JP7396225B2 - semiconductor ceramic electronic components - Google Patents

Description

The present invention relates to semiconductor ceramic electronic components.

Patent Document 1 listed below discloses a semiconductor ceramic electronic component in which internal electrodes are provided within an element body made of a semiconductor ceramic material.

Japanese Patent Application Publication No. 2014-170874

In the semiconductor ceramic electronic component according to the prior art described above, when providing a terminal electrode on the end face of the element body, a conductive paste containing metal powder and glass powder is applied to the end face and then fired.

The inventors have conducted repeated research on the connection between internal electrodes and terminal electrodes in semiconductor ceramic electronic components, and as a result, have newly discovered a technique that can improve connectivity.

An object of the present invention is to provide a semiconductor ceramic electronic component in which connectivity between internal electrodes and terminal electrodes is improved.

A semiconductor ceramic electronic component according to one embodiment of the present invention includes an element body made of semiconductor ceramic, a protective layer that covers the end face of the element body and is made of a material containing a glass component, and a protective layer provided inside the element body. An internal electrode whose end is exposed from the end face of the body and a protective layer covering the end face, and an internal electrode that covers the end face of the element body through the protective layer and is connected to the end of the internal electrode exposed from the protective layer, and a glass component. The device includes a terminal electrode made of a material that does not contain , and a hole adjacent to a connecting portion that is provided in the protective layer and where the end of the internal electrode and the terminal electrode are connected.

In the above-mentioned semiconductor ceramic electronic component, a glass component is supplied from the protective layer adjacent to the connection part to the connection part where the end of the internal electrode and the terminal electrode are connected, and the connection part between the internal electrode and the terminal electrode is supplied with a glass component from the protective layer of the part adjacent to the connection part. Connectivity is enhanced. In the above semiconductor ceramic electronic component, a hole is provided in the portion of the protective layer that supplies the glass component to the connection portion.

In a semiconductor ceramic electronic component according to another embodiment, a plurality of holes are provided in the protective layer, and the plurality of holes are located with the ends of the internal electrodes sandwiched therebetween.

The semiconductor ceramic electronic component according to another embodiment further includes a pore smaller than the hole, provided within the protective layer.

In another embodiment of the semiconductor ceramic electronic component, the size of the hole is 1.8 to 15.0 times the size of the pore.

In a semiconductor ceramic electronic component according to another embodiment, a connection portion where an end of an internal electrode and a terminal electrode are connected is surrounded by a glass component.

According to the present invention, it is possible to provide a semiconductor ceramic electronic component with improved connectivity between internal electrodes and terminal electrodes.

FIG. 1 is a schematic cross-sectional view showing a chip varistor according to one embodiment. FIG. 2 is an enlarged view of a main part of the chip varistor shown in FIG. 1; 2 is an electron micrograph showing a main part of the chip varistor shown in FIG. 1. FIG. 2 is an electron micrograph showing a main part of the chip varistor shown in FIG. 1. FIG. 1 is an electron micrograph showing a main part of a chip varistor according to the prior art. 1 is an electron micrograph showing a main part of a chip varistor according to the prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same function will be denoted by the same reference numerals, and redundant description will be omitted.

In this embodiment, a chip varistor, which is a type of semiconductor ceramic electronic component, will be described.

As shown in FIG. 1, the chip varistor 1 includes an element body 10, a pair of internal electrodes 12 provided in the element body 10, and a pair of terminal electrodes 14 provided on the end surface 10a of the element body 10. It is composed of The chip varistor 1 has a substantially rectangular parallelepiped outer shape, and as an example, the length in the longitudinal direction is 1.6 mm, the length in the transverse direction is 0.8 mm, and the height is 0.8 mm (so-called 1608 size). .

The element body 10 is a laminated structure having a substantially rectangular parallelepiped outer shape. The element body 10 has a pair of end surfaces 10a facing each other in the longitudinal direction.

The element body 10 is made of a sintered body (semiconductor ceramic) that exhibits varistor characteristics. The element body 10 is a laminated structure including a plurality of semiconductor ceramic layers made of a sintered body exhibiting varistor characteristics. In the actual element body 10, the constituent layers are integrated to such an extent that the boundaries between them are not visible. The element body 10 contains ZnO (zinc oxide) as a main component, and also contains Co, rare earth metal elements, group IIIb elements (B, Al, Ga, In), Si, Cr, Mo, and alkali metal elements (K) as subcomponents. , Rb, Cs) and alkaline earth metal elements (Mg, Ca, Sr, Ba) and their oxides. In this embodiment, the element body 21 contains Co, Pr, Cr, Ca, K, and Al as subcomponents. The content of ZnO in the element body 10 is not particularly limited, but is usually 99.8 to 69.0 mass % when the entire material constituting the element body 10 is 100 mass %. A rare earth metal element (for example, Pr) acts as a substance that exhibits varistor characteristics. The content of the rare earth metal element in the element body 10 is set, for example, to about 0.01 to 10 atomic %.

The pair of internal electrodes 12 are provided within the element body 10 so as to extend along the opposing direction of the pair of end surfaces 10a. The pair of internal electrodes 12 overlap in the stacking direction of the element body 10 inside the element body 10, and are drawn out to mutually different end faces 10a. Each end 12a of the pair of internal electrodes 12 is exposed at the end surface 10a of the element body 10. Each of the pair of internal electrodes 12 is made of a metal (for example, Pd) or an alloy (for example, Ag--Pd). In this embodiment, the pair of internal electrodes 12 are both made of Pd, and have a linear expansion coefficient of 11.8×10 ⁻⁶ K ⁻¹ .

The pair of terminal electrodes 14 are provided so as to cover the end surface 10a of the element body 10, and are electrically connected to each of the pair of internal electrodes 12. Both of the pair of terminal electrodes 14 are made of metal (Ag as an example). In this embodiment, each of the pair of terminal electrodes 14 is made of Ag, and its linear expansion coefficient is 18.9×10 ⁻⁶ K ⁻¹ . Neither of the pair of terminal electrodes 14 contains a glass component. Each terminal electrode 14 is formed by applying a conductive paste containing metal powder (Ag powder) and not containing a glass component to the end surface 10a of the element body 10 via a protective layer 16, which will be described later, and then firing it. be done.

Here, the connection points between the internal electrode 12 and the terminal electrode 14 will be explained with reference to FIG. 2.

As shown in FIG. 2, a protective layer 16 is interposed between the element body 10 and the terminal electrode 14, although it is omitted in FIG. The protective layer 16 is made of a material containing glass. In this embodiment, the protective layer 16 is made of silica-based glass (an example of the composition is SiO ₂ --B ₂ O ₃ --ZrO ₂ --R ₂ O (alkali metal oxide)). The linear expansion coefficient of the glass material constituting the protective layer 16 is, for example, 6.4×10 ⁻⁶ K ⁻¹ . Therefore, the linear expansion coefficient of the protective layer 16 is smaller than that of the internal electrode 12 and smaller than that of the terminal electrode 14. The thickness t of the protective layer 16 is designed to be thinner than the thickness of the terminal electrode 14 (for example, 20 to 100 μm), and is, for example, 1 to 4 μm (3 μm as an example).

The protective layer 16 is penetrated by the end portion 12a of the internal electrode 12 at a location where the internal electrode 12 is exposed from the end surface 10a of the element body 10. The internal electrode 12 that penetrates the protective layer 16 is connected to the terminal electrode 14 at the connecting portion 13 . In the connection portion 13, the metal component constituting the internal electrode 12 and the metal component constituting the terminal electrode 14 are considered to be in a mixed (diffused) state. In the connecting portion 13, the end portion 12a of the internal electrode 12 protrudes toward the terminal electrode 14 due to the Kirkendall effect, and the tip portion of the internal electrode 12 may become thick in the shape of a bump as shown in the cross-sectional view of FIG.

A hole 20 is provided in the protective layer 16 at a position adjacent to the connecting portion 13 . In this embodiment, a plurality of holes 20 are provided. In the cross-sectional view shown in FIG. 2, two holes 20 are located with the end 12a of the internal electrode 12 sandwiched therebetween. Furthermore, a plurality of substantially spherical pores 22 (holes) are arranged in a dispersed manner within the protective layer 16 . The dimensions of the pores 22 (for example, 1 μm diameter) are smaller than the dimensions of the holes 20 (for example, 10 μm). The dimensions of the hole 20 are 1.8 to 15.0 times the dimensions of the pore 22.

The protective layer 16 is formed by applying a glass paste containing glass powder and an organic binder to the end surface 10a of the element body 10 and then firing it. It is thought that the locations where the pores 22 are formed are locations where the organic binder disappeared during firing of the glass paste. On the other hand, the location where the hole 20 is formed is considered to be a location where the glass component has disappeared as a result of the glass component being supplied from the protective layer 16 in the portion adjacent to the connection section 13 .

As shown in the electron micrographs of FIGS. 3 and 4, it can be seen that the hole 20 is hollow (particularly the hole 20 located on the right side of the internal electrode 12 in FIG. 4). Further, from the electron micrographs shown in FIGS. 3 and 4, it can be seen that the connecting portion 13 is surrounded by the glass component 17. As shown in the electron micrographs of FIGS. 3 and 4, since the terminal electrode 14 does not contain a glass component, the purity and density of the metal component (Ag), which is the main component, are significantly high.

On the other hand, as shown in FIGS. 5 and 6, in the electron micrograph of the chip varistor according to the prior art, no hole was observed at a position adjacent to the connection part 13. The chip varistor according to FIGS. 5 and 6 differs from the chip varistor 1 described above in that the terminal electrode 14 contains 25.7 wt % of a glass component.

In the chip varistor 1, the inventors provided a hole 20 in the protective layer 16 at a portion adjacent to the connection portion 13, so that the glass component present in the portion corresponding to the hole 20 was removed from the connection portion 13. It has been found that the connectivity between the internal electrodes 12 and the terminal electrodes 14 is improved as a result of being supplied so as to be caught up in the internal electrodes.

Note that when the internal electrode 12 penetrates the protective layer 16 and protrudes toward the terminal electrode 14, it is considered that the protrusion progresses while the terminal electrode 14 takes in the glass material of the protective layer 16. Therefore, when the length of the internal electrode 12 protruding from the end surface 10a of the element body 10 and penetrating the protective layer 16 (protrusion length) is short, the size of the hole 20 is small, and the hole 20 is connected to the protective layer 16 and the terminal. It is thought that it exists near the interface with the electrode 14 (that is, at a long distance from the end surface 10a of the element body 10). It is considered that as the protruding length of the internal electrode 12 becomes longer, the dimensions of the hole 20 become larger and the hole 20 approaches the end surface 10a of the element body 10.

Furthermore, in the chip varistor 1, the stress is relaxed by the holes 20, thereby suppressing the occurrence of cracks around the connecting portion 13. Since the linear expansion coefficient of the protective layer 16 is smaller than that of the internal electrode 12 and the terminal electrode 14, stress is likely to occur around the connection part 13 due to heat cycles, etc.; The stress is effectively alleviated by the holes 20 provided in the protective layer 16 at the matching portions. Furthermore, the stress generated in the protective layer 16 can also be alleviated by the pores 22 provided in the protective layer 16.

Although the preferred embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-described embodiments, and various changes can be made without departing from the gist thereof.

For example, the semiconductor ceramic electronic component is not limited to a chip varistor, but may also be a chip NTC thermistor or the like. The external dimensions of the semiconductor ceramic electronic component, the external dimensions of the element body, etc. can be increased or decreased as appropriate. Furthermore, the constituent materials of the element body, internal electrodes, protective layer, and terminal electrodes can also be changed as appropriate.

DESCRIPTION OF SYMBOLS 1... Chip varistor, 10... Element body, 10a... End surface, 12... Internal electrode, 13... Connection part, 14... Terminal electrode, 16... Protective layer, 20... Hole part, 22... Pore.

Claims (5)

An element body made of semiconductor ceramic,
a protective layer that covers the end face of the element body and is made of a material containing a glass component;
an internal electrode that is provided in the element body and has a connection part that is thickened in the shape of a knob exposed from an end face of the element body and the protective layer that covers the end face;
a terminal electrode that covers an end face of the element body via the protective layer, is connected to a connecting portion of the internal electrode exposed from the protective layer, and is made of a material that does not contain a glass component;
A semiconductor ceramic electronic component, comprising a hole provided in the protective layer and adjacent to the connection part. 2. The semiconductor ceramic electronic component according to claim 1, wherein a plurality of the holes are provided in the protective layer, and the plurality of holes are located with ends of the internal electrodes interposed therebetween. The semiconductor ceramic electronic component according to claim 1 or 2, further comprising a pore provided in the protective layer and smaller than the hole. The semiconductor ceramic electronic component according to claim 3, wherein the size of the hole is 1.8 to 15.0 times the size of the pore. Semiconductor ceramic electronic component according to any one of claims 1 to 4, wherein the connecting portion is surrounded by a glass component.

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