JP2013162006A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer ceramic capacitor capable of preventing deterioration of insulation resistance and occurrence of delamination.SOLUTION: A multilayer ceramic capacitor 10 includes a capacitor body 11. The capacitor body 11 includes: a capacitance part 11a made of an alternate laminate comprised of a plurality of internal electrode layers 13-1 to 13-n and a plurality of dielectric layers 14-1 to 14-m; a first protection part 11b1 made of a laminate of the plurality of dielectric layers and contacted with the lowermost internal electrode layer 13-1 of the capacitance part 11a; and a second protection part 11b2 made of a laminate of the plurality of dielectric layers and contacted with the uppermost internal electrode layer 13-n of the capacitance part 11a. The lowermost internal electrode layer 13-1 contacted with the first protection part 11b1 has an oxide containing a metal element forming the internal electrode layer 13-1, and is insulated.

Description

  The present invention relates to a monolithic ceramic capacitor having a capacitor portion composed of an alternating laminate of a plurality of internal electrode layers and a plurality of dielectric layers.

This type of multilayer ceramic capacitor is generally
-Step 1: A step of producing a green laminate in which a plurality of slurry layers for dielectric layers and a plurality of paste layers for internal electrode layers are stacked in a predetermined order-Step 2: cutting the green laminate Process / Step 3: Producing unfired chip corresponding to the capacitor body: Producing a fired chip by firing the unfired chip (including binder removal process) Process / Process 4: Producing an external electrode on the fired chip The manufacturing process is performed in order (see Patent Document 1).

Although various methods have been proposed for the step 1 (unfired laminate manufacturing step), in reality,
Step 1: A first laminating sheet having a dielectric layer slurry layer formed on the upper surface of the base film is prepared, and an internal electrode layer paste is formed on the upper surface of the slurry layer of the first laminating sheet. Step 2 for producing a second laminating sheet in which the layers are formed in a predetermined arrangement Step 2: The slurry layer of the first laminating sheet is punched out at a predetermined size, and the punched slurry layer is placed on the upper surface of the laminating table. Similarly, a step of repeating the operation of thermocompression bonding the punched slurry layer on the upper surface of the slurry layer on the stacking table is repeated a predetermined number of times. Step 3: The slurry layer of the second laminating sheet is punched and punched at a predetermined size A slurry layer (including a large number of paste layers on the upper surface side) is superposed on the upper surface of the thermocompression-bonded slurry layer and thermocompression bonded. Step 4: Repeat the operation for a predetermined number of times by stacking the paste layer on the top of the heat-bonded paste layer. Step 4: Stamping out the slurry layer of the first laminating sheet to a predetermined size Step 5: Repeat the work of layering the layer on the upper surface of the paste layer that has been thermocompression bonded and thermocompression bonding the same stamped layer of slurry on the surface of the slurry layer that has been thermocompression bonded. A method in which the final thermocompression bonding is performed on the thermocompression-bonded product to sequentially perform the steps of producing a green laminate is most frequently used.

  By the way, there is still a high need for miniaturization and large capacity for multilayer ceramic capacitors, and it is necessary to further reduce the thickness of the internal electrode layer and the dielectric layer in order to satisfy the needs. However, when the internal electrode layer and the dielectric layer are made thinner, for example, when the average thickness of each of the internal electrode layer and the dielectric layer becomes 1.0 μm or less, the steps 1 to 5 are performed as the step 1 (unfired laminate manufacturing step) When implemented in sequence, the following problems may appear in the multilayer ceramic capacitor.

  Steps 2 to 4 of the process 1 (unfired laminate manufacturing process) are performed by thermocompression bonding the second layer on the first layer, and the nth layer on the (n-1) th layer. Since it is a sequential stacking method in which the layers are thermocompression-bonded, the lower layer side of the unfired laminate is more susceptible to damage such as deformation according to the number of accumulated pressures than the upper layer side. As a remarkable phenomenon that occurs in the multilayer ceramic capacitor due to this damage, there is a short circuit between the lowest internal electrode layer and the second internal electrode layer from the bottom. If this phenomenon occurs, the insulation of the multilayer ceramic capacitor Resistance will deteriorate.

  In order to prevent this inconvenience, if the pressure of thermocompression bonding in steps 2 to 4 of step 1 (unfired laminate preparation step) is reduced, damage such as deformation received on the lower layer side can be prevented, but the interlayer adhesion on the upper layer side. Tends to decrease. As a remarkable phenomenon that occurs in the multilayer ceramic capacitor due to the decrease in the interlayer adhesion, there is a decrease in the bonding force between the uppermost internal electrode layer and the dielectric layer in contact with the upper surface of the internal electrode layer. When this phenomenon occurs, delamination occurs in the multilayer ceramic capacitor.

JP 2011-139028 A

  An object of the present invention is to provide a multilayer ceramic capacitor that can prevent the deterioration of insulation resistance and the occurrence of delamination.

  In order to achieve the above object, the present invention provides a capacitor unit composed of an alternating laminate of a plurality of internal electrode layers and a plurality of dielectric layers and a laminate of a plurality of dielectric layers. A multilayer ceramic capacitor comprising a capacitor body having a first protective portion in contact with the internal electrode layer and a second protective portion made of a laminate of a plurality of dielectric layers and in contact with an internal electrode on the other side of the capacitor portion in the stacking direction And at least one of the internal electrode layer on one side in the stacking direction of the capacitor unit in contact with the first protective unit and the internal electrode layer on the other side in the stacking direction of the capacitor unit in contact with the second protective unit It is characterized by having an oxide containing a metal element that forms the electrode layer and being an insulator.

  According to the present invention, at least one of the internal electrode layer on one side in the stacking direction of the capacitor unit in contact with the first protective unit and the internal electrode layer on the other side in the stacking direction of the capacitor unit in contact with the second protective unit is at least Since the oxide containing the metal element that forms the internal electrode layer is held and insulated, as a result of adopting the sequential stacking method in the green laminate manufacturing process at the time of manufacturing, the stacking of the capacitor portion Even when the internal electrode layer on one side of the direction and the internal electrode layer facing the internal electrode layer are short-circuited, the internal electrode layer on the one side in the stacking direction of the capacitor portion has lost its function as an electrode. Therefore, the insulation resistance of the multilayer ceramic capacitor does not deteriorate. In addition, as a result of adopting the sequential stacking method in the unfired laminate manufacturing process at the time of manufacture, the internal electrode layer on the other side in the stacking direction of the capacitor portion and the dielectric layer of the second protective portion in contact with the internal electrode layer Even in the case where the phenomenon of a decrease in the bonding force occurs, the decrease in the bonding force can be compensated for by the oxide held by the internal electrode layer on the other side in the stacking direction of the capacitor portion. It does not occur.

  The above object and other objects, structural features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.

1A is a longitudinal sectional view of the multilayer ceramic capacitor according to the first embodiment of the present invention; FIG. 1B is a longitudinal section along the line S1-S1 of the multilayer ceramic capacitor shown in FIG. FIG. 2 (A) to 2 (D) are explanatory views of a green laminate manufacturing process in the method for manufacturing the multilayer ceramic capacitor shown in FIGS. 1 (A) and 1 (B). 3 (A) to 3 (H) are explanatory views of a green laminate manufacturing process in the method for manufacturing the multilayer ceramic capacitor shown in FIGS. 1 (A) and 1 (B). FIG. 4 is a longitudinal sectional view corresponding to FIG. 1 (B) showing a modification of the multilayer ceramic capacitor shown in FIGS. 1 (A) and 1 (B). 5A is a longitudinal sectional view of the multilayer ceramic capacitor according to the second embodiment of the present invention; FIG. 5B is a longitudinal section along the line S2-S2 of the multilayer ceramic capacitor shown in FIG. FIG. 6 (A) to 6 (F) are explanatory diagrams of an unfired laminate manufacturing process in the method for manufacturing the multilayer ceramic capacitor shown in FIGS. 5 (A) and 5 (B). FIG. 7 is a longitudinal sectional view corresponding to FIG. 5B showing a modification of the multilayer ceramic capacitor shown in FIGS. 5A and 5B.

<< First Embodiment >>
<Structure of multilayer ceramic capacitor 10>
First, the structure of the multilayer ceramic capacitor 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 (A) and 1 (B).

  In this multilayer ceramic capacitor 10, the reference dimensions of length L, width W and height H have a relationship of length L> width W = height H, or length L> width W> height H. A substantially rectangular parallelepiped capacitor body 11 and a pair of external electrodes 12 provided at both ends in the length direction of the capacitor body 11 are provided.

  The capacitor main body 11 includes a capacitor portion 11a that contributes to capacitance formation, a first protection portion 11b1 that does not contribute to capacitance formation and contacts the lower surface of the capacitor portion 11a, and a capacitor portion 11a that does not contribute to capacitance formation. The second protection portion 11b2 is in contact with the upper surface of the second protection portion 11b2.

  The capacitor portion 11a is composed of an alternating laminate of a plurality of internal electrode layers 13-1 to 13-n and a plurality of dielectric layers 14-1 to 14-m (m = n-1). The lowest internal electrode layer 13-1 is located, and the uppermost internal electrode layer 13-n is located on the upper side in the stacking direction. The first protective part 11b1 is composed of a laminate of a plurality of dielectric layers (no reference), and the upper surface thereof is in contact with the lowest internal electrode layer 13-1 of the capacitor part 11a. The second protective part 11b2 is formed of a laminate of a plurality of dielectric layers (no reference), and the lower surface thereof is in contact with the uppermost internal electrode layer 13-n of the capacitor part 11a.

  The plurality of internal electrode layers 13-1 to 13-n constituting the capacitor portion 11a are made of a metal selected from the group of nickel, copper, and nickel-copper alloy, and the average thickness thereof is 1.0 μm or less. It is. Further, the plurality of dielectric layers 14-1 to 14-m constituting the capacitor portion 11a, the plurality of dielectric layers constituting the first protection portion 11b1, and the plurality of dielectric layers constituting the second protection portion 11b2 are: It is formed from one dielectric selected from the group of barium titanate, barium zirconate titanate, barium calcium titanate, barium calcium zirconate titanate, strontium titanate, calcium zirconate, and the average thickness is 1.0 μm or less. Incidentally, in FIGS. 1A and 1B, for convenience of illustration, n is 22 and m is 21, but the internal electrode layer 13 − in the multilayer ceramic capacitor 10 corresponding to miniaturization and large capacity is shown. The number of layers 1 to 13-n is over 100.

  Further, the plurality of internal electrode layers 13-1 to 13-n constituting the capacitor portion 11a have a substantially rectangular shape having a length and width smaller than the length and width of the capacitor body 11, and FIG. , The left edge of the odd-numbered internal electrode layers 13-1... 13- (n-1) from the bottom is electrically connected to the left external electrode 12, and the even-numbered internal electrode layers 13-2 from the bottom. ... The right edge of 13-n is electrically connected to the right external electrode 12. That is, the portion of the internal electrode layers 13-1 to 13-n that do not oppose each other in the stacking direction is used as the lead portion 13a. Therefore, the lead portion 13a does not substantially contribute to the formation of capacitance. Incidentally, although not shown, each external electrode 12 has a base layer made of nickel, copper, silver, or an alloy thereof, and a surface layer made of tin, tin-silver alloy, or the like on the surface of the base layer. It has a two-layer structure or a three-layer structure in which an intermediate layer made of nickel, copper, palladium, or the like is interposed between the base layer and the surface layer.

  Further, among the plurality of internal electrode layers 13-1 to 13-n constituting the capacitor portion 11a, the lowest internal electrode layer 13-1 in contact with the first protection portion 11b1 has at least the internal electrode layer 13-1. It contains an oxide containing a metal element to be formed and is made into an insulator. That is, the lowest internal electrode layer 13-1 among the plurality of internal electrode layers 13-1 to 13-n constituting the capacitor portion 11a is insulated and does not function as an electrode. Hereinafter, oxides held in the lowest internal electrode layer 13-1 will be described.

  As described above, since the lowest internal electrode layer 13-1 is formed of a metal selected from the group of nickel, copper, and nickel-copper alloy, for example, "lowest internal electrode layer 13-1" In the case where “the metal element forming the metal” is nickel, the “oxide containing the metal element forming the lowest internal electrode layer 13-1” is an oxide containing nickel.

  In addition, the oxide held in the lowest internal electrode layer 13-1 includes “the lowest internal electrode layer in addition to the“ oxide containing a metal element that forms the lowest internal electrode layer 13-1 ””. 13-1 may be included and an oxide including a metal element having a standard oxidation-reduction potential lower than that of the metal element ”. For example, when “the metal element forming the lowest internal electrode layer 13-1” is nickel, “the metal element having a lower standard oxidation-reduction potential than the metal element forming the lowest internal electrode layer 13-1”. In order from the lowest, lithium, cesium, rubidium, potassium, barium, strontium, calcium, sodium, magnesium, aluminum, manganese, tantalum, zinc, chromium, iron, cadmium, cobalt, etc. Is considered, at least one selected from the group of calcium, magnesium, aluminum, zinc, chromium, and cobalt is preferable. That is, “the metal element forming the lowest internal electrode layer 13-1” is nickel, and “the metal element having a lower standard oxidation-reduction potential than the metal element forming the lowest internal electrode layer 13-1” is magnesium. In this case, “an oxide containing a metal element forming the lowest internal electrode layer 13-1 and a metal element having a standard oxidation-reduction potential lower than that of the metal element” is an oxide containing nickel and magnesium.

  Furthermore, the amount of oxide held in the lowest internal electrode layer 13-1 is the case of holding “an oxide containing a metal element that forms the lowest internal electrode layer 13-1,” and “An oxide containing a metal element forming the lowest internal electrode layer 13-1” and “A metal element forming the lowest internal electrode layer 13-1 and a metal element having a lower standard oxidation-reduction potential than the metal element” Regardless of possessing “oxide containing”, it is desirable that it is 100 vol% with respect to the volume of the lowest internal electrode layer 13-1, but if it falls within the range of 70 to 100 vol%, the lowest The internal electrode layer 13-1 can be made into an insulator.

<Method for Manufacturing Multilayer Ceramic Capacitor 10>
Next, referring to FIG. 2A to FIG. 2D and FIG. 3A to FIG. 3H, the multilayer ceramic capacitor 10, specifically, the capacitance portion 11 a is configured. The plurality of internal electrode layers 13-1 to 13-n are made of nickel, and the plurality of dielectric layers 14-1 to 14-m constituting the capacitor portion 11a and the plurality of dielectric layers constituting the first protection portion 11b1. And a plurality of dielectric layers constituting the second protective portion 11b2 are formed of barium titanate, and the lowest internal electrode layer 13-1 includes "oxide containing nickel" and "oxide containing nickel and magnesium". A method for manufacturing the multilayer ceramic capacitor 10 that is held and insulated will be described.

  In manufacturing, first, a first ceramic slurry, a second ceramic slurry, and an electrode paste are prepared. The first ceramic slurry includes at least barium titanate particles having a predetermined particle size distribution, a solvent, a binder, and an oxidation accelerator, and includes various additives as necessary. The second ceramic slurry includes at least barium titanate particles having the same particle size distribution, a solvent, and a binder, and various additives as necessary. Furthermore, the electrode paste includes at least nickel particles having a predetermined particle size distribution, a solvent, and a binder, and various additives as necessary.

  The solvent of the first and second ceramic slurries is made of ethanol, and the binder is made of polyvinyl butyral, acrylic resin, or the like. In addition, a dispersant can be used as various additives in the first and second ceramic slurries, and the dispersant includes a carboxylic acid-based dispersant.

  In addition, as the oxidation accelerator for the first ceramic slurry, a magnesium compound containing an oxygen element such as magnesium oxide or magnesium carbonate can be used alone, or a nickel compound containing an oxygen element such as nickel oxide or nickel carbonate can be used in combination. However, the nickel compound alone is not used here because the oxidation action described later can be sufficiently obtained with the magnesium compound alone. Incidentally, the content of the oxidation accelerator (magnesium compound) in the first ceramic slurry is preferably in the range of 11 to 15 wt%.

  The electrode paste solvent is made of terpineol or the like, and the binder is made of polyvinyl butyral or ethyl cellulose.

[Step 1 of the unfired laminate manufacturing process]
Subsequently, as shown in FIG. 2 (A), the first ceramic slurry is applied to the upper surface of the base film BF made of polyethylene terephthalate or the like by a coating machine using a doctor blade, a slit die, or the like. A thing is dried and the 1st sheet | seat for lamination | stacking in which 1st slurry layer SL1 of predetermined thickness was formed on base film BF is produced.

  Further, as shown in FIG. 2B, the second ceramic slurry is applied to the upper surface of the equivalent base film BF by the equivalent coating machine, and the applied material is dried, so that the base film BF is obtained. A second laminating sheet on which a second slurry layer SL2 having a predetermined thickness is formed is produced.

  Further, as shown in FIG. 2C, the electrode paste is printed on the upper surface of the first slurry layer SL1 of the first lamination sheet by a printing machine using a screen or an intaglio, and the printed matter is dried. Thus, a third laminating sheet in which paste layers PL having a predetermined thickness and a predetermined shape are formed in a predetermined arrangement on the first slurry layer SL1 is manufactured.

  Furthermore, as shown in FIG. 2D, the electrode paste is printed on the upper surface of the second slurry layer SL1 of the second lamination sheet by the equivalent printer, and the printed matter is dried. Then, a fourth lamination sheet is produced in which paste layers PL having a predetermined shape and a predetermined thickness are formed in a predetermined arrangement on the second slurry layer SL2.

[Step 2 of the unfired laminate manufacturing process]
Subsequently, as shown in FIGS. 3A and 3B, the first slurry layer SL1 of the first lamination sheet shown in FIG. 2A is punched out to a predetermined size and punched out. One slurry layer SL1 is sucked and transported to the flat lower surface of the suction head AH, and the first slurry layer SL1 is placed on the flat upper surface of the stacking table LT. Similarly, the punched first slurry layer SL1 is sucked and transported to the flat lower surface of the suction head AH, and the first slurry layer SL1 is stacked on the upper surface of the first slurry layer SL1 on the stacking table LT. Repeat the process of thermocompression bonding a predetermined number of times.

[Step 3 of the unfired laminate manufacturing process]
Subsequently, as shown in FIGS. 3C and 3D, the first slurry layer SL1 of the third lamination sheet shown in FIG. 2C is punched out to a predetermined size and punched out. The first slurry layer SL1 (including many paste layers PL) is sucked and conveyed on the flat lower surface of the suction head AH, and the first slurry layer SL1 is subjected to thermocompression bonding. The operation of thermocompression bonding over the upper surface of the layer SL1 is performed once. Then, as shown in FIGS. 3 (E) and 3 (F), the second slurry layer SL2 of the fourth lamination sheet shown in FIG. The slurry layer SL2 (including a number of paste layers PL) is transported by sucking and transporting the paste layer PL side to the flat lower surface of the suction head AH, and the upper surface of the paste layer PL having undergone thermocompression bonding. Repeat the process of thermocompression bonding over a predetermined number of times.

[Step 4 of the unfired laminate manufacturing process]
Subsequently, as shown in FIGS. 3 (G) and 3 (H), the second slurry layer SL2 of the second lamination sheet shown in FIG. The second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 is superimposed on the upper surface of the heat-pressed paste layer PL and thermocompression bonded. Similarly, the punched second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 is stacked on the upper surface of the second slurry layer SL2 that has been thermocompression bonded. The operation of thermocompression bonding is repeated a predetermined number of times.

  Steps 2 to 4 of the green laminate manufacturing process adopt a sequential stacking method, and the conditions of thermocompression bonding in each of steps 2 to 4 are, for example, a temperature of 150 ° C. and a pressure of 10 MPa.

[Step 5 of the unfired laminate manufacturing process]
Subsequently, the thermocompression-bonded product is subjected to final thermocompression bonding with a press such as a hot isostatic press to produce an unfired laminate. Incidentally, the final thermocompression bonding conditions are, for example, a water temperature of 70 ° C. and a pressure of 2000 kg / cm ² .

[Unbaked chip manufacturing process]
Subsequently, the unfired laminate is cut into a lattice shape by a cutting machine such as a dicing device, and an unfired chip corresponding to the capacitor body 11 shown in FIGS. 1A and 1B is manufactured.

[Unfired chip firing process]
Subsequently, a large number of non-fired chips are put into a firing furnace, and fired according to a firing temperature profile having a peak temperature of about 1200 ° C. in an atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure of Ni—NiO (including binder removal treatment). )I do.

  In this firing step, each first slurry layer SL1, each second slurry layer SL2, and each paste layer PL constituting each unsintered chip are sintered, but each first slurry layer SL1 is oxidized. Since the agent (magnesium compound) is contained, the sintering of the first slurry layers SL1 is promoted, and the magnesium moves from the uppermost first slurry layer SL1 to the lowermost paste layer PL, and the uppermost slurry layer SL1. Oxidation of the lower paste layer PL is promoted. In other words, the sintered product of the lowermost paste layer PL has “an oxide containing nickel” and “an oxide containing nickel and magnesium”, whereby the sintered product of the lowermost paste layer PL is It becomes an insulator and loses its function as an electrode.

[External electrode manufacturing process]
Subsequently, an electrode paste equivalent to the above electrode paste is applied to both ends in the length direction of the baked chip by a coating machine such as a dip coating machine or a roller coating machine, and the coated material is subjected to a baking treatment, and FIG. A base layer of the external electrode 12 shown in FIGS. 1A and 1B is formed. Then, a surface layer is formed on the surface of the underlayer by a plating method such as electrolytic plating to produce the external electrode 12 having a two-layer structure. Alternatively, the intermediate layer and the surface layer are sequentially formed on the surface of the base layer by a plating method such as electrolytic plating to produce the external electrode 12 having a three-layer structure.

<Effects obtained by the multilayer ceramic capacitor 10>
Next, the effects obtained by the multilayer ceramic capacitor 10 and the verification results of the effects will be described with reference to FIG. 1 (A) and FIG. 1 (B).

  The multilayer ceramic capacitor 10 includes at least the internal electrode layer 13-1 in contact with the first protection portion 11b1 among the plurality of internal electrode layers 13-1 to 13-n constituting the capacitance portion 11a. Since the oxide containing the metal element forming the layer 13-1 is held and insulated, as a result of adopting the sequential stacking method in the green laminate manufacturing process at the time of manufacture, the multilayer ceramic capacitor 10 Even in the case where the phenomenon occurs in which the lowest internal electrode layer 13-1 and the second lowest internal electrode layer 13-2 are short-circuited, the lowest internal electrode layer 13-1 loses its function as an electrode. Therefore, the insulation resistance of the multilayer ceramic capacitor 10 does not deteriorate.

  In the multilayer ceramic capacitor 10, only the lowest internal electrode layer 13-1 in contact with the first protection portion 11a1 among the plurality of internal electrode layers 13-1 to 13-n constituting the capacitance portion 11a is insulated. Therefore, among the plurality of internal electrode layers 13-1 to 13-n constituting the capacitance part 11a, the number of internal electrode layers that do not contribute to the formation of capacitance is minimized, and a multilayer ceramic is provided. The loss of the capacitance of the capacitor 10 can be suppressed as much as possible.

  In order to verify the above-described effects, the specified specifications (size 1.0 mm × 0.5 mm × 0.5 mm, number of internal electrode layers 300, capacitance 10 μF, rated voltage 6.3 V are applied in accordance with the manufacturing method described above. , X7R characteristic) 1000 products (multilayer ceramic capacitor) were produced. Further, in [Step 2 of unbaked laminate manufacturing step], the second layer shown in FIG. 2B instead of the first lamination sheet (first slurry layer SL1) shown in FIG. 3 (second slurry layer SL2) and the third lamination sheet (first slurry layer) shown in FIG. 2C in [Step 3 of unfired laminate preparation step]. Instead of SL1 (including a large number of paste layers PL), the fourth lamination sheet (second slurry layer SL2 (including a large number of paste layers PL)) shown in FIG. Except for the above, 1000 comparative products (multilayer ceramic capacitors) having substantially the same specifications were produced according to the manufacturing method described above.

  Then, a moisture resistance load test (temperature 85 ° C., humidity 90%, application of rated voltage, test time 500 hours) was performed on each of the implemented product and the comparative product, and the insulation resistance after the test was measured. 0/1000 were below the defect judgment standard value (10 MΩ), and 100/1000 were below the defect judgment standard value in the comparative product.

  In addition, the electrostatic capacity of each of the implemented product and the comparative product was measured using an LCR meter (Agilent Technology's LCR meter 4284A) at a measurement voltage of 0.5 V and a measurement frequency of 1 kHz. When comparing the average capacitance value of the comparative product, the average capacitance value of the implementation product was 99.7% of the average capacitance value of the comparative product.

<Modification of First Embodiment>
FIG. 4 shows a modified example of the multilayer ceramic capacitor 10. The multilayer ceramic capacitor 10 ′ shown in FIG. 4 is the same as [Step 2 of the unfired laminate manufacturing step] in <Method for manufacturing multilayer ceramic capacitor 10>. “Subsequently, the second slurry layer SL2 of the second lamination sheet shown in FIG. 2B is punched out to a predetermined size, and the punched second slurry layer SL2 is placed on the flat lower surface of the suction head AH. The second slurry layer SL2 is placed on the flat upper surface of the stacking table LT, and the punched second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH. The second slurry layer SL2 is overlaid on the upper surface of the second slurry layer SL2 on the lamination table LT, and the operation of thermocompression bonding is repeated a predetermined number of times. " The

  That is, in the multilayer ceramic capacitor 10 ′ shown in FIG. 4, only the dielectric layer DL in contact with the lowest internal electrode layer 13-1 among the plurality of dielectric layers constituting the first protection portion 11b1 is accelerated in oxidation. Although the structure is different from that of the multilayer ceramic capacitor 10 in that it is made of a sintered product of the first slurry layer SL1 containing an agent, the multilayer ceramic capacitor 10 ′ has the same effect as the multilayer ceramic capacitor 10. can get.

<< Second Embodiment >>
<Structure of multilayer ceramic capacitor 20>
First, the structure of the multilayer ceramic capacitor 20 according to the second embodiment of the present invention will be described with reference to FIGS. 5 (A) and 5 (B).

  In this multilayer ceramic capacitor 20, the reference dimensions of length L, width W and height H have a relationship of length L> width W = height H, or length L> width W> height H. A capacitor body 21 having a substantially rectangular parallelepiped shape and a pair of external electrodes 22 provided at both ends in the length direction of the capacitor body 21 are provided.

  The capacitor body 21 includes a capacitance portion 21a that contributes to capacitance formation, a first protection portion 21b1 that does not contribute to capacitance formation and contacts the lower surface of the capacitance portion 21a, and a capacitance portion 21a that does not contribute to capacitance formation. The second protective portion 21b2 is in contact with the upper surface of the second protective portion 21b2.

  The capacitor portion 21a is composed of an alternating laminate of a plurality of internal electrode layers 23-1 to 23-n and a plurality of dielectric layers 24-1 to 24-m (m = n-1). The lowest internal electrode layer 23-1 is located, and the uppermost internal electrode layer 23-n is located on the upper side in the stacking direction. The first protective part 21b1 is composed of a laminate of a plurality of dielectric layers (no reference), and the upper surface thereof is in contact with the lowest internal electrode layer 23-1 of the capacitor part 21a. The second protective portion 21b2 is formed of a laminate of a plurality of dielectric layers (no reference), and the lower surface thereof is in contact with the uppermost internal electrode layer 23-n of the capacitor portion 21a.

  The plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a are made of a metal selected from the group of nickel, copper, and nickel-copper alloy, and the average thickness thereof is 1.0 μm or less. It is. In addition, the plurality of dielectric layers 24-1 to 24-m constituting the capacitor portion 21a, the plurality of dielectric layers constituting the first protection portion 21b1, and the plurality of dielectric layers constituting the second protection portion 21b2 are: It is formed from one dielectric selected from the group of barium titanate, barium zirconate titanate, barium calcium titanate, barium calcium zirconate titanate, strontium titanate, calcium zirconate, and the average thickness is 1.0 μm or less. Incidentally, in FIGS. 5A and 5B, for convenience of illustration, n is 22 and m is 21, but the internal electrode layer 23 − in the multilayer ceramic capacitor 20 corresponding to miniaturization and large capacity is shown. The number of layers from 1 to 23-n reaches 100 or more.

  Further, the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a have a substantially rectangular shape having a length and width smaller than the length and width of the capacitor body 21, and FIG. , The left edge of the odd-numbered internal electrode layers 23-1... 23- (n-1) from the bottom is electrically connected to the left external electrode 22, and the even-numbered internal electrode layers 23-2 from the bottom. ... The right edge of 23-n is electrically connected to the right external electrode 22. That is, the portion of each internal electrode layer 23-1 to 23-n that does not oppose in the stacking direction is used as the lead portion 23a, and thus the lead portion 23a does not substantially contribute to the formation of capacitance. Incidentally, although not shown, each external electrode 22 has a base layer made of nickel, copper, silver, or an alloy thereof, and a surface layer made of tin, tin-silver alloy, or the like on the surface of the base layer. It has a two-layer structure or a three-layer structure in which an intermediate layer made of nickel, copper, palladium, or the like is interposed between the base layer and the surface layer.

  Further, of the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a, the uppermost internal electrode layer 23-n in contact with the second protective portion 21b2 has at least the internal electrode layer 23-n. It contains an oxide containing a metal element to be formed and is made into an insulator. That is, the uppermost internal electrode layer 23-n among the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor 21a is insulated and does not function as an electrode. Hereinafter, the oxide held in the uppermost internal electrode layer 23-n will be described.

  As described above, since the uppermost internal electrode layer 23-n is made of a metal selected from the group of nickel, copper, and nickel-copper alloy, for example, “the uppermost internal electrode layer 23-n In the case where the “metal element forming the metal layer” is nickel, the “oxide containing the metal element forming the uppermost internal electrode layer 23-n” is an oxide containing nickel.

  Further, the oxide held in the uppermost internal electrode layer 23-n includes “the uppermost internal electrode layer 23-n” in addition to “the oxide containing the metal element forming the uppermost internal electrode layer 23-n”. 23-n and a metal element having a standard oxidation-reduction potential lower than that of the metal element ”may be included. For example, when “the metal element forming the uppermost internal electrode layer 23-n” is nickel, the “metal element having a lower standard oxidation-reduction potential than the metal element forming the uppermost internal electrode layer 23-n” is used. In order from the lowest, lithium, cesium, rubidium, potassium, barium, strontium, calcium, sodium, magnesium, aluminum, manganese, tantalum, zinc, chromium, iron, cadmium, cobalt, etc. Is considered, at least one selected from the group of calcium, magnesium, aluminum, zinc, chromium, and cobalt is preferable. That is, “the metal element forming the uppermost internal electrode layer 23-n” is nickel, and “the metal element having a lower standard oxidation-reduction potential than the metal element forming the uppermost internal electrode layer 23-n” is magnesium. In this case, “the metal element forming the uppermost internal electrode layer 23-n and the oxide containing a metal element having a standard oxidation-reduction potential lower than that of the metal element” is an oxide containing nickel and magnesium.

  Furthermore, the amount of oxide retained in the uppermost internal electrode layer 23-n includes “the oxide containing the metal element that forms the uppermost internal electrode layer 23-n”, and "Oxide containing metal element forming uppermost internal electrode layer 23-n" and "Metal element forming uppermost internal electrode layer 23-n and metal element having lower standard oxidation-reduction potential than the metal element" It is desirable that the volume of the uppermost internal electrode layer 23-n is 100 vol% regardless of the possession of the “oxide containing”, but the uppermost layer is within the range of 70 to 100 vol%. The internal electrode layer 23-n can be made into an insulator.

<Method for Manufacturing Multilayer Ceramic Capacitor 20>
Next, referring to FIG. 6 (A) to FIG. 6 (F) and appropriately using FIG. 2 (A), FIG. 2 (B) and FIG. Specifically, the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a are formed of nickel, and the plurality of dielectric layers 24-1 to 24-m constituting the capacitor portion 21a and the first protection are formed. The plurality of dielectric layers constituting the portion 21b1 and the plurality of dielectric layers constituting the second protective portion 21b2 are formed of barium titanate, and the uppermost internal electrode layer 23-n is “oxide containing nickel”. A method of manufacturing the laminated ceramic capacitor 20 that has “an oxide containing nickel and magnesium” and is insulated will be described.

  In production, first, a first ceramic slurry, a second ceramic slurry, and an electrode paste are prepared in the same manner as in <Manufacturing Method of Multilayer Ceramic Capacitor 10> in << First Embodiment >>.

[Step 1 of the unfired laminate manufacturing process]
Subsequently, the first ceramic slurry is applied to the upper surface of the base film BF made of polyethylene terephthalate or the like by a coating machine using a doctor blade, a slit die, etc. A first lamination sheet on which a first slurry layer SL1 having a predetermined thickness is formed is manufactured (see FIG. 2A).

  In addition, the second ceramic slurry is applied to the upper surface of the equivalent base film BF by the equivalent coating machine, the applied product is dried, and a second slurry layer having a predetermined thickness is formed on the base film BF. A second lamination sheet on which SL2 is formed is manufactured (see FIG. 2B).

  Further, the electrode paste is printed on the upper surface of the second slurry layer SL2 of the second laminating sheet by a printing machine using a screen or an intaglio, and the printed matter is dried, and then on the second slurry layer SL2. A fourth lamination sheet in which paste layers PL having a predetermined shape and a predetermined shape are formed in a predetermined arrangement is produced (see FIG. 2D).

  In this step 1, only the three types of lamination sheets shown in FIGS. 2 (A), 2 (B) and 2 (D) are produced. In order to clarify the difference from the manufacturing method 10 described above, the following steps 2 to 4 will be described without daringly rephrasing the fourth laminating sheet shown in FIG. 2D as the “third laminating sheet”. To do.

[Step 2 of the unfired laminate manufacturing process]
Subsequently, as shown in FIGS. 6 (A) and 6 (B), the second slurry layer SL2 of the second lamination sheet shown in FIG. 2 (B) is punched out to a predetermined size and punched out. The second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 is placed on the flat upper surface of the stacking table LT. Similarly, the punched second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 is stacked on the upper surface of the second slurry layer SL2 on the stacking table LT. Repeat the process of thermocompression bonding a predetermined number of times.

[Step 3 of the unfired laminate manufacturing process]
Subsequently, as shown in FIG. 6C and FIG. 6D, the second slurry layer SL2 of the fourth lamination sheet shown in FIG. The second slurry layer SL2 (including a large number of paste layers PL) is transported by sucking and transporting the paste layer PL side of the second slurry layer SL2 onto the flat lower surface of the suction head AH. Thermocompression bonding is performed on the upper surface of the layer SL2. Then, the second slurry layer SL2 (including a large number of paste layers PL) punched out in the same manner is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 is heated. The operation of thermocompression bonding over the upper surface of the pasted paste layer PL is repeated a predetermined number of times.

[Step 4 of the unfired laminate manufacturing process]
Subsequently, as shown in FIGS. 6E and 6F, the first slurry layer SL1 of the first lamination sheet shown in FIG. 2A is punched out to a predetermined size and punched out. One slurry layer SL1 is sucked and transported to the flat lower surface of the suction head AH, and the first slurry layer SL1 is thermocompression bonded to the upper surface of the paste layer PL that has been subjected to thermocompression bonding. Similarly, the first slurry layer SL1 punched out is sucked and transported to the flat lower surface of the suction head AH, and the first slurry layer SL1 is stacked on the upper surface of the thermocompression-bonded first slurry layer SL1. The operation of thermocompression bonding is repeated a predetermined number of times.

  Steps 2 to 4 of the unfired laminate manufacturing process adopt a sequential stacking method, and the conditions of thermocompression bonding in steps 2 to 4 are, for example, a temperature of 60 ° C. and a pressure of 2 MPa.

[Step 5 of the unfired laminate manufacturing process]
Subsequently, the thermocompression-bonded product is subjected to final thermocompression bonding with a press such as a hot isostatic press to produce an unfired laminate. Incidentally, the final thermocompression bonding conditions are, for example, a water temperature of 70 ° C. and a pressure of 2000 kg / cm ² .

[Unbaked chip manufacturing process]
Subsequently, the unfired laminate is cut into a lattice shape by a cutting machine such as a dicing device, and an unfired chip corresponding to the capacitor main body 21 shown in FIGS. 5A and 5B is manufactured.

[Unfired chip firing process]
Subsequently, a large number of non-fired chips are put into a firing furnace, and fired according to a firing temperature profile having a peak temperature of about 1200 ° C. in an atmosphere having an oxygen partial pressure equal to or lower than the equilibrium oxygen partial pressure of Ni—NiO (including binder removal treatment). )I do.

  In this firing step, each first slurry layer SL1, each second slurry layer SL2, and each paste layer PL constituting each unsintered chip are sintered, but each first slurry layer SL1 is oxidized. Since the agent (magnesium compound) is contained, the sintering of each first slurry layer SL1 is promoted, and magnesium moves from the lowest first slurry layer SL1 to the uppermost paste layer PL. Oxidation of the upper paste layer PL is promoted. That is, the sintered product of the uppermost paste layer PL has “an oxide containing nickel” and “an oxide containing nickel and magnesium”, whereby the sintered product of the uppermost paste layer PL is It becomes an insulator and loses its function as an electrode.

[External electrode manufacturing process]
Subsequently, an electrode paste equivalent to the electrode paste is applied to both ends in the lengthwise direction of the baked chip by a coating machine such as a dip coating machine or a roller coating machine, and the coated material is subjected to a baking process, as shown in FIG. A base layer of the external electrode 22 shown in FIGS. 5A and 5B is formed. Then, a surface layer is formed on the surface of the base layer by a plating method such as electrolytic plating to produce the external electrode 22 having a two-layer structure. Alternatively, the intermediate layer and the surface layer are sequentially formed on the surface of the base layer by a plating method such as electrolytic plating to produce the external electrode 22 having a three-layer structure.

<Effects obtained by the multilayer ceramic capacitor 20>
Next, the effects obtained by the multilayer ceramic capacitor 20 and the verification results of the effects will be described with reference to FIGS. 5 (A) and 5 (B).

  The multilayer ceramic capacitor 20 includes at least the internal electrode layer 23-n in contact with the second protection portion 21b1 among the plurality of internal electrode layers 23-1 to 23-n constituting the capacitance portion 21a. Since the oxide containing the metal element forming the layer 23-n is held and insulated, as a result of adopting the sequential stacking method in the green laminate manufacturing process at the time of manufacture, the multilayer ceramic capacitor 20 The uppermost internal electrode layer 23-n and a dielectric layer in contact with the upper surface of the internal electrode layer 23-n (the lowermost dielectric layer among the plurality of dielectric layers constituting the second protective portion 21b2) Even in the case where the phenomenon of a reduction in the bonding force occurs, delamination occurs in the multilayer ceramic capacitor 20 because the lowering of the bonding force can be compensated by the oxide held in the uppermost internal electrode layer 23-n. Rukoto is not.

  In the multilayer ceramic capacitor 20, only the uppermost internal electrode layer 23-n in contact with the second protective portion 21a1 among the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a is insulated. Therefore, among the plurality of internal electrode layers 23-1 to 23-n constituting the capacitor portion 21a, the number of internal electrode layers that do not contribute to the formation of capacitance is minimized, and the laminated ceramic The loss of the capacitance of the capacitor 20 can be suppressed as much as possible.

  In order to verify the above-described effects, the specified specifications (size 1.0 mm × 0.5 mm × 0.5 mm, number of internal electrode layers 300, capacitance 10 μF, rated voltage 6.3 V are applied in accordance with the manufacturing method described above. , X7R characteristic) 1000 products (multilayer ceramic capacitor) were produced. Further, in [Step 4 of the unfired laminate manufacturing process], the second laminate shown in FIG. 2B instead of the first laminate sheet (first slurry layer SL1) shown in FIG. 1000 comparative products (multilayer ceramic capacitors) having substantially the same specifications were produced according to the manufacturing method described above, except that the stacking sheets (second slurry layer SL2) were sequentially stacked.

  Then, when the longitudinal section corresponding to FIG. 5A of each of the implemented product and the comparative product was observed with a scanning electron microscope, 0/1000 samples were found to have delamination. In the comparative product, the delamination was generated at 50/1000.

  In addition, the electrostatic capacity of each of the implemented product and the comparative product was measured using an LCR meter (Agilent Technology's LCR meter 4284A) at a measurement voltage of 0.5 V and a measurement frequency of 1 kHz. When comparing the average capacitance value of the comparative product, the average capacitance value of the implementation product was 99.7% of the average capacitance value of the comparative product.

<Modification of Second Embodiment>
FIG. 7 shows a modified example of the multilayer ceramic capacitor 20. The multilayer ceramic capacitor 20 ′ shown in FIG. 7 is the [Step 4 of the unfired laminate manufacturing process] in the <Method for manufacturing multilayer ceramic capacitor 20>. “Subsequently, the first slurry layer SL1 of the first lamination sheet shown in FIG. 2A is punched out to a predetermined size, and the punched first slurry layer SL1 is placed on the flat lower surface of the suction head AH. The first slurry layer SL1 is superposed on the upper surface of the heat-pressed paste layer PL and thermocompression-bonded once, and the second lamination shown in FIG. The second slurry layer SL2 of the sheet is punched at a predetermined size, and the punched second slurry layer SL2 is sucked and transported to the flat lower surface of the suction head AH, and the second slurry layer SL2 has been thermocompression bonded. The operation of thermocompression bonding over the upper surface of the first slurry layer SL1 is repeated a predetermined number of times. "

  That is, in the multilayer ceramic capacitor 20 ′ shown in FIG. 7, only the dielectric layer DL in contact with the uppermost internal electrode layer 23-n among the plurality of dielectric layers constituting the second protective portion 21b2 is accelerated in oxidation. Although the structure is different from that of the multilayer ceramic capacitor 20 in that it is made of a sintered product of the first slurry layer SL1 containing an agent, the multilayer ceramic capacitor 20 ′ has the same effect as the multilayer ceramic capacitor 10. can get.

  DESCRIPTION OF SYMBOLS 10, 10 '... Multilayer ceramic capacitor, 11 ... Capacitor main body, 11a ... Capacitance part, 11b1 ... 1st protection part, 11b2 ... 2nd protection part, 12 ... External electrode, 13-1-13-n ... Internal electrode layer, 14-1 to 14-m: Dielectric layer, 20, 20 '... Multilayer ceramic capacitor, 21 ... Capacitor body, 21a ... Capacitor part, 21b1 ... First protection part, 21b2 ... Second protection part, 22 ... External electrode, 23-1 to 23-n: internal electrode layers, 24-1 to 24-m: dielectric layers.

Claims (4)

A capacitor part composed of an alternating laminate of a plurality of internal electrode layers and a plurality of dielectric layers; a first protective part comprising a laminate of a plurality of dielectric layers and in contact with the internal electrode layer on one side of the capacitor part in the stacking direction; A multilayer ceramic capacitor comprising a capacitor body comprising a plurality of dielectric layer laminates and having a second protective portion in contact with the internal electrode on the other side of the capacitor portion in the lamination direction,
At least one of the internal electrode layer on one side in the stacking direction of the capacitor unit in contact with the first protective unit and the internal electrode layer on the other side in the stacking direction of the capacitor unit in contact with the second protective unit forms at least the internal electrode layer It has an oxide containing a metal element to be insulated,
A multilayer ceramic capacitor characterized by that. The oxide includes an oxide containing a metal element forming the internal electrode layer, a metal element forming the internal electrode layer, and a metal element having a standard oxidation-reduction potential lower than that of the metal element. Contains,
The multilayer ceramic capacitor according to claim 1. The metal element forming the internal electrode layer is nickel.
The multilayer ceramic capacitor according to claim 1, wherein the multilayer ceramic capacitor is provided. The metal element forming the internal electrode layer is nickel,
The metal element having a standard oxidation-reduction potential lower than the metal element forming the internal electrode layer is at least one selected from the group consisting of calcium, magnesium, aluminum, zinc, chromium, and cobalt.
The multilayer ceramic capacitor according to claim 2.

Images