JP4792707B2 - Manufacturing method of multilayer ceramic capacitor - Google Patents

Description

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

  In recent years, it has been desired to reduce the thickness of a dielectric layer (interlayer dielectric layer) existing between two opposing internal electrode layers as much as possible in order to realize a reduction in size and capacity of a multilayer ceramic capacitor. . As the thickness of the interlayer dielectric layer is reduced and the number of dielectric particles constituting the interlayer dielectric layer is reduced, the importance of appropriately controlling the existence state of the dielectric particles is increasing.

  For example, in Patent Document 1, in a multilayer ceramic capacitor composed of a dielectric layer and an internal electrode layer, the grain growth of dielectric particles constituting the interlayer dielectric layer is promoted, and the particle structure of the interlayer dielectric layer is controlled. Therefore, a technique capable of realizing a high dielectric constant without deteriorating electrical characteristics has been proposed.

  According to Patent Document 1, an internal electrode layer paste contains an additive component for promoting grain growth of dielectric particles constituting an interlayer dielectric layer, and the internal electrode layer paste and the dielectric layer paste After the green laminate is formed using, the laminate is fired. However, the composition of the additive component does not overlap even partly with the composition of the dielectric particles constituting the interlayer dielectric layer. Thus, even if the additive component contained in the internal electrode layer paste does not overlap with the composition of the dielectric particles constituting the interlayer dielectric layer, the thickness of the interlayer dielectric layer is relatively thick at about 10 μm. In case, there was no problem.

However, in the technique described in Patent Document 1, when the interlayer dielectric layer is further thinned, for example, when it is thinned to 3.5 μm or less, the characteristics of the obtained capacitor (bias characteristics at 85 ° C.) are inferior. There was a trend.
JP 2003-1224049 A

  An object of the present invention is to provide a method of manufacturing a multilayer ceramic capacitor that can be expected to improve bias characteristics at 85 ° C. even when an interlayer dielectric layer is thinned.

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 3.5 μm or less,
A laminate formed using a dielectric layer paste including a dielectric material composed of barium titanate as a main component material and subcomponent materials, and an internal electrode layer paste including a dielectric material for addition Having a step of firing
The additive dielectric material includes at least barium titanate as a main component material for addition,
The barium titanate has substantially the same composition system as barium titanate as the main component material contained in the dielectric material in the dielectric layer paste, and has an average particle size of 0.01 to 0.2 μm And having a pH of 7.5 or more and 12 or less .
In this method, “substantially the same composition system” means that the type of each element and the type of each element are the same except that the composition molar ratio of each element is completely the same. This is intended to include cases where the composition molar ratio is slightly different. In the former case, for example, when the main component material contained in the dielectric material in the dielectric layer paste is (BaO) _m TiO ₂ (where m = 1), the addition in the internal electrode layer paste 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). In 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).

  In the present invention, the dielectric material for addition only needs to contain “at least the main component material for addition”, and may further contain subcomponent materials for addition.

In the present invention, at least the main component material for addition contained in the dielectric material for addition and the main component material contained in the dielectric material in the dielectric layer paste need only have substantially the same composition system. .
Therefore, in the case where the dielectric material for addition contains an additive subcomponent material in addition to the additive main component material,
(1) 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. 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 dielectric layer paste.
(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 dielectric layer paste. The same composition system may be used.

  The 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. When the internal electrode layer is made of a base metal, the dielectric layer includes Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and R (R) in addition to the main component such as barium titanate. May contain subcomponents including one or more kinds of oxides of one or more rare earth elements such as Y) and compounds that become these oxides upon firing. 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, when manufacturing a multilayer ceramic capacitor having a dielectric layer containing subcomponents in addition to the main component, the dielectric material contained in the dielectric layer paste contains the main component and subcomponents after firing. Contains the main component raw material and subcomponent raw material to be formed. In this case, as described above, the additive dielectric material contained in the internal electrode layer paste contains the additive subcomponent material in addition to the additive main component material.

  Preferably, the dielectric layer contains barium titanate as a main component, magnesium oxide and rare earth element oxide as subcomponents, and at least selected from barium oxide and calcium oxide as other subcomponents. 1 type and at least 1 sort (s) selected from silicon oxide, manganese oxide, vanadium oxide, and molybdenum oxide are contained.

  At this time, the dielectric material for addition contained in the internal electrode layer paste contains barium titanate as the main component material for addition, and magnesium oxide as a subcomponent material for addition (including a compound that becomes magnesium oxide after firing) And at least one selected from barium oxide (including a compound that becomes barium oxide after firing) and calcium oxide (including a compound that becomes calcium oxide after firing). It is preferable to contain seeds and at least one selected from silicon oxide, manganese oxide (including a compound that becomes manganese oxide after firing), vanadium oxide, and molybdenum oxide.

  The firing step may be a step of raising the atmospheric temperature toward the firing holding temperature T2, holding the T2 for a predetermined time, and then lowering the temperature. Details of each step of raising temperature, holding T2, and lowering the temperature Is not particularly limited.

  The first feature of the present invention is that the main component material for addition contained in the dielectric material for addition in the internal electrode layer paste is substantially different from the main component material contained in the dielectric material in the dielectric layer paste. The same composition system. By doing so, even if the dielectric material for addition diffuses from the internal electrode layer 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 3.5 μm or less, if the final composition of the dielectric layer fluctuates in comparison with the initial composition, the characteristics of the obtained capacitor, particularly at 85 ° C. It is not possible to sufficiently improve the bias characteristics (the amount of change in capacitance when a predetermined bias voltage is applied at 85 ° C. as compared with the capacitance at room temperature). By using an additive dielectric material that does not change the final composition of the dielectric layer, an improvement in bias characteristics of the obtained capacitor at 85 ° C. can be expected.

The second feature of the present invention is that a main component material for addition contained in the dielectric material for addition in the internal electrode layer paste has a specific average particle diameter and pH . By doing so, the particle structure of the finally obtained dielectric layer is effectively controlled, and improvement of the characteristics of the obtained capacitor, in particular, the bias characteristic at 85 ° C. can be expected.

  That is, according to the present invention, it is possible to manufacture a multilayer ceramic capacitor that can be expected to improve the bias characteristics at 85 ° C. even when the interlayer dielectric layer is thinned.

  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 graph showing temperature changes during binder removal processing, firing and annealing in the examples.

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 (0.6 to 5.6 mm) × width (0.3 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 thickness of the interlayer dielectric layer 2 is preferably 3.5 μm or less, more preferably 2.5 μm or less, and even more preferably 2.0 μm or less. In the present embodiment, even when the thickness of the interlayer dielectric layer 2 is reduced as described above, the bias characteristics at 85 ° C. of the capacitor 1 are improved. The number of interlayer dielectric layers 2 may be appropriately determined according to the purpose and application, but is usually multi-layered to 50 layers or more.

  The interlayer dielectric layer 2 and the outer dielectric layer 20 are composed of dielectric particles 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 preferably as thin as 2.0 μm or less, more preferably 1.2 μm or less.

  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, the dielectric layer paste that will form the interlayer dielectric layer 2 and the outer dielectric layer 20 shown in FIG. 1 after firing, and the internal electrode layer 3 shown in FIG. 1 after firing. An internal electrode layer paste is prepared.

Dielectric Layer Paste A dielectric layer paste is prepared by kneading a dielectric material and an organic vehicle.

  As a dielectric material, the main component material and subcomponent material which will form the main component and subcomponent which comprise the dielectric material layer 2 after baking are contained.

  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, at least if the main component material for addition contained in the dielectric material for addition and the main component material contained in the dielectric material in the dielectric layer paste are substantially the same composition system Good. 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. Thus, by making at least the main component material for addition and the main component material substantially the same composition system, the composition of the dielectric layer due to diffusion from the internal electrode layer to the dielectric layer is not changed. .

In the present invention, a material having a pH in a specific range is used as the main component material for addition in the dielectric material for addition. The present inventors have found that by using a main component material having a specific pH as an additive, the particle structure of the dielectric layer 2 can be effectively controlled and the bias characteristics of the capacitor 1 at 85 ° C. can be improved. It was. The pH of the main component material for addition is preferably 7.5 or more, more preferably 8 to 11. If the pH is too low, the effect of improving the bias characteristics at 85 ° C. cannot be achieved. On the other hand, if it is too high, it is difficult to manufacture.

  In the present invention, as the main component material for addition in the dielectric material for addition, one having an average particle diameter in a specific range is used. In addition to the above pH, the present inventors can effectively control the particle structure of the dielectric layer 2 by using a main component material having a specific average particle diameter for addition, and the capacitor 1 at 85 ° C. It has been found that the bias characteristics of can be improved. The average particle size of the main component material for addition may be the same as the particle size of the dielectric material contained in the dielectric layer paste, but is preferably smaller, more preferably 0.01 to 0.2 μm, particularly preferably. Is 0.01 to 0.15 μm.

  The dielectric material for addition (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. The same applies hereinafter unless otherwise specified) The layer paste is preferably contained in an amount of 5 to 30% by weight, more preferably 10 to 20% by weight, based on the conductive material. If the content of the dielectric material for addition in the paste is too small, the effect of suppressing the sintering of the conductive material is lowered, and if too much, the continuity of the internal electrodes is lowered. That is, if the content of the dielectric material for addition is too small or too large, both can cause inconveniences such as a sufficient capacitance as a capacitor cannot be secured.

  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, a green chip is produced using the dielectric layer paste and the internal electrode layer paste. 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.) toward the debuy holding temperature T1 at a predetermined heating rate, and holds the T1 for a predetermined time. Thereafter, the temperature is lowered at a predetermined temperature lowering 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 buy-out holding temperature T1 is preferably 200 to 400 ° C., more preferably 220 to 380 ° C., and the holding time of the T1 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 example, as shown in FIG. 2, the firing is performed by increasing the ambient temperature T0 from a room temperature (25 ° C.) toward a firing holding temperature T2, for example, at a predetermined heating rate, and holding the T2 for a predetermined time. This is a step of lowering the ambient temperature at a predetermined temperature drop rate (see the solid line portion in FIG. 2).

  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 T2 is preferably 1100 to 1300 ° C, more preferably 1150 to 1250 ° C, and the holding time of T2 is preferably 0.5 to 8 hours, more preferably 1 to 3 hours. If T2 is too low, densification will be insufficient even if the holding time of T2 is lengthened. If it is too high, discontinuity of the electrode due to abnormal sintering of the internal electrode layer, or diffusion of the conductive material constituting the internal electrode layer Deterioration of the capacitance-temperature characteristics due to the above, and reduction of the dielectric ceramic composition constituting the dielectric layer is 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, in firing, it is preferable to raise the temperature in a N ₂ gas or humidified N ₂ gas atmosphere to a holding temperature T1 at the time of binder removal, and then continue to raise the temperature by changing the atmosphere. After cooling to T3, it is preferable to continue the cooling by changing to an N ₂ gas or humidified N ₂ gas atmosphere again.

The oxygen partial pressure in the firing atmosphere is preferably 6 × 10 ⁻⁹ to 10 ⁻⁴ Pa. If the oxygen partial pressure is too low, the conductive material of the internal electrode layer may be abnormally sintered and interrupted, and if it is too high, the internal electrode layer tends to oxidize.

  In the present embodiment, as indicated by the wavy line in FIG. 2, the atmospheric temperature T0 may be raised to T2 after being held for a predetermined time at the predetermined temperature T4 before reaching the firing holding temperature T2. Thus, by keeping for a predetermined time at T4 before reaching T2, it is easier to adjust to a desired particle structure, and as a result, the bias characteristics at 85 ° C. are further improved. That is, by keeping for a predetermined time at T4 before reaching T2, the bias characteristic at 85 ° C. of the obtained multilayer ceramic capacitor 1 can be improved.

  T4 in this case is preferably 400 to 1050 ° C, more preferably 600 to 1000 ° C. This T4 holding time is preferably 0.5 to 10 hours, more preferably 1 to 2 hours.

  (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.

  For example, as shown in FIG. 2, the annealing is performed by increasing the ambient temperature T0 from, for example, room temperature (25 ° C.) toward the annealing holding temperature T3 at a predetermined heating rate, and holding T3 for a predetermined time. This is a step of lowering the ambient temperature T0 at a predetermined temperature drop rate.

  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 T3 is preferably 800 to 1100 ° C., more preferably 900 to 1100 ° C., and the holding time of T3 is preferably 0 to 20 hours, more preferably 2 to 10 hours. If T3 is too low, oxidation of the dielectric layer 2 becomes insufficient, so the IR is low and the IR life tends to be short. If T3 is too high, not only will the internal electrode layer 3 oxidize and the capacity will decrease, but the internal electrode layer 3 will react with the dielectric substrate, causing deterioration in capacity-temperature characteristics, IR, and IR life. 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 the holding temperature T3 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 T3 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. In the case of performing continuously, after removing the binder, the atmosphere is changed without cooling, the temperature is raised to the holding temperature T2 at the time of firing, firing is performed, and then the temperature is lowered to reach the annealing holding temperature T3. Sometimes 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%, V ₂ as subcomponent raw material with respect to BaTiO ₃ having an average particle diameter of about 0.2 μm as the main component raw material. 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. Manufactured.

  Next, 10% by weight of binder, 5% by weight of plasticizer, and 150% by weight of solvent are weighed with respect to the dielectric material, kneaded with a ball mill, and slurried to obtain a dielectric layer paste. Obtained.

Preparation of Internal Electrode Layer Paste Ni particles having an average particle size of 0.2 μm as a conductive material, an additive dielectric material, an ethylcellulose 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. However, as for BaTiO ₃ as the main component material for addition, as shown in each table, a sample whose average particle diameter and pH were changed was used for each sample.

In addition, the average particle diameter of the main component raw material for addition in each table is a value obtained by observing the raw material with a scanning electron microscope (SEM) at n number = 300 to 400 and calculating the arithmetic average thereof. The pH in each table is as follows: BaTiO ₃ : 30 g of the main ingredient raw material powder for addition is added to 100 ml of ion-exchanged water, which is stirred for 5 minutes by ultrasonic dispersion, and the supernatant portion after standing for 100 hours is pH It is a value measured with a meter at a water temperature of 25 ° C.

  Next, 20% by weight of dielectric material for addition was added to 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 of 1.5 μm. In this example, this ceramic green sheet was used as the first green sheet, 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 of 1.5 μm. In this example, this ceramic green sheet was used as the second green sheet, and a plurality of these were prepared.

The first green sheets were laminated to a thickness of 300 μm to form a green sheet group. 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. Pressurized to obtain a green laminate.

  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. FIG. 2 shows a graph showing each temperature change of the binder removal processing, firing and annealing.

  The binder removal was performed under the conditions of a temperature rising rate: 30 ° C./hour, a holding temperature T1: 250 ° C., a holding time: 8 hours, a temperature falling 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 T2: 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 to N ₂ And a mixed gas of H ₂ was adjusted by passing water vapor).

As for annealing, temperature rising rate: 200 ° C./hour, holding temperature T3: 1050 ° C., holding time: 2 hours, cooling rate: 200 ° C./hour, treatment atmosphere: neutral atmosphere (oxygen partial pressure: 0.1 Pa to N ₂ The gas was adjusted by passing water vapor).

In addition, about the samples 12-14, as shown with the wavy line of FIG. 2, holding temperature T2
After being held at a temperature T4 before reaching for a predetermined time, the ambient temperature was raised to T2.

  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, the thickness of the dielectric layer 2 was 1.0 μm, and the thickness of the internal electrode layer 3 was 1.2 μm.

  The bias characteristics at 85 ° C. of the obtained capacitor samples were evaluated. The bias characteristics of the capacitor at 85 ° C. were measured using a LCR meter with a bias voltage of 1 kHz, 0.7 Vrms, 2.6 V in a thermostatic chamber maintained at 85 ° C. The capacity change rate was calculated and evaluated from the measured value when no bias voltage was applied. The evaluation criterion is that it is favorable that it is larger than -21.0%. The results are shown in Tables 1-3.

As shown in Table 1, in Sample 1 where the pH of BaTiO ₃ as the main ingredient material for addition contained in the dielectric material for addition in the internal electrode layer paste deviates from 7.5 or more, bias characteristics at 85 ° C. Is inferior. In contrast, in Samples 2 to 6 within the scope of the present invention, the capacitance change rate at 25 ° C. to 85 ° C. is within ± 10% on the basis of 20 ° C., and the bias characteristics at 85 ° C. are excellent. I was able to confirm.

As shown in Table 2, in the samples 7 and 11 in which the average particle diameter of BaTiO ₃ as the main ingredient material for addition contained in the dielectric material for addition in the internal electrode layer paste deviates from 0.01 to 0.2 μm Bias characteristics at 85 ° C. are inferior. On the other hand, in Samples 8 to 10 within the scope of the present invention, the capacitance change rate at 25 ° C. to 85 ° C. is within ± 10% on the basis of 20 ° C., and the bias characteristics at 85 ° C. are excellent. I was able to confirm.

  As shown in Table 3, as shown by the wavy line in FIG. 2, after holding for a predetermined time at a temperature T4 before reaching the firing holding temperature T2, the ambient temperature T0 was raised to T2 and the samples 12 to 12 were fired. 18, the effect of improving the bias characteristics at 85 ° C. is recognized as compared with Sample 2 in which this is not performed. In the sample 18 where T4 exceeds 1050 ° C., the effect of improving the bias characteristics tends to be reduced. Note that the capacitance change rate at 25 ° C. to 85 ° C. on the basis of 20 ° C. was within ± 10% for all samples.

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 temperature changes in the binder removal processing, firing, and annealing in the examples.

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 (3)

A method of manufacturing a multilayer ceramic capacitor having an internal electrode layer and a dielectric layer having a thickness of 3.5 μm or less,
A laminate formed using a dielectric layer paste including a dielectric material composed of barium titanate as a main component material and subcomponent materials, and an internal electrode layer paste including a dielectric material for addition Having a step of firing
The additive dielectric material includes at least barium titanate as a main component material for addition,
The barium titanate has substantially the same composition system as barium titanate as the main component material contained in the dielectric material in the dielectric layer paste, and has an average particle size of 0.01 to 0.2 μm And having a pH of 7.5 or more and 12 or less . The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein the additive dielectric material includes barium titanate as an additive main component material and an additive subcomponent material. A method of manufacturing a multilayer ceramic capacitor having an internal electrode layer and a dielectric layer having a thickness of 3.5 μm or less,
A laminate formed using a dielectric layer paste including a dielectric material composed of barium titanate as a main component material and subcomponent materials, and an internal electrode layer paste including a dielectric material for addition Having a step of firing
The dielectric material for addition includes barium titanate as a main component material for addition and an auxiliary component material for addition,
The additive dielectric material is substantially the same composition system as the dielectric material in the dielectric layer paste,
A method for producing a multilayer ceramic capacitor, wherein barium titanate as the main ingredient for addition has an average particle diameter of 0.01 to 0.2 μm and a pH of 7.5 to 12 .

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