JP2005347288A - Method of manufacturing multilayered ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayered ceramic capacitor 1 which can be effectively prevented from deterioration in temperature characteristics and can also be suppressed in impairment of dielectric constant even if interlayer dielectric layers 2 are made thin. <P>SOLUTION: The multilayered ceramic capacitor 1 contains internal electrode layers 3, and the interlayer dielectric layers 2 having a thickness of 1.5 μm or less. The manufacturing method includes a process of calcinating the main body of an alternately stacked element before calcination which has such a structure of a plurality of dielectric layers before calcination containing a dielectric material, and of a plurality of internal electrode layers before calcination containing a base metal conductive material and an additive dielectric material. The content of the additive dielectric material in the internal electrode layers before calcination is controlled within a range of 4.5-30 wt.% compared with 100 wt.% of the dielectric material contained in the dielectric layers before calcination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a multilayer ceramic capacitor.

  The multilayer ceramic capacitor includes an element body having a structure in which a plurality of dielectric layers and internal electrode layers are alternately stacked, and a pair of external terminal electrodes formed at both ends of the element body. In this multilayer ceramic capacitor, first, a pre-firing dielectric layer and a pre-firing internal electrode layer are alternately laminated in a necessary number to produce a pre-firing element body, and then, after firing this, the post-firing element body It is manufactured by forming a pair of external terminal electrodes at both ends.

  A ceramic green sheet is used as the dielectric layer before firing. The ceramic green sheet can be manufactured by a sheet method or the like. The sheet method is produced by applying a dielectric layer paste containing a dielectric raw material powder, a binder, a plasticizer, an organic solvent, etc. onto a carrier sheet such as PET using a doctor blade method, and drying by heating. Is the method.

  As the internal electrode layer before firing, for example, a predetermined pattern of internal electrode layer paste is used. The internal electrode layer paste having a predetermined pattern is manufactured, for example, by a printing method. The printing method is a method in which a conductive material containing a metal such as Pd, Ag—Pd, Ni, and an internal electrode layer paste containing a binder and an organic solvent are formed in a predetermined pattern on a ceramic green sheet.

  Thus, when manufacturing the multilayer ceramic capacitor, the pre-firing dielectric layer and the pre-firing internal electrode layer are fired simultaneously. Therefore, the conductive material contained in the internal electrode layer before firing has a melting point higher than the sintering temperature of the dielectric material powder contained in the dielectric layer before firing, does not react with the dielectric material powder, It is required not to diffuse into the post-dielectric layer.

  Conventionally, in order to satisfy these requirements, noble metals such as Pt and Pd have been used for the conductive material contained in the internal electrode layer before firing. However, the noble metal itself is expensive, and as a result, there is a disadvantage that the finally obtained multilayer ceramic capacitor is expensive. Therefore, the sintering temperature of the dielectric material powder is lowered, and an Ag—Pd alloy is used for the conductive material contained in the internal electrode layer before firing, or reduction resistance is imparted to the dielectric material, which can be fired in a reducing atmosphere. Those using inexpensive base metals such as Ni have been developed.

  The case where Ni is used for the conductive material contained in the internal electrode layer before firing is illustrated. This Ni has a lower melting point than the dielectric raw material powder contained in the pre-firing dielectric layer. For this reason, when the pre-firing dielectric layer and the pre-firing internal electrode layer containing Ni as the conductive material are co-fired, the difference in sintering start temperature between the dielectric raw material powder and Ni is greater than that of the dielectric. Since sintering occurs quickly, breaks are likely to occur. That is, the line property (continuity) of the internal electrode layer is deteriorated. Therefore, there is a technique for adding a dielectric material for addition as a sintering inhibitor to the internal electrode layer paste for forming the internal electrode layer for the purpose of suppressing discontinuity and sintering suppression due to this kind of firing. It has been proposed (see Patent Documents 1 to 6).

  By the way, in recent years, with the miniaturization of various electronic devices, it has been required to realize the miniaturization and large capacity of the multilayer ceramic capacitor mounted inside the electronic device. In order to reduce the size and increase the capacity of the multilayer ceramic capacitor, the thickness of the post-fired interlayer dielectric layer disposed between the opposed fired internal electrode layers has been increasing. Specifically, the fired thickness per layer of the interlayer dielectric layer after firing has been reduced to about 1 μm, and accordingly, the thickness before firing per layer of the interlayer dielectric layer before firing is also reduced. Layered.

  The thinner the interlayer dielectric layer before firing, the lower the dielectric material content in the dielectric layer forming it.

  In the techniques of Patent Documents 1 to 6 described above, an internal electrode layer paste in which about 20% by weight of the dielectric material for addition is added to 100% by weight of Ni as a conductive material is used.

  The conventional paste for internal electrode layers is formed by, for example, a plurality of pre-firing layers in which the pre-firing thickness is gradually reduced to 5.0 μm, 4.0 μm, 3.0 μm, 2.0 μm, 1.5 μm, etc. When the interlayer dielectric layer is applied and formed with a predetermined thickness of 1.3 μm, for example, the dielectric material for addition in the internal electrode layer paste with respect to the content of the dielectric material in the interlayer dielectric layer before firing The weight ratio of the content (content of dielectric material for addition in internal electrode layer paste / content of dielectric material in interlayer dielectric layer before firing) is, for example, 9.0% by weight, 11.5% by weight %, 16.2 wt%, 26.9 wt%, 40.4 wt%, etc., as the thickness of the pre-firing interlayer dielectric layer on which the internal electrode layer paste is applied and formed decreases stepwise. Will increase. As the thickness of the interlayer dielectric layer before firing decreases, the content of the dielectric material decreases, so the denominator of the above weight ratio formula decreases, and as a result, the weight ratio value increases. Is.

  That is, when the addition amount of the dielectric material for addition in the internal electrode layer paste is constant, the weight ratio increases as the thickness of the pre-firing interlayer dielectric layer on which this is applied is thinned. For example, a paste for internal electrode layers in which about 20% by weight of a dielectric material for addition is added to 100% by weight of Ni as a conductive material is an interlayer dielectric layer before firing having a predetermined thickness and a thickness before firing of 5.0 μm. When compared with the case of coating and forming on a pre-firing interlayer dielectric layer having a thickness before firing of 1.5 μm, the latter is more suitable for the pre-firing interlayer dielectric layer than the former. The weight ratio of the amount of the dielectric material for addition contained in the internal electrode layer paste to the amount of the dielectric material contained is increased.

  Since the dielectric material for addition in the internal electrode layer paste diffuses into the interlayer dielectric layer after firing during firing of the element body before firing, the higher the weight ratio, the more during the firing, The rate of diffusion into the interlayer dielectric layer after firing increases.

It was found that the temperature characteristics of the obtained capacitor tend to deteriorate when the amount of the dielectric material for addition diffused from the internal electrode layer before firing during firing is increased. In particular, when the thickness of the interlayer dielectric layer is reduced to 1.5 μm or less after firing, the present inventors have confirmed that this tendency is remarkable.
JP-A-5-62855 JP 2000-277369 A JP 2001-307939 A JP 2003-77761 A Japanese Patent Application Laid-Open No. 2003-100544 JP2003-1224049A.

  An object of the present invention is to provide a method of manufacturing a multilayer ceramic capacitor that can effectively prevent deterioration of temperature characteristics and suppress deterioration of dielectric constant even when an interlayer dielectric layer is thinned. That is.

In order to achieve the above object, according to the present invention,
A method of manufacturing a multilayer ceramic capacitor having an internal electrode layer and a dielectric layer having a thickness of 1.5 μm or less,
A step of firing a pre-fired element body having a structure in which a plurality of pre-fired dielectric layers containing a dielectric material and base metal conductive materials and pre-fired internal electrode layers containing a dielectric material for addition are alternately stacked;
The content of the dielectric material for addition in the internal electrode layer before firing is controlled in the range of 4.5 to 30% by weight with respect to 100% by weight of the dielectric material contained in the dielectric layer before firing. A method for manufacturing a featured multilayer ceramic capacitor is provided.

  In order to control the content of the dielectric material for addition in the internal electrode layer before firing to the above range, the dielectric material for addition in the internal electrode layer before firing is controlled according to the target thickness of the dielectric layer. It can be performed by changing the content itself and / or the thickness of the internal electrode layer before firing.

  Preferably, the dielectric material for addition in the internal electrode layer before firing includes a main component material for addition, and the main component material for addition is a main component in the dielectric material contained in the dielectric layer before firing. The composition system is substantially the same as the raw material and has an average particle size smaller than the average particle size of the main component raw material. Preferably, the additive main component material has an average particle diameter of 0.01 to 0.2 μm. In addition, the value of the average particle diameter of each raw material powder can be determined from, for example, the specific surface area (= surface area per unit weight, sometimes abbreviated as SSA) of each raw material powder actually measured.

“Substantially the same composition system” means that the type of each element and the composition molar ratio between the elements are completely the same, but the type of each element is the same, but the composition molar ratio is This is intended to include cases that are slightly different. As the former case, for example, when the main component material contained in the dielectric material in the dielectric layer before firing is (BaO) _m TiO ₂ (where m = 1), the addition in the internal electrode layer before firing This is a case where the main component raw material for addition contained in the dielectric raw material is (BaO) _{m ′} TiO ₂ (where m ′ = 1). As the latter case, for example, when the main component material is (BaO) _m TiO ₂ (where m = 1), the main component material for addition is (BaO) _{m ′} TiO ₂ (where m ′ = 0. 990 to 1.050).

  The additive dielectric material in the pre-fired internal electrode layer may contain “at least the main component material for addition”, and may further contain the subcomponent material for addition.

  In the present invention, the main component material for addition in the dielectric material for addition and the main component material contained in the dielectric material in the paste for dielectric layer are preferably substantially the same composition system.

  Therefore, when the additive dielectric material includes the additive subcomponent material in addition to the additive main component material, (1) only the additive main component material that is a part of the additive dielectric material is fired. The composition system may be substantially the same as the main component material contained in the dielectric material in the previous dielectric layer. In other words, the composition of the additive subcomponent material that is the balance of the additive dielectric material may be different from the composition of the subcomponent material contained in the dielectric material in the pre-firing dielectric layer. (2) All of the dielectric material for addition (which naturally includes the main component material for addition) is substantially the same as all of the dielectric material (which naturally includes the main component material) in the pre-firing dielectric layer. The same composition system may be used.

  The material (conductive material) constituting the internal electrode layer of the multilayer ceramic capacitor is not particularly limited in the present invention, and a noble metal can be used in addition to the base metal. This is particularly effective when a base metal such as Ni is used.

  The dielectric layer is composed of a dielectric composition comprising a sintered body of a dielectric material and an additive dielectric material.

  When the internal electrode layer is made of a base metal, the dielectric composition constituting the dielectric layer includes Mn, Cr, Si, Ca, Ba, Mg, V, W, in addition to the main components such as barium titanate. An accessory component including one or more of oxides of Ta, Nb, and R (R is one or more rare earth elements such as Y) and a compound that becomes these oxides by firing may be contained. By containing an auxiliary component, even if baked in a reducing atmosphere, it is not made into a semiconductor, and the characteristics as a capacitor can be maintained. Thus, in the case of manufacturing a multilayer ceramic capacitor having a dielectric layer composed of a dielectric composition (sintered body) containing a subcomponent in addition to the main component, the dielectric in the dielectric layer before firing is used. A raw material contains the main component raw material and subcomponent raw material which will form the said main component and subcomponent after baking. In this case, as described above, the additive dielectric material in the internal electrode layer before firing also contains the additive subcomponent material in addition to the additive main component material.

  Preferably, the dielectric material in the dielectric layer before firing and the dielectric material for addition in the internal electrode layer before firing contain barium titanate as a main component material and main component material for addition, It contains magnesium oxide (including a compound that becomes magnesium oxide after firing) and rare earth element oxide as an auxiliary component raw material for addition, and barium oxide (including a compound that becomes barium oxide after firing) as another accessory component, and At least one selected from calcium oxide (including a compound that becomes calcium oxide after firing) and at least one selected from silicon oxide, manganese oxide (including a compound that becomes manganese oxide after firing), vanadium oxide, and molybdenum oxide It is preferable to contain seeds.

  The firing step may be a step of raising the atmospheric temperature toward the firing holding temperature, holding the firing holding temperature for a predetermined time, and then lowering the temperature. The details about the process are not particularly limited.

  Preferably, the multilayer ceramic capacitor has an element body having a structure in which an internal electrode layer and an interlayer dielectric layer having a thickness of 1.5 μm or less are alternately stacked between a pair of outer dielectric layers. Is.

  In the present invention, the dielectric layer simply expressed as “dielectric layer” means one or both of the interlayer dielectric layer and the outer dielectric layer.

  In the prior art, the content of the dielectric material for addition in the internal electrode layer before firing formed using the internal electrode layer paste is controlled by a predetermined amount with respect to 100% by weight of Ni as a conductive material. . For this reason, the thinner the thickness of the pre-fired dielectric layer composed of the ceramic green sheet formed using the dielectric layer paste, the more the dielectric for addition to the dielectric material in the pre-fired dielectric layer. The weight ratio of the body material was large.

  When the weight ratio of the dielectric material for addition to the dielectric material in the dielectric layer before firing is increased, when the dielectric layer is thinned (particularly, 1.5 μm or less), after firing from the internal electrode layer before firing. The amount of the additive dielectric material that diffuses into the dielectric layer increases. As a result, the tendency of the temperature characteristics of the obtained capacitor to deteriorate significantly appeared.

  In the present invention, a pre-fired element body having a structure in which a plurality of pre-fired dielectric layers containing a dielectric material and pre-fired internal electrode layers containing a base metal conductive material and an additive dielectric material are alternately stacked is fired. Thus, the dielectric material for addition is diffused into the dielectric layer to form the dielectric layer made of a dielectric composition composed of a sintered body of the dielectric material and the dielectric material for addition.

  When the dielectric layer is extremely thinned to 1.5 μm or less, the present inventors have found that the additive dielectric material diffused from the internal electrode layer before firing affects the microstructure of the dielectric layer. The inventors have found that the temperature characteristics of the capacitor deteriorate when the particle size of the sintered body of the dielectric composition (sintered body) constituting the dielectric layer increases. As a result of further research, in order to reduce the influence on the fine structure of the dielectric layer, the content of the dielectric material for addition in the internal electrode layer before firing is reduced by the content of the conductive material in the internal electrode layer before firing. It has been concluded that it is effective to control to a predetermined range with respect to 100% by weight of the dielectric material in the dielectric layer before firing rather than with respect to 100% by weight of the material.

  Thus, by controlling the content of the dielectric material for addition in the internal electrode layer before firing to a predetermined range with respect to 100% by weight of the dielectric material in the dielectric layer before firing, the dielectric layer is reduced to 1 Even when the thickness is reduced to 5 μm or less, an increase in the particle size of the sintered body of the dielectric composition (sintered body) constituting the dielectric layer can be prevented. As a result, deterioration of the temperature characteristics of the obtained capacitor can be effectively prevented, and deterioration of the dielectric constant is also suppressed.

  That is, according to the present invention, there is provided a method for manufacturing a multilayer ceramic capacitor that can effectively prevent deterioration of temperature characteristics and suppress deterioration of dielectric constant even when the interlayer dielectric layer is thinned. Can be provided.

  In the present invention, the main component material for addition contained in the dielectric material for addition in the internal electrode layer before firing is made substantially the same composition system as the main component material contained in the dielectric material in the dielectric layer before firing. It is preferable to do. By doing so, even if the additive dielectric material diffuses from the internal electrode layer before firing to the dielectric layer, the final composition of the dielectric layer does not change. In the present invention, since the dielectric layer is extremely thin as 1.5 μm or less, if the final composition of the dielectric layer fluctuates in comparison with the original composition of the design, the deterioration of the temperature characteristics of the obtained capacitor is avoided. I can't. By using an additive dielectric material that does not change the final composition of the dielectric layer, it is possible to prevent the deterioration of the temperature characteristics of the obtained capacitor even more remarkably.

  Conventionally, a fine dielectric material is often used as a main component material for addition in an additive dielectric material. The reason is that finer raw materials are more likely to enter between the conductive powders in the electrode, the dried electrode paste and the packing state are improved, and the sintering suppression effect can be more effectively achieved. However, fine raw materials are unstable with respect to sintering and thus tend to grow abnormal grains, and there is a concern about the influence on the fine structure. In the present invention, the main component material for addition in the additive dielectric material preferably has an average particle size of 0.01 to 0.2 μm, more preferably 0.01 to 0.15 μm. By using a main component material having a specific average particle size as an additive, it is possible to control the effect of suppressing electrode breakage and abnormal grain growth.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 2 is a dielectric for addition in an internal electrode layer paste with respect to 100% by weight of a dielectric material in the dielectric layer paste in the example. It is a graph which shows the relationship between content of a body raw material, and a temperature characteristic.

Multilayer Ceramic Capacitor Before describing a method for manufacturing a multilayer ceramic capacitor according to the present invention, a multilayer ceramic capacitor will be described first.

  As shown in FIG. 1, a multilayer ceramic capacitor 1 as an example manufactured by the method of the present invention has a capacitor element body 10 having a configuration in which interlayer dielectric layers 2 and internal electrode layers 3 are alternately stacked. A pair of external electrodes 4 are formed at both ends of the capacitor element body 10 so as to be electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. The internal electrode layers 3 are laminated such that the side end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor element body 10.

  The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and are connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

  The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Also, there is no particular limitation on the size, and it may be an appropriate size according to the application. Usually, the length (0.4 to 5.7 mm) × width (0.2 to 5.0 mm) × height (0.3 to 1.9 mm).

  In the capacitor element body 10, outer dielectric layers 20 are disposed at both outer end portions in the stacking direction of the internal electrode layer 3 and the interlayer dielectric layer 2 to protect the inside of the element body 10.

The composition of the interlayer dielectric layer 2 and the outer dielectric layer 20 is not particularly limited in the present invention, and is composed of, for example, the following dielectric ceramic composition.
The dielectric ceramic composition of the present embodiment is a dielectric ceramic composition having, for example, barium titanate as a main component. Subcomponents included in the dielectric ceramic composition together with the main component include Mn, Cr, Ca, Ba, Mg, V, W, Ta, Nb and R (R is one or more of rare earth elements such as Y). Examples include oxides and one or more compounds that become oxides upon firing. By adding the subcomponent, the characteristics as a capacitor can be obtained even in firing in a reducing atmosphere. As impurities, trace components such as C, F, Li, Na, K, P, S, and Cl may be contained in an amount of about 0.1 wt% or less. However, in the present invention, the composition of the interlayer dielectric layer 2 and the outer dielectric layer 20 is not limited to the above.

In the present embodiment, it is preferable to use a material having the following composition as the interlayer dielectric layer 2 and the outer dielectric layer 20.
The composition contains barium titanate as a main component, magnesium oxide and rare earth element oxide as subcomponents, and at least one selected from barium oxide and calcium oxide as other subcomponents; It contains at least one selected from silicon oxide, manganese oxide, vanadium oxide and molybdenum oxide.
Then, barium titanate is BaTiO ₃ , magnesium oxide is MgO, rare earth oxide is R ₂ O ₃ , barium oxide is BaO, calcium oxide is CaO, silicon oxide is SiO ₂ , and manganese oxide is When converted to MnO, vanadium oxide to V ₂ O ₅ and molybdenum oxide to MoO ₃ , the ratio to 100 mol of BaTiO ₃ is MgO: 0.1 to 3 mol, R ₂ O ₃ : more than 0 mol and less than 5 mol BaO + CaO: 0.5 to 12 mol, SiO ₂ : 0.5 to 12 mol, MnO: more than 0 mol to 0.5 mol or less, V ₂ O ₅ : 0 to 0.3 mol, MoO ₃ : 0 to 0. 3 moles.

  The interlayer dielectric layer 2 has a very thin thickness of 1.5 μm or less, preferably 1.0 μm or less. In the present embodiment, even when the thickness of the interlayer dielectric layer 2 is extremely reduced as described above, the temperature characteristics of the capacitor 1 are not deteriorated, and the decrease in dielectric constant can be suppressed. The number of interlayer dielectric layers 2 may be determined as appropriate according to the purpose and application, but usually exhibits a sufficient effect even when it is multi-layered to 50 layers or more, preferably 100 layers or more.

  The interlayer dielectric layer 2 and the outer dielectric layer 20 are composed of dielectric particles (sintered bodies) and a grain boundary phase. The grain boundary phase usually includes an oxide of a material constituting the dielectric material or the internal electrode material, an oxide of a material added separately, or an oxide of a material mixed as an impurity during the process.

  The internal electrode layer 3 shown in FIG. 1 is composed of a base metal conductive material that substantially acts as an electrode. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more selected from Mn, Cr, Co, Al, Ru, Rh, Ta, Re, Os, Ir, Pt and W, and the Ni content in the alloy is It is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components such as P, C, Nb, Fe, Cl, B, Li, Na, K, F, and S may be contained in an amount of about 0.1% by weight or less. .

  In the present embodiment, the thickness of the internal electrode layer 3 is extremely thin, preferably 1.5 μm or less, more preferably 1.3 μm or less, but the continuity (line property) is improved.

  As the external electrode 4 shown in FIG. 1, at least one of Ni, Pd, Ag, Au, Cu, Pt, Rh, Ru, Ir, or an alloy thereof can be used. Usually, Cu, Cu alloy, Ni, Ni alloy, etc., Ag, Ag—Pd alloy, In—Ga alloy, etc. are used. Although the thickness of the external electrode 4 should just be determined timely according to a use, it is preferable that it is normally about 10-200 micrometers.

Method for Manufacturing Multilayer Ceramic Capacitor Next, an example of a method for manufacturing the multilayer ceramic capacitor 1 according to this embodiment will be described.

(1) First, for a dielectric layer that constitutes the pre-firing interlayer dielectric layer and the pre-firing outer dielectric layer for forming the interlayer dielectric layer 2 and the outer dielectric layer 20 shown in FIG. 1 after firing. A paste and an internal electrode layer paste that will form the internal electrode layer before firing for forming the internal electrode layer 3 shown in FIG. 1 after firing are prepared.
Dielectric Layer Paste A dielectric layer paste is prepared by kneading a dielectric material and an organic vehicle.

  The dielectric material contains a main component material and subcomponent material that will form the main component and subcomponents constituting the dielectric layers 2 and 20 after firing.

  Each of these component raw materials can be appropriately selected from various compounds to be composite oxides and oxides, such as carbonates, nitrates, hydroxides, organometallic compounds, and the like, and can be used in combination.

  The dielectric material is usually used as a powder having an average particle size of 0.4 μm or less, preferably about 0.1 to 3.0 μm.

  The organic vehicle contains a binder and a solvent. As a binder, various usual binders, such as ethyl cellulose, polyvinyl butyral, an acrylic resin, can be used, for example. The solvent is not particularly limited, and organic solvents such as terpineol, butyl carbitol, acetone, toluene, xylene and ethanol are used.

  The dielectric layer paste can also be formed by kneading a dielectric material and a vehicle in which a water-soluble binder is dissolved in water. The water-soluble binder is not particularly limited, and polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, water-soluble acrylic resin, emulsion and the like are used.

  The content of each component in the dielectric layer paste is not particularly limited. For example, the dielectric layer paste can be prepared so as to contain about 1 to about 50% by weight of a solvent.

  The dielectric layer paste may contain additives selected from various dispersants, plasticizers, dielectrics, subcomponent compounds, glass frit, insulators, and the like, if necessary. When these additives are added to the dielectric layer paste, the total content is desirably about 10% by weight or less.

Internal Electrode Layer Paste In this embodiment, the internal electrode layer paste is prepared by kneading a conductive material, an additive dielectric material, and an organic vehicle.

  As the conductive material, Ni, Ni alloy, or a mixture thereof is used. There are no particular restrictions on the shape of such a conductive material, such as a spherical shape or a flake shape, and a mixture of these shapes may be used. Moreover, the particle diameter of the conductive material is generally 0.5 μm or less, preferably about 0.01 to 0.4 μm, in the case of a spherical shape. This is because a more advanced thinning can be realized.

  The conductive material is preferably contained in the internal electrode layer paste in an amount of 35 to 60% by weight.

  The dielectric material for addition has an effect of suppressing the sintering of the internal electrode (conductive material) during the firing process.

  In this embodiment, the dielectric material for addition contains the main component material for addition and the subcomponent material for addition.

  In the present invention, the dielectric material for addition in the internal electrode layer paste (may be only the main component material for addition, or may contain both the main component material for addition and the subcomponent material for addition. Unless otherwise specified, the content is 4.5 to 30% by weight, preferably 5 to 28% by weight, more preferably 8%, based on 100% by weight of the dielectric material in the dielectric layer paste. It is characterized in that it is controlled in the range of ˜27% by weight.

  Thus, as a means for controlling the content of the dielectric material for addition in the internal electrode layer paste to a specific range, depending on the target thickness of the interlayer dielectric layer 2, Examples thereof include changing the content of the dielectric material for addition itself, changing the thickness (attachment amount) of the internal electrode layer before firing made of the internal electrode layer paste to be formed, or a combination thereof.

  The content of the dielectric material for addition in the internal electrode layer paste is not 100% by weight of the conductive material in the internal electrode layer paste, but 100% by weight of the dielectric material in the dielectric layer paste. On the other hand, the dielectric composition (sintered body) constituting the interlayer dielectric layer 2 even when the interlayer dielectric layer 2 is thinned to 1.5 μm or less by controlling it within a predetermined range An increase in the particle size of the sintered body can be prevented. As a result, deterioration of the temperature characteristics of the obtained capacitor 1 can be effectively prevented, and deterioration of the dielectric constant can also be suppressed. More specifically, the temperature characteristic TC at 85 ° C. can be set to −10% or more, and the relative dielectric constant ε can be maintained to 1500 or more.

  If the content of the dielectric material for addition in the internal electrode layer paste is too small relative to 100% by weight of the dielectric material in the dielectric layer paste, the temperature characteristics can be prevented from deteriorating, but the conductive material The sintering suppression effect is lowered, the lineability (continuity) of the internal electrode layer 3 is deteriorated, and the apparent dielectric constant is lowered. Even if the content becomes too small in this way, theoretically, if any one of the following means (a) to (d) is adopted, the dielectric material for addition in the internal electrode layer paste The content can be controlled in the range of 4.5 to 30% by weight with respect to 100% by weight of the dielectric material in the dielectric layer paste.

(A) The thickness of the dielectric layer paste is extremely increased to 10 μm or more.
(B) The content of the dielectric material for addition in the internal electrode layer paste is extremely reduced to 5% by weight or less with respect to 100% by weight of the base metal conductive material.
(C) A conventional internal electrode layer paste in which the content of the dielectric material for addition is adjusted to 20% by weight with respect to 100% by weight of the base metal conductive material is formed to be extremely thin, for example, 0.2 μm or less (adhesion amount is Reduce),
(D) Any combination of (i) to (c).

  However, in this case, the linearity (continuity) of the internal electrode layer 3 is deteriorated by any of the methods (A) to (D), and the apparent dielectric constant is reduced accordingly.

  If the content of the dielectric material for addition in the internal electrode layer paste is too large relative to 100% by weight of the dielectric material in the dielectric layer paste, the dielectric composition constituting the interlayer dielectric layer 2 The sintered body particle size of the object (sintered body) is increased, and accordingly, the temperature characteristics are deteriorated, the lineability of the internal electrode layer 3 is easily deteriorated, and the apparent dielectric constant tends to be lowered. .

  In the present invention, at least the main component material for addition in the dielectric material for addition and the main component material contained in the dielectric material in the paste for dielectric layer have substantially the same composition system. preferable. Therefore, only the main component material for addition that is a part of the dielectric material for addition may be substantially the same composition system as the main component material contained in the dielectric material in the dielectric layer paste. Further, all of the dielectric material for addition may be substantially the same composition system as all of the dielectric material in the dielectric layer paste.

  In the present invention, the main component material for addition in the additive dielectric material preferably has an average particle size of 0.01 to 0.2 μm, more preferably 0.01 to 0.15 μm. By using a main component material having a specific average particle size as an additive, it is possible to control the effect of suppressing electrode breakage and abnormal grain growth.

  The organic vehicle contains a binder and a solvent.

  Examples of the binder include ethyl cellulose, acrylic resin, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, and copolymers thereof. The binder is preferably contained in the internal electrode layer paste in an amount of 1 to 5% by weight with respect to the mixed powder of the conductive material and the dielectric material for addition. If the amount of the binder is too small, the strength tends to decrease. If the amount is too large, the metal filling density of the electrode pattern before firing decreases, and it becomes difficult to maintain the smoothness of the internal electrode layer 3 after firing. is there.

  As the solvent, any known solvent such as terpineol, dihydroterpineol, butyl carbitol, and kerosene can be used. The solvent content is preferably about 20 to 50% by weight with respect to the entire paste.

  The internal electrode layer paste may contain a plasticizer. Examples of the plasticizer include phthalic acid esters such as benzylbutyl phthalate (BBP), adipic acid, phosphoric acid esters, glycols, and the like.

  (2) Next, using the dielectric layer paste and the internal electrode layer paste, a green chip in which the pre-fired dielectric layer and the pre-fired internal electrode layer are laminated is manufactured. When the printing method is used, the dielectric layer paste and the internal electrode layer paste having a predetermined pattern are stacked and printed on the carrier sheet, cut into a predetermined shape, and then peeled off from the carrier sheet to obtain a green chip. When using the sheet method, a dielectric layer paste is formed on a carrier sheet with a predetermined thickness to form a green sheet, and the internal electrode layer paste is printed in a predetermined pattern on the green sheet. Laminate to make a green chip.

  (3) Next, the obtained green chip is debindered. For example, as shown in FIG. 2, the debinder increases the ambient temperature T0 from, for example, room temperature (25 ° C.) to the debuy holding temperature at a predetermined rate of temperature rise and holds the debuy holding temperature for a predetermined time. This is a step of lowering at a predetermined temperature drop rate.

  In the present embodiment, the rate of temperature rise is preferably 5 to 300 ° C./hour, more preferably 10 to 100 ° C./hour.

  The debye holding temperature is preferably 200 to 400 ° C., more preferably 220 to 380 ° C., and the holding time of the holding temperature is preferably 0.5 to 24 hours, more preferably 2 to 20 hours.

  The temperature lowering rate is preferably 5 to 300 ° C./hour, more preferably 10 to 100 ° C./hour.

The treatment atmosphere of the binder removal is preferably air or a reducing atmosphere. As the atmosphere gas in the reducing atmosphere, it is preferable to use, for example, a wet mixed gas of N ₂ and H ₂ . The oxygen partial pressure in the treatment atmosphere is preferably 10 ⁻⁴⁵ to 10 ⁵ Pa. If the oxygen partial pressure is too low, the binder removal effect is reduced, and if it is too high, the internal electrode layer tends to be oxidized.

  (4) Next, the green chip is fired. For firing, the ambient temperature is raised from a room temperature (25 ° C.), for example, toward the firing holding temperature at a predetermined rate of temperature rise, held for a predetermined time, and then lowered at a predetermined temperature drop rate. It is a process to make.

  During this firing, the dielectric material for addition in the pre-fired internal electrode layer formed of the internal electrode layer paste is transferred into the interlayer dielectric layer 2 formed from the pre-fired dielectric layer formed of the green sheet. Finally, a dielectric layer made of a dielectric composition composed of a sintered body of the dielectric material and the additive dielectric material is formed.

  In the present embodiment, the rate of temperature rise is preferably 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour.

  The firing holding temperature is preferably 1000 to 1350 ° C., more preferably 1100 to 1300 ° C., and the holding time of the holding temperature is preferably 0.5 to 8 hours, more preferably 1 to 3 hours. If the firing holding temperature is too low, the densification is insufficient even if the holding time of the holding temperature is increased, and if too high, the electrode breaks due to abnormal sintering of the internal electrode layer or the conductivity constituting the internal electrode layer. Deterioration of the capacity-temperature characteristic due to diffusion of the material and reduction of the dielectric ceramic composition constituting the dielectric layer are likely to occur.

  The temperature lowering rate is preferably 50 to 500 ° C./hour, more preferably 150 to 300 ° C./hour.

The treatment atmosphere for firing is preferably a reducing atmosphere. As the atmosphere gas in the reducing atmosphere, it is preferable to use, for example, a wet mixed gas of N ₂ and H ₂ . In particular, upon firing, it is preferable to raise the temperature in a N ₂ gas or humidified N ₂ gas atmosphere to a holding temperature at the time of binder removal, and then continue to raise the temperature by changing the atmosphere. After cooling, it is preferable to change to N ₂ gas or a humidified N ₂ gas atmosphere and continue cooling.

  (5) Next, when the green chip is fired in a reducing atmosphere, it is preferable to perform a heat treatment (annealing) subsequently. Annealing is a process for re-oxidizing the dielectric layer, thereby obtaining the characteristics of the final capacitor.

  In the annealing, the ambient temperature is increased from, for example, room temperature (25 ° C.) toward the annealing holding temperature at a predetermined temperature rising rate, and the holding temperature is maintained for a predetermined time, and then the atmospheric temperature is decreased at a predetermined temperature decreasing rate. It is a process to make.

  In the present embodiment, the rate of temperature rise is preferably 100 to 300 ° C./hour, more preferably 150 to 250 ° C./hour.

  The annealing holding temperature is preferably 800 to 1100 ° C., more preferably 900 to 1100 ° C., and the holding time of the holding temperature is preferably 0 to 20 hours, more preferably 2 to 10 hours. If the annealing holding temperature is too low, oxidation of the dielectric layer 2 becomes insufficient, so that the IR is low and the IR life tends to be short. If the holding temperature is too high, not only the internal electrode layer 3 is oxidized and the capacity is lowered, but also the internal electrode layer 3 reacts with the dielectric substrate, the capacity temperature characteristic is deteriorated, the IR is lowered, and the IR lifetime is reduced. Decrease is likely to occur.

  The temperature lowering rate is preferably 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour.

The annealing treatment atmosphere is preferably a neutral atmosphere. As the atmospheric gas in the neutral atmosphere, for example, it is preferable to use humidified N ₂ gas. In annealing, the temperature may be changed to an annealing holding temperature in an N ₂ gas atmosphere, and the atmosphere may be changed, or the entire annealing process may be a humidified N ₂ gas atmosphere. The oxygen partial pressure in the annealing atmosphere is preferably 2 × 10 ^{−4 to 1} Pa. If the oxygen partial pressure is too low, reoxidation of the dielectric layer 2 is difficult, and if it is too high, the internal electrode layer 3 tends to oxidize.

  In the present embodiment, the annealing may be composed of only a temperature raising process and a temperature lowering process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N ₂ gas or mixed gas. In this case, the water temperature is preferably about 0 to 75 ° C. The binder removal, firing, and annealing may be performed continuously or may be performed separately.

  The capacitor element body 10 made of a sintered body is formed by the above processes.

  (6) Next, the external electrode 4 is formed on the obtained capacitor element body 10. The external electrode 4 is formed by polishing the end face of the capacitor element body 10 composed of the sintered body by, for example, barrel polishing or sand blasting, and then, generally, Ni, Pd, Ag, Au, Cu, It can be formed by a known method such as baking an external electrode paste containing at least one of Pt, Rh, Ru, Ir, or an alloy thereof, or applying an In—Ga alloy. If necessary, a coating layer may be formed on the surface of the external electrode 4 by plating or the like.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. . For example, in the above-described embodiment, the binder removal processing, firing, and annealing are performed independently, but the present invention is not limited to this, and at least two steps may be performed continuously. When performing continuously, after removing the binder, the atmosphere is changed without cooling, then the temperature is raised to the holding temperature at the time of firing, firing is performed, and then cooled, when the annealing holding temperature is reached It is preferable to perform annealing by changing the atmosphere.

  Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

Preparation of Dielectric Layer Paste First, a dielectric material, PVB (polyvinyl butyral) resin as a binder, DOP (dioctyl phthalate) as a plasticizer, and ethanol as a solvent were prepared. The dielectric raw material is MnCO ₃ : 0.2 mol%, MgO: 0.5 mol%, VO as the subcomponent raw material, with respect to BaTiO ₃ having an average particle diameter of about 0.2 μm as the main component raw material. ₂ O ₅ : 0.3 mol%, Y ₂ O ₃ : 2 mol%, CaCO ₃ : 3 mol%, BaCO ₃ : 3 mol%, SiO ₂ : 3 mol% were wet mixed in a ball mill for 16 hours and dried. And manufactured.

  Next, 10% by weight of binder, 5% by weight of plasticizer, and 150% by weight of solvent with respect to 100% by weight of dielectric material are weighed, kneaded by a ball mill, and slurried to form a dielectric layer. A paste was obtained.

Preparation of Internal Electrode Layer Paste First, an additive dielectric material, Ni particles having an average particle size of 0.2 μm as a conductive material, an ethyl cellulose resin as a binder, and terpineol as a solvent were prepared. Examples of the dielectric material for addition include BaTiO ₃ as the main component material for addition and MnCO ₃ , MgO as the subcomponent material for addition, having the same composition system as the dielectric material in the dielectric layer paste. , V ₂ O ₅ , Y ₂ O ₃ , CaCO ₃ , BaCO ₃ and SiO ₂ were used. As for BaTiO ₃ as the main component material for addition, the sample of Table 1 used an average particle size of 0.05 μm, and the sample of Table 2 used an average particle size changed. The value of the average particle diameter of BaTiO ₃ as the main component material for addition is a value obtained by converting the value of the specific surface area (SSA) measured by the nitrogen adsorption method (BET method).

  Next, in Samples 6 to 15 in Table 1 and 9-1 to 9-5 in Table 2, for the addition of the amount shown in each table with respect to 100% by weight of the dielectric material in the dielectric layer paste described above. Dielectric material was added. That is, the content of the dielectric material for addition in the internal electrode layer paste is changed by changing the content itself of the dielectric material for addition in the internal electrode layer paste according to the target dielectric layer thickness. The amount was controlled. Then, 5% by weight of binder and 35% by weight of solvent are weighed and added to the mixed powder of conductive material and dielectric material for addition, and kneaded with a ball mill, and slurried to form an internal electrode layer paste. Got.

  On the other hand, in samples 1 to 5 in Table 1, 20% by weight of dielectric material for addition was added to 100% by weight of the conductive material. 5% by weight of binder and 35% by weight of solvent are weighed and added to the mixed powder of conductive material and dielectric material for addition, kneaded with a ball mill, and slurried to obtain an internal electrode layer paste. It was.

Production of Multilayer Ceramic Chip Capacitor Sample Using the obtained dielectric layer paste and internal electrode layer paste, a multilayer ceramic chip capacitor 1 shown in FIG. 1 was produced as follows.

  First, a dielectric layer paste was applied to a predetermined thickness on a PET film by a doctor blade method and dried to form a ceramic green sheet having a thickness shown in each table. In this example, this ceramic green sheet was used as a first green sheet (interlayer dielectric layer before firing), and a plurality of these were prepared.

  An internal electrode layer paste was formed in a predetermined pattern on the obtained first green sheet by a screen printing method to obtain a ceramic green sheet having an electrode pattern with a thickness shown in each table. In this example, this ceramic green sheet was used as a second green sheet (internal electrode layer before firing + interlayer dielectric layer before firing), and a plurality of these were prepared.

The first green sheet was laminated to a thickness of 300 μm to form a green sheet group (an outer dielectric layer before firing). Five second green sheets are laminated on this green sheet group, and the same green sheet group as above is further laminated and formed thereon, and heated under conditions of a temperature of 80 ° C. and a pressure of 1 ton / cm ^2. The green laminate (element body before firing) was obtained by applying pressure.

  Next, the obtained laminate was cut into a size of 3.2 mm in length, 1.6 mm in width, and 1.0 mm in height, and then subjected to binder removal treatment, firing and annealing under the following conditions to obtain a sintered body. Obtained.

  The binder removal was performed under the conditions of a temperature rising rate: 30 ° C./hour, a holding temperature: 250 ° C., a holding time: 8 hours, a temperature lowering rate: 200 ° C./hour, and a processing atmosphere: an air atmosphere.

Firing is performed at a heating rate of 200 ° C./hour, a holding temperature of 1240 ° C., a holding time of 2 hours, a cooling rate of 200 ° C./hour, a processing atmosphere: a reducing atmosphere (oxygen partial pressure: 10 ⁻⁶ Pa with N ₂ The mixed gas with H ₂ was adjusted by passing water vapor).

Annealing is performed at a heating rate of 200 ° C./hour, a holding temperature of 1050 ° C., a holding time of 2 hours, a cooling rate of 200 ° C./hour, a processing atmosphere: a neutral atmosphere (oxygen partial pressure: 0.1 Pa with N ₂ gas Was adjusted by passing water vapor).

  The obtained sintered body was cut and polished on a surface perpendicular to the stacking direction of the internal electrode layers, subjected to thermal etching (1200 ° C., 10 minutes), and observed with a scanning electron microscope (SEM). The average particle size (sintered particle size D50) of the dielectric particles constituting the interlayer dielectric layer was determined by converting the grain area into a circle area and multiplying the diameter by 1.5. The value of D50 is calculated as an average value when n number = 250. The results are shown in each table.

  Regarding the measurement of electrical characteristics, the end surface of the obtained sintered body was polished by sand blasting, and then an In—Ga alloy was applied to form a test electrode to obtain a multilayer ceramic chip capacitor sample. The size of the capacitor sample was 3.2 mm in length × 1.6 mm in width × 1.0 mm in height, and the thickness of the dielectric layer 2 and the thickness of the internal electrode layer 3 were the values shown in each table.

  The temperature characteristics (TC) and relative dielectric constant (ε) of the obtained capacitor samples were evaluated.

  The temperature characteristic (TC) was measured at 120 Hz, 0.5 Vrms, and 0.5 V / μm with a LCR meter in a constant temperature bath at 85 ° C. (ΔC / C (85 ° C.)), −10.0% It became good that it became larger.

  The relative dielectric constant ε was measured with respect to a capacitor sample at a reference temperature of 25 ° C. with a digital LCR meter (YHP 4274A) under a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms. Calculated from capacitance (no unit). The evaluation standard was 1500 or more.

  The results are shown in each table.

FIG. 2 is a graph showing the relationship between the content of the dielectric material for addition in the internal electrode layer paste and the temperature characteristics with respect to 100% by weight of the dielectric material in the dielectric layer paste.

  As shown in Table 1, when a conventional internal electrode layer paste having a content of the dielectric material for addition adjusted to 20% by weight with respect to 100% by weight of the conductive material was formed with a thickness of 1.3 μm, Inclusion of dielectric material in the interlayer dielectric layer before firing as the thickness of the dielectric layer is reduced to 5.0 μm, 4.0 μm, 3.0 μm, 2.0 μm, and 1.5 μm. The weight ratio of the content of the dielectric material for addition in the internal electrode layer paste with respect to the amount is 9.0 wt%, 11.5 wt%, 16.2 wt%, 26.9 wt%, 40.4 wt% It can be seen that the percentage increases.

  In Samples 1 to 4, where the thickness of the interlayer dielectric layer after firing exceeds 1.5 μm, even if the content of the dielectric material for addition in the internal electrode layer before firing changes, TC and ε are affected. I found that there were few.

  On the other hand, in samples 5 to 12 in which the thickness of the interlayer dielectric layer after firing is 1.5 μm or less, in the internal electrode layer before firing of the dielectric material for addition relative to 100% by weight of the dielectric material in the dielectric layer before firing. As the content of TC changed, TC and ε fluctuated greatly. From these, when the interlayer dielectric layer is extremely thin after firing, it is easily affected by the additive dielectric material diffused from the internal electrode layer before firing, and as a result, It was confirmed that the electrical characteristics such as TC and ε are affected.

In particular, in the samples 5 and 6 in which the content of the dielectric material for addition in the internal electrode layer before firing exceeds 30% by weight with respect to 100% by weight of the dielectric material in the interlayer dielectric layer before firing, ε is good However, TC is inferior as a result of increasing the sintered body particle size (D50). Moreover, in the sample 12 in which the addition amount is less than 4.5% by weight, TC is good, but ε is inferior. On the other hand, in samples 7 to 11 within the scope of the present invention, it was confirmed that all of TC and ε were good.

Table 2 shows how TC and ε are affected when the average particle size of BaTiO ₃ as the main ingredient material for addition contained in the dielectric material for addition in the internal electrode layer before firing is changed. . As shown in Table 2, when the average particle size of BaTiO ₃ as the main component material for addition contained in the dielectric material for addition in the internal electrode layer paste is too small, the temperature characteristics tend to deteriorate, It was confirmed that as the average particle size increases, TC improves, but ε decreases. The cause of the decrease in ε is that the effective area due to the interruption is decreased.

FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the content of the dielectric material for addition in the internal electrode layer paste and the temperature characteristics with respect to 100% by weight of the dielectric material in the dielectric layer paste in the example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor element main body 2 ... Interlayer dielectric layer 20 ... Outer dielectric layer 3 ... Internal electrode layer 4 ... External electrode

Claims (6)

A method of manufacturing a multilayer ceramic capacitor having an internal electrode layer and a dielectric layer having a thickness of 1.5 μm or less,
A step of firing a pre-fired element body having a structure in which a plurality of pre-fired dielectric layers containing a dielectric material and base metal conductive materials and pre-fired internal electrode layers containing a dielectric material for addition are alternately stacked;
The content of the dielectric material for addition in the internal electrode layer before firing is controlled in the range of 4.5 to 30% by weight with respect to 100% by weight of the dielectric material contained in the dielectric layer before firing. A method for producing a multilayer ceramic capacitor, which is characterized. According to the target thickness of the dielectric layer, the content of the dielectric material for addition in the internal electrode layer before firing and / or the thickness of the internal electrode layer before firing is changed, and the internal electrode before firing is changed. The method for producing a multilayer ceramic capacitor according to claim 1, wherein the content of the dielectric material for addition in the layer is controlled within the range. The dielectric material for addition in the internal electrode layer before firing includes a main component material for addition,
The additive main component material has substantially the same composition system as the main component material in the dielectric material contained in the dielectric layer before firing, and has an average particle size smaller than the average particle size of the main component material. The manufacturing method of the multilayer ceramic capacitor of Claim 1 or 2 which has. The method for producing a multilayer ceramic capacitor according to claim 3, wherein the additive main component material has an average particle diameter of 0.01 to 0.2 μm. The method for producing a multilayer ceramic capacitor according to claim 3 or 4, wherein the main component material and the main component material for addition are barium titanate. The multilayer ceramic capacitor has an element body having a structure in which an internal electrode layer and an interlayer dielectric layer having a thickness of 1.5 μm or less are alternately stacked between a pair of outer dielectric layers. The manufacturing method of the multilayer ceramic capacitor in any one of Claims 1-5.

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