JP2012209506A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor that suppresses delamination.SOLUTION: A capacitor 1 includes: a stack 2 in which a plurality of dielectric layers 5 are stacked; first internal electrodes 3a and second internal electrodes 3b disposed between the dielectric layers 5 so as to be opposite via the dielectric layers 5; and a first external electrode 4a and a second external electrode 4b electrically connected to the first internal electrodes 3a and the second internal electrodes 3b, respectively. In a section perpendicular to the arrangement direction of the first external electrode 4a and the second external electrode 4b, there are more voids 6 between the first internal electrodes 3a and second internal electrodes 3b and side surfaces of the stack 2 to reduce a residual stress in a direction perpendicular to the stack direction of the dielectric layers 5. This can suppress delamination between the dielectric layers 5 and the internal electrodes 3 even in the event of an external impact on the capacitor 1.

Description

  The present invention relates to a capacitor.

  Generally, a capacitor is provided on both end surfaces of a laminate in which a plurality of dielectric layers are laminated, an internal electrode provided between the dielectric layers of the laminate, and an internal electrode. External electrodes (see Patent Document 1).

JP 2009-146732 A

  A capacitor as shown in Patent Document 1 is manufactured by laminating a green sheet as a dielectric layer and an electrode paste as an internal electrode to obtain a molded body, and then sintering this. However, in general, the internal electrode has a faster sintering shrinkage than the dielectric layer. Therefore, in the capacitor as shown in Patent Document 1, the dielectric layer is pulled in the direction in which the internal electrode contracts due to sintering. In particular, the internal electrode tends to shrink greatly in a direction perpendicular to the stacking direction. Therefore, the dielectric layer is likely to generate residual stress in the direction perpendicular to the stacking direction due to the internal electrodes. Therefore, there is a problem that delamination is easily caused when an external impact is applied to the capacitor in which such residual stress is generated.

  The capacitor of the present invention includes a laminate in which a plurality of dielectric layers are laminated, a first internal electrode and a second internal electrode provided between the dielectric layers so as to face each other via the dielectric layer, A first external electrode and a second external electrode electrically connected to the first internal electrode and the second internal electrode, respectively, in a cross section perpendicular to the arrangement direction of the first external electrode and the second external electrode; In addition, there are many voids between the first internal electrode and the second internal electrode and the side surface of the multilayer body.

  According to the capacitor of the present invention, a laminated body in which a plurality of dielectric layers are laminated, a first internal electrode and a second internal electrode provided between the dielectric layers so as to face each other through the dielectric layer, A first external electrode and a second external electrode electrically connected to the first internal electrode and the second internal electrode, respectively, in a cross section perpendicular to the arrangement direction of the first external electrode and the second external electrode, Since there are many voids between the electrode and the second internal electrode and the side surface of the laminated body, even if the dielectric layer receives a tensile force due to sintering shrinkage of the internal electrode, To ease. Therefore, the residual stress in the direction perpendicular to the stacking direction in the dielectric layer is reduced. Therefore, even when the capacitor receives an impact from the outside, it is possible to suppress the occurrence of delamination between the dielectric layer and the internal electrode.

It is a perspective view which shows an example of embodiment of the capacitor | condenser of this invention. (A) is sectional drawing in the AA line of the capacitor | condenser shown in FIG. 1, (b) is sectional drawing in the BB line of the capacitor | condenser shown in FIG. It is a cross-sectional view of the capacitor shown in FIG.

  Hereinafter, an example of an embodiment of a capacitor of the present invention will be described in detail with reference to the drawings. A capacitor 1 shown in FIG. 1 includes a multilayer body 2, an internal electrode 3, and an external electrode 4 as a basic configuration.

  The laminate 2 is formed by laminating a plurality of dielectric layers 5. This laminated body 2 is a rectangular parallelepiped dielectric block formed by laminating, for example, 20 to 2000 layers of a plurality of rectangular dielectric layers 5 formed to have a thickness of 1 to 5 μm per layer, for example.

Moreover, the dimension of the laminated body 2 makes the length of the long side of the laminated body 2 0.4-3.2 mm, for example, and makes the length of the short side of the laminated body 0.2-1.6 mm, for example. Examples of the material for the dielectric layer 5 include BaTiO ₃ , CaTiO ₃ , SrTiO _{3, and} CaZrO ₃ . As another _example, BaTiO _3, CaTiO 3, and SrTiO ₃ or CaZrO ₃ as a main component, Mn compound, Fe compound, Cr compounds, Co compounds, or may be Ni compound or the like is added .

  As shown in FIGS. 1 to 3, the laminate 2 includes a first main surface 2 a (upper surface) and a second main surface (lower surface) 2 b that face each other, and a first side surface 2 c and a second surface that face each other. The side surface 2d is formed in a substantially rectangular parallelepiped shape having a first end surface 2e and a second end surface 2f facing each other.

  As shown in FIG. 3, the first external electrode 4a and the second external electrode 4b are connected to the first internal electrode 3a and the second internal electrode 3b, respectively. The first external electrode 4 a and the second external electrode 4 b are provided on the surface of the multilayer body 2. In the following description, when the term “external electrode 4” is simply used, it means both the first external electrode 4a and the second external electrode 4b.

  In the example shown in FIG. 3, the first external electrode 4 a and the second external electrode 4 b are provided at the end of the multilayer body 2. The external electrode 4 has a thickness of 5 to 50 μm. The external electrode 4 is electrically connected to an electrode pad on the wiring board and plays a role of ensuring electrical continuity with the wiring board.

  As shown in FIG. 3, the first external electrode 4a is formed on the second end face 2f. As shown in FIG. 1, the end of the first external electrode 4a reaches the first and second main surfaces 2a and 2b and the first and second side surfaces 2c and 2d. As shown in FIG. 3, the first external electrode 4a is electrically connected to each of the plurality of first internal electrodes 3a drawn to the second end face 2f.

  As shown in FIG. 3, the second external electrode 4b is formed on the first end face 2e. As shown in FIG. 1, the end of the second external electrode 4b reaches the first and second main surfaces 2a and 2b and the first and second side surfaces 2c and 2d. As shown in FIG. 3, the second external electrode 4b is electrically connected to each of the plurality of second internal electrodes 3b drawn to the first end face 2e.

  For example, one or a plurality of plating films such as a Ni plating film and a Sn plating film may be formed on the surface of the external electrode 4 in order to protect the external electrode 4 and improve mountability. preferable. For example, a laminate of a Ni plating film and a Sn plating film may be formed on the surface of the external electrode 4.

The method for bonding the external electrode 4 to the wiring board is not particularly limited. For example, high temperature solder such as Sn—Sb high temperature solder, Sb—Pb eutectic solder, Sn—Ag—Cu Pb free solder, Sn
The external electrode 4 and the wiring board can be bonded using an appropriate bonding member such as a Cu-based Pb-free solder or a resin containing conductive fine particles.

  The first internal electrode 3a and the second internal electrode 3b are provided between the dielectric layers 5 so as to face each other with the dielectric layer 5 interposed therebetween. In the following description, the expression “internal electrode 3” simply means both the first internal electrode 3a and the second internal electrode 3b.

  In the example illustrated in FIG. 3, a plurality of first internal electrodes 3 a and a plurality of second internal electrodes 3 b are alternately arranged in the stacked body 2 along the stacking direction. Thereby, the plurality of first internal electrodes 3a and the plurality of second internal electrodes 3b are insulated from each other.

  As shown in FIGS. 2A and 3, one end of the plurality of first internal electrodes 3 a is drawn out to the second end face 2 f. The plurality of first internal electrodes 3a are arranged at equal intervals in the stacking direction of the capacitor 1 so as to extend in a direction parallel to the first and second main surfaces 2a, 2b. The first internal electrode 3a does not reach the first and second side surfaces 2c and 2d.

  As shown in FIG. 3, one end of the plurality of second internal electrodes 3b is drawn out to the first end face 2e. The plurality of second internal electrodes 3b are arranged at equal intervals in the stacking direction of the capacitor 1 so as to extend in a direction parallel to the first and second main surfaces 2a, 2b. The second internal electrode 3b does not reach the first and second side surfaces 2c and 2d.

  The internal electrode 3 is formed between 20 and 2000 layers between the dielectric layers 5 of the laminate 2. Examples of the material of the internal electrode 3 include metals such as Ni, Cu, Ag, Pd, and Au, or alloys such as an Ag—Pd alloy containing one or more of these metals. All the internal electrodes 3 are preferably formed of the same metal or alloy.

  The overall dimensions of the internal electrode 3 are, for example, 0.39 to 3.1 mm in the long side direction of the multilayer body 2 in FIG. 2A, and are 0.19 to 1.5 mm, for example, in the short side direction of the multilayer body 2. The thickness of the internal electrode 3 is not particularly limited. The thickness of the internal electrode 3 may be, for example, about 0.3 to 2 μm.

  2B, in the cross section perpendicular to the arrangement direction of the first external electrode 4a and the second external electrode 4b, the first internal electrode 3a, the second internal electrode 3b, and the side surface of the multilayer body 2 There are many holes 6 between 2c and 2d. With such a configuration, even if the dielectric layer 5 receives a tensile force due to the sintering shrinkage of the internal electrode 3, the holes 6 relieve this force. Therefore, the residual stress in the direction perpendicular to the stacking direction in the dielectric layer 5 is reduced. Therefore, even when the capacitor 1 receives an impact from the outside, the occurrence of delamination between the dielectric layer 5 and the internal electrode 3 can be suppressed.

  Here, “there are many vacancies 6” means that the porosity between the internal electrode 3 and the side surfaces 2 c and 2 d of the multilayer body 2 in the cross section perpendicular to the arrangement direction of the external electrodes 4 It means that it is higher than the porosity between the main surfaces 2a and 2b of the laminate 2. The porosity means the area ratio occupied by the holes in the cross section perpendicular to the arrangement direction of the external electrodes 4. In addition, these areas can be measured by analyzing an image taken by an electron micrograph (SEM) after polishing a cross section as shown in FIG.

Further, the porosity of the central portion between the internal electrode 3 and the side surfaces 2 c and 2 d is preferably higher than the porosity in the vicinity of the internal electrode 3. Here, the porosity of the central portion between the internal electrode 3 and the side surfaces 2c and 2d is the distance from the end of the internal electrode 3 to the side surfaces 2c and 2d in the cross section perpendicular to the arrangement direction of the external electrodes 4. Means the area ratio occupied by the vacancies in the middle divided region. Further, the porosity in the vicinity of the internal electrode 3 means the area ratio occupied by the voids in the divided region on the internal electrode 3 side. The distance from the end of the internal electrode 3 to the side surfaces 2c and 2d is generally about 30 to 100 μm. The diameter of the holes 6 is about 0.1 to 1 μm.

  Specifically, the porosity of the central portion between the internal electrode 3 and the side surfaces 2c and 2d is about 15 to 30%, and the porosity in the vicinity of the internal electrode 3 is about 1 to 5%. is there. Thereby, since there are not many vacancies 6 in the vicinity of the internal electrode 3, the insulation between the internal electrodes 3 can be maintained.

  It is preferable that the porosity is even lower at a predetermined interval from the end of the internal electrode 3 in the divided region on the internal electrode 3 side. Specifically, it is about 0.5 to 2.5%. The predetermined interval is an interval of about 1/3 to 1/2 of the divided region on the internal electrode 3 side.

  Moreover, it is preferable that the porosity of the center part between the internal electrode 3 and the side surfaces 2c and 2d is higher than the porosity in the vicinity of the side surfaces 2c and 2d. As a result, there are not many holes 6 in the vicinity of the side surfaces 2c and 2d. Therefore, when an impact is applied to the side surfaces 2c and 2d of the laminate 2, it is possible to suppress the occurrence of cracks starting from the holes 6 in the vicinity of the side surfaces 2c and 2d. Moreover, it can suppress that a plating solution etc. penetrate | invade into the inside from the surface of a laminated body.

  Here, the porosity in the vicinity of the side surfaces 2c and 2d means the area ratio occupied by the holes in the divided region on the side surface 2c and 2d side when divided into three as described above. Specifically, the porosity of the central portion between the internal electrode 3 and the side surfaces 2c and 2d is about 15 to 30%, and the porosity in the vicinity of the side surfaces 2c and 2d is about 1 to 5%. It is.

It is preferable that the porosity is further lower at a predetermined distance from the side surfaces 2c and 2d in the divided regions on the side surfaces 2c and 2d. Specifically, it is about 0, 5 to 2.5%. The predetermined interval is an interval of about 1/3 to 1/2 of the divided region on the side surface 2c, 2d side.

  The capacitor 1 having the above configuration is manufactured by a ceramic green sheet lamination method as described below.

  Specifically, a plurality of green sheets to be the dielectric layer 5 are prepared. In this step, the ceramic green sheet is obtained by preparing a slurry-like ceramic slurry by adding and mixing a suitable organic solvent or the like to the ceramic raw material powder and the organic binder, and molding the slurry by a doctor blade method or the like. .

  Next, the internal electrode 3 is formed on the green sheet. In this step, a conductive material to be a pattern of the internal electrode 3 is formed on the obtained ceramic green sheet by screen printing or the like. In addition, the pattern of the several internal electrode 3 is printed on this one green sheet so that many capacitors can be obtained from one green sheet.

  In addition, it is good to arrange | position the ceramic slurry with less quantity of a sintering aid than a ceramic green sheet between the patterns of the internal electrode 3 and on the parting line used as the side surfaces 2c and 2d of the laminated body 2. FIG. Thereby, in this part, since sinterability falls rather than a ceramic green sheet, the density of a dielectric material does not rise and it becomes easy to produce the void | hole 6. FIG. Moreover, you may reduce sinterability by making the particle size of the ceramic raw material powder in the ceramic slurry arrange | positioned in this part larger than the ceramic raw material powder in a ceramic green sheet.

  It is assumed that the same ceramic slurry as described above is also disposed on the end side of the internal electrode 3 pattern printed on a plurality of green sheets.

  Also in the ceramic slurry described here, a desired porosity distribution can be set by changing the amount of the sintering aid and the particle size of the ceramic raw material powder.

  Next, after laminating and pressing a plurality of ceramic green sheets, a raw laminated body in which many pieces are integrated is produced. This laminated body is cut to obtain a raw body of the capacitor 1 as a single laminated body.

Next, the capacitor body 1 in a raw state is fired to obtain a laminate 2. In this step, for example, the laminate 2 is obtained by baking at 800 to 1050 ° C. By this step, the green sheet becomes the dielectric layer 6 and the conductive material becomes the internal electrode 3.

  Next, the external electrode 4 is formed by applying a conductive paste to both ends of the laminate 2 and baking it. The external electrode 4 may be formed by a thin film forming method such as vapor deposition, plating, or sputtering.

  The material of the external electrode 4 thus obtained may be a metal material such as silver, nickel, palladium, or an alloy thereof other than copper.

  Next, a plating layer such as a nickel (Ni) plating layer, a gold (Au) plating layer, a tin (Sn) plating layer, or a solder plating layer is formed on the surface of the obtained external electrode 4 as necessary. Capacitor 1 is obtained.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, the laminate 2 may be chamfered to form a rounded portion. By this step, it is possible to prevent microcracks from being removed and chipped in the rounded portion of the obtained laminate 2. Furthermore, the barrel polishing has an effect of removing the surface oxide film of the metal particles and exposing the metal surface to improve the plating adhesion.

  In addition, for example, in the vicinity of the corner between the main surfaces 2a and 2b and the side surfaces 2c and 2d of the multilayer body 2, there are more holes than between the internal electrode 3 and the main surfaces 2a and 2b of the multilayer body 2. 6 is preferably increased. As a result, the holes 6 play a role of impact relaxation in the two corners of the laminated body that is susceptible to external impact. Therefore, a capacitor having impact resistance can be obtained.

  In addition, for example, it is preferable that the number of holes 6 between the internal electrode 3 and the side surfaces 2 c and 2 d of the multilayer body 2 increase in the central portion in the arrangement direction of the external electrodes 4. The center portion means a middle region when the laminate 2 is divided into three in the arrangement direction of the external electrodes 4. The impact from the outside to the laminated body 2 tends to be most frequent in this region. Therefore, in the case of this configuration, the effect of absorbing an external impact by the air holes 6 is easily improved. Therefore, the highly durable capacitor 1 can be provided.

1: Capacitor 2: Laminate 3: Internal electrode 4: External electrode 5: Dielectric layer 6: Hole

Claims (3)

A laminate in which a plurality of dielectric layers are laminated;
A first internal electrode and a second internal electrode provided between the dielectric layers so as to face each other through the dielectric layer;
A first external electrode and a second external electrode electrically connected to the first internal electrode and the second internal electrode, respectively.
In a cross section perpendicular to the arrangement direction of the first external electrode and the second external electrode, there are many voids between the first internal electrode and the second internal electrode and the side surface of the multilayer body. Capacitor characterized by that.   The central portion between the first internal electrode and the second internal electrode and the side surface of the laminate has a higher porosity than the vicinity of the first internal electrode and the second internal electrode. The capacitor according to claim 1.   The center portion between the first internal electrode and the second internal electrode and the side surface of the multilayer body has a higher porosity than the vicinity of the side surface of the multilayer body. Item 3. The capacitor according to Item 2.

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