS=PD/20140612

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

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