HK1107975B - Dielectric ceramics and multi-layer ceramic capacitor - Google Patents

Abstract

Dielectric ceramics include a sintered body comprising a principal ingredient, when represented by: ABO3 + aRe + bM + Zr oxide where AB03 is a barium titanate-based solid solution having a perovskite structure, Re is at least one oxide of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and/or Y, M is at least one oxide of Mg, Al, Cr, Mn, Fe, Ni, Cu, and/or Zn, a and b each represents a mol number of the oxides per 1 rnol of AB03 within a range of: 1.100 ≤ Ba/Ti ≤ 1.700, 0.05 ≤ a ≤ 0.25, 0.05≤ b ≤ 0.25, Ti:Zr = 95:5 to 60:40.

Description

Dielectric ceramic and laminated ceramic capacitor

Technical Field

The invention relates to a barium titanate (BaTiO)₃) A dielectric ceramic mainly composed of Ni or a Ni alloy, and a multilayer ceramic capacitor using the dielectric ceramic are provided.

Background

Multilayer ceramic capacitors used in electronic devices such as mobile devices and communication devices are increasingly required to be smaller and have larger capacities. In order to produce such a small-sized large-capacity multilayer ceramic capacitor, for example, a dielectric ceramic composition containing a barium titanate-based solid solution and an additive component and having a small loss and heat generation at high frequency and high voltage has been proposed in japanese patent No. 3567759.

Further, in patent No. 3361531, a dielectric ceramic composition is proposed which is mainly composed of barium titanate, can be fired simultaneously with Ni in a reducing atmosphere, and has a high dielectric constant.

[ patent document 1] patent No. 3567759

[ patent document 2] patent No. 3361531

Disclosure of Invention

In recent years, there has been a demand for further miniaturization and increase in capacity of multilayer ceramic capacitors, and the thickness of ceramic layers after firing has reached a level of 10 μm or less, and further 5 μm or less. In the dielectric ceramic composition disclosed in japanese patent No. 3567759, the green sheet thickness of the order of 20 μm described in the examples of the above publication has a long high-temperature load life and sufficient reliability, but there are the following problems: when the thickness of the ceramic layer after firing is further on the order of 10 μm or less, the reliability is lowered.

Further, in recent years, low distortion capacitors with small distortion have been demanded, but the dielectric ceramic composition disclosed in patent No. 3361531 has a high dielectric constant of 7000 or more, and is suitable for increasing the capacitance, but is not suitable for the application of low distortion capacitors.

The present invention provides a dielectric ceramic having a dielectric constant of 250 to 850 and a temperature characteristic of a dielectric constant satisfying X6S characteristics, which is more reliable than conventional ones, and a Ni inner electrode multilayer ceramic capacitor.

The invention provides a dielectric ceramic which is characterized by comprising a main component and SiO₂Or with SiO₂A sintered body of a glass component as a main body, and the SiO₂Or with SiO₂The glass component mainly comprises 1.0 to 10.0 parts by weight of ABO based on 100 parts by weight of the barium titanate solid solution₃+ aRe + bM + Zr oxide (wherein, ABO₃A barium titanate-based solid solution represented by a general formula representing a perovskite structure, Re is an oxide of at least 1 metal selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, M is an oxide of a metal element selected from Mg, Al, Cr, Mn, Fe, Ni, Cu and Zn, and a and b represent ABO per 1mol in terms of a chemical formula including 1 metal element in each oxide₃The number of mols) is 1.100. ltoreq.Ba/Ti is less than or equal to 1.700, a is less than or equal to 0.05 and less than or equal to 0.25, and b is less than or equal to 0.05 and less than or equal to 0.25, wherein when the ratio of Zr oxide to Zr of Ti is 95: 5 to 60: 40. Further, a part of Ba in the barium titanate solid solution is substituted with Sr or Ca.

The Ba/Ti ratio represents the ratio of Ba and Ti contained in the barium titanate solid solution, and does not necessarily match the a/B ratio in the perovskite structure. For example with BaTiO₃And (Ba)_1-x-yCa_xSr_y)TiO₃For example, the A/B ratio of any one is 1, but with respect to the Ba/Ti ratio, BaTiO₃Is 1, and (Ba)_1-x-yCa_xSr_y)TiO₃Is 1-x-y.

The present invention also provides a multilayer ceramic capacitor including a plurality of dielectric ceramic layers, internal electrodes formed between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, wherein the dielectric ceramic layers are formed of the dielectric ceramic described above, and the internal electrodes are formed of Ni or a Ni alloy.

According to the present invention, a dielectric ceramic which can be fired at 1280 ℃ or less, has a dielectric constant of 250 to 850, and has a temperature characteristic satisfying X6S can be obtained.

Further, the present invention can improve reliability such as life characteristics compared with conventional dielectric ceramics by specifying Ba/Ti.

The dielectric constant of the present invention is about 250 to 850, and the present invention can be applied to a low distortion multilayer ceramic capacitor.

Drawings

FIG. 1 is a schematic sectional view of a multilayer ceramic capacitor.

[ description of symbols ]

1 laminated ceramic capacitor

2 ceramic laminate

3 dielectric ceramic layer

4 internal electrode

5 external electrode

6 first plating layer

7 second plating layer

Detailed Description

The following describes embodiments of the dielectric ceramic of the present invention. The dielectric ceramic of the present invention contains a barium titanate-based solid solution, Re (Re is an oxide of at least 1 metal selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y), M (M is an oxide of a metal element selected from Mg, Al, Cr, Mn, Fe, Ni, Cu and Zn), and Zr oxide in the above composition ratio, and is a sintered body formed by sintering SiO₂Or SiO₂The glass component as a main component is added as a sintering aid. As the glass component, Li is exemplified₂O-SiO₂Is glass or B₂O₃-SiO₂Glass, etc.

The dielectric ceramic is obtained as follows. First, BaCO was weighed and prepared in such a manner as to satisfy the range of the present invention₃、TiO₂、ZrO₂As starting material. In this case, CaCO may be appropriately prepared₃、SrCO₃. Moreover, BaZrO may also be used₃、CaZrO₃、SrZrO₃Substituted for ZrO₂. Water is added to each raw material, and wet mixing is performed using a ball mill, a bead mill, a dispersion mill, or the like. Drying the mixed substance, and pre-sintering the dried substance at 1100-1250 ℃ to obtain the barium titanate solid solution.

The Re component (e.g., Ho) will be aligned in a compositional ratio consistent with the scope of this invention₂O₃) M component (e.g., MgO and MnO; and may be MnCO)₃、Mn₃O₄) And a sintering aid (e.g., SiO)₂) The weighed substances are added to the obtained barium titanate solid solution, wet-mixed by a ball mill or the like, dried, and then calcined at 700 to 900 ℃ to obtain dielectric ceramic powder. The obtained dielectric ceramic powder is used for forming dielectric ceramic layers of a laminated ceramic capacitor.

Next, a multilayer ceramic capacitor according to an embodiment of the present invention will be described. As shown in fig. 1, the multilayer ceramic capacitor 1 of the present embodiment includes a plurality of dielectric ceramic layers 3; and a ceramic laminate 2 including internal electrodes 4 formed between the dielectric ceramic layers. On both end surfaces of the ceramic laminate 2, external electrodes 5 are formed so as to be electrically connected to the internal electrodes, and if necessary, first and second plating layers 6 and 7 are formed on the external electrodes 5.

Next, a method for manufacturing the multilayer ceramic capacitor 1 will be described. First, a raw material powder for forming the dielectric ceramic of the present invention is prepared. The raw material powder is mixed with a butyral-based or acrylic organic binder, a solvent, and other additives to form a ceramic slurry. The ceramic slurry is formed into a thin layer by using a coating device such as a roll coater, thereby forming a ceramic green sheet having a specific thickness as the dielectric ceramic layer 3. On the ceramic green sheet, a conductive paste of Ni or Ni alloy is applied in a specific pattern shape by screen printing to form a conductor layer as the internal electrode 4.

After stacking a necessary number of ceramic green sheets on which conductor layers are formed, the ceramic green sheets are pressure-bonded to form an original laminate. The laminate is cut into individual pieces, and then the adhesive is removed in air or a non-oxidizing gas such as nitrogen. After removing the binder, a conductive paste is applied to the exposed surface of the internal electrode of each individual chip, and a conductive film as the external electrode 5 is formed. In a nitrogen-hydrogen environment at a specific temperature (oxygen partial pressure of 10)^-10atm or so), and firing the individual chips after the formation of the conductor film. In addition, the external electrode 5 may be formed by firing individual piecesAfter the ceramic laminate 2 was formed, a conductive paste containing glass frit was applied to the exposed surface of the internal electrode, and then fired. The external electrodes 5 may be made of the same metal as the internal electrodes, or may be made of Ag, Pd, AgPd, Cu alloy, or the like. Further, first plating layers 6 are formed on the external electrodes 5 with Ni, Cu, or the like, and second plating layers 7 are formed on the first plating layers 6 with Sn, an Sn alloy, or the like, thereby obtaining the multilayer ceramic capacitor 1.

[ examples ]

(example 1)

Preparation of BaCO₃、TiO₂、ZrO₂、Gd₂O₃MgO was used as a starting material to obtain a sintered body having a composition of table 1. In table 1, Ba, Ti, and Zr are represented by ratios when Ti + Zr is 100.

[ Table 1]

Outside the scope of the invention

Using a ball mill to mix the prepared BaCO₃、TiO₂、ZrO₂Wet mixing, drying, and pre-sintering at 1100 deg.C to obtain barium titanate solid solution. Next, Gd was added to the barium titanate-based solid solution so as to have the composition shown in table 1₂O₃MgO, MnO and SiO₂Wet mixing in a ball mill, drying, and pre-sintering at 900 deg.c to obtain ceramic dielectric powder. In table 1, the sintering aid is represented by parts by weight relative to 100 parts by weight of the barium titanate-based solid solution.

Polyvinyl butyral, an organic solvent, and a plasticizer are added to and mixed with the powder to form a ceramic slurry. The ceramic slurry was formed into a thin layer by a roll coater to obtain a ceramic green sheet having a thickness of 5 μm. An Ni internal electrode paste was applied to the ceramic green sheet by screen printing to form internal electrodesAnd (4) patterning. 21 ceramic green sheets having internal electrode patterns formed thereon were stacked and bonded, and the bonded ceramic green sheets were cut and divided into original chips with a size of 4.0X 2.0 mm. The original chips were freed of binder in a nitrogen atmosphere, coated with Ni external electrode paste, and subjected to a reducing atmosphere (nitrogen-hydrogen atmosphere, oxygen partial pressure of 10)^-10atm), at the firing temperature shown in table 2. The dielectric ceramic capacitors having a size of 3.2X 1.6mm and a dielectric ceramic layer thickness of 3 μm obtained as described above were measured for ε r (dielectric constant), tan δ, temperature characteristics, and the average life for reliability evaluation, and are summarized in Table 2. Further, the average lifetime was measured for 15 samples at 150 ℃ under a load of 25V/. mu.m, and the average lifetime was O when the time for which the insulation resistance value was 1 M.OMEGA.or less was 48 hours or more.

[ Table 2]

Sample number	Firing temperature of	εr	tanδ％	TCC	Average life
						101*	1280	760	0.38	×	×
102	1280	650	0.35	X6S	○
						103	1280	430	0.30	X6S	○
104*	1280	-	-	-	-
						105*	1280	-	-	-	-
106	1280	510	0.31	X6S	○
						107*	1280	400	0.28	X6S	×

According to the results, a dielectric ceramic and Ni internal electrode laminated ceramic capacitor having high reliability, satisfying X6S characteristic in temperature characteristic of dielectric constant and having dielectric constant in the range of 250 to 850 can be obtained if Ba/Ti is in the range of 1.100 to 1.700 and Ti/Zr is in the range of 95: 5 to 60: 40. Further, the samples 104, 105 sintered NG (failure).

(example 2)

A dielectric ceramic powder was formed in the same manner as in example 1 to obtain sintered bodies having the compositions shown in table 3. Here, the addition amount of Re was increased to verify the effect.

[ Table 3]

Outside the scope of the invention

The dielectric ceramic powders were formed into multilayer ceramic capacitors in the same manner as in example 1, and ∈ r, tan δ, temperature characteristics, and average lifetimes were measured and summarized in table 4.

[ Table 4]

Sample number	Firing temperature of	εr	tanδ％	TCC	Average life
						201	1280	300	0.32	X6S	○
202	1280	310	0.30	X6S	○
						203	1280	315	0.25	X6S	○
204	1280	330	0.20	X6S	○
						205	1280	335	0.22	X6S	○
206	1280	360	0.21	X6S	○
						207	1280	380	0.21	X6S	○
208	1280	400	0.22	X6S	○
						209	1280	570	0.25	X6R	○
210	1280	600	0.27	X6R	○
						211	1280	560	0.30	X6R	○
212	1280	565	0.28	X6R	○
						213	1280	560	0.28	X6R	○
214	1280	570	0.30	X6R	○
						215	1280	650	0.30	X6R	○
216*	1280	970	0.35	X6S	×

217	1280	850	0.32	X6S	○
						218	1280	250	0.25	X6S	○
219*	1280	260	0.30	X6S	×

From the above results, if the composition ratio of Re, i.e., a, is in the range of 0.05. ltoreq. a.ltoreq.0.25, a dielectric ceramic and a Ni inner electrode laminated ceramic capacitor having high reliability, satisfying X6S characteristic as the temperature characteristic of dielectric constant and having a dielectric constant in the range of 250 to 850 can be obtained.

(example 3)

A dielectric ceramic powder was formed in the same manner as in example 1 to obtain sintered bodies having the compositions shown in table 5. Here, the addition amount of M was increased to verify the effect.

[ Table 5]

Outside the scope of the invention

Multilayer ceramic capacitors were formed by using the above dielectric ceramic powders in the same manner as in example 1, and ∈ r, tan δ, temperature characteristics, and average lifetime were measured and summarized in table 6.

[ Table 6]

Sample number	Firing temperature of	εr	tanδ％	TCC	Average life
						301	1280	450	0.35	X6S	○
302	1280	460	0.40	X6S	○
						303	1280	380	0.29	X6S	○
304	1280	370	0.31	X6S	○
						305	1280	430	0.33	X6S	○
306	1280	420	0.32	X6S	○
						307*	1280	530	0.25	×	-
308	1280	450	0.20	X6S	○
						309	1280	290	0.22	X6S	○
310*	1280	260	0.24	X6S	×

From the above results, if the composition ratio of M, that is, b is in the range of 0.05. ltoreq. b.ltoreq.0.25, a dielectric ceramic and Ni inner electrode laminated ceramic capacitor having high reliability, satisfying X6S characteristic as temperature characteristic of dielectric constant and having dielectric constant in the range of 250 to 850 can be obtained.

(example 4)

A dielectric ceramic powder was formed in the same manner as in example 1 to obtain sintered bodies having compositions in table 7. Here, sample 408 is an example of patent document 1, and 409 is a well-known composition. Here, moreover, B is used₂O₃-SiO₂BaO glass as a glass component for the sintering aid.

[ Table 7]

Outside the scope of the invention

Multilayer ceramic capacitors were formed by using the above dielectric ceramic powders in the same manner as in example 1, and ∈ r, tan δ, temperature characteristics, and average lifetime were measured and are summarized in table 8.

[ Table 8]

Sample number	Firing temperature of	εr	tanδ％	TCC	Average life
						401*	1280	-	-	-	-
402	1280	550	0.25	X6S	○
						403	1260	270	0.35	X6S	○
404*	1260	240	0.40	X6S	×
						405	1260	330	0.45	X6S	○
406	1280	340	0.25	X6S	○
						407	1280	320	0.24	X6S	○
408*	1280	400	0.20	X6S	×
						409	1280	6000	0.65	×	○

From the above results, if the composition of the sintering aid is in the range of 1.0 to 10.0 parts by weight based on 100 parts by weight of the barium titanate-based solid solution, a dielectric ceramic and a Ni internal electrode multilayer ceramic capacitor having high reliability, satisfying X6S characteristic in temperature characteristic of dielectric constant and having a dielectric constant in the range of 250 to 850 can be obtained. Further, it is found that the dielectric ceramic and the multilayer ceramic capacitor of the present invention have more excellent characteristics than the conventional ones.

According to the above results, the present invention can provide a dielectric ceramic and a Ni inner electrode multilayer ceramic capacitor having higher reliability than the conventional ones, satisfying X6S characteristic in temperature characteristic of dielectric constant, and having a dielectric constant of 250 to 850.

Claims (3)

1. A dielectric ceramic, characterized by:

which comprises a sintered body containing a main component represented by ABO3+ aRe + bM + Zr oxide and SiO2 or a glass component mainly composed of SiO2 and having a dielectric constant of 250 to 850,

ABO3 represents a barium titanate-based solid solution in a general formula representing a perovskite structure, Re represents an oxide of at least 1 metal selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, M represents an oxide of a metal element selected from Mg, Al, Cr, Mn, Fe, Ni, Cu and Zn, a and b represent the number of moles of ABO3 per 1 mole when each oxide is converted into a chemical formula containing 1 metal element,

wherein

1.100≤Ba/Ti≤1.700

0.05≤a≤0.25

0.05≤b≤0.25

Zr oxide is in a Zr ratio with respect to Ti

Ti∶Zr＝95∶5～60∶40

And the SiO2 or SiO 2-based glass component is in the range of 1.0 to 10.0 parts by weight per 100 parts by weight of the barium titanate solid solution.

2. A dielectric ceramic as claimed in claim 1 wherein:

a part of Ba in the barium titanate solid solution is substituted with Sr or Ca.

3. A multilayer ceramic capacitor having a plurality of dielectric ceramic layers, internal electrodes formed between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes, characterized in that:

the dielectric ceramic layer is ABO₃A main component represented by + aRe + bM + Zr oxide, and SiO₂Or with SiO₂A sintered body of a glass component as a main body, and a dielectric constant of 250-850,

ABO₃a barium titanate-based solid solution represented by a general formula representing a perovskite structure, Re is an oxide of at least 1 metal selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, M is an oxide of a metal element selected from Mg, Al, Cr, Mn, Fe, Ni, Cu and Zn, and a and b represent ABO per 1mol of the oxide in terms of a chemical formula including 1 metal element₃The number of moles of (a) in the composition,

wherein

1.100≤Ba/Ti≤1.700

0.05≤a≤0.25

0.05≤b≤0.25

Zr oxide is in a Zr ratio with respect to Ti

Ti∶Zr＝95∶5～60∶40

And the SiO₂Or with SiO₂A glass component mainly containing a glass in an amount of 1.0 to 10.0 parts by weight based on 100 parts by weight of the barium titanate solid solution,

and the internal electrodes are formed of Ni or a Ni alloy.