JP2012231047A - Chip shaped electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip shaped electronic component which has good electrical characteristics of an external electrode and the adhesion to a component body and is suitable for downsizing.SOLUTION: A chip shaped electronic component 1 includes: a component body 10 where an internal electrode 11 is buried; and an external electrode 20 formed on an outer surface of the component body 10. In the chip shaped electronic component 1, the external electrode 20 is formed by a physical deposition method at a portion contacting with at least the component body 10 and includes a mixed layer 21 formed by mixing a first electrode material 23 with a second electrode material 24. The mixture ratio of the second electrode material 24 to the first electrode material 23 is gradually reduced as the mixed layer 21 separates from the component body.

Description

  The present invention relates to a chip-shaped electronic component such as a multilayer ceramic capacitor, and more particularly to a structure of an external electrode.

  A chip-shaped electronic component such as a multilayer ceramic capacitor generally includes a rectangular parallelepiped component main body in which an internal electrode is embedded, and an external electrode formed on the outer surface of the component main body and electrically connected to the internal electrode. . The shape, number, and position of the external electrode vary depending on the type of chip-shaped electronic component. For example, in a general multilayer ceramic capacitor, external electrodes are formed from both longitudinal end surfaces of a rectangular parallelepiped component body to side surfaces adjacent to the end surfaces. As a general method for forming the external electrode, a conductive paste is applied and baked by a dip method or the like, and then one or more layers are formed by electrolytic plating or the like for the purpose of improving solder wettability or preventing solder erosion. A method for forming a plating layer is known.

  In recent years, there has been an increasing demand for further miniaturization and thinning of chip electronic components. As a result, the external electrodes are required to be thin and easy to process finely. Therefore, it has been proposed to form all or part of the external electrodes by a dry process such as physical vapor deposition (see Patent Documents 1 and 2).

  In Patent Document 1, an external electrode is configured by forming a single electrode base layer on a component main body by physical vapor deposition and forming an electrode surface layer on the electrode base layer by electrolytic plating. ing. On the other hand, the thing of patent document 2 forms the external electrode which consists of multiple layers by the physical vapor deposition method.

No. 3-10527 JP 10-251837 A

  In the above-mentioned Patent Document 1, a material that ensures solder wettability and the like is selected for the electrode surface layer, and the electrode base layer is electrically connected to the internal electrode such as good connectivity and low resistivity. Materials that ensure properties are selected. Such material selection is made from the same viewpoint as when the conventional thick film method was used. However, the electrode underlayer is formed by a physical vapor deposition method and has a problem that it is difficult to ensure sufficient adhesion to the component body because the film thickness is smaller than that of the conventional one. On the other hand, in the thing of patent document 2, materials, such as Ti with favorable adhesive force with a component main body, are selected as a material of an innermost layer. However, materials having good adhesion tend to have high electrical resistivity, so that there is a problem that electrical characteristics are deteriorated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a chip-like electronic device that has both good electrical characteristics of external electrodes and good adhesion to a component body, and is suitable for downsizing. To provide parts.

  In order to achieve the above object, the present invention provides a chip-shaped electronic component comprising a component main body in which an internal electrode is embedded and an external electrode formed on the outer surface of the component main body, wherein the external electrode is at least in the component main body. It includes a mixed layer formed by physical vapor deposition at a contact portion and mixed with the first electrode material and the second electrode material, and the mixed layer is formed with respect to the first electrode material as the distance from the component body increases. We propose a material characterized in that the mixing ratio of the second electrode material is gradually reduced.

  Here, the mixed layer according to the present invention is not an alloy of the first electrode material and the second electrode material, but is in a state where the single particles of both materials are mixed while maintaining their respective characteristics. I want to be. And in this invention, the external electrode is formed with the mixed layer in the site | part which contacts a component main body at least. With such a configuration, by selecting a material with good electrical characteristics as the first electrode material and selecting a material with good adhesion to the component body as the second electrode material, in the vicinity of the component body The first electrode material ensures electrical characteristics, and the second electrode material ensures adhesion with the component body.

  On the other hand, it is not necessary to secure the adhesion by the second electrode material as the distance from the component body increases. Therefore, in the present invention, the mixed layer is formed so that the mixing ratio (in other words, the abundance ratio) of the second electrode material decreases as the distance from the component body increases, that is, the outer electrode surface layer (outer layer). doing. Thereby, the effect of the electrical characteristics by the first electrode material can be ensured to the maximum extent.

  As an example of a preferred aspect of the present invention, the external electrode includes a single layer formed in the outer layer of the mixed layer and formed only of the first electrode material. According to the present invention, the adherence to a mounting destination such as a printed wiring board and electrical characteristics are good. Note that it is preferable that the single layer and the mixed layer are integrally formed in the same physical vapor deposition process in terms of adhesion to the mixed layer and manufacturing cost.

  As an example of a preferable aspect of the present invention, the mixed layer is formed by depositing a first target made of a first electrode material and a second target made of a second electrode material disposed in one chamber on a component main body. And the mixing rate is controlled by varying the film forming rate of either one or both of the first electrode material and the second electrode material.

  As described above, according to the present invention, by forming a mixed layer of the first electrode material and the second electrode material and controlling the mixing ratio, the electrical characteristics of the external electrode in a trade-off relationship It is possible to achieve both securing the adhesion and securing the adhesion to the component body.

Cross section of multilayer ceramic capacitor Partially enlarged sectional view of multilayer ceramic capacitor explaining the structure of external electrode The figure explaining the 1st formation method of a mixed layer The figure explaining the 2nd formation method of a mixed layer The figure explaining the 3rd formation method of a mixed layer Measurement graph of electrode fixing force of chip-like electronic component according to first embodiment Measurement graph of resistance value of chip-shaped electronic component according to first embodiment Measurement graph of electrode fixing force of chip-like electronic component according to second embodiment Measurement graph of resistance value of chip-shaped electronic component according to second embodiment

  A chip-shaped electronic component according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a multilayer ceramic capacitor will be described as an example of a chip-shaped electronic component. FIG. 1 is a sectional view of a multilayer ceramic capacitor, and FIG. 2 is an enlarged view for explaining the structure of an external electrode. It should be noted that in the present application, dimensions and shapes are appropriately modeled for simplicity of explanation.

  As shown in FIG. 1, the multilayer ceramic capacitor 1 includes a substantially rectangular parallelepiped laminated body 10 that is a component main body, and a pair of external electrodes 20 formed at both longitudinal ends of the laminated body 10.

  The laminate 10 is made of a ceramic sintered body in which a plurality of internal electrode layers 11 and dielectric layers 12 are alternately laminated. The internal electrode layers 11 are arranged so as to overlap each other with a predetermined interval, and the end portions thereof are alternately exposed at one end face of the laminate 10 and are electrically connected to the external electrode 20 at the end face. Yes. That is, every other internal electrode layer 11 is electrically connected to the same external electrode 20. The internal electrode layer 11 is made of a base metal such as Ni or Cu, a noble metal such as Pd or Ag, or a metal mainly composed of an Ag—Pd alloy, but Ni is preferable from the viewpoint of cost reduction. In the present embodiment, the multilayer ceramic capacitor 1 is of a high dielectric constant class 2, and the dielectric layer 12 is made of a dielectric ceramic based on barium titanate.

  The external electrode 20 is formed so as to wrap around from the both end surfaces in the longitudinal direction to the side surface adjacent to the end surface of the surface of the multilayer body 10. The external electrode 20 includes an innermost layer, that is, a mixed layer 21 formed in a portion in contact with the stacked body 10, a single layer 22 formed on the outer layer of the mixed layer 21, and a solder wetting formed on the outer layer of the single layer 22. In order to improve the property, it is composed of a single-layer or multi-layer plating layer 25 (in FIG. 1, one layer is used for the sake of simplicity) formed by an electrolytic plating method.

  As shown in FIG. 2, the mixed layer 21 is in a state in which the material particles of the first electrode material 23 and the second electrode material 24 are mixed and maintained while maintaining their respective characteristics. Here, it should be noted that the mixed layer 21 is not an alloy of the first electrode material 23 and the second electrode material 24. In FIG. 2, it is assumed that the second electrode material 24 is expressed in a circular shape and a portion other than the second electrode material 24 is configured by the first electrode material 23 for the sake of simplicity.

  The first electrode material 23 is preferably selected by paying attention to the electrical characteristics of the external electrode 20. Specifically, the first electrode material 23 is preferably selected from the viewpoint of low electrical resistivity and good connectivity with the internal electrode layer 11, such as Cu, Ni, Ag, Au, etc. For example, an alloy material such as Ag—Pd may be used. On the other hand, it is preferable that the second electrode material 24 is selected by paying attention to the adhesion force of the external electrode 20 to the laminated body 10, for example, a pure metal material such as Ti or Cr or an alloy material thereof. The thing which has electroconductivity is mentioned. In addition, as the second electrode material 24, a non-conductive material such as borosilicate glass or lead borosilicate glass may be used. One of the features of the present invention is that the first electrode material 23 has a lower electrical resistivity than the second electrode material 24, and the second electrode material 24 is a laminated body than the first electrode material 23. 10 having a high physical adhesion strength to 10.

  Further, as shown in FIG. 2, the mixed layer 21 moves away from the outer surface of the laminated body 10, in other words, the second electrode with respect to the first electrode material 23 as it goes to the surface layer (outer layer) of the external electrode 20. The material 24 is characterized in that it is formed so that the mixing ratio (in other words, the existence ratio) of the material 24 becomes small. In other words, the mixed layer 21 depicts a gradation in which the concentration of the second electrode material 24 decreases as the distance from the outer surface of the stacked body 10 increases. With such a configuration, since the second electrode material 24 is in contact with the outer surface of the laminate 10, high adhesion can be obtained, and the first electrode material 23 is also in contact with the outer surface of the laminate 10. Good connectivity with the electrode layer 11 and good electrical characteristics are obtained. Since the strong adhesion and good electrical characteristics of the external electrode 20 to the laminate 10 are in a trade-off relationship in the conventional structure as described above, the present invention is extremely useful. The mixing ratio of the second electrode material 24 may be gradually decreased or may be decreased stepwise, but the former is preferable from the viewpoint of the strength of the mixed layer 21 and the like.

  The mixed layer 21 is formed by physical vapor deposition. Physical vapor deposition methods are broadly classified into sputtering, vacuum vapor deposition, and ion plating. Sputtering is suitable for forming the mixed layer 21 according to the present invention from the viewpoint of wide selection of materials. Further, there are various sputtering methods such as DC sputtering, RF sputtering, magnetron sputtering, and ion beam sputtering, and these methods can be appropriately used. In the present embodiment, a magnetron sputtering apparatus is used particularly from the viewpoint of the ease of structure formation of the mixed layer 21 and the spread of the apparatus. In the case of using a magnetron sputtering apparatus, the mixed layer 21 having the structure shown in FIG. 1 can be formed by controlling the deposition rate of the electrode materials 23 and 24. Below, the formation method of the mixed layer 21 using a magnetron sputtering apparatus is demonstrated.

  First, the first forming method will be described with reference to FIG. In the first forming method, a magnetron sputtering apparatus of a type provided with a plurality of targets 111 and 112 in one chamber 101 is used. In this case, the first electrode material 23 is set on the first target 111, and the second electrode material 24 is set on the second target 112. And the laminated body 10 is set to the anode 121 side, and sputtering is started. Here, the mixing ratio of the second electrode material 24 to the first electrode material 23 is controlled by controlling the voltage applied between the first target 111 and the second target 112 and the anode 121 over time. Is possible. That is, the voltage applied to the second target 112 may be controlled to be reduced stepwise or continuously relative to the voltage applied to the first target 111. Specifically, it is preferable that the voltage applied to the first target 111 is fixed and the voltage applied to the second target 112 is controlled to be decreased stepwise or continuously.

  Next, a second forming method will be described with reference to FIG. In the second forming method, a magnetron sputtering apparatus of a type provided with a plurality of chambers 201 and 202 and provided with one target 211 and 212 in each chamber 201 and 202 is used. In this case, the first electrode material 23 is set on the target 211 of the first chamber 201, and the second electrode material 24 is set on the target 212 of the second chamber 202. Then, the mixed layer 21 is formed by reciprocating the laminate 10 between the two chambers 201 and 202. When film formation is started in one chamber, initially, the particles of the material adhere to the mottle, but when the film is formed for a certain period of time, the particles become layered. In the present invention, since the material should not be formed in layers, the laminate 10 is moved to the other chamber before this occurs. The switching time is from milliseconds to several seconds under high-rate film formation conditions, but in order to facilitate switching and prevention of layer formation, the film formation rate is lowered to a unit of several tens of seconds to several minutes. Also good. The overall film formation rate may be adjusted by adjusting parameters such as the degree of vacuum during film formation, the target application voltage, the distance between the target and the laminate 10, the anode application bias voltage, and the like. The mixing rate is controlled by controlling the staying time in each chamber 201, 202. The staying time in each chamber 201, 202 is fixed, but the applied voltage to each target is controlled. It is possible by such a method.

  Next, a third forming method will be described with reference to FIG. In the third forming method, a magnetron sputtering apparatus of a type provided with one chamber 301 and a target 311 is used. In this case, the mixture 26 in which the first electrode material 23 and the second electrode material 24 are mixed is set on the target 311. The composition distribution of the mixture 26 may be such that the material particles of the first electrode material 23 and the second electrode material 24 may be mixed as a whole, or the consumption part may be appropriately divided for each material. . However, the condition is that both materials are not alloyed. Further, when vapor deposition is performed, it is preferable to rotate the target or the laminated body 10 because variation in composition can be reduced. In the case of this method, the mixed layer 21 in which the mixing ratio of the second electrode material 24 decreases stepwise can be formed by sequentially replacing the mixture 26 set on the target 311 with one having a different composition distribution.

  The single layer 22 is formed of a single material by physical vapor deposition. Preferably, the single layer 22 is formed of only the first electrode material 23. The single layer 22 is preferably formed integrally from the viewpoint of adhesion with the mixed layer 21. When the mixed layer 21 is formed by the first method, the single layer 22 is formed integrally with the mixed layer 21 in the same vapor deposition process by finally setting the deposition rate of the second electrode material 24 to zero. can do. When the mixed layer 21 is formed by the second method, the single layer 22 is formed by forming only the first electrode material 23 in the first chamber 201 after forming the mixed layer 21. And can be formed integrally. When the mixed layer 21 is formed by the third method, the single layer 22 is formed by a magnetron sputtering apparatus in which only the first electrode material 23 is set as a target after the formation of the mixed layer 21 is completed. That's fine.

  As described above, in the chip-shaped electronic component according to the present invention, the mixed layer 21 in which the first electrode material 23 and the second electrode material 24 are mixed is physically vapor-deposited at a position in contact with the outer surface of the laminate 10 that is the component main body. It is formed by the law. In the mixed layer 21, the mixing ratio of the second electrode material 24 to the first electrode material 23 gradually decreases as the distance from the stacked body 10 increases. Further, as the first electrode material 23, a material having good electrical characteristics is selected, and as the second electrode material 24, a material having good adhesion to the laminate 10 is selected. With such a configuration, the effect of thinning the external electrode by using the physical thin film method, good electrical characteristics by the first electrode material, and good adhesion by the second electrode material can be obtained.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this. For example, in the above embodiment, a multilayer ceramic capacitor has been described as an example of a chip-shaped electronic component. However, the present invention can also be implemented with other chip-shaped electronic components. That is, in the present invention, the material of the component main body is not required, and the shape and number of the external electrodes are not required.

  Further, materials other than those listed in the above embodiment may be appropriately selected as the first electrode material 23 and the second electrode material 24. In this case, the first electrode material 23 is preferably selected by paying attention to the electrical characteristics of the external electrode 20. On the other hand, the second electrode material 24 is preferably selected by paying attention to the adhesion force of the external electrode 20 to the laminate 10. In addition, the first electrode material 23 has a lower electrical resistivity than the second electrode material 24, and the second electrode material 24 has a physical adhesion strength to the laminate 10 that is greater than that of the first electrode material 23. Use a high value.

  In the above embodiment, the single layer 22 made of the same material as the first electrode material 23 is provided, but the single layer 22 may be omitted.

  Further, in the above-described embodiment, the mixed layer is formed using the magnetron sputtering method as an example of the physical vapor deposition method. However, the present invention can be carried out using another physical vapor deposition method.

  Examples of the present invention will be described. As Example A, a chip inductor in which the external electrode 20 was formed under the following conditions was prepared. The first electrode material 23: Cu, the second electrode material 24: Ti, a layer of only the first electrode material is formed on the outer layer side of the mixed layer 21. The mixed layer 21 is formed by the first forming method. The component size is 2.0 mm × 1.25 mm × 1.0 mm, and external electrodes are formed at both ends in the longitudinal direction of the component body.

  Further, as Comparative Example A1, a chip-shaped inductor was prepared in which only Cu was vapor-deposited on the outer surface of the laminate by a physical vapor deposition method to form an external electrode. Comparative Example A2 was prepared by depositing Ti on the outer surface of the laminate by physical vapor deposition and then depositing Cu to form an external electrode. The component size and external electrode shape are the same as in Example A.

  With respect to the above Example A and Comparative Examples A1 and A2, the fixing force and the electric resistance value of the external electrode were measured, respectively, and the graphs of FIGS. 6 and 7 were obtained. The adhesion force of the external electrode indicates the force with which the side surface of the component main body is pushed horizontally and the external electrode is peeled off from the component main body after mounting the measurement target on the printed wiring board. The electric resistance value is a value measured between both external electrodes. As shown in FIGS. 6 and 7, Comparative Example A1 has good electrical characteristics but insufficient strength, and Comparative Example A2 has good strength but somewhat poor electrical characteristics. On the other hand, it was confirmed that Example A according to the present invention has both good adhesion and electrical characteristics of the external electrodes.

  Next, as Example B, a chip-shaped inductor in which the external electrode 20 was formed under the conditions shown below as Example A was prepared. The first electrode material 23: Ni, the second electrode material 24: borosilicate glass, and a layer of only the first electrode material is formed on the outer layer side of the mixed layer 21. The mixed layer 21 is formed by the first forming method. The component size is 2.0 mm × 1.25 mm × 1.0 mm, and the external electrodes are formed at both ends in the longitudinal direction of the component body.

  Further, as Comparative Example B1, a chip-shaped inductor was prepared in which only Ni was vapor-deposited on the outer surface of the laminate by a physical vapor deposition method to form an external electrode. Comparative Example B2 was prepared by depositing borosilicate glass on the outer surface of the laminate by physical vapor deposition and then depositing Ni to form external electrodes. The component size and external electrode shape are the same as in Example B.

  With respect to the above Example B and Comparative Examples B1 and B2, the adhesion force and the electric resistance value of the external electrode were measured, respectively, and the graphs of FIGS. 8 and 9 were obtained. The measurement environment is the same as in Example A. As shown in FIGS. 8 and 9, Comparative Example B1 has good electrical characteristics but insufficient strength. On the other hand, in Comparative Example B2, peeling occurs at the interface between the Ni layer and the borosilicate glass layer, and it is difficult to ensure the strength. In the first place, the conductivity between the external electrode and the internal conductor lead portion cannot be ensured by the borosilicate glass layer. . On the other hand, it was confirmed that Example B according to the present invention has both good adhesion and electrical characteristics of the external electrodes.

  DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor, 10 ... Laminated body, 11 ... Internal electrode layer, 12 ... Dielectric layer, 20 ... External electrode, 21 ... Mixed layer, 22 ... Single layer, 23 ... 1st electrode material, 24 ... 2nd Electrode material, 25 ... plating layer, 100, 200, 300 ... magnetron sputtering apparatus, 101, 201, 202, 301 ... chamber, 111, 112, 211, 212, 311 ... target

Claims (5)

In a chip-like electronic component comprising a component main body in which an internal electrode is embedded and an external electrode formed on the outer surface of the component main body,
The external electrode is formed by physical vapor deposition at least at a portion in contact with the component body, and includes a mixed layer in which the first electrode material and the second electrode material are mixed, and the mixed layer is separated from the component body. The mixing ratio of the second electrode material to the first electrode material is gradually reduced according to the above. 2. The chip-shaped electronic component according to claim 1, wherein the external electrode includes a single layer formed in the outer layer of the mixed layer and formed only of the first electrode material. The chip-like electronic component according to claim 2, wherein the single layer and the mixed layer are integrally formed in the same physical vapor deposition process. The mixed layer is formed by vapor-depositing a first target made of a first electrode material and a second target made of a second electrode material disposed in one chamber on a component body, and the first electrode material 4. The chip-shaped electronic component according to claim 1, wherein the mixing rate is controlled by varying a film forming speed of one or both of the second electrode materials. 5. The first electrode material has a lower electrical resistivity than the second electrode material, and the second electrode material has a higher physical adhesion strength to the component body than the first electrode material. The chip-shaped electronic component according to claim 1, wherein the electronic component is a chip-shaped electronic component.

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