JP2014187317A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer ceramic capacitor that allows preventing acoustic noise by a configuration of a multilayer ceramic capacitor itself.SOLUTION: A laminated body 11 is formed by bonding a ceramic dielectric element body 12, which includes dielectric layers 12k and internal electrodes 13 and 15 disposed along primary surfaces of the dielectric layers 12k that are stacked on one another, and an insulating substrate 18. External electrodes 14 and 16 cover end surfaces 11s and 11t of the laminated body 11, and are connected to the internal electrodes 13 and 15. A multilayer ceramic capacitor 10 is mounted on a circuit board with the substrate 18 being faced to a mounting surface of the circuit board.

Description

  The present invention relates to a multilayer ceramic capacitor.

  In recent years, downsizing and high performance of electronic devices are rapidly progressing, and the capacity of multilayer ceramic capacitors is increasing correspondingly. High dielectric constant ceramics such as barium titanate are used as dielectric ceramic materials for large-capacity multilayer ceramic capacitors. These high dielectric constant ceramics have piezoelectricity and electrostrictive properties. For this reason, when the ceramic body is composed of high dielectric constant ceramics, mechanical distortion occurs with application of voltage (electric field). Therefore, when an AC voltage or a DC voltage on which an AC component is superimposed is applied to this type of multilayer ceramic capacitor, vibration due to mechanical distortion occurs in the ceramic body. When the vibration is transmitted to the circuit board, the circuit board vibrates. When the vibration sound generated by the vibration of the circuit board is in the audible frequency range of 20 Hz to 20 kHz, it can be heard by the human ear as an unpleasant sound. This pronunciation phenomenon is called “acoustic noise”.

  Various proposals have been made to prevent and reduce such “squeal”.

  For example, Patent Document 1 proposes that ceramic capacitors 1A and 1B having the same specifications are arranged on the front surface 2a and the back surface 2b of the circuit board 2 so as to be plane-symmetric as shown in FIG. In this technique, the vibration transmitted from one capacitor to the circuit board and the vibration transmitted from the other capacitor to the circuit board cancel each other, thereby reducing the occurrence of squealing.

JP 2000-23320 A

  However, in the mounting form described in Patent Document 1, since it is necessary to mount two monolithic ceramic capacitors of equivalent specifications on the front and back surfaces of the circuit board, there is a problem that the degree of freedom in designing the circuit board is lost. .

  In view of such circumstances, the present invention intends to provide a multilayer ceramic capacitor capable of suppressing noise by the configuration of the multilayer ceramic capacitor itself.

  In order to solve the above problems, the present invention provides a multilayer ceramic capacitor configured as follows.

  The multilayer ceramic capacitor includes a multilayer body, a first external electrode, and a second external electrode. The laminate includes a ceramic dielectric element and an insulating substrate. The ceramic dielectric body includes: (a) a dielectric layer composed mainly of dielectric ceramics, and (b) a first end face of the dielectric layer disposed along a main surface of the dielectric layer. And (c) a second internal electrode disposed along the main surface of the dielectric layer and extending to the second end surface of the dielectric layer. In the multilayer body, the one-side main surface in the stacking direction of the ceramic dielectric element body and the one main surface of the substrate are joined. The first external electrode covers the first end surface of the multilayer body including the first end surface of the dielectric layer, and is connected to the first internal electrode. The second external electrode covers the second end surface of the multilayer body including the second end surface of the dielectric layer, and is connected to the second internal electrode.

  In the above configuration, the dielectric layer mainly composed of the dielectric ceramic has a piezoelectric effect. Therefore, when a voltage is applied between the first and second internal electrodes, the dielectric layer is deformed, and the ceramic dielectric body. Distortion occurs. When the applied voltage varies, the distortion of the ceramic dielectric element varies. A phenomenon called “squeal” is more likely to occur as the vibration of distortion transmitted to the circuit board on which the multilayer ceramic capacitor is mounted increases.

  According to the above configuration, since the Young's modulus of the substrate is higher than the Young's modulus of the ceramic dielectric body, mounting the multilayer ceramic capacitor so that the substrate faces the mounting surface of the circuit board causes distortion of the ceramic dielectric body. Vibration is less likely to be transmitted to the circuit board. Therefore, squeal can be suppressed.

  Further, the strain increases at the central portion on the first and second end faces of the ceramic dielectric element. When the multilayer ceramic capacitor is mounted so that the substrate faces the mounting surface of the circuit board, the solder fillet is at a position higher than the circuit board by the thickness of the board. It becomes difficult to wet up to the center of the second end face, and distortion vibration of the ceramic dielectric element is less likely to be transmitted to the circuit board. Therefore, squeal can be suppressed.

  Preferably, the substrate is an alumina substrate.

  The alumina substrate has a high hardness and the stress of the dielectric layer is not easily transmitted to the substrate. In addition, when firing, the shape is difficult to shrink, the shape is stable, and the dielectric layer can be fired at the same time, and the adhesiveness to the dielectric layer is excellent.

  The present invention also provides a multilayer ceramic capacitor mounting structure configured as follows.

  In a multilayer ceramic capacitor mounting structure, a multilayer ceramic capacitor is mounted on a circuit board. The circuit board has a mounting surface on which first and second lands are formed. The multilayer ceramic capacitor includes a multilayer body, a first external electrode, and a second external electrode. The laminate includes a ceramic dielectric element and an insulating substrate. The ceramic dielectric body includes: (a) a dielectric layer composed mainly of dielectric ceramics, and (b) a first end face of the dielectric layer disposed along a main surface of the dielectric layer. And (c) a second internal electrode disposed along the main surface of the dielectric layer and extending to the second end surface of the dielectric layer. In the multilayer body, the one-side main surface in the stacking direction of the ceramic dielectric element body and the one main surface of the substrate are joined. The first external electrode covers the first end surface of the multilayer body including the first end surface of the dielectric layer, and is connected to the first internal electrode. The second external electrode covers the second end surface of the multilayer body including the second end surface of the dielectric layer, and is connected to the second internal electrode. The first external electrode is bonded to the first land and the second external electrode is bonded to the second land in a state where the substrate of the laminated body faces the mounting surface of the circuit board. Has been.

  According to the above configuration, squealing can be suppressed by mounting the multilayer ceramic capacitor so that the substrate faces the mounting surface of the circuit board.

  The present invention also provides a method for manufacturing a multilayer ceramic capacitor configured as follows.

  The method for manufacturing a multilayer ceramic capacitor includes (i) a first step of preparing an insulating substrate, and (ii) applying an insulating photosensitive paste containing a dielectric ceramic to one main surface side of the substrate. Then, an operation of forming a dielectric layer by exposure and development, and an operation of forming an internal electrode layer by applying a conductive photosensitive paste to the one main surface side of the substrate, and then exposing and developing. The main surface on one side in the stacking direction of the multilayer element including the dielectric layers stacked on each other and the internal electrode layer disposed along the main surface of the dielectric layer, and the substrate A second step of forming a laminate in which one main surface is bonded; and (iii) a third step of firing the laminate and sintering the dielectric ceramic.

  By the above method, the multilayer body of the multilayer ceramic capacitor of the present invention can be efficiently produced.

  The present invention also provides a method for manufacturing a multilayer ceramic capacitor configured as follows.

  The method for manufacturing a multilayer ceramic capacitor includes: (i) a first step of preparing an insulating substrate; (ii) unfired ceramic green sheets laminated together and a main surface of the unfired ceramic green sheet. A second step of forming a laminate in which one side main surface in the stacking direction of the laminate element including the formed internal electrode and one main surface of the substrate are joined, and (iii) firing the laminate A third step of sintering the green ceramic green sheet.

  By the above method, the multilayer body of the multilayer ceramic capacitor of the present invention can be efficiently produced.

  According to the present invention, noise can be suppressed by the configuration of the multilayer ceramic capacitor itself.

It is a perspective view which shows the mounting structure of a multilayer ceramic capacitor. Example 1 It is sectional drawing of a multilayer ceramic capacitor. Example 1 It is sectional drawing which shows the manufacturing process of a multilayer ceramic capacitor. Example 1 It is sectional drawing which shows the manufacturing process of a multilayer ceramic capacitor. Example 1 It is a flowchart which shows the manufacturing process of a multilayer ceramic capacitor. Example 1 It is a flowchart which shows the manufacturing process of a multilayer ceramic capacitor. (Modification 1) It is explanatory drawing of the measuring method of a sound pressure level. (Experimental example 1) It is sectional drawing which shows the mounting structure of a multilayer ceramic capacitor. (Conventional example 1)

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  Example 1 A multilayer ceramic capacitor 10 and a mounting structure 20 of Example 1 showing an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a perspective view showing a mounting structure 20 in which a multilayer ceramic capacitor 10 is bonded to a circuit board 22. FIG. 2 is a cross-sectional view showing a cross section of the multilayer ceramic capacitor 10 taken along line AA in FIG.

  As shown in FIG. 2, the multilayer ceramic capacitor 10 includes a multilayer body 11 in which a ceramic dielectric body 12 and a substrate 18 are joined, and first and second external electrodes 14 and 16.

  In the ceramic dielectric body 12, dielectric layers 12k laminated together are integrally laminated, and first and second internal electrodes 13, 15 are arranged along the main surface of the dielectric layer 12k. The first internal electrode 13 extends to the first end face 12i of the dielectric layer 12k. The second inner electrode 15 extends to the second end face 12j of the dielectric layer 12k.

  As shown in FIGS. 1 and 2, the ceramic dielectric body 12 is formed in a rectangular parallelepiped shape, the main surfaces 12a and 12b on both sides in the stacking direction (vertical direction in the figure) of the dielectric layer 12k, and the first and second End surfaces 12s and 12t, and first and second side surfaces. The substrate 18 is also formed in a rectangular parallelepiped shape, and has first and second main surfaces 18a and 18b, first and second end surfaces 18s and 18t, and first and second side surfaces.

  As shown in FIG. 2, in the multilayer body 11, the second main surface 12 b of the ceramic dielectric body 12 and the first main surface 18 a of the substrate 18 are joined. The first end face 12 s of the ceramic dielectric body 12 and the first end face 18 s of the substrate 18 are aligned so as to be included in the same plane, thereby forming the first end face 11 s of the multilayer body 11. The second end face 12t of the ceramic dielectric body 12 and the second end face 18t of the substrate 18 are aligned so as to be included in the same plane, thereby forming the second end face 11t of the multilayer body 11.

  The first external electrode 14 covers the first end face 11 s of the multilayer body 11 and the vicinity thereof, and is connected to the first internal electrode 13. The second external electrode 16 covers the second end surface 11 t of the multilayer body 11 and the vicinity thereof, and is connected to the second internal electrode 15.

The main component of the dielectric layer 12k is BaTiO ₃ which is a dielectric ceramic. The main component may be CaTiO ₃ , SrTiO ₃ , CaZrO ₃ or the like. Further, a Mn compound, Mg compound, Si compound, Co compound, Ni compound, rare earth compound, or the like may be added as a subcomponent of the ceramic powder.

  The first and second internal electrodes 13 and 15 are, for example, Ni, Cu, Ag, Pd, an Ag—Pd alloy, Au, or the like.

  The first and second external electrodes 14 and 16 include, for example, a sintered metal layer and a plating layer, and the sintered metal layer is baked with a paste such as Cu, Ni, Ag, Pd, Ag-Pd alloy, Au, or the like. Is formed. A plated layer is formed on the sintered metal layer. For example, an Sn plated layer is formed on the Ni plated layer. The plating layer may be a Cu plating layer or an Au plating layer. Note that the first and second external electrodes 14 and 16 may have only a plated layer without a sintered metal layer.

  The board | substrate 18 should just have insulation, for example, is an alumina substrate.

  As shown in FIG. 1, the multilayer ceramic capacitor 10 is mounted on a circuit board 22. The circuit board 22 has a mounting surface 22s on which the first and second lands 24 and 26 are formed. The first and second external electrodes 14 and 16 of the multilayer ceramic capacitor 10 are bonded to the first and second lands 24 and 26 of the circuit board 22 via bonding materials (not shown), respectively. At this time, the substrate 18 of the multilayer ceramic capacitor 10 faces the mounting surface 22 s of the circuit substrate 22.

  For example, the multilayer ceramic capacitor 10 is mounted on the first and second lands 24 and 26 to which a conductive adhesive or solder paste as a bonding material is previously applied by a method such as screen printing, and then passed through a reflow furnace. . Thereby, a fillet is formed, and the multilayer ceramic capacitor 10 is fixed to the circuit board 22.

  Since the dielectric layer 12k containing the dielectric ceramic as a main component has a piezoelectric effect, when a voltage is applied between the first and second internal electrodes 13 and 15, the dielectric layer 12k is deformed, and the ceramic dielectric The body 12 is distorted. When the applied voltage varies, the distortion of the ceramic dielectric element 12 varies. The phenomenon called squeal is more likely to occur as the strain vibration transmitted to the circuit board on which the multilayer ceramic capacitor is mounted increases.

  Since the Young's modulus of the substrate 18 is higher than the Young's modulus of the ceramic dielectric element 12, if the multilayer ceramic capacitor 10 is mounted so that the substrate 18 faces the mounting surface 22 s of the circuit board 22, the distortion of the ceramic dielectric element 12 is reduced. Is difficult to be transmitted to the circuit board 22. Therefore, squeal can be suppressed.

  Further, in the first and second end faces 12 s and 12 t of the ceramic dielectric body 12, the strain becomes large at the center portion. When the multilayer ceramic capacitor 10 is mounted so that the substrate 18 faces the mounting surface 22 s of the circuit board 22, the solder fillet is unlikely to wet up to the central portions of the first and second end surfaces 12 s and 21 t of the ceramic dielectric body 12. Therefore, the distortion vibration of the ceramic dielectric body 12 is not easily transmitted to the circuit board 22. Therefore, squeal can be suppressed.

  When an alumina substrate is used as the substrate 18, the alumina substrate has a high hardness, so that distortion vibration is not easily transmitted to the circuit substrate. In addition, the shape is stable, it can be fired simultaneously with the dielectric layer, and the adhesiveness with the dielectric layer is excellent.

  Next, a process for manufacturing the multilayer ceramic capacitor 10 will be described with reference to FIGS. 3 and 4 are cross-sectional views showing the manufacturing process of the multilayer ceramic capacitor 10. FIG. 5 is a flowchart showing manufacturing steps of the multilayer ceramic capacitor 10.

  (Process 0) First, as shown to Fig.3 (a), the board | substrate 18 which has insulation is prepared (step S10).

  (Step 1) Next, as shown in FIG. 3B, a slurry containing a dielectric ceramic, which is a photosensitive slurry, is applied to the entire surface of the substrate, and then the dielectric slurry is dried and cured by exposure. Thus, a dielectric layer is formed (step S20).

  (Step 2) Next, as shown in FIG. 3C, an internal electrode paste, which is a conductive photosensitive slurry, is applied over the entire surface of the dielectric layer and dried (step S30).

  (Step 3) Next, as shown in FIG. 3D, exposure is performed through a mask 14k in which light is applied to a portion serving as an internal electrode (step S32).

  (Step 4) Next, as shown in FIG. 3 (e), development is performed by sprinkling a developer, and the conductive photosensitive slurry other than the portion that becomes the internal electrode is removed to form the internal electrode (step S34). ).

  (Step 5) Next, by repeating the above steps 1 to 4, a mother block is formed in which the assembly of the substrate and the assembly of the ceramic dielectric bodies in which the internal electrodes and the dielectric layers are laminated are joined ( Step S50).

  (Step 6) Next, the mother block is pressed in the stacking direction (step S52).

  (Step 7) Next, the mother block is divided into chip-like laminates so that the internal electrodes are exposed (step S54).

  (Step 8) Next, the laminate is fired (step S56).

  (Step 8) Next, an external electrode is formed on the end face where the internal electrode of the laminate is exposed, and sintered to form a sintered metal layer on the end face (step S58).

  (Step 9) Next, Ni plating and Sn plating are performed on the sintered metal layer (step S60).

  Through the above steps, the multilayer ceramic capacitor 10 shown in FIG. 1 is completed (step S62).

  <Modification 1> The manufacturing process of Modification 1 for manufacturing the multilayer ceramic capacitor 10 using a ceramic green sheet will be described with reference to the flowchart of FIG.

  (Step 0) First, an insulating substrate is prepared (step S10).

  (Step 1) Next, a ceramic green sheet is prepared, and an internal electrode is formed on a part of the ceramic green sheet by a method such as applying a conductive paste by screen printing (step 40).

  (Step 3) Next, a laminated body in which the ceramic dielectric body and the substrate are joined is formed (step S50). For example, a ceramic green sheet in which internal electrodes are formed in a matrix is laminated on a substrate aggregate, and then a ceramic green sheet in which no internal electrodes are formed is laminated, thereby forming a ceramic dielectric element aggregate. Form. Alternatively, only a ceramic dielectric element assembly is produced by laminating ceramic green sheets in an appropriate order, and then a mother block is formed by bonding the ceramic dielectric element assembly and the substrate assembly together. May be. When bonding, an adhesive may be applied between the ceramic dielectric element assembly and the substrate assembly.

  (Step 4) Next, the mother block is pressed in the stacking direction (step S52).

  (Step 5) Next, the mother block is fired (step S53). By integrally firing the ceramic dielectric body and the substrate, the adhesion between the substrate and the ceramic dielectric body is increased.

  (Step 6) Next, the fired laminate is divided into chip-like laminates so that the internal electrodes are exposed on the end faces (step S55).

  (Step 6) Next, the end face from which the internal electrode is exposed is immersed in a conductive paste, dried, and then sintered to form a sintered metal layer on the end face (step S58).

  (Step 7) Next, Ni plating and Sn plating are applied to the sintered metal layer (step 60).

  Through the above steps, the multilayer ceramic capacitor 10 shown in FIG. 1 is completed (step S62).

  The ceramic green sheet is easily contracted during firing, and the position of the internal electrodes formed on vertical and horizontal straight lines (matrix shape) varies within the mother block due to the contraction. When the mother block is divided into chip-shaped laminates, it is cut with a straight cutting blade. However, if the internal electrode fluctuates in the mother block, the internal electrodes are exposed from the laminate or laminated with the internal electrodes. The distance between body surfaces cannot be kept above a certain level. However, after the manufacturing process of the present invention, the alumina substrate and the ceramic dielectric body on the alumina substrate are integrated, and the alumina substrate is unlikely to shrink, so the position of the internal electrode is unlikely to fluctuate within the mother block. There is an effect.

  <Experimental Example> An experimental example in which the squeal of the circuit board 22 on which the multilayer ceramic capacitor 10 is mounted will be described with reference to the explanatory diagram of FIG.

  As shown in FIG. 9, a sample 28 having a multilayer ceramic capacitor 10 mounted on a circuit board 22 is prepared, the sample 28 is placed in an anechoic box 72, and an AC voltage having a frequency of 3 kHz and a voltage of 1 Vp-p. Was applied to the multilayer ceramic capacitor 10. The sound collecting microphone 74 was disposed so as to face the circuit board 22 and collected, and the collected sound pressure level was measured using the sound collecting device 76 and the FFT analyzer 78.

  For the sample 28, a solder paste is applied onto the lands 24 and 26 formed on the mounting surface 22 s of the circuit board 22, the multilayer ceramic capacitor 10 is mounted, and then passed through a reflow furnace so that the multilayer ceramic capacitor 10 is connected to the circuit board 22. It was prepared by adhering to.

  As a sample of Example 1, a ceramic dielectric element having a length (dimension between end faces) of 1.0 mm, a width (dimension between side faces) of 0.5 mm, and a thickness (dimension between main faces) of 0.5 mm; A laminated ceramic conde having an external electrode formed by joining an alumina substrate having a thickness (dimension between main surfaces) of 0.1 mm was prepared. As a sample of Comparative Example 1, a multilayer ceramic capacitor in which an external electrode was formed only on a ceramic dielectric body having the same dimensions as the ceramic dielectric body of the sample of Example 1 and no alumina substrate was prepared. Here, in the sample of Example 1, the solder fillet did not wet up to the center of the first and second end faces of the ceramic dielectric body.

  As a result of measuring the sound pressure level for the circuit board on which the sample of Example 1 was mounted and the circuit board on which the sample of Comparative Example 1 was mounted, the sound pressure level of the circuit board on which the sample of Example 1 was mounted Was lower than the sound pressure level of the circuit board on which the sample of Comparative Example 1 was mounted.

    As described above, the multilayer ceramic capacitor to which the substrate is bonded can suppress squeal by the configuration of the multilayer ceramic capacitor itself.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications.

DESCRIPTION OF SYMBOLS 10 Multilayer ceramic capacitor 11 Laminated body 11s 1st end surface 11t 2nd end surface 12 Ceramic dielectric element 12a 1st main surface 12b 2nd main surface 12i 1st end surface 12j 2nd end surface 12k Dielectric layer 12m 1st 1 side surface 12n second side surface 12s first end surface 12t second end surface 13 first internal electrode 14 first external electrode 15 second internal electrode 16 second external electrode 18 substrate 18a first main surface 18b Second main surface 18s First end surface 18t Second end surface 20 Mounting structure 22 Circuit board 22s Mounting surface 24 First land 26 Second land

Claims (5)

A dielectric layer comprising dielectric ceramics as a main component and laminated with each other; a first internal electrode disposed along a main surface of the dielectric layer and extending to a first end surface of the dielectric layer; and the dielectric A ceramic dielectric element including a second internal electrode disposed along a main surface of the body layer and extending to a second end face of the dielectric layer; and an insulating substrate, the ceramic dielectric element A laminated body in which the one-side principal surface of the body and the one principal surface of the substrate are joined;
A first external electrode that covers the first end face of the laminate including the first end face of the dielectric layer and is connected to the first internal electrode;
A second external electrode covering the second end surface of the laminate including the second end surface of the dielectric layer and connected to the second internal electrode;
A multilayer ceramic capacitor comprising:   The multilayer ceramic capacitor according to claim 1, wherein the substrate is an alumina substrate. In a multilayer ceramic capacitor mounting structure in which a multilayer ceramic capacitor is mounted on a circuit board,
The circuit board has a mounting surface on which first and second lands are formed,
The laminate is
A dielectric layer comprising dielectric ceramics as a main component and laminated with each other; a first internal electrode disposed along a main surface of the dielectric layer and extending to a first end surface of the dielectric layer; and the dielectric A ceramic dielectric element including a second internal electrode disposed along a main surface of the body layer and extending to a second end face of the dielectric layer; and an insulating substrate, the ceramic dielectric element A joined body in which the one-side principal surface of the body and the one principal surface of the substrate are joined;
A first external electrode that covers the first end face of the laminate including the first end face of the dielectric layer and is connected to the first internal electrode;
A second external electrode covering the second end surface of the laminate including the second end surface of the dielectric layer and connected to the second internal electrode;
With
The first external electrode is bonded to the first land and the second external electrode is bonded to the second land in a state where the substrate of the laminated body faces the mounting surface of the circuit board. A multilayer ceramic capacitor mounting structure, wherein A first step of preparing an insulating substrate;
After applying an insulating photosensitive paste containing a dielectric ceramic on one main surface side of the substrate, exposure and development to form a dielectric layer, and conducting on the one main surface side of the substrate After the photosensitive photosensitive paste is applied, it is disposed along the main surface of the dielectric layer and the dielectric layer laminated together by repeating the operations of exposing and developing to form an internal electrode layer. A second step of forming a laminated body in which a main surface on one side in a stacking direction of a multilayer element including the internal electrode layer and the one main surface of the substrate are joined;
A third step of firing the laminate and sintering the dielectric ceramic;
A method for producing a multilayer ceramic capacitor, comprising: A first step of preparing an insulating substrate;
One side main surface of the ceramic dielectric body in the stacking direction, including unfired ceramic green sheets laminated together and internal electrodes arranged along the main surface of the green ceramic green sheet, and one main surface of the substrate A second step of forming a laminated body in which
A third step of firing the laminate and sintering the green ceramic green sheet;
A method for producing a multilayer ceramic capacitor, comprising:

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