JP2019117901A - Electronic component and multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic component in which a defect is less likely to occur in a thermal shock test. An electronic component having a ceramic element body having an internal electrode layer and an external electrode formed on an end surface of the ceramic element body, wherein the external electrode is electrically connected to at least a part of the internal electrode layer. A first electrode layer formed directly on the end surface of the ceramic body so as to be connected, and a second electrode layer formed on the outer surface of the first electrode layer, the first electrode layer containing Cu; The second electrode layer contains Ag, Pd and Cu as main components, and the second electrode layer contains at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as subcomponents. An electronic component in which the sub-component is contained in an amount of 0.5 to 5.0 wt% with respect to 100 wt% of the main component of the second electrode layer. [Selection diagram] Figure 2

Description

  The present invention relates to an electronic component in which an external electrode is formed, for example, to a multilayer ceramic capacitor.

  In recent years, many electronic components such as ceramic electronic components are mounted on a wiring substrate mounted inside an electronic device.

  Although Pb-free solder is used for mounting these electronic components on a wiring board, since the melting point of Pb-free solder is relatively high, processing at a high temperature is required at the time of soldering.

  As a result, due to the difference in thermal expansion coefficient between the ceramic element of the ceramic electronic component and the external electrode, a crack is easily generated in the ceramic element, which causes insulation failure.

  Also, in recent years, while the engine room has shrunk due to the progress of computerization of the car and the expansion of the living space in the car, the ECU (Electronic Control Unit) of the car is installed closer to the engine, transmission, etc. It has become

  Therefore, electronic components are used under higher temperature environment, and mechanical stress is generated from displacement amount of expansion and contraction of external electrodes and solder due to temperature change under such environment, and solder itself is generated. May crack.

  Then, it replaces with solder and the conductive adhesive which contained the filler of Ag in epoxy-type thermosetting resin attracts attention. The heat curing temperature of the conductive adhesive used for this type of application is lower than the melting point of the Pb free solder. Therefore, when a conductive adhesive is used to mount the ceramic electronic component, the thermal stress applied to the ceramic body can be reduced.

  In addition, since the conductive adhesive contains a highly elastic resin, the problem of cracks in the bonding material itself can be eliminated.

  An example of a ceramic electronic component that can correspond to such mounting with a conductive adhesive is disclosed in Patent Document 1 below.

  In Patent Document 1, for example, as a ceramic electronic component mountable using a conductive adhesive, a first metal formed by applying and baking a conductive paste containing Cu on the first layer of the outer electrode A ceramic capacitor is disclosed having a layer and a second metal layer formed by applying and baking a conductive paste containing Ag-Pd to the second layer (the outermost layer) of the external electrode. Patent Document 1 describes that having this electrode structure enables mounting with a conductive adhesive.

JP, 2013-197186, A

  However, as described in Patent Document 1, when the second metal layer is formed as the second layer (the outermost layer) of the outer electrode on the first layer (the first metal layer) of the outer electrode. Thermal diffusion may occur between the second metal layer and the first metal layer, and voids may be generated in the second metal layer due to the Kargendal effect. When a temperature cycle test (−55 ° C. to 200 ° C.) is carried out, there is a problem that the holes grow as holes and the bonding strength with the bonding material decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electronic component in which a defect in a thermal shock test is less likely to occur.

  The present inventors diligently studied to achieve the above object, and completed the present invention.

That is, the electronic component according to the present invention is
A ceramic body having an internal electrode layer,
And an external electrode formed on an end face of the ceramic body.
The external electrode is
A first electrode layer formed directly on an end face of the ceramic body so as to be electrically connected to at least a part of the internal electrode layer;
And a second electrode layer formed on the outer surface of the first electrode layer,
The first electrode layer contains Cu,
The second electrode layer contains Ag, Pd and Cu as main components,
The second electrode layer contains at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as a minor component,
The subcomponent of the second electrode layer is contained in an amount of 0.5 to 5.0 wt% with respect to 100 wt% of the main component of the second electrode layer.

  By having the above features, defects of the external electrode due to thermal diffusion are not formed, and the moisture resistance can be improved. As a result, it is possible to provide an electronic component in which a defect in a thermal shock test is less likely to occur, while enabling suitable mounting using a conductive adhesive on an ECU or the like of a car.

Moreover, the multilayer ceramic capacitor according to the present invention is
A ceramic body in which a ceramic layer and an internal electrode layer are alternately laminated;
And an external electrode formed on the end face of the ceramic body.
The external electrode is
A first electrode layer formed directly on an end face of the ceramic body so as to be electrically connected to at least a part of the internal electrode layer;
And a second electrode layer formed on the outer surface of the first electrode layer,
The first electrode layer contains Cu,
The second electrode layer contains Ag, Pd and Cu as main components,
The second electrode layer contains at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as a minor component,
The subcomponent of the second electrode layer is contained in an amount of 0.5 to 5.0 wt% with respect to 100 wt% of the main component of the second electrode layer.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the external electrode of the multilayer ceramic capacitor according to one embodiment of the present invention.

  First, a multilayer ceramic capacitor will be described as an embodiment of the present invention. FIG. 1 shows a cross-sectional view of a general laminated ceramic capacitor 1.

  Multilayer ceramic capacitor 1 has ceramic layer 2 and internal electrode layer 3 substantially parallel to a plane including X axis and Y axis, and ceramic layer 2 and internal electrode layer 3 alternate along the direction of Z axis. The ceramic body 10 is laminated on the

  Here, "substantially parallel" means that most of the portions are parallel but may have portions that are not parallel, and the ceramic layer 2 and the internal electrode layer 3 have some unevenness The idea is that they may or may be inclined.

  The shape of the ceramic body 10 is not particularly limited, but the external dimensions (L, W, T dimensions) are preferably larger than 3.2 mm × 1.6 mm × 1.6 mm.

  The internal electrode layers 3 are laminated so that each end is alternately exposed on the surfaces of the two opposing end faces of the ceramic body 10. The pair of external electrodes 4 are formed on both end faces 10a of the ceramic body 10 and connected to the exposed ends of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

  The thickness of the ceramic layer 2 is not particularly limited, but is preferably 100 μm or less, more preferably 30 μm or less per layer. The lower limit of the thickness is not particularly limited, and is, for example, about 0.5 μm.

  The number of laminated layers of the ceramic layer 2 is not particularly limited, but is preferably 20 or more, and more preferably 50 or more.

The material of the ceramic layer 2 is, for example, a dielectric comprising a main component such as BaTiO ₃ , CaTiO ₃ , SrTiO ₃ , CaZrO ₃ , (K _1-x Na _x ) Sr ₂ Nb ₅ O ₁₅ , Ba ₃ TiNb ₄ O ₁₅ or the like. Body ceramic can be used. Moreover, you may use what added secondary components, such as Mn compound, Mg compound, Cr compound, Co compound, Ni compound, rare earth elements, Si compound, Li compound, etc. to these main components. In addition, piezoelectric ceramic such as PZT ceramic, semiconductor ceramic such as spinel ceramic, magnetic ceramic such as ferrite, etc. can also be used.

  The conductive material contained in the internal electrode layer 3 is not particularly limited, but is preferably Ni, a Ni-based alloy, Cu or a Cu-based alloy. In addition, about 0.1 mass% or less of various trace components, such as P, may be contained in Ni, a Ni-type alloy, Cu, or a Cu-type alloy. Alternatively, the internal electrode layer 3 may be formed using a commercially available electrode paste. The thickness of the internal electrode layer 3 may be appropriately determined according to the application and the like.

  More preferably, the conductive material contained in the internal electrode layer 3 is Ni or a Ni-based alloy because the constituent material of the ceramic layer 2 has reduction resistance. It is more preferable to use this Ni or Ni-based alloy as a main component and to this one or more kinds of internal electrode subcomponents selected from Al, Si, Li, Cr, and Fe.

  By incorporating one or more types of internal electrode subcomponents selected from Al, Si, Li, Cr, and Fe into the Ni or Ni-based alloy that is the main component of the internal electrode layer 3, Ni becomes oxygen in the atmosphere and Before reacting to NiO, the subcomponent for internal electrode and oxygen react to form an oxide film of the subcomponent for internal electrode on the surface of Ni. That is, since it becomes impossible to react with Ni if oxygen in the outside air does not pass through the oxide film of the subcomponent of the internal electrode, Ni becomes difficult to oxidize. As a result, even when continuously used at a high temperature of 250 ° C., the deterioration of the continuity due to the oxidation of the internal electrode layer 3 containing Ni as a main component is unlikely to occur and the conductivity is not likely to occur.

  As shown in FIG. 2, in the external electrode 4 of the present embodiment, the external electrode end face portions 4 a formed on both end surfaces 10 a in the X axis direction of the ceramic element body 10 and both side surfaces in the Y axis direction of the ceramic element body 10 It is preferable to integrally have an external electrode extension 4b that covers both end portions in the X-axis direction and both end portions in the X-axis direction of both main surfaces of the ceramic body 10 in the Z-axis direction.

  The external electrode 4 of the present embodiment has a first electrode layer 401 formed directly on the end face 10 a of the ceramic body 10 so as to be electrically connected to at least a part of the internal electrode layer 3, and a first electrode layer 401. And a second electrode layer 402 formed on the outer surface of the

  An upper electrode layer 403 may be formed on the outer surface of the second electrode layer 402 as the outermost layer.

  Although one external electrode 4 is shown in FIG. 2, the other external electrode also has a similar configuration.

  The first electrode layer 401 contains Cu, and may further contain a glass component and other metals. As another metal used for the 1st electrode layer 401, Ag, Pd, an Ag-Pd alloy, Au etc. can be used, for example.

  It is preferable that the thickness of the 1st electrode layer 401 is 5 micrometers-25 micrometers in the lower surface side (for example, main surface side of the ceramic element body 10) at the time of mounting.

  The second electrode layer 402 contains Ag, Pd and Cu as main components, and at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as auxiliary components. As a result, defects in the thermal shock test are less likely to occur.

  In addition, a thermal shock test means the thermal shock cycle test between -55 degreeC-200 degreeC.

  The minor component of the second electrode layer 402 is 0.5 to 5.0 wt% with respect to 100 wt% of the main component of the second electrode layer 402. As a result, defects in the thermal shock test are less likely to occur. From the above viewpoint, the accessory component of the second electrode layer 402 is preferably 1.0 wt% to 2.5 wt% with respect to 100 wt% of the main component of the second electrode layer 402.

  Ag is preferably 80 wt% to 90 wt%, Pd is preferably 1 wt% to 10 wt%, and Cu is preferably 1 wt% to 10 wt% when the total amount of the main components of the second electrode layer 402 is 100 wt%. It is.

  The subcomponents of the second electrode layer 402 include at least one selected from the group consisting of NiAl, WC, SiC, TaN, and TiN. This can suppress the thermal diffusion of Cu of the first electrode layer 401 into the second electrode layer 402. Therefore, defects in the external electrode 4 can be suppressed, and the moisture resistance can be improved. Note that P, B, and the like may be contained in the second electrode layer 402 as auxiliary components.

  As shown in FIG. 2, the second electrode layer 402 b of the external electrode extension 4 b is continuously connected to the end of the central portion of the external electrode extension 4 b along the X-axis direction.

  The thickness of the second electrode layer 402a formed on the external electrode end face portion 4a is preferably 5 μm to 20 μm. Moreover, it is preferable that the thickness of the 2nd electrode layer 402b formed in the external electrode extension part 4b is 3 micrometers-15 micrometers.

  The upper electrode layer 403 may be formed of Pd plating, Au plating, Au-Pd-Ni alloy or Au-Pd alloy film. When the upper electrode layer 403 is the outermost layer of the external electrode 4 and an Au-based solder material is used for mounting on the wiring substrate, the outermost layer of the external electrode 4 is plated with Pd, Au, Au-Pd-Ni By forming an alloy or an Au-Pd alloy film, it is possible to ensure the reliability of the solder material and the electrical connection.

  The thickness of the upper electrode layer 403 is preferably 0.5 μm to 5.0 μm.

  The multilayer ceramic capacitor of the present embodiment can improve the moisture resistance without forming a defect of the external electrode due to thermal diffusion. As a result, it is possible to provide an electronic component in which a defect in a thermal shock test is less likely to occur, while enabling suitable mounting using a conductive adhesive on an ECU or the like of a car.

  Next, an example of a method of manufacturing the multilayer ceramic capacitor 1 shown in FIG. 1 will be described.

  In order to manufacture the multilayer ceramic capacitor 1 as shown in FIG. 1, a ceramic green sheet containing a ceramic material for forming the ceramic layer 2 is prepared.

As the ceramic material, ceramic materials containing main components such as BaTiO ₃ , CaTiO ₃ , SrTiO ₃ , CaZrO ₃ , (K _1-x Na _x ) Sr ₂ Nb ₅ O ₁₅ , Ba ₃ TiNb ₄ O ₁₅ or the like may be used. it can.

  Next, a conductive paste is applied on the ceramic green sheet to form a conductive pattern corresponding to the internal electrode layer. The application of the conductive paste can be performed by, for example, various printing methods such as screen printing. The conductive paste may contain known binders and solvents in addition to the conductive particles. As the conductive fine particles, Ni, Ni-based alloy, Cu or Cu-based alloy can be used.

  A plurality of ceramic green sheets not having a conductive pattern formed thereon, a ceramic green sheet having a conductive pattern formed thereon, and a plurality of ceramic green sheets not having a conductive pattern formed thereon are laminated in this order and pressed in the laminating direction. , And a mother laminate is produced.

  A plurality of green ceramic bodies are produced by cutting the mother laminate along virtual cut lines on the mother laminate. The cutting of the mother laminate can be performed by dicing or die cutting. Furthermore, barrel grinding etc. may be performed with respect to a green ceramic body, and a ridgeline part and a corner part may be rounded.

  By firing the green ceramic body, the ceramic body 10 is obtained. The firing temperature at this time can be, for example, 1100 ° C. to 1400 ° C.

  The first electrode layer is applied by coating and baking a metal paste by a method such as dipping or printing method so as to cover both main surfaces and both side surfaces of ceramic body 10 from both end faces of ceramic body 10 after firing. 401 is formed. It is preferable that the baking temperature of a metal paste is 700-900 degreeC.

  The second electrode layer 402 is formed on the first electrode layer 401. The method of forming the second electrode layer 402 is not particularly limited, and is formed by barrel plating or the like.

  Thus, the multilayer ceramic capacitor 1 is manufactured.

  In the multilayer ceramic capacitor 1 of the present embodiment, the defect of the external electrode 4 due to heat diffusion is not formed, and the moisture resistance can be improved. As a result, it is possible to provide an electronic component in which a defect in a thermal shock test is less likely to occur, while enabling suitable mounting using a conductive adhesive on an ECU or the like of a car.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments in any way, and various modifications can be made without departing from the scope of the present invention.

  The electronic component of the present invention is applicable not only to the multilayer ceramic capacitor but also to other electronic components. Other electronic components include, for example, a band pass filter, an inductor, a laminated three-terminal filter, a piezoelectric element, a PTC thermistor, an NTC thermistor, a varistor and the like.

    Hereinafter, the present invention will be described in more detail by way of examples of the present invention, but the present invention is not limited to these examples.

A ceramic body 10 for a multilayer ceramic capacitor includes a ceramic layer 2 mainly composed of CaZrO ₃ and an internal electrode layer 3 containing Ni, and has a chip size L × W × T = 1.6 mm × 0.8 mm Ceramic element of × 0.8 mm, chip size L × W × T = 3.2 mm × 1.6 mm × 1.6 mm ceramic element, chip size L × W × T = 4.5 mm × 3.2 mm × 2 Preparation of ceramic body 10 for four kinds of multilayer ceramic capacitors of different chip sizes of .0 mm ceramic body, chip size L × W × T = 5.7 mm × 5.0 mm × 2.0 mm ceramic body did. The chip size of each capacitor sample is as shown in Table 1.

  A metal paste containing Cu was applied and baked on both main surfaces and both side surfaces of the ceramic element 10 from both end surfaces of the ceramic element 10 after firing, to form a first electrode layer 401. The baking temperature of the metal paste was 700 ° C to 900 ° C.

  Next, the second electrode layer 402 was formed by barrel plating to obtain a capacitor sample (multilayer ceramic capacitor 1) shown in Table 1.

Each capacitor sample was mounted using a conductive adhesive on a wiring substrate made of Si ₃ N ₄ on the top of which first and second lands containing Cu were formed.

  A thermal shock test (thermal shock cycle test) was performed on these capacitor samples to confirm cracks.

  As a thermal shock cycle test, twenty capacitor samples were prepared by repeating 2000 cycles of 30 minutes of holding at -55.degree. C. and 30 minutes of holding at 200.degree. The thermal shock cycle test was conducted in a state where the capacitor sample was mounted on the wiring board.

  After the thermal shock cycle test, the capacitor sample was polished to the center of the capacitor sample in the Y-axis direction in a direction perpendicular to the substrate mounting surface and along the Y-axis direction of the capacitor sample and parallel to the ZX plane. .

  Next, the polished surface is observed at a magnification of 100 to 500 times with a metallographic microscope to confirm the presence or absence of a crack extending from the edge of the boundary between the external electrode end face 4a and the external electrode extension 4b to the ceramic body did. The results are shown in Table 1.

  From Table 1, when Ag, Pd and Cu are contained as main components in the second electrode layer (sample numbers 2 to 6, 8, 9, 11, 12, 14, 15, 17 to 20, 22 to 24 and 26), It has been confirmed that the percent defective in the thermal shock test is lower than that in the case where the second electrode layer does not contain Cu as a main component (Sample Nos. 13 and 21).

  From Table 1, when the second electrode layer contains 0.5 to 5.0 wt% of a predetermined subcomponent (sample numbers 2 to 6, 8, 9, 11, 12, 14, 15, 17 to 20, 22 to 22) 24 and 26) were able to confirm that the defect rate of a thermal shock test was low compared with the case (A sample number 1 and 25) in which a 2nd electrode layer does not contain a subcomponent.

  From Table 1, when the second electrode layer contains 0.5 to 5.0 wt% of a predetermined subcomponent (sample numbers 2 to 6, 8, 9, 11, 12, 14, 15, 17 to 20, 22 to 22) In 24 and 26), it was confirmed that the percentage defective in the thermal shock test was lower than in the case where the second electrode layer contained 5.0 wt% or more of the predetermined subcomponent (Sample Nos. 7, 10 and 16) .

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor ......... Ceramic layer 3 ... Internal electrode layer 4 ... External electrode 4a ... External electrode end surface part 4b ... External electrode extension part 401 ... 1st electrode layer 402 ... 2nd electrode layer 402a ... 2nd of the external electrode end surface part 1 electrode layer 402b ... first electrode layer 403 of external electrode extension portion ... upper layer electrode layer 10 ... ceramic element 10a ... end face of ceramic element

Claims (2)

A ceramic body having an internal electrode layer,
And an external electrode formed on an end face of the ceramic body.
The external electrode is
A first electrode layer formed directly on an end face of the ceramic body so as to be electrically connected to at least a part of the internal electrode layer;
And a second electrode layer formed on the outer surface of the first electrode layer,
The first electrode layer contains Cu,
The second electrode layer contains Ag, Pd and Cu as main components,
The second electrode layer contains at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as a minor component,
The electronic component in which 0.5 to 5.0 wt% of the subcomponent of the second electrode layer is contained with respect to 100 wt% of the main component of the second electrode layer. A ceramic body in which a ceramic layer and an internal electrode layer are alternately laminated;
And an external electrode formed on the end face of the ceramic body.
The external electrode is
A first electrode layer formed directly on an end face of the ceramic body so as to be electrically connected to at least a part of the internal electrode layer;
And a second electrode layer formed on the outer surface of the first electrode layer,
The first electrode layer contains Cu,
The second electrode layer contains Ag, Pd and Cu as main components,
The second electrode layer contains at least one selected from the group consisting of NiAl, WC, SiC, TaN and TiN as a minor component,
The multilayer ceramic capacitor, wherein the subcomponent of the second electrode layer is contained in an amount of 0.5 to 5.0 wt% with respect to 100 wt% of the main component of the second electrode layer.

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