JP2011165935A - Laminated electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated electronic component in which poor connection between an internal electrode and a baked electrode layer is prevented and the occurrence of stress corrosion cracking of an element body is prevented. <P>SOLUTION: The laminated electronic component includes the element body 2, the internal electrode 3 arranged in the element body 2, and terminal electrodes 5 arranged on end faces 13, 14 of the element body 2 and connected to the internal electrode 3. The terminal electrodes 5 have baked electrode layers 5a formed on the end faces 13, 14 and plating layers 5b formed on the baked electrode layers 5a respectively. The internal electrode 3 has a lead-out portion 3b exposed in center regions of the end faces 13, 14 and connected to the baked electrode layers 5a. The lead-out portion 3b has its width set to 100 to 180 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multilayer electronic component such as a multilayer capacitor.

  A multilayer electronic component includes an element body, an internal electrode disposed in the element body, and a terminal electrode disposed on an end surface of the element body and connected to the internal electrode, and the internal electrode is connected to the baking electrode layer. One having a drawn-out portion is known (see, for example, Patent Document 1). In the multilayer electronic component (multilayer capacitor) described in Patent Document 1, the width of the lead portion is set to 0.19 to 0.45 mm in order to improve the thermal shock resistance.

JP-A-8-97071

  The terminal electrode of the multilayer electronic component generally has a baked electrode layer formed on the end face of the element body and a plating layer formed on the baked electrode layer. The plating layer is formed by a wet plating method in which an element body on which a baked electrode layer is formed is immersed in a plating solution for plating. The multilayer electronic component is subjected to heat treatment under desired conditions in various processes (for example, a charge discharge process after the characteristic inspection process, a reflow process for soldering, and the like).

  As a result of investigations by the present inventors, it has been found that there is a possibility of stress corrosion cracking occurring in the element body after the heat treatment. In the multilayer electronic component, the element body is obtained by laminating a green layer containing a ceramic (for example, dielectric ceramic) and an electrode layer made of a conductive paste containing a metal (for example, Ni). The body is formed by firing the body. By firing the laminated body, an element body is obtained from the green layer, and an internal electrode is obtained from the electrode layer. However, since the shrinkage rate of ceramic and metal is different, stress accumulates in the element body. End up. In addition, fine concave portions are formed on the surface of the element body due to the sintering of the ceramic.

  The baked electrode layer is formed by applying a conductive paste over the end face of the element body and the side surface adjacent to the end face, subjecting the applied conductive paste to heat treatment under desired conditions, and baking the element body. For this reason, it is difficult to apply the conductive paste to the ridge line portion formed by the end surface and the side surface adjacent to the end surface, and the thickness of the portion corresponding to the ridge line portion in the baking electrode layer becomes thin. When the plating layer is formed by the wet plating method under such circumstances, the plating solution enters from a portion having a small thickness, that is, a portion corresponding to the ridge line portion in the baked electrode layer, and the element body is corroded by the invading plating solution. Will go. When heat treatment is performed on the element body, a crack is generated by the interaction with the corrosion of the element body so as to release the accumulated stress starting from the minute recesses and the like. It grows together with stress corrosion cracking. Cracks in the element body not only cause poor appearance, but also cause deterioration of electrical characteristics due to moisture, flux residues, and the like entering from the cracks.

  An object of the present invention is to provide a laminated electronic component capable of preventing poor connection between an internal electrode and a baked electrode layer and preventing stress corrosion cracking from occurring in an element body.

  The inventors of the present invention have conducted extensive research on multilayer electronic components that can prevent stress corrosion cracking from occurring in the element body. As a result, the present inventors made stress corrosion on the element body by setting the position where the lead part on the end face of the element body is exposed as the central region of the end face and setting the width of the lead part to be small, particularly 180 μm or less. It came to discover the new fact that it can prevent a crack from occurring. This is considered to be due to the fact that the lead portion is positioned relatively far from the ridge line portion, and even when the plating solution enters, the plating solution is difficult to reach the position where the lead portion is exposed.

  When the inventors reduce the width of the lead-out part, the connection length between the lead-out part and the baked electrode layer is shortened, resulting in poor connection between the lead-out part (internal electrode) and the baked electrode layer. I have also found the fact that there is a fear that a new problem will occur. Therefore, as a result of intensive research on a configuration that can prevent a connection failure between the lead portion (internal electrode) and the baked electrode layer, the present inventors set the width of the lead portion to 100 μm or more. It came to discover the new fact that the connection failure of a part and a baking electrode layer can be prevented.

  Based on such research results, the multilayer electronic component according to the present invention includes an element body, an internal electrode disposed in the element body, and a terminal electrode disposed on an end surface of the element body and connected to the internal electrode. The terminal electrode has a baked electrode layer formed on the end surface and a plating layer formed on the baked electrode layer, and the internal electrode is exposed to the central region of the end surface and connected to the baked electrode layer. And a width of the drawer portion is set to 100 to 180 μm.

  Preferably, the element body has an inner layer portion in which the internal electrode is disposed and an outer layer portion disposed so as to sandwich the inner layer portion, and is formed by an end surface and a side surface adjacent to the end surface. The curvature radius of the portion is set to 1.2 times or less of the thickness of the outer layer portion. In this case, the lead portion is exposed at a position further away from the ridge line portion. Therefore, even when the plating solution enters, it is possible to reliably suppress the lead portion from being exposed.

  Preferably, the curvature radius of the ridge line portion formed by the end surface and the side surface adjacent to the end surface is set to 90 μm or more. In this case, occurrence of chipping in the element body can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing the connection failure between an internal electrode and a baking electrode layer, the laminated electronic component which can prevent that a stress corrosion crack arises in an element | base_body can be provided.

1 is a schematic perspective view of a multilayer capacitor according to an embodiment. 1 is a schematic perspective view of a multilayer capacitor according to an embodiment. It is a schematic perspective view which decomposes | disassembles and shows the element body of the multilayer capacitor concerning this embodiment for every layer. It is a mimetic diagram showing the section composition of the multilayer capacitor concerning this embodiment. It is a chart which shows the result of the 1st experiment. It is a chart which shows the result of the 1st experiment. It is a chart which shows the result of the 1st experiment. It is a chart which shows the result of the 2nd experiment. It is a chart which shows the result of the 2nd experiment. It is a chart which shows the result of the 2nd experiment. It is a chart which shows the result of the 3rd experiment.

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

  A multilayer capacitor 1 which is an example of a multilayer electronic component according to the present embodiment will be described with reference to FIGS. 1 and 2 are schematic perspective views of the multilayer capacitor. FIG. 3 is an exploded perspective view schematically showing each element layer of the multilayer capacitor. FIG. 4 is a schematic diagram showing a cross-sectional configuration of the multilayer capacitor.

  As shown in FIG. 1, the multilayer capacitor 1 includes an element body 2 having a substantially rectangular parallelepiped shape, a plurality of internal electrodes 3 disposed in the element body 2, and a pair of elements disposed on the outer surface of the element body 2. And a terminal electrode 5. The multilayer capacitor 1 is, for example, a 2012 type (length 2.0 mm, width 1.2 mm, and height 1.2 mm), 3216 type (length 3.2 mm, width 1.6 mm, and height 1.6 mm). Or 3225 type (length: 3.2 mm, width: 2.5 mm, and height: 2.5 mm).

  The element body 2 includes a rectangular first side surface 11 and a second side surface 12 facing each other, a first end surface 13 and a second end surface 14 facing each other, a third side surface 15 and a fourth side surface 16 facing each other, Is included. The first end surface 13 and the second end surface 14 extend in the short side direction of the first side surface 11 and the second side surface 12 so as to connect the first side surface 11 and the second side surface 12. The third side surface 15 and the fourth side surface 16 extend in the long side direction of the first side surface 11 and the second side surface 12 so as to connect the first side surface 11 and the second side surface 12.

  As shown in FIGS. 3 and 4, the element body 2 has a plurality of dielectric layers 21. Each dielectric layer 21 extends in a direction parallel to the first side surface 11 and the second side surface 12, and is laminated in a direction opposite to the first side surface 11 and the second side surface 12. That is, the facing direction of the first side surface 11 and the second side surface 12 and the stacking direction of the element body 2 coincide with each other. The element body 2 has a structure in which the internal electrodes 3 are stacked so as to face each other with the dielectric layer 21 in between. The element body 2 includes a capacitance forming portion (inner layer portion) 2 a including the internal electrode 3 and an outer layer portion 2 b sandwiching the capacitance forming portion 2 a in the opposing direction of the first side surface 11 and the second side surface 12.

  In the present embodiment, the radius of curvature (r) of the ridge formed by the end faces 13, 14 and the side faces 11, 12, 15, 16 is set to 1.2 times or less the thickness (t) of the outer layer part 2b. ing. The radius of curvature (r) of the ridge line portion is set to 90 μm or more, and the thickness (t) of the outer layer portion 2b is set to 100 to 150 μm. For example, the thickness (t) of the outer layer portion 2b is 100 μm, and the radius of curvature (r) of the ridge line portion is 120 μm. The ridge portion is formed by polishing the element body 2 by a technique such as barrel polishing. The magnitude of the radius of curvature (r) of the ridge line portion can be controlled by, for example, the polishing time.

Each dielectric layer 21 is composed of a sintered body of a ceramic green sheet containing BaTiO ₃ as a main component. In the actual multilayer capacitor 1, each dielectric layer 21 is integrated to such an extent that the boundary between the dielectric layers 21 is not visible.

  As shown in FIG. 3, each internal electrode 3 has a main electrode portion 3a having a rectangular shape and a lead portion 3b. The lead portion 3 b extends from the main electrode portion 3 a toward the end surfaces 13 and 14 so that the ends thereof are exposed at the end surfaces 13 and 14. Specifically, the lead portion 3b extends from a central region in the opposing direction of the third side surface 15 and the fourth side surface 16 in the main electrode portion 3a. Accordingly, as shown in FIGS. 2 and 4, the lead-out portion 3 b is exposed in a central region in the opposing direction of the third side surface 15 and the fourth side surface 16 on the end surfaces 13 and 14. The width (w) of the lead portion 3b (the length in the opposing direction of the third side surface 15 and the fourth side surface 16) is shorter than the width of the main electrode portion 3a. In the present embodiment, the width (w) of the lead portion 3b is set to 100 to 180 μm.

  The internal electrode 3 having the lead portion 3b exposed on the first end face 13 and the internal electrode 3 having the lead portion 3b exposed on the second end face 14 are formed in the element body 2 in the stacking direction of the dielectric layers 21, that is, the first The first side surface 11 and the second side surface 12 are alternately arranged in the facing direction. The main electrode portions 3a adjacent to each other in the stacking direction of the dielectric layer 21 face each other. The internal electrode 3 is made of a conductive material (for example, Ni that is a base metal) that is normally used as an internal electrode of a multilayer electric element. The internal electrode 3 is configured as a sintered body of a conductive paste containing the conductive material.

  Each terminal electrode 5 is disposed on the end faces 13 and 14. The terminal electrode 5 has a baked electrode layer 5a and a plating layer 5b. The baked electrode layer 5 a is formed so as to cover the entire end surfaces 13 and 14 and a part of the four side surfaces 11, 12, 15 and 16 adjacent to the end surfaces 13 and 14. Therefore, the baked electrode layer 5 a covers the ridge line portion formed by the end faces 13 and 14 and the side faces 11, 12, 15 and 16. The baked electrode layer 5a is formed by applying a conductive paste containing a conductive metal powder (for example, Cu powder or the like) to a corresponding location on the outer surface of the element body 2 and baking it. The plating layer 5b is formed on the baking electrode layer 5a by a wet plating method (for example, an electrolytic plating method or the like). For electrolytic plating, for example, Ni / Sn plating or the like can be used.

  The baked electrode layer 5a covers all the exposed portions of the end faces 13 and 14 in the lead portion 3b, and the lead portion 3b and the baked electrode layer 5a are directly connected. Thereby, the internal electrode 3 is physically and electrically connected to the corresponding terminal electrode 5.

  Here, the relationship between the width (w) of the lead portion 3b, the poor connection between the internal electrode 3 and the baked electrode layer 5a, and the stress corrosion cracking generated in the element body 2 will be described in detail.

  In order to clarify the relationship between the width (w) of the lead-out portion 3b, the connection failure between the internal electrode 3 and the baked electrode layer 5a, and the stress corrosion cracking generated in the element body 2, The following first experiment was conducted. Regarding stress corrosion cracking, multilayer capacitors (2012-type, 3216-type, and 3225-type multilayer capacitors) with different width (w) of the lead-out portion 3b are used as samples A-1 to A-5, B-1 to B-7, A predetermined number of specimens were prepared for each of C-1 to C-5, and the presence or absence of occurrence of cracks (stress corrosion cracks) in each specimen was confirmed by appearance inspection. Regarding the connection failure between the internal electrode 3 and the baked electrode layer 5a, the capacitance of each specimen was measured, and it was determined that a connection failure occurred when the measured value was lower than the design value −20%. Further, in order to evaluate the thermal shock resistance, the specimen was immersed in a 320 ° C. solder bath for a predetermined time (about 3 seconds), and then the presence or absence of cracks was confirmed by appearance inspection.

  The results of the first experiment are shown in FIGS. The experimental results shown in FIG. 5 relate to a 2012 type multilayer capacitor. The experimental results shown in FIG. 6 relate to a 3216 type multilayer capacitor. The experimental results shown in FIG. 7 relate to a 3225 type multilayer capacitor. Each sample A-1 to A-5, B-1 to B-7, C-1 to C-5 in any type of multilayer capacitor is different except that the width (w) of the lead portion 3b is different. The configuration is the same as that of the multilayer capacitor 1 of the above-described embodiment, and in each type of multilayer capacitor, the samples have the same electrical characteristics (for example, B characteristics). In any type of multilayer capacitor, the thickness (t) of the outer layer portion 2b is set to 100 μm, and the curvature radius (r) of the ridge line portion is set to 120 μm.

  From the experimental results shown in FIGS. 5 to 7, it can be seen that when the width (w) of the lead-out portion 3 b is set to 180 μm or less, the occurrence of cracks (stress corrosion cracking) is prevented. In addition, it can be seen that when the width (w) of the lead-out portion 3b is set to 100 μm or more, the occurrence of connection failure is prevented. Therefore, when the width (w) of the lead portion 3b is set to 100 to 180 μm, the connection failure between the internal electrode 3 and the baked electrode layer 5a is prevented, and stress corrosion cracking occurs in the element body 2. Can be prevented. It can be seen that when the width (w) of the lead portion 3b is set to 100 to 180 μm, the thermal shock resistance was also good.

  Subsequently, in order to clarify the relationship between the thickness (t) of the outer layer portion 2b and the radius of curvature (r) of the ridge line portion, and the stress corrosion cracking generated in the element body 2, A second experiment was conducted. Regarding stress corrosion cracking, multilayer capacitors (2012-type, 3216-type, and 3225-type multilayer capacitors) having different thicknesses (t) of the outer layer portion 2b and curvature radii (r) of the ridge line portions are used as samples D-1 to D-13. , E-1 to E-13, F-1 to F-13, a predetermined number of specimens were prepared, and the presence or absence of chipping and stress corrosion cracking in each specimen was confirmed by visual inspection. Regarding the thermal shock resistance, the same evaluation as in the first experiment was performed.

  The results of the second experiment are shown in FIGS. The experimental results shown in FIG. 8 relate to a 2012 type multilayer capacitor. The experimental results shown in FIG. 9 relate to a 3216 type multilayer capacitor. The experimental results shown in FIG. 10 relate to a 3225 type multilayer capacitor. The samples D-1 to D-13, E-1 to E-13, and F-1 to F-13 in any type of multilayer capacitor have a thickness (t) of the outer layer portion 2b and a radius of curvature (r ) And the width (w) of the lead portion 3b are the same as those of the multilayer capacitor 1 of the embodiment described above, and in each type of multilayer capacitor, each sample has the same electrical characteristics (for example, B characteristics, etc.).

  From the experimental results shown in FIGS. 8 to 10, when the curvature radius (r) of the ridge line portion is smaller than 90 μm, the occurrence of chipping becomes remarkable, and the curvature radius (r) of the ridge line portion is set to 90 μm or more. In this case, it can be seen that the occurrence of chipping is suppressed. When the curvature radius (r) of the ridge line portion is set to 1.2 times or less of the thickness (t) of the outer layer portion 2b, it can be seen that the occurrence of cracks (stress corrosion cracking) is prevented. Even when the curvature radius (r) of the ridge line portion is set to 1.2 times or less of the thickness (t) of the outer layer portion 2b, the thickness (t) of the outer layer portion 2b is smaller than 100 μm. Since the distance between the ridge line portion and the lead portion 3b is relatively small, a crack (stress corrosion cracking) occurs. It can also be seen that the thermal shock resistance was good in any specimen.

  As described above, in the present embodiment, the lead portion 3b is exposed to the central region of the end faces 13 and 14 and connected to the baked electrode layer 5a, and its width (w) is set to 100 to 180 μm. Therefore, it is possible to prevent poor connection between the internal electrode 3 (leading portion 3b) and the baked electrode layer 5a and to prevent stress corrosion cracking from occurring in the element body 2.

  In the present embodiment, the radius of curvature (r) of the ridge line formed by the end faces 13, 14 and the side faces 11, 12, 15, 16 adjacent to the end faces 13, 14 is the thickness of the outer layer 2b ( Since it is set to 1.2 times or less of t), the lead-out portion 3b is exposed at a position further away from the ridge line portion. As a result, even when the plating solution enters, it is possible to reliably suppress the lead portion 3b from reaching the exposed position.

  In the present embodiment, the radius of curvature (r) of the ridge line portion is set to 90 μm or more. Thereby, it is possible to suppress chipping from occurring in the element body 2.

  Here, the present inventors conducted a third experiment in order to clarify the relationship between the thickness (t) of the outer layer portion 2b and the short-circuit failure. A multilayer capacitor (2012 type, 3216 type, and 3225 type multilayer capacitors) having different thicknesses (t) of the outer layer portion 2b is prepared for each sample G-1 to G-12, and a predetermined number of specimens are produced. Was measured, and it was determined that a short circuit defect occurred when the measured value was equal to or less than the reference value (10 kΩ).

  The result of the third experiment is shown in FIG. In each sample G-1 to G-12 in any type of multilayer capacitor, in particular, in order to set the same capacitance, the thickness of the dielectric layer 21 is set according to the thickness (t) of the outer layer portion 2b. It has changed. That is, in order to obtain the element body 2 having the same size, the thickness of the capacitance forming portion 2a must be reduced by an amount corresponding to the increase in the thickness (t) of the outer layer portion 2b. In this state, in order to ensure an equivalent capacitance, it is necessary to reduce the thickness of the dielectric layer 21 and increase the number of stacked layers.

  From the experimental results shown in FIG. 11, when the thickness (t) of the outer layer portion 2 b is larger than 150 μm, the occurrence of short-circuit defects becomes significant. This is presumably because, as described above, by reducing the thickness of the dielectric layer 21, a short circuit or voltage breakdown is likely to occur between the internal electrodes 3. Therefore, in order to suppress the occurrence of short circuit defects, it is preferable that the thickness (t) of the outer layer portion 2b is set to 150 μm or less.

  The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  The present invention is not limited to a multilayer capacitor, and can also be applied to multilayer electronic components such as multilayer varistors and multilayer piezoelectric actuators.

  DESCRIPTION OF SYMBOLS 1 ... Multilayer capacitor, 2 ... Element body, 2a ... Capacitance formation part, 2b ... Outer layer part, 3 ... Internal electrode, 3a ... Main electrode part, 3b ... Lead-out part, 5 ... Terminal electrode, 5a ... Baking electrode layer, 5b ... Plating layer, 11 ... first side surface, 12 ... second side surface, 13 ... first end surface, 14 ... second end surface, 15 ... third side surface, 16 ... fourth side surface, 21 ... dielectric layer.

Claims (3)

With the body,
An internal electrode disposed in the element body;
A terminal electrode disposed on an end face of the element body and connected to the internal electrode,
The terminal electrode has a baked electrode layer formed on the end surface, and a plating layer formed on the baked electrode layer,
The internal electrode has a lead portion that is exposed to the central region of the end face and connected to the baking electrode layer;
A multilayer electronic component, wherein a width of the lead portion is set to 100 to 180 μm. The element body includes an inner layer portion in which the internal electrode is disposed, and an outer layer portion disposed so as to sandwich the inner layer portion,
2. The stacked electron according to claim 1, wherein a radius of curvature of a ridge line portion formed by the end surface and a side surface adjacent to the end surface is set to 1.2 times or less of a thickness of the outer layer portion. parts. 3. The multilayer electronic component according to claim 1, wherein a radius of curvature of a ridge line portion formed by the end surface and a side surface adjacent to the end surface is set to 90 μm or more.

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