JP6168721B2 - Multilayer ceramic electronic component and manufacturing method thereof - Google Patents

Description

  The present invention relates to a multilayer ceramic electronic component and a method for manufacturing the same, and more particularly to an improvement for improving the moisture resistance reliability of the multilayer ceramic electronic component.

  A multilayer ceramic electronic component typified by a multilayer ceramic capacitor includes a plurality of laminated ceramic layers and a plurality of internal electrodes respectively disposed along a plurality of interfaces between the ceramic layers, and each end of the internal electrodes is on the end surface. It has a component body that is exposed. An external electrode is formed on the end surface of the component body. The external electrode is connected to each exposed end of the internal electrode exposed at the end face of the component body.

  In order to make such a multilayer ceramic electronic component highly reliable with respect to mechanical, electrical or thermal shock, Japanese Patent No. 3716746 (Patent Document 1) discloses an internal electrode. An oxide layer of a base metal constituting the internal electrode is provided at the interface between both main surfaces of the lead portion that provides the exposed end and the ceramic layer, so that strong bonding is provided at least between the lead portion of the internal electrode and the ceramic layer. It is described to make it powerful.

  However, it has been found that even a multilayer ceramic electronic component that has taken the above-described measures may not be able to exhibit a sufficient effect in terms of moisture resistance reliability. Deterioration of moisture resistance reliability, for example, appears as deterioration of electrical characteristics such as insulation resistance (IR) in a moisture resistance reliability test. By pursuing the cause, not the lead part of the internal electrode but the component body. It has been confirmed that peeling between the internal electrode and the ceramic layer at the end located inside, that is, the built-in end can occur as a starting point. Such peeling between the internal electrode and the ceramic layer at the built-in end portion tends to concentrate residual stress and electric field at the time of voltage application, particularly at the built-in end portion, which causes the internal electrode and the ceramic layer to be separated. It is presumed that this is because cracks are likely to occur at the interface.

  Therefore, it is desired that the strength at the interface portion between the internal electrode and the ceramic layer at the built-in end can be increased.

Japanese Patent No. 3716746

  An object of the present invention is to provide a multilayer ceramic electronic component and a method for manufacturing the same, which can satisfy the above-described demand.

The present invention includes a component body including a plurality of laminated ceramic layers and an internal electrode disposed along an interface between the ceramic layers, and an external electrode formed on the component body. The internal electrode is a base metal. Is first directed to a multilayer ceramic electronic component having an exposed end exposed on the surface of the component main body and a built-in end positioned inside the component main body so as to be connected to the external electrode. In order to solve the technical problem described above, an oxide layer containing a base metal is formed along the interface with the ceramic layer at least at the built-in end portion of the internal electrode, from the tip of the built-in end portion to 20 μm. In this region, the total thickness of the oxide layers along both surfaces of the internal electrode is characterized by being in the range of 13 to 50% of the thickness of the internal electrode.

In the present invention , the component main body has a rectangular parallelepiped shape having first and second main surfaces facing each other, first and second side surfaces facing each other, and first and second end surfaces facing each other. The layer extends in parallel with the main surface, and the internal electrode includes a plurality of first internal electrodes whose exposed end portions are located on the first end surface side, and a first internal electrode facing the first internal electrode through the ceramic layer. It is further characterized in that it comprises are arranged alternately with the internal electrodes of 1, and a second internal electrodes to position the exposed end portion on the second end face side. In particular, in the multilayer ceramic electronic component having such a configuration, the residual stress and the electric field at the time of voltage application are likely to be concentrated at the built-in end portion, so that the present invention can be advantageously applied.

In the laminated ceramic electronic component according to the present invention, the ceramic layer is mainly composed of the dielectric ceramic having a perovskite structure represented by ABO _3, and the oxide layer, further characterized by further comprising a B-site element in the ABO ₃ It is said . Thereby, the covalent bond strength at the interface between the internal electrode and the ceramic layer is increased, and further improvement in strength at the interface portion between the internal electrode and the ceramic layer is expected.

  The base metal which is the main component of the internal electrode is preferably nickel from the viewpoint of cost.

  The present invention is also directed to a method for manufacturing the above-described multilayer ceramic electronic component. The manufacturing method of the multilayer ceramic electronic component according to the present invention includes a step of preparing a raw component body as described above, a step of firing the raw component body, Forming an external electrode so as to be connected to the exposed end of the electrode. And what is characterized is the firing step. That is, the firing process includes a temperature raising process for raising the firing temperature from room temperature to the top temperature, a top temperature keeping process for keeping the top temperature when the top temperature is reached, and then a drop from the top temperature to the room temperature. During the temperature lowering process, while maintaining the temperature at a temperature lower than the top temperature so that oxidation reaches the built-in end of the internal electrode while controlling the oxygen partial pressure of the firing atmosphere. It is characterized by including.

  According to the present invention, the strength at the interface portion between the internal electrode and the ceramic layer at the built-in end can be increased, and therefore the moisture resistance reliability of the multilayer ceramic electronic component can be improved.

  As described above, the built-in end portion of the internal electrode tends to concentrate residual stress and an electric field at the time of voltage application. For this reason, for example, during a moisture resistance reliability test, peeling occurs at the built-in end portion starting from the interface between the internal electrode and the ceramic layer, and as a result, it is presumed that IR deterioration has occurred. Therefore, the present inventor, as a means for suppressing peeling between the internal electrode and the ceramic layer at the built-in end, which occurs during the moisture resistance reliability test, the ceramic layer in the region from the tip of the built-in end to at least 20 μm It was found that it is effective to form an oxide layer for the internal electrode in contact with the electrode. As described above, by forming the oxide layer, the strength of the interface portion between the internal electrode and the ceramic layer at the built-in end portion is improved, and as a result, peeling between the internal electrode and the ceramic layer is suppressed. As a result, it is presumed that the IR deterioration can be suppressed and the moisture resistance reliability of the multilayer ceramic electronic component is improved.

1 is a cross-sectional view showing a multilayer ceramic capacitor 1 as an example of a multilayer ceramic electronic component to which the present invention is applied. FIG. 2 is an enlarged cross-sectional view showing a portion corresponding to a portion A of the multilayer ceramic capacitor 1 shown in FIG. 1. It is a figure for demonstrating the firing profile employ | adopted in the manufacturing method of the multilayer ceramic electronic component which concerns on this invention.

  A multilayer ceramic capacitor 1 as an example of a multilayer ceramic electronic component to which the present invention is applied will be described with reference to FIG.

  The multilayer ceramic capacitor 1 includes a component body 2 having a multilayer structure. The component main body 2 includes first and second end faces 5 and 6 facing the first and second side faces (not shown) facing the first and second main faces 3 and 4 facing each other. It has a rectangular parallelepiped shape having

  The component body 2 includes a plurality of laminated ceramic layers 7 extending in parallel with the main surfaces 3 and 4, and a plurality of first and second internal electrodes 8 and 9 disposed along an interface between the ceramic layers 7. And. The first internal electrode 8 and the second internal electrode 9 are opposed to each other in part through the ceramic layer 7 and are alternately arranged as viewed in the stacking direction. The internal electrodes 8 and 9 are mainly composed of a base metal such as nickel, nickel alloy, copper, or copper alloy. Preferably, nickel is used as the main component of the internal electrodes 8 and 9.

  On the first and second end faces 5 and 6 of the component body 2, first and second external electrodes 10 and 11 are formed, respectively. External electrodes 10 and 11 are composed of, for example, a thick film formed by baking a conductive paste containing copper, a nickel plating film formed thereon, and a tin plating film formed thereon. .

  The internal electrodes 8 and 9 have an exposed end portion 12 exposed on the surface of the component main body 2 so as to be connected to the external electrode 10 or 11 and a built-in end portion 13 positioned inside the component main body 2. The first inner electrode 8 has the exposed end 12 positioned on the first end face 5 side. On the other hand, the second inner electrode 9 has the exposed end 12 positioned on the second end face 6 side.

Such a multilayer ceramic capacitor 1 is characterized in that at least the built-in end 13 of the internal electrodes 8 and 9 has a ceramic layer as shown in FIG. 2 for the first internal electrode 8. That is, the oxide layer 14 is formed along the interface with. The oxide layer 14 includes the base metal contained in the internal electrodes 8 and 9, and in the region 15 from the tip of the built-in end portion 13 to 20 μm, the oxide layer 14 along both surfaces of each of the internal electrodes 8 and 9. The total thickness t1 + t2 is set to be within a range of 13 to 50% of the thickness T of each of the internal electrodes 8 and 9.

  As described above, by providing the oxide layer 14, it is possible to increase the strength at the interface between the internal electrodes 8 and 9 and the ceramic layer 7 at the built-in end 13, and thus the moisture resistance of the multilayer ceramic capacitor 1. Reliability can be improved.

In this multilayer ceramic capacitor 1, the ceramic layer 7 is mainly composed of a dielectric ceramic having a perovskite structure represented by ABO ₃ . Accordingly, the oxide layer 14, B-site elements in the ABO _3, for example, further including Ti or Zr. Thereby, the covalent bond force at the interface between the internal electrodes 8 and 9 and the ceramic layer 7 is increased, and the strength at the interface portion between the internal electrodes 8 and 9 and the ceramic layer 7 can be further improved.

  In manufacturing the multilayer ceramic capacitor 1 shown in FIG. 1, first, a raw component body 2 is prepared. For the raw component body, a ceramic green sheet containing a dielectric ceramic material is prepared, and then a conductive paste film containing a base metal to be the internal electrodes 8 and 9 with a predetermined pattern is formed on the ceramic green sheet. Next, a plurality of ceramic green sheets including a ceramic green sheet on which a conductive paste film is formed is laminated to obtain a mother block in a raw state, and then obtained by cutting the mother block.

  Next, the raw component body is fired. In this firing step, as shown in FIG. 3, a temperature raising process 21 for raising the firing temperature from room temperature to the top temperature, and then a top temperature keeping process 22 for keeping the top temperature when the top temperature is reached, Next, a temperature lowering process 23 for lowering the temperature from the top temperature to room temperature is performed. The difference from the normal firing step is that the temperature is lowered from the top temperature so that the oxidation reaches the built-in end portions 13 of the internal electrodes 8 and 9 while controlling the oxygen partial pressure of the firing atmosphere in the middle of the temperature lowering step 23. An intermediate keep process 24 for keeping at a low temperature is performed, and in this intermediate keep process 24, an oxide layer 14 made of a base metal oxide as a main component of the internal electrodes 8 and 9 is formed.

For example, when the top temperature keep process 22 is kept at a top temperature of 1200 ° C. and an oxygen partial pressure of 10 ⁻⁹ to 10 ⁻¹⁰ MPa, the keep process 24 during the temperature lowering process 23 has a temperature of 1000 ° C. Then, while being controlled to an oxygen partial pressure of 10 ⁻⁵ to 10 ⁻⁷ MPa, the internal electrodes 8 and 9 are kept for 2 to 3 hours so that the oxidation reaches the built-in end portions 13. Here, the reason why the oxygen partial pressure is controlled is to prevent the internal electrodes 8 and 9 from being broken due to excessive oxidation.

  In the intermediate keeping process 24 described above, oxygen for forming the oxide layer 14 shown in FIG. 2 is supplied to the inside of the component body 2 through the outer surface of the component body 2. Most of this oxygen enters the interior of the component body 2 through the gap between the exposed end portions 12 of the internal electrodes 8 and 9 exposed on the end faces 5 and 6 of the component body 2 and the ceramic layer 7. Therefore, the oxide layer 14 is formed not only at the built-in end 13 of the internal electrodes 8 and 9 but also at the exposed end 12, and as a result, as shown in FIG. 2, the ceramic layers of the internal electrodes 8 and 9 are formed. As a result, the oxide layer 14 is formed over the entire area of the interface with the semiconductor layer 7.

  In this case, oxygen for forming the oxide layer 14 in the portion located on the side opposite to the exposed end 12 in the built-in end 13 of the first internal electrode 8 is mainly the second opposite to this. The internal electrode 9 is assumed to be supplied from the exposed end 12 side through the ceramic layer 7. On the other hand, the oxygen for forming the oxide layer 14 in the portion located on the side opposite to the exposed end 12 in the built-in end 13 of the second internal electrode 9 is mainly the first opposite to this. It is assumed that the internal electrode 8 is supplied through the ceramic layer 7 from the exposed end 12 side.

When the ceramic layer 7 is mainly composed of a dielectric ceramic having a perovskite structure represented by ABO ₃ , as a result of the above-described firing step, the oxide layer 14 becomes a B site element in ABO ₃ , for example, Ti or Zr. It becomes the composition which further contains.

  Next, external electrodes 10 and 11 are formed on end surfaces 5 and 6 of component body 2 after firing so as to be connected to exposed end portions 12 of internal electrodes 8 and 9, respectively. At this time, in order to prevent the oxide layer 14 at the exposed end portion 12 of the internal electrodes 8 and 9 from hindering electrical continuity with the external electrodes 10 and 11, the end surfaces 5 and 6 of the component body 2 are previously formed. On the other hand, it is preferable to remove the oxide on the exposed end 12 side of the internal electrodes 8 and 9 by performing a polishing process. In forming the external electrodes 10 and 11, for example, a conductive paste containing copper is baked to form a thick film, and then nickel plating and tin plating are sequentially performed, and the nickel plating film and the tin plating are formed on the thick film made of copper. A film is formed.

  The multilayer ceramic capacitor 1 is completed as described above.

  When the multilayer ceramic electronic component is the multilayer ceramic capacitor 1 as shown in FIG. 1, the ceramic layer 7 is made of a dielectric ceramic. The multilayer ceramic electronic component to which the present invention is applied may be an inductor, a thermistor, a piezoelectric component, or the like. Therefore, according to the function of the multilayer ceramic electronic component, the ceramic layer may be composed of a dielectric ceramic, a magnetic ceramic, a semiconductor ceramic, a piezoelectric ceramic, or the like.

  The illustrated multilayer ceramic capacitor 1 is a two-terminal type including two external electrodes 10 and 11, but the present invention can also be applied to a multi-terminal type multilayer ceramic electronic component.

[Experimental example]
Next, experimental examples carried out to confirm the effects of the present invention will be described.

First, as shown in the “dielectric ceramic main component” and “A / B ratio” in Table 1 as the dielectric ceramic powder having a perovskite structure represented by ABO ₃ , the A / B ratio of barium titanate is set to 0. Various powders of 9 to 1.1 and calcium zirconate (A / B = 1) were prepared.

  Next, a ceramic slurry was prepared by mixing the dielectric ceramic powder with an organic binder, an organic solvent, a plasticizer, and a dispersant in a predetermined ratio.

  Next, the ceramic slurry was formed into a sheet shape on the resin film so that the thickness after drying was 4.0 μm, and a ceramic green sheet was obtained.

  Next, a conductive paste film to be an internal electrode was formed on the ceramic green sheet by screen printing so that the thickness after drying was 2 μm. Here, as the conductive paste, 50 parts by weight of nickel powder having an average particle size of 0.3 μm, 45 parts by weight of a resin solution in which 10 parts by weight of ethyl cellulose is dissolved in 100 parts by weight of butyl carbitol, and a dispersant and a thickener What mix | blended a total of 5 weight part was used.

  Next, as described above, after peeling the ceramic green sheet on which the conductive paste film is formed from the resin film, 350 layers of these ceramic green sheets are stacked and pressure-bonded to form a stacked body. Was cut into a predetermined size to obtain a plurality of raw component bodies for individual multilayer ceramic capacitors.

Next, the raw component body is degreased in a nitrogen atmosphere at 400 ° C. for 10 hours, and then in a nitrogen-hydrogen-steam mixed atmosphere, the top temperature is 1200 ° C., and the oxygen partial pressure is 10 ⁻⁹ to 10 ^−10. Firing was performed under the condition of MPa. Thereafter, when the firing temperature reaches 1000 ° C. in the process of lowering the firing temperature from the top temperature of 1200 ° C. to the room temperature, the oxygen partial pressure is within the range shown in the column of “Oxygen partial pressure in the midway keep process” in Table 1. Changed and kept for 3 hours.

  Next, 20 parts by weight of ethyl cellulose is dissolved in 70 parts by weight of copper powder, 3 parts by weight of zinc borosilicate glass frit, and 100 parts by weight of butyl carbitol in the component main body obtained by finishing the firing process as described above. The conductive paste containing 27 parts by weight of the resin solution is applied by dipping so that the thickness after drying is 50 μm, dried, and baked at a temperature of 800 ° C. A baked thick film was formed. Next, by sequentially performing nickel plating and tin plating on the copper-baked thick film, a three-layered external electrode composed of the copper-baked thick film, nickel-plated film, and tin-plated film is formed, and a multilayer ceramic as a sample A capacitor was obtained.

  Next, the following evaluation was performed on the obtained multilayer ceramic capacitor.

(Formation state of oxide layer)
In order to investigate the formation state of the oxide layer at the interface between the internal electrode and the ceramic layer in the region from the tip of the built-in end of the internal electrode to 20 μm, the corresponding part is polished using FIB (Focuced Ion Beam) Then, it observed using SIM (Secondary Ion Microscopy).

  From the observed SIM image, the thickness of the internal electrode and the thickness of the oxide layer were read, and the ratio of the total thickness of the oxide layer along both sides of the internal electrode to the thickness of the internal electrode was calculated. The result is shown in the column of “thickness ratio” in Table 1.

(Element characteristics of oxide layer)
In order to investigate the composition of the oxide layer at the interface between the internal electrode and the ceramic layer in the region from the tip of the built-in end of the internal electrode to 20 μm, the corresponding part is processed using FIB, and then the TEM (Transmission Observation was performed using an Electron Microscope.

  From the TEM measurement, detection of the base metal component (Ni) of the internal electrode paste in the oxide layer, detection of the B site element component (Ti or Zr) of barium titanate or calcium zirconate, which is the main component of the dielectric ceramic material, Was done. In Table 1, the detection result of the base metal component is shown in the “presence / absence of base metal” column, and the detection result of the B site element component is shown in the “presence / absence of B element” column.

(Moisture resistance reliability test)
A PCB (Pressure Cooker Bias Test) apparatus was used for the moisture resistance reliability test. The conditions were a temperature of 125 ° C., a humidity of 95%, a pressure of 0.2 MPa, a voltage of 10 V, a direct current, and a test time of 200 hours. The insulation resistance (IR value) was measured, and an IR value that was deteriorated by 4 digits from the initial stage was determined as an IR deteriorated product. In the “IR deterioration number” column of Table 1, the number of samples determined to be IR deteriorated products among 1000 samples is shown.

(Crack observation)
The appearance of the sample after the moisture resistance reliability test was observed with a metal microscope to check for cracks. In the column “Number of occurrence of cracks” in Table 1, the number of cracking samples in 1000 samples is shown.

  In Table 1, since the oxide layer for obtaining the “thickness ratio” was not at a level at which the sample 1 could be confirmed, the TEM measurement for obtaining “presence of base metal” and “presence of B element” was not performed. .

  For Samples 6 to 8, the internal electrode and the external electrode were not electrically connected and the initial electrical characteristics were not obtained, so it was determined as a defective product, and “presence / absence of base metal” and “presence / absence of B element” The TEM measurement for the evaluation of “and the moisture resistance reliability test for the evaluation of the“ number of IR deterioration ”and the“ number of occurrence of cracks ”were not performed.

According to the samples 3 to 5 in which the “thickness ratio” is in the range of 13 to 50%, the “IR degradation number” and the “crack occurrence number” related to the moisture resistance reliability are both “0”, and the moisture resistance reliability It was confirmed that the property is high. In these samples 3 to 5, “presence / absence of base metal” and “presence / absence of B element” are both “present”, and the oxide layer is a B metal element of the ceramic represented by the base metal component of the internal electrode and ABO _3. It was confirmed that it contains. For sample 2, good moisture resistance reliability was obtained, but since the “thickness ratio” was out of the range of 13 to 50%, it was out of the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Component main body 3, 4 Main surface 5, 6 End surface 7 Ceramic layer 8, 9 Internal electrode 10, 11 External electrode 12 Exposed end part 13 Built-in end part 14 Oxide layer 15 Area | region 21 to 20 micrometers from the front Temperature process 22 Top temperature keep process 23 Cooling process 24 Midway keep process t1, t2 Oxide layer thickness T Internal electrode thickness

Claims (3)

A rectangular parallelepiped shape having first and second side surfaces facing each other and first and second side surfaces facing each other and extending parallel to the main surface. A component body comprising a plurality of laminated ceramic layers and internal electrodes disposed along an interface between the ceramic layers;
An external electrode formed on the component body,
The ceramic layer is mainly composed of a dielectric ceramic having a perovskite structure represented by ABO ₃ ;
The internal electrode includes a base metal as a main component, and has an exposed end exposed on the surface of the component main body and a built-in end positioned inside the component main body so as to be connected to the external electrode,
The internal electrode includes a plurality of first internal electrodes that position the exposed end portion on the first end surface side, and the first internal electrode so as to face the first internal electrode through the ceramic layer. Second internal electrodes that are alternately arranged with electrodes and that position the exposed end portion on the second end face side,
An oxide layer containing the base metal and the B site element in the ABO ₃ is formed at least at the built-in end portion of the internal electrode along the interface with the ceramic layer, from the tip of the built-in end portion to 20 μm. In this region, the total thickness of the oxide layers along both surfaces of the internal electrode is in the range of 13 to 50% of the thickness of the internal electrode.
Multilayer ceramic electronic components. The multilayer ceramic electronic component according to claim 1, wherein the base metal that is a main component of the internal electrode is nickel. A method of manufacturing a multilayer ceramic electronic component according to claim 1 or 2,
Preparing a raw state of the component body;
Firing the component body in a raw state;
Forming the external electrode on the component body after firing so as to be connected to the exposed end of the internal electrode;
The firing step includes a temperature raising process for raising the firing temperature from room temperature to the top temperature, a top temperature keeping process for keeping the top temperature when the top temperature is reached, and then a temperature drop from the top temperature to the room temperature. A temperature lowering process, and during the temperature lowering process, while maintaining the oxygen partial pressure of the firing atmosphere, while maintaining at a temperature lower than the top temperature so that oxidation reaches the built-in end of the internal electrode Including the keep process,
Manufacturing method of multilayer ceramic electronic component.

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