JPH053684B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a high-permittivity ceramic composition, and is particularly suitable for a low-temperature sintering type high-permittivity multilayer ceramic capacitor synthesized by solid-phase reaction of complex oxides. . [Technical background of the invention and its problems] Conventionally, high dielectric constant ceramic compositions have barium titanate (BaTiO ₃ ) as a main component, and further contain calcium zirconate (CaZrO ₃ ) and calcium titanate (CaTiO ₃ ). Composite dielectric porcelain materials with the addition of such materials are widely used. These porcelain materials are usually
Especially in the case of multilayer ceramic capacitors, since they must be sintered at high temperatures of 1200 to 1400℃,
The internal electrode suitable for this sintering temperature has the disadvantage that gold, platinum, palladium, or an alloy thereof, whose main component is a solid metal, must be used. Furthermore, since it is sintered at a high temperature, it requires a lot of thermal energy such as electric power and gas, which causes significant thermal deterioration of the firing furnace and firing pod, which also has the disadvantage of contributing to an increase in costs. For this reason, we use inexpensive internal electrodes mainly composed of silver, etc., which enables sintering at low temperatures below 1000°C, and creates high-permittivity porcelain compositions with a high dielectric constant and low dielectric loss. development was desired. In _{response to} these requirements _, Pb( _{Fe 2/3} W _{1/3 )} (X is 0.2≦0.5) materials are known. Further, in Japanese Patent Application Laid-open No. 15591/1984, an attempt was made to add SiO to this material system. However, this material system has poor temperature characteristics of dielectric loss (tan δ) and low insulation resistance. Furthermore, it has low mechanical strength and is prone to cracking and chipping, which poses a major practical problem when producing multilayer ceramic capacitors. [Objective of the invention] To improve the above-mentioned drawbacks, to provide a material with high dielectric constant and insulation resistance, excellent tan δ temperature characteristics and mechanical strength,
Another object of the present invention is to provide a low-temperature sintering type high dielectric constant ceramic composition that has improved high-temperature load and moisture resistance. [Summary of the invention] The present invention provides at least one of barium oxide (BaO), calcium oxide (CaO), lead oxide (PbO),
It consists _of iron oxide (Fe _{2 O 3} ), niobium oxide (Nb ₂ O ₅ ), tungsten oxide (WO ₃ ), and copper oxide (CuO) _{. 1/2} ) W _1/2 O ₃ (where M is at least one of Ba and Ca), x = 90 to 99.5,
A high permittivity ceramic composition containing 0.01 to 1.0% by weight of cobalt oxide (CoO) as an additive based on 100% by weight of the basic composition of y = 0.5 to 10, and if necessary, the high permittivity ceramic composition. Furthermore, 0.01 to 1.0% by weight of manganese oxide (MnO) is added as an additive. Next, the reasons for limiting the composition of the present invention will be described. First, the basic composition represented by xPb(Fe _1/2 Nb _1/2 ) O ₃ −yM (Cu _1/2 W _1/2 ) O ₃ has a composition range in which x is 90 to 99.5 and y is 0.5 to 10. The reason for limiting this is that when x = less than 90, the dielectric constant at room temperature decreases and it is not suitable as a capacitor material. When y = less than 0.5, M (Cu _{1/ 2} W _1/2 ) O ₃ (M: Ba,
This is because the effect of Ca) is hardly obtained, and when y=10 or more, the dielectric constant decreases and tan δ increases.
The reason for limiting the CoO content to 0.01 to 1.0% by weight is that if it is less than 0.01% by weight, it will have little effect in reducing the bores (holes) inside the sintered body, increasing the specific gravity, and improving mechanical strength. Not present, 1.0% by weight
This is because, if it exceeds this amount, sufficient sintering will not be achieved and the mechanical strength will decrease. Also, addition of CoO increases insulation resistance. Furthermore, MnO if necessary
The reason for limiting the content to 0.01 to 1.0% by weight is that less than 0.01% by weight improves the temperature characteristics of tan δ and improves the high temperature load characteristics and moisture resistance characteristics when used as a multilayer capacitor. hardly appears, and if it exceeds 1.0% by weight,
This is because tanδ increases. [Examples of the Invention] A high dielectric constant ceramic composition according to the present invention is produced, for example, as follows. First, as a starting material,
PbO _{, Fe2O3} , _WO3 , _Nb2O5 , _{CaCO3 , BaCO3} ,
CuO, CoCO ₃ , MnCO ₃ and the like were weighed so as to have the compounding ratio shown in Table 1. After wet mixing these raw materials in a ball mill, they are roasted at 700 to 800℃, and then ground again in a ball mill to form a dry powder.
A binder such as PVA was added and a disk-shaped sample with a diameter of 17 mmφ and a thickness of 1.2 mm was prepared under a pressure of approximately 0.8 ton/cm ² . These molded bodies were placed in a magnesia pod and fired for 2 hours at 850 to 950°C in an oxygen atmosphere or air, and then silver paste was applied to the sintered body and heated to 600°C.
The measurement sample was baked at ~700°C. Here, the dielectric constant and tan δ were measured at a frequency of 1 KHz and are shown in Table 1.

【table】

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[Table] In Table 1, the reference examples are outside the scope of the present invention and are shown for comparison. As is clear from Table 1, those within the scope of the present invention have large dielectric constants of about 22,000 to 27,000, and dielectric loss (tan δ) of about 0.3 to 0.8%, which is extremely small. However, firing at temperatures below 900°C is possible. Further, Fig. 1 shows Example 7, Fig. 2 shows Example 18,
FIG. 3 shows the temperature characteristics of the dielectric constant and tan δ of Example 29, and FIG. 4 shows the temperature characteristics of Example 40. Also,
Reference examples 1 and 24 are shown in Figure 5 as reference examples, and reference example 15 is shown in Figure 5.
FIG. 6 shows the temperature characteristics of the dielectric constant and tan δ of Reference Example 38. As is clear from Table 1 and FIGS. 1 to 7, the porcelain composition of the present invention contains Pb(Fe _1/2 Nb _1/2 )
Due to the solid solution of M (Cu _1/2 W _1/2 ) O ₃ (M: Ba, Ca) in O ₃ , the dielectric constant at room temperature becomes Pb (Fe _1/2
Nb _1/2 )O ₃ is dramatically improved by 3.5 to 5 times compared to the case where O 3 is 100 mol %. Furthermore, it can be seen that tan δ is significantly reduced to about 1/2 to 1/10. Addition of a small amount of CoO significantly improves the resistivity. Furthermore, since the specific gravity of the sintered body is also improved, the densification of the sintered body is promoted. Also, the addition of a small amount of MnO
It can be seen that tan δ at low temperature (-55°C) is reduced by about 20% to 50% compared to the case without addition, and at high temperature (125°C), tan δ is reduced to about 1/5. The amount of CoO and MnO added is 0.01~
It can be seen that when they coexist in the range of 1.0% by weight, each acts independently and improves the properties, and has the great feature that there is no effect that cancels out the advantages of each other. Next, bending strength was used to evaluate mechanical strength. To measure the bending strength, the obtained dielectric ceramic disks were ground on both sides to a thickness of 1 mm to give a mirror finish, and then a sample plate with a width of 3 mm was cut from the center of each disk using a diamond cutter. In order to remove the effects of scratches on the surface, the cut surface was polished with SiC sandpaper to 800# → 1500# → 2000#, then the edges were rounded and finished, and the three-point bending method was performed using an Instron universal testing machine. Ivy. The bending strength (transverse rupture strength) is determined by the following formula. Transverse rupture strength = 3/2 Pml/d ² W where, Pm: Maximum breaking load (Kg) l: Distance between supporting points (cm) d: Thickness of sample (cm) W: Width of sample (cm) . Data of the examples of the present invention are shown in Table 2 together with reference examples.

【table】

[Table] As is clear from the results in Table 2, a small amount of CoO
It is clear that mechanical strength can also be significantly improved by adding . This fact is very advantageous for chip components that are soldered directly onto circuit boards. Note that when CoO or MnO is added in an amount exceeding 1.0% by weight, no improvement in mechanical strength is observed. Next, a high temperature load test and a moisture resistance test were conducted. The multilayer capacitors used in this high-temperature load test and moisture resistance test were made by adding an appropriate amount of a binder such as privinyl butyral, polyethylene glycol, or octyl phthalate, and a solvent such as trichlorethylene or ethyl alcohol to the powder after roasting. , create a normal slurry, create a 50 μm thick sheet using a doctor blade device, print electrodes, laminate and cut, then bake, attach external electrodes, and create a 4.5 x 3.2 mm 1 μF multilayer chip capacitor. It was created. 100 of these multilayer capacitors were subjected to high-temperature load tests and moisture resistance tests as specified in the Japan Electronics Industry Association standard RC-3698B multilayer capacitors for electronic equipment (chip type), and the failure rate and capacitance changes after the tests. were investigated and shown in Tables 3 and 4, respectively. In addition, each test was based on the above standards, and the high temperature load test was conducted at 50V, DC applied condition, and the characteristics after 125℃ x 1000 hours, and the moisture resistance test was conducted at 25V, DC applied condition,
Characteristics were evaluated after 500 hours at 40°C and 95%RH.

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[Table] As is clear from Tables 3 and 4, a small amount of
By adding MnO, the failure rate was significantly improved, the rate of change in capacity was reduced, and it was confirmed that the product had excellent high-temperature load characteristics and moisture resistance. In the above examples, oxides,
Although carbonate was used, it goes without saying that the same effect can be obtained by using other organometallic compounds such as sulfur oxides instead of oxides at high temperatures. [Effects of the Invention] As described above, in the present invention, the dielectric constant is large;
Low-temperature sintering with excellent tan δ temperature characteristics and mechanical strength, and by containing a small amount of CoO, the specific resistance has been greatly improved, and by further containing a small amount of MnO, the high temperature load characteristics and moisture resistance have been improved. A type of high dielectric constant ceramic composition was obtained, which can be said to be extremely excellent industrially.

[Brief explanation of drawings]

Figures 1 to 4 are curve diagrams showing characteristic examples of a high dielectric constant ceramic composition according to the present invention, and Figures 5 to 7 are curve diagrams showing characteristic examples of a high dielectric constant ceramic composition as a reference example. It is a diagram.

Claims (1)

[Claims] 1. Consists of at least one of barium oxide, calcium oxide, lead oxide, iron oxide, niobium oxide, tungsten oxide, and copper oxide, xPb(Fe _1/2 Nb _1/2 ) O ₃ −yM( When expressed as Cu _1/2 W _1/2 ) O ₃ (M is at least one of Ba and Ca), added to 100% by weight of the basic composition where x = 90 to 99.5 and y = 0.5 to 10. A high dielectric constant ceramic composition characterized by containing 0.01 to 1.0% by weight of cobalt oxide. 2. A high dielectric constant ceramic composition according to claim 1, further comprising 0.01 to 1.0% by weight of manganese oxide as an additive.