JP2008189542A - Dielectric paste, capacitor, and capacitor embedded multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric paste which is free from the occurrence of calcination cracking, conductor peeling, warpage or the like owing to the shrinkage during firing at a temperature of not higher than 900°C, and can be suitably used for making a capacitor of a large capacitance and a capacitor-embedded multilayer ceramic substrate. <P>SOLUTION: The dielectric paste includes an inorganic powder material composed of not less than 80 wt.% and not greater than 87.5 wt.% of a dielectric powder expressed by BaTi<SB>1-x</SB>Zr<SB>x</SB>O<SB>3</SB>(where x=0-0.2), and the rest of Bi<SB>2</SB>O<SB>3</SB>-ZnO-B<SB>2</SB>O<SB>3</SB>type glass powder having a softening temperature of not lower than 400°C and not higher than 500°C and a specific inductive capacity of not less than 20; and a liquid organic vehicle containing a binder and a plasticizer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dielectric paste, a capacitor, and a multilayer ceramic substrate with a built-in capacitor. More particularly, the present invention relates to a capacitor excellent in high frequency characteristics such as a microwave and a millimeter wave band and a dielectric paste that provides a multilayer ceramic substrate with a built-in capacitor in fields such as information communication and automobiles.

  In recent years, glass-alumina-based green sheets that are densified at a temperature of 900 ° C. or less have been put into practical use for low-temperature fired multilayer ceramic substrates. Since such a green sheet can be co-fired with a silver conductor, its use is expanding as it can utilize the high electrical conductivity of silver. Typical applications of such a low-temperature fired multilayer ceramic substrate are a multilayer ceramic substrate with a built-in capacitor and a ceramic package in which semiconductor devices, resistors, and capacitors are mounted on the ceramic substrate. Therefore, if capacitors, resistors, etc. can be built into a low-temperature fired ceramic substrate through a simultaneous firing process, mounting can be simplified and high-density mounting can be achieved. Can be strengthened. In addition, in a multilayer ceramic substrate with a built-in capacitor, if the capacitor portion can be made smaller, the degree of design freedom increases, the application range expands, and the industrial value becomes higher. Therefore, development of a capacitor having a dielectric having a high relative dielectric constant is desired.

In such a multilayer ceramic substrate with a built-in capacitor, generally, a conductive paste is applied on a green sheet, a dielectric paste is applied on the conductive paste, and a conductive paste is applied on the dielectric paste, By stacking and integrating another green sheet on top of it, a capacitor having a dielectric sandwiched between two electrodes can be formed between the ceramic substrates.
Conventionally, as a dielectric paste used for manufacturing such a capacitor, {(Ba _1-x Ca _x ) O} _m (Ti _1-y Zr _y ) O ₂ (where 0.02 ≦ x ≦ 0. 22, 0.05 ≦ y ≦ 0.20, 1.00 ≦ m ≦ 1.05) and a Bi ₂ O ₃ —SiO ₂ glass component (for example, Patent Document 1). This dielectric paste can provide a dielectric having a high relative dielectric constant.

JP 2001-247365 A

However, when a conventional dielectric paste or conductor paste is applied to the surface of a green sheet and fired, the shrinkage behavior between the dielectric paste and the green sheet is different, resulting in firing cracks, conductor peeling, warping, etc. There was a problem peculiar to simultaneous firing.
A problem peculiar to such simultaneous firing is considered that if the relative dielectric constant of the capacitor is high, the size difference after firing can be reduced by reducing the area of the capacitor to be manufactured. However, in fact, Patent Document 1 does not recognize a problem peculiar to co-firing and does not show the shape and area of a capacitor to such an extent that the problem peculiar to co-firing can be industrially allowed.
Therefore, the present inventors used a dielectric paste and a conductor paste of Patent Document 1 to print a 2 mm square pattern on a green sheet, and then fired at a temperature of 900 ° C. or lower to cause firing cracks or peeling of the conductor. It was experimentally investigated whether or not warpage occurred. As a result, the multilayer ceramic substrate with a built-in capacitor using the dielectric paste disclosed in Patent Document 1 is warped and the capacitance of the capacitor is not sufficient.

The present invention has been made in order to solve the above-described problems, and provides a capacitor having a large electric capacity and a multilayer ceramic substrate with a built-in capacitor, and shrinkage behavior upon simultaneous firing at a temperature of 900 ° C. or lower. An object of the present invention is to provide a dielectric paste that does not cause firing cracks, conductor peeling, warpage, and the like.
Another object of the present invention is to provide a capacitor having a large electric capacity and a multilayer ceramic substrate with a built-in capacitor that can be manufactured by a co-firing process at a temperature of 900 ° C. or lower.

  The present inventors have made firing with shrinkage behavior at the time of co-firing at a temperature of 900 ° C. or lower by making the firing shrinkage amount of the green paste that can be co-fired with the conductor paste and the dielectric paste comparable. Based on the viewpoint that cracks, peeling of conductors, warping, etc. could be suppressed, the inorganic powder material used for the dielectric paste was selected by paying attention to the firing shrinkage and specific permittivity of the specific inorganic powder material. . As a result, it has been found that a dielectric paste using a specific inorganic powder material gives a dielectric having an excellent relative dielectric constant and has a firing shrinkage comparable to that of a glass-alumina green sheet.

That is, in the present invention, the dielectric powder represented by BaTi _1-x Zr _x O ₃ (wherein x = 0 to 0.2) is 80 wt% or more and 87.5 wt% or less, and the balance is 400 ° C. An inorganic powder material which is a Bi ₂ O ₃ —ZnO—B ₂ O ₃ glass powder having a softening temperature of 500 ° C. or less and a relative dielectric constant of 20 or more;
A dielectric paste comprising a liquid organic vehicle containing a binder and a plasticizer.

Further, the present invention is a capacitor formed on a ceramic substrate made of a dielectric sandwiched between two electrodes,
The capacitor is obtained by firing the dielectric paste at a temperature of 900 ° C. or less.

Furthermore, the present invention is a multilayer ceramic substrate with a built-in capacitor in which a capacitor made of a dielectric sandwiched between two electrodes is disposed between two laminated ceramic substrates,
A multilayer ceramic substrate with a built-in capacitor, wherein the dielectric is obtained by firing the dielectric paste at a temperature of 900 ° C. or lower.

  According to the present invention, a capacitor having a large electric capacity and a multilayer ceramic substrate with a built-in capacitor are provided, and at the same time firing at a temperature of 900 ° C. or less, a dielectric that does not cause firing cracks, conductor peeling, warpage, etc. accompanying shrinkage behavior Body paste can be provided.

Embodiment 1 FIG.
The present inventors conducted the following experiments in order to select an inorganic powder material to be used for the dielectric paste.
A dielectric paste that can be fired at a low temperature is required to be densified at a firing temperature of 1000 ° C. or less, and in particular, when silver, which is a good conductor, is used for a wiring pattern (electrode, etc.), 900 ° C. or less. It is required that densification proceeds at the firing temperature. Therefore, the glass powder of Table 1 having a low softening temperature was used as a constituent component of the inorganic powder material so that densification progressed at a firing temperature of 900 ° C. or lower.

Further, as the dielectric powder, BaTiO ₃ powder, SrTiO ₃ powder and Ba _1-x Sr _x TiO ₃ (wherein x = 0.2, 0.4, 0.6, 0.8) powder are inorganic powders. Used as a constituent of the material.

Various glass powders A to I in Table 1 and the above various dielectric powders are mixed at a predetermined ratio using an automatic mortar, compacted into a disk shape, and then fired at a predetermined temperature to be sintered. Samples (Samples 1 to 5 and Comparative Samples 1 to 13) were prepared. Moreover, the sintered compact sample (comparative samples 14-16) using only dielectric powder was also produced for the comparison. In addition, although the comparative sample 14 performed low-temperature baking at 850 degreeC, it was the green compact form which was hardly sintered. Further, the comparative samples 15 and 16 were fired at 1250 ° C. in order to be sintered.
With respect to the sintered body sample thus obtained, the shrinkage rate (ΔD / D) accompanying firing was determined from the dimension before firing (D) and the dimensional change after firing (ΔD). Moreover, the electrostatic capacity | capacitance in the measurement frequency of 100 kHz was measured using the impedance meter about the sintered compact sample which grind | polished the disk surface of the sintered compact sample in parallel, and formed the silver electrode on both surfaces. From the capacitance values thus measured, the relative permittivity (ε ′ _r ) was calculated by considering the sintered body sample as a capacitor. These results are shown in Table 2.

In Table 2, a sintered body using SrTiO ₃ powder and Ba _1-x Sr _x TiO ₃ (where x = 0.2, 0.4, 0.6, 0.8) powder as the dielectric powder. Although the results of the samples are not shown, all of these samples had a shrinkage rate (ΔD / D) of 2% or less and a relative dielectric constant (ε ′ _r ) as small as 20 to 30. On the other hand, as shown in Table 2, all sintered body samples using BaTiO ₃ powder as the dielectric powder were sintered using SrTiO ₃ powder and Ba _1-x Sr _x TiO ₃ powder. The relative dielectric constant was larger than that of the consolidated sample. Therefore, it was judged that BaTiO ₃ powder is suitable as a dielectric powder that gives a dielectric having a large relative dielectric constant.

Among the sintered body samples using the BaTiO ₃ powder, the comparative sample 14 is a sample obtained by firing at a low temperature at 850 ° C. using the BaTiO ₃ powder alone. Therefore, the relative dielectric constant of the sample is BaTiO ₃ powder and glass. This is a criterion for determining a change in relative dielectric constant of a sintered body sample using powder. That is, if the relative dielectric constant of the sintered body sample using the BaTiO ₃ powder and the glass powder is larger than the relative dielectric constant of the comparative sample 14, it can be determined that the relative dielectric constant has been improved. Therefore, it was judged that the relative dielectric constant could be improved by the combination of BaTiO ₃ powder and glass powder as in Samples 1 to 5 and Comparative Samples 7, 10 and 11.

In general, when a green compact comprising a dielectric powder and a glass powder is fired at a low temperature, the relative permittivity is 1 for any glass component, assuming that the glass powder melts and fills the gaps between the particles of the dielectric powder. Therefore, it is considered that the relative dielectric constant of the obtained sintered body sample is larger than the relative dielectric constant of the sintered body sample using the dielectric powder alone.
However, in reality, the volume of the sintered body sample using the dielectric powder and the glass powder is larger than the volume of the sintered body sample using the dielectric powder alone, Body powder may be eroded by glass and its volume may be reduced. As a result, the relative dielectric constant may not be improved even with a sintered body sample using dielectric powder and glass powder.

  Therefore, in order for the relative permittivity of the sintered body sample using the dielectric powder and the glass powder to exceed the relative permittivity of the sintered body sample using the dielectric powder alone, In addition to having a relative dielectric constant of a specific value or more, it is considered necessary that the sintered body sample has a contraction rate of a specific value or more. That is, the glass powders A, C, F, G and I used in Samples 1 to 5 and Comparative Samples 7, 10 and 11 have a large relative dielectric constant and excellent fluidity in the vicinity of the firing temperature. It is considered that the gap between the powder particles can be quickly filled and densified. Furthermore, it is considered that such glass powder can reduce the mixing amount of the glass powder in the inorganic powder material, and can also suppress a decrease in relative dielectric constant. Furthermore, since these glass powders are glass powders having low basicity, it is considered that erosion of the dielectric powder can be suppressed by analogy that the oxide easily dissolves in the basic molten salt.

Next, various synthetic methods BaTiO ₃ powder produced by (general solid-phase reaction method, an alkoxide method which gives the BaTiO ₃ powder sinterability and gives a highly crystalline BaTiO ₃ powder hydrothermal synthesis method) baked was tried to compare the properties of the sintered body samples, sintered powder using a BaTiO ₃ powder produced by hydrothermal synthesis, using BaTiO ₃ powder produced by other synthetic method using The relative dielectric constant was larger than that of the consolidated sample. Therefore, it was judged that BaTiO ₃ powder produced by a hydrothermal synthesis method is suitable as an inorganic powder material that gives a dielectric having a higher relative dielectric constant.

Moreover, when Table 2 is seen, all the sintered compact samples (samples 1-5 and comparative samples 1-13) using the inorganic powder material which consists of dielectric powder and glass powder are shrink | contracted, and 850 degreeC It can be seen that densification proceeds at the firing temperature. Therefore, these inorganic powder materials were judged to be capable of low-temperature firing at 850 ° C.
However, when a wiring pattern (silver-based conductor paste, dielectric paste, etc.) is formed on a green sheet that can be fired simultaneously with the conductor paste, and these are simultaneously fired at 900 ° C. or less, the wiring pattern warps or peels off. In order to eliminate this, it is required that the difference in shrinkage ratio due to firing between the conductive sheet and the green sheet that can be fired simultaneously and the wiring pattern (particularly, the dielectric paste) is small.
Since the shrinkage rate of a green sheet that can be co-fired with such a conductor paste is generally about 12 to about 15%, the shrinkage rate of the dielectric paste needs to be within this range. Therefore, since the sintered body samples of Samples 1 to 5 and Comparative Samples 2 to 3, 5 to 6 and 13 have shrinkage in this range, the inorganic powder material used for the sintered body sample is It was judged that it was suitable as a material for the dielectric paste.

From the above experimental results, samples 1 to 5 satisfy the condition that they have excellent dielectric properties and have the same degree of shrinkage as that of a green sheet that can be fired simultaneously with the conductor paste. A (Bi ₂ O ₃ —ZnO—B ₂ O ₃ ) or I (Bi ₂ O ₃ —ZnO—B ₂ O ₃ —SiO ₂ ) was used. As shown in Table 1, the glass powders A and I have a large relative dielectric constant and a low softening temperature among the examined glass powders, and have higher fluidity during low-temperature firing than other glass powders. it is conceivable that. The glass powder A and I does not contain alkali oxides (R 2 _O) and alkaline earth oxides (R'O), basic also considered to be low.
In addition, although it has not evaluated about what increased the dielectric constant further by adjusting the composition ratio of glass powder A, if the softening temperature is 400 degreeC or more and 500 degrees C or less, it is suitable as the glass powder of this invention. Needless to say.

Next, the temperature dependence of the relative dielectric constant of Sample 3 was evaluated. For comparison, the comparative sample 16 was also evaluated in the same manner. The result is shown in FIG.
In FIG. 1, the vertical axis of the graph is a value obtained by normalizing the measured relative dielectric constant with the relative dielectric constant at room temperature (ε ′ _r / ε ′) so that the sample 3 and the comparative sample 16 can be easily compared. _r (20 ° C.)) was used.
As shown in FIG. 1, the sintered body sample of Sample 3 is clearly flattened regardless of the temperature change, and is found to be preferable for use as a general electric component. On the other hand, the sintered body sample of the comparative sample 16 exhibited a typical ferroelectric phase behavior having a sharp peak at about 130 ° C.

The present inventors further performed the following experiment in order to further select inorganic powder materials.
As the dielectric powder, BaTiO ₃ powder and BaTi _0.8 Zr _0.2 O ₃ powder produced by various synthesis methods were used, and as the glass powder, glass powders A and I that were effective in the above experiment were used. It was. Various glass powders and various dielectric powders shown in Table 3 were mixed at a predetermined ratio using an automatic mortar, compacted into a disk shape, fired at a predetermined temperature, and sintered body samples (samples) 6 to 10 and comparative samples 17 and 18) were prepared. Next, the disk surface of this sintered body sample was polished in parallel, and the capacitance at a measurement frequency of 100 kHz was measured using an impedance meter for the sintered body sample having silver electrodes formed on both surfaces thereof. From the capacitance values thus measured, the relative permittivity (ε ′ _r ) was calculated by considering the sintered body sample as a capacitor. The results are shown in Table 3.
For dielectric powder, X-ray diffraction measurement using a Cu target and θ / 2θ drive is performed using an X-ray diffractometer manufactured by Bruker Ax, Inc., and the half-value width of a diffraction peak serving as an index of crystallinity of the powder is measured. Went. The results are shown in Table 3. Here, the smaller the half width of the diffraction peak, the higher the crystallinity. For the half-value width of the diffraction peak in Table 3, the value of the half-value width at the diffraction peak of the (111) plane having the highest diffraction peak intensity was used.

As shown in Table 3, the half width of the diffraction peak was the smallest for the dielectric powder by the hydrothermal synthesis method, and then the dielectric powder by the solid phase reaction method was the smallest. Therefore, it can be said that the dielectric powder by the hydrothermal synthesis method has the highest crystallinity of the dielectric powder, and then the dielectric powder by the solid-phase reaction method.
Since the comparative sample 14 in Table 2 is a sample obtained by firing at a low temperature at 850 ° C. using BaTiO ₃ powder alone, the relative dielectric constant of the sample is that of a sintered body sample using BaTiO ₃ powder and glass powder. This is a criterion for determining the change in relative permittivity. That is, if the relative dielectric constant of the sintered body sample using the BaTiO ₃ powder and the glass powder is larger than the relative dielectric constant of the comparative sample 14, it can be determined that the relative dielectric constant has been improved. Therefore, when the relative dielectric constants of the samples 6, 8 and 10 using the BaTiO ₃ powder in Table 3 and the comparative samples 17 and 18 are compared with the relative dielectric constant of the comparative sample 14 in Table 2, the samples 6, 8 and The relative dielectric constant of 10 was higher than that of Comparative Sample 14. Therefore, it can be determined that the relative permittivity of Samples 6, 8, and 10 has improved. From this result, in order to improve the relative dielectric constant, the crystallinity of the dielectric powder is preferably high, and the half width at the diffraction peak of the (111) plane of the dielectric powder is preferably 0.086 ° or less. It was judged.

From the above several experimental results, as the inorganic powder material in the dielectric paste of the present embodiment, a dielectric represented by BaTi _1-x Zr _x O ₃ (where x = 0 to 0.2) Bi ₂ O ₃ —ZnO—B ₂ O ₃ -based glass powder having a relative permittivity of 20 or more and a softening temperature of 400 ° C. or more and 500 ° C. or less, 12.5 wt% It was concluded that a combination with no less than 20% and no more than 20% by weight is suitable. Based on these conclusions, the composition of the dielectric paste and the like were examined, and the dielectric paste of the present embodiment was developed.
Hereinafter, the dielectric paste of the present embodiment will be described in detail.

The dielectric paste of the present embodiment includes a predetermined inorganic powder material and a liquid organic vehicle containing a binder and a plasticizer.
The inorganic powder material used for the dielectric paste includes a dielectric powder represented by BaTi _1-x Zr _x O ₃ (where x = 0 to 0.2), Bi ₂ O ₃ —ZnO—B ₂ O _It is comprised from ₃ type | system | group glass powder.
The dielectric powder used in the present embodiment is not particularly limited, and those synthesized by a solid phase reaction method, an alkoxide method, a hydrothermal synthesis method, or the like can be used. Among these, a dielectric powder synthesized by a hydrothermal synthesis method is preferable because it has good crystallinity and can increase the electric capacity of the capacitor.

The average particle size of the dielectric powder may be appropriately set according to the thickness of the dielectric to be obtained, and is not particularly limited. For example, when forming a dielectric having a thickness of 15 μm, the average particle diameter of the dielectric powder is generally preferably 0.5 μm or more and 8 μm or less. When the average particle size of the dielectric powder is less than 0.5 μm, a dielectric paste in which the powder is sufficiently dispersed may not be obtained due to secondary aggregation of the powders. On the other hand, when the average particle size of the dielectric powder exceeds 8 μm, the electrical characteristics of the obtained capacitor may not be stabilized.
The content of the dielectric powder in the inorganic powder material is 80% by weight or more and 87.5% by weight or less. When the content of the dielectric powder is less than 80% by weight, a capacitor having a desired electric capacity cannot be obtained. On the other hand, when the content of the dielectric powder exceeds 87.5% by weight, desired shrinkage behavior cannot be obtained, and cracks, conductor peeling, warpage, and the like occur during firing.

The Bi ₂ O ₃ —ZnO—B ₂ O ₃ glass powder used in the present embodiment is a glass powder containing three components of Bi ₂ O ₃ , ZnO, and B ₂ O ₃ . Bi ₂ O ₃ —ZnO—B ₂ O ₃ -based glass powder may contain not only three components but also a small amount of SiO ₂ . This Bi ₂ O ₃ —ZnO—B ₂ O ₃ -based glass powder containing a small amount of SiO ₂ is particularly expressed as Bi ₂ O ₃ —ZnO—B ₂ O ₃ —SiO ₂ -based glass powder.
Such glass powder has a relative dielectric constant of 20 or more. The larger the relative dielectric constant, the higher the electric capacity of the obtained capacitor. From this point, the upper limit of the relative dielectric constant is not limited. On the other hand, if the relative dielectric constant is less than 20, a capacitor having a desired electric capacity cannot be obtained. Moreover, this glass powder has a softening temperature of 400 degreeC or more and 500 degrees C or less. When the softening temperature is less than 400 ° C., the organic component contained in the green sheet is prevented from being rapidly removed, and bubbles, swelling, peeling, and the like are caused. On the other hand, if the softening temperature exceeds 500 ° C., the fluidity during low-temperature firing is too low, and a capacitor having a desired electric capacity cannot be obtained.

As long as the glass powder has a relative dielectric constant and a softening temperature as described above, the ratio of Bi ₂ O ₃ , ZnO, B ₂ O ₃ and arbitrary SiO ₂ is not particularly limited. The glass powder having such characteristics can be produced according to a conventionally known method. For example, Bi ₂ O ₃ —ZnO—B ₂ O ₃ glass powder includes Bi ₂ O ₃ , ZnO, and B ₂ O _3. Are mixed in equimolar amounts and melted at 1300 ° C., and then the melt is dropped onto a metal plate, rapidly cooled to vitrify, and pulverized.

The average particle diameter of the glass powder may be set as appropriate according to the thickness of the dielectric to be obtained, and is not particularly limited, like the average particle diameter of the dielectric powder. For example, when a dielectric having a thickness of 15 μm is formed, the average particle size of the glass powder is generally preferably 0.5 μm or more and 8 μm or less. When the average particle size of the glass powder is less than 0.5 μm, a dielectric paste in which the powder is sufficiently dispersed may not be obtained due to secondary aggregation between the powders. On the other hand, if the average particle size of the glass powder exceeds 8 μm, the electrical characteristics of the obtained capacitor may not be stabilized.
The content of the glass powder in the inorganic powder material is 12.5 wt% or more and 20 wt% or less. If the content of the glass powder is less than 12.5% by weight, desired shrinkage behavior cannot be obtained, and cracks, conductor peeling, warpage, and the like occur during firing. On the other hand, when the content of the glass powder exceeds 20% by weight, the electric capacity suddenly decreases, and a capacitor having an industrially useful electric capacity value cannot be obtained.

  The organic vehicle used for the dielectric paste of the present embodiment is liquid and includes a binder and a plasticizer. The binder and plasticizer are not particularly limited, and conventionally known binders and plasticizers can be used. Specific examples of the binder include ethyl cellulose and the like, and specific examples of the plasticizer include n-butyl phthalate and the like. Such an organic vehicle can also contain a lubricant such as polypropylene glycol, a solvent such as terpineol, and the like.

  What is necessary is just to adjust suitably according to the printing method etc. to be used about the weight ratio of the inorganic powder material and organic vehicle in the dielectric paste of this Embodiment, and there is no restriction | limiting in particular. In general, the weight ratio of the inorganic powder material and the organic vehicle in the dielectric paste is preferably 7: 3 to 8: 2. If the weight ratio of the organic vehicle in the dielectric paste is too large, printing may blur and a desired dielectric shape may not be obtained. On the other hand, if the weight ratio of the organic vehicle in the dielectric paste is too small, printing may be faint.

  The dielectric paste of the present embodiment can be manufactured according to a known method using the above inorganic powder material and organic vehicle. Specifically, an organic vehicle may be added to the inorganic powder material to make a paste.

Next, a capacitor and a multilayer ceramic substrate with a built-in capacitor according to the present invention will be described with reference to the drawings.
FIG. 2 is a cross-sectional view of the capacitor in the present embodiment. In FIG. 2, the capacitor is composed of a dielectric 3 sandwiched between two electrodes 2 and is formed on the surface of the ceramic substrate 1. The dielectric 3 is obtained by firing the dielectric paste of the present invention at a temperature of 900 ° C. or less, and the electrode 2 is obtained by firing the conductor paste at a temperature of 900 ° C. or less.

  In the capacitor of this embodiment, the conductive paste is applied to the surface of the green sheet, then the dielectric paste is applied on the conductive paste, and then the conductive paste is applied on the dielectric paste. , By simultaneous firing at a temperature of 900 ° C. or less. Here, a plurality of green sheets may be laminated on the opposite surface of the green sheet to which the conductor paste and the dielectric paste are applied, and may be baked at a temperature of 900 ° C. or less after being pressure-bonded and integrated by an isostatic press.

  The green sheet is a green sheet that can be fired simultaneously with the conductor paste. Such a green sheet generally has a shrinkage ratio of about 12 to about 15% when fired at a temperature of 900 ° C. or lower, and specifically, a conventionally known glass-alumina ceramic green sheet. Can be mentioned. Such a green sheet of glass-alumina ceramic is, for example, a slurry of glass-alumina ceramic powder prepared by mixing glass powder such as boric acid silicate or boric acid alumina silicate and alumina powder at about 1: 1. Then, it can be produced by molding into a sheet shape. Such a molding method is not particularly limited, and a doctor blade method, an extrusion method, a roll coater method, a printing method, or the like may be used depending on the desired thickness of the green sheet. Further, the thickness of the green sheet is not particularly limited, and may be appropriately set in consideration of the thickness after firing.

  Here, when preparing the said slurry, what is necessary is just to add a binder, a plasticizer, and a solvent to glass-alumina ceramic powder, and to mix with a ball mill etc. Examples of the binder include polyvinyl butyral and acrylic resin. Examples of the plasticizer include dioctyl phthalate, di-n-butyl phthalate, and polyethylene glycol. Examples of the solvent include alcohols such as toluene and ethanol.

As said conductor paste, baking at the temperature of 900 degrees C or less is possible, and silver-type conductor pastes, such as Ag, Ag-Pd, and Ag-Pt, can be used. Among these, an Ag paste having good conductivity is preferable.
Moreover, the application method of the said electrode paste is not restrict | limited in particular, It can apply to the surface of a green sheet using a conventionally well-known method (for example, screen printing etc.).
What is necessary is just to set suitably the thickness of the electrode 2 formed by baking a conductor paste at the temperature of 900 degrees C or less according to the magnitude | size of a desired capacitor | condenser, and generally it is preferable that they are 10 micrometers or more and 20 micrometers or less.
When the dielectric 3 is thinned to a thickness of about 10 μm, the conductor paste is applied and then a Teflon roller or the like is pressed to reduce the unevenness of the conductor paste formed on the surface of the green sheet. It is preferable to flatten the paste. By doing so, a short circuit between the two electrodes 2 can be prevented.
On the other hand, if a conductive paste containing silver particles of 0.5 μm or more and 5 μm or less is used except for silver particles of 10 μm or more, the dielectric 3 can be formed to a thickness of about 10 μm without introducing the planarization step. Even when the thickness is reduced, a short circuit between the two electrodes 2 can be prevented.

  The application method of the dielectric paste is also not particularly limited, and can be applied onto the conductor paste using a conventionally known method (for example, screen printing) in the same manner as the conductor paste. What is necessary is just to set suitably the thickness of the dielectric material 3 formed by baking such a dielectric paste at the temperature of 900 degrees C or less according to the magnitude | size of a desired capacitor | condenser, and generally it is preferable that they are 10 micrometers or more and 20 micrometers or less.

The method of laminating a plurality of green sheets and performing hydrostatic pressure pressing is not particularly limited, and may be performed according to a conventionally known method.
Thus, the capacitor of the present invention manufactured by the co-firing process at a temperature of 900 ° C. or less has a large electric capacity.

The multilayer ceramic substrate with a built-in capacitor according to the present embodiment is a ceramic substrate with a built-in capacitor in which a capacitor made of a dielectric 3 sandwiched between two electrodes 2 is disposed between two laminated ceramic substrates 1. The dielectric 3 is obtained by firing the dielectric paste of the present embodiment at a temperature of 900 ° C. or lower.
Since the multilayer ceramic substrate with a built-in capacitor having such a structure is conventionally known, it can be manufactured according to a conventionally known method except that the dielectric paste of the present embodiment is used. For example, in the multilayer ceramic substrate with a built-in capacitor according to the present embodiment, a conductive paste is applied to the surface of a green sheet, then a dielectric paste is applied on the conductive paste, and then a conductive paste is applied on the dielectric paste. After application, another green sheet can be further laminated thereon, and then co-fired at a temperature of 900 ° C. or lower. Here, a via conductor having a desired wiring can be provided on the green sheet. As other manufacturing conditions, the conditions described in the above capacitor manufacturing method can be used.
As described above, the multilayer ceramic substrate with a built-in capacitor according to the present invention manufactured by the simultaneous firing process at a temperature of 900 ° C. or less has a large electric capacity.

FIG. 3 is a cross-sectional view of a multilayer ceramic substrate with a built-in capacitor in the present embodiment. In FIG. 3, the capacitor built-in multilayer ceramic substrate has a capacitor made of a dielectric 3 sandwiched between two electrodes 2 in a cavity 4 formed between two stacked ceramic substrates 1. .
Such a multilayer ceramic substrate with a built-in capacitor according to the present embodiment can be manufactured as follows.
First, apply a conductor paste on the surface of the green sheet, then apply a dielectric paste on the conductor paste, then apply a conductor paste on the dielectric paste, and place the portion that will become the capacitor after firing on the surface. The green sheet which has is produced. Separately from this, a green sheet having a cavity (concave portion) of a size that can accommodate a capacitor is produced. And after laminating the green sheet which has this cavity on the green sheet which has the part which becomes a capacitor | condenser on the surface after baking, it should just be baked at the temperature of 900 degrees C or less after pressure-bonding and integrating with an isostatic press. . Here, the cavity portion of the green sheet is desirably as small as possible since there is a problem of depression or distortion caused by the cavity portion during firing, and as a result, the capacitance of the capacitor may be reduced. As other manufacturing conditions, the conditions described in the above capacitor manufacturing method can be used.

  On the other hand, the present inventors examined a method for suppressing the problem of depression and distortion caused by the cavity portion during firing, and the deformation behavior during firing approximates that of a green sheet and the like, and the material volatilizes during firing. It has been found that such a problem can be suppressed by filling the cavity portion by the above. That is, first, a green sheet having a cavity portion is produced, and then the cavity portion is filled with a material that has a deformation behavior similar to that of a green sheet or the like and that volatilizes during firing. By laminating a green sheet filled with such a material on a green sheet having a portion that becomes a capacitor after firing on the surface, and then pressing and integrating with a hydrostatic press, firing is performed at a temperature of 900 ° C. or less. The problem of depression and distortion caused by the cavity during firing can be suppressed.

  The material filled in the cavity portion of the green sheet is not particularly limited as long as the deformation behavior upon firing approximates that of the green sheet and the like and volatilizes upon firing. As such a material, for example, a sheet formed from a slurry obtained by mixing acrylic powder with an ethanol solution of PVA can be used. What is necessary is just to cut | disconnect such a sheet | seat to a desired magnitude | size according to the magnitude | size of a cavity, when filling a cavity part.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the following Example.
[Example 1]
(Production of dielectric paste)
Automatic mortar containing 50 g (85 wt%) of BaTiO ₃ powder (hydrothermal synthesis method, average particle size: about 1 μm) and 8.8 g (15 wt%) of Bi ₂ O ₃ —ZnO—B ₂ O ₃ powder 19.6 g of an organic vehicle consisting of ethyl cellulose, polypropylene glycol, di-n-butyl phthalate, Kao's homogenol and terpineol, which are commercially available dispersants, and kneaded well, followed by dielectric paste Was made.
(Production of green sheets)
A low temperature fired ceramic composition was prepared by mixing 50 g of borosilicate glass powder and 50 g of alumina powder having an average particle diameter of 2 μm (purity 99% or more) using a ball mill. Appropriate amounts of di-n-butyl, triolein and ethanol were further added to prepare a slurry. Next, a green sheet having a thickness of about 100 μm was produced by using this slurry by a doctor blade method.

(Manufacture of capacitors)
A capacitor sample was prepared according to the flow chart of FIG.
Specifically, first, silver paste was screen-printed on the surface of the green sheet in the pattern shape of FIG. 5a (about 15 μm thick, about 5 mm square). This part becomes the lower electrode of the capacitor. Next, a dielectric paste was screen-printed on the silver paste in the pattern shape of FIG. 5b (about 15 μm thick, about 4 mm square). This part becomes a dielectric filling the inside of the capacitor. Next, on the dielectric paste, a silver paste was screen-printed in the pattern shape of FIG. 5c (about 15 μm thick, about 0.5, 1 and 2 mm square). This part becomes the upper electrode of the capacitor. The electrode was provided with a lead pattern on the side for correcting the parasitic capacitance. FIG. 5d is a view of the pattern shape of the printed silver paste and dielectric paste as seen from above. Through the above steps, a capacitor structure having a dielectric between the insulated upper electrode and lower electrode can be formed. In this sample, six capacitors are formed in one sample.
Next, another green sheet is laminated on the surface opposite to the green sheet on which the silver paste and the dielectric paste are printed, and is pressed and integrated by isostatic pressing, followed by firing at 850 ° C. for 1 hour. A sample of was prepared.

[Example 2]
(Production of dielectric paste)
Dielectric material as in Example 1 except that BaTi _1-x Zr _x O ₃ (wherein x = 0.1 to 0.2) (average particle size: 1 μm) was used instead of BaTiO _3. A paste was prepared. Hereinafter, a case where x = 0.1 is represented as Example 2-1, and a case where x = 0.2 is represented as Example 2-2.
(Production of green sheets)
A green sheet was produced in the same manner as in Example 1.
(Manufacture of capacitors)
A capacitor sample was prepared in the same manner as in Example 1 except that the above dielectric paste was used.

[Example 3]
(Production of dielectric paste)
A dielectric paste was produced in the same manner as in Example 1 except that BaTi _1-x Zr _x O ₃ (wherein x = 0.05) (average particle diameter: 1 μm) was used instead of BaTiO ₃ . .
(Production of green sheets)
A green sheet was produced in the same manner as in Example 1.
(Manufacture of capacitors)
A capacitor sample was prepared in the same manner as in Example 1 except that the above dielectric paste was used.

[Comparative Example 1]
(Production of dielectric paste)
47 g (80% by weight) of BaTiO ₃ powder (hydrothermal synthesis method, average particle diameter: about 1 μm) and 11.8 g (20% by weight) of ZnO—B ₂ O ₃ powder were sufficiently mixed using an automatic mortar. After mixing, 19.6 g of an organic solvent consisting of ethyl cellulose, polypropylene glycol, di-n-butyl phthalate, and commercially available dispersants Kaogen Co., Ltd. homogenol and terpineol were added and kneaded well to prepare a dielectric paste.
(Production of green sheets)
A green sheet was produced in the same manner as in Example 1.
(Manufacture of capacitors)
A capacitor sample was prepared in the same manner as in Example 1 except that the above dielectric paste was used.

The capacitors of Examples 1, 2-1, 2-2, and 3 and Comparative Example 1 obtained in this way were visually evaluated for warpage and peeling.
As a result, none of the capacitors of Examples 1, 2-1, 2-2 and 3 and Comparative Example 1 was warped or peeled off.

In addition, in these capacitors, an impedance meter (Y192, 4192A) was used to evaluate the capacitance at a measurement frequency of 100 kHz. In this evaluation, the capacitance of the capacitor portion and the parasitic capacitance correction lead portion were measured, and the value obtained by subtracting the capacitance value of the parasitic capacitance correction lead portion from the capacitance value of the capacitor portion was the area of the upper electrode. Was obtained as a capacitance value per unit area by linear approximation. The results of the temperature dependence of the capacitance are shown in FIG.
As a result, as shown in FIG. 6, the capacitors of Examples 1, 2-1, 2-2 and 3 had a larger capacitance per unit area than the capacitor of Comparative Example 1. In addition, the capacitors of Examples 1 and 3 had a substantially constant capacitance per unit area with respect to a temperature change of about 20 ° C. to about 150 ° C., and had a flatness of the capacitance with respect to the temperature change. On the other hand, in the capacitors of Examples 2-1 and 2-2, although the capacitance per unit area slightly increased or decreased with respect to the temperature change of about 20 ° C. to about 150 ° C., the practicality was hindered. If it is used for an application where the flatness of the capacitance with respect to the temperature change is not so required, it can be considered that it can be sufficiently used.

Furthermore, with respect to the capacitors of Examples 1, 2-1, 2-2, and 3, the withstand voltage characteristics at direct current were evaluated using a power source and a current meter. In this evaluation, the power source was set to a predetermined measurement voltage at room temperature, the current value after 1 minute was read, and this operation was repeated for each predetermined measurement voltage. In this evaluation, the maximum value of the current was set to 0.1 mA, and the voltage when the current value was exceeded was evaluated as the limit value of the withstand voltage. The relationship between such voltage and current is shown in FIG.
As a result, as shown in FIG. 7, in the capacitor of Example 1, the current increased rapidly from above 70 V and became 0.1 mA at 90 V. Therefore, the withstand voltage at 0.1 mA in the capacitor of Example 1 was 90 V, which was within the usable range in the voltage used for portable electronic devices and the like.
In addition, in the capacitors of Examples 2-1 and 2-2, even if the voltage exceeds 70V, the current does not increase rapidly as in the capacitor of Example 1, and the current does not increase even at the measurement limit of 100V in this evaluation. It was low. From this, the withstand voltage at 0.1 mA in the capacitors of Examples 2-1 and 2-2 is considered to be 100 V or more.
Further, in the capacitor of Example 3, although the current gradually increased from around 80 V, the current was as low as 0.001 mA even at 100 V.

[Example 4]
A capacitor sample was prepared in the same manner as in Example 2 except that about 10 μm thick dielectric paste was screen-printed.
[Example 5]
Example 2 Except that the surface of the green sheet was screen-printed with silver paste, the surface was flattened by pressing a Teflon roller, and then a 10 μm dielectric paste was screen-printed on the surface of the silver paste. A capacitor sample was prepared in the same manner as described above.

Twenty samples of the capacitors of Examples 4 and 5 were prepared, and the occurrence rate of short circuits was measured. The occurrence rate of the short circuit was measured by examining the conduction between the upper electrode and the lower electrode in the same capacitor using a normal tester. If there is continuity, it is judged as a short circuit.
As a result, in the capacitor of Example 4, the occurrence rate of short circuit was 74.2%, whereas in the capacitor of Example 5, the occurrence rate of short circuit was 7.5%. Therefore, when a capacitor having a dielectric thickness of about 10 μm is manufactured, it is considered necessary to flatten the electrode from the viewpoint of preventing occurrence of a short circuit.

  As can be seen from the above results, the dielectric paste of the present invention gives a capacitor having a large electric capacity and a multilayer ceramic substrate with a built-in capacitor, and at the same time firing at a temperature of 900 ° C. or lower, firing cracks accompanying shrinkage behavior. Does not cause the conductor to peel off or warp.

It is a graph about the temperature dependence of the dielectric constant in the sample 3 and the comparative sample 16 in Embodiment 1 of this invention. It is sectional drawing of the capacitor | condenser in Embodiment 1 of this invention. It is sectional drawing of the multilayer ceramic substrate with a built-in capacitor in Embodiment 1 of this invention. It is a flowchart at the time of producing the sample of a capacitor | condenser in an Example. It is the pattern shape of the silver paste screen-printed in the Example. It is the pattern shape of the dielectric paste screen-printed in the Example. It is the pattern shape of the silver paste screen-printed in the Example. It is the pattern shape of the silver paste and dielectric paste which were screen-printed in the Example. It is a figure which shows the relationship between the temperature and the capacitance value per unit area in the capacitors of Examples 1, 2-1, 2-2 and 3 and Comparative Example 1. It is a figure which shows the relationship between the voltage in the capacitor | condenser of Example 1, 2-1, 2-2, and 3 and an electric current.

Explanation of symbols

  1 Ceramic substrate, 2 electrodes, 3 dielectric, 4 cavities.

Claims (9)

Softening of dielectric powder represented by BaTi _1-x Zr _x O ₃ (where x = _{0 to} 0.2) is 80 wt% or more and 87.5 wt% or less, and the balance is 400 ° C. or more and 500 ° C. or less. An inorganic powder material which is Bi ₂ O ₃ —ZnO—B ₂ O ₃ -based glass powder having a temperature and a relative dielectric constant of 20 or more;
A dielectric paste comprising a liquid organic vehicle containing a binder and a plasticizer. The dielectric paste according to claim 1, wherein the glass powder is Bi ₂ O ₃ —ZnO—B ₂ O ₃ —SiO ₂ glass powder.   The dielectric paste according to claim 1 or 2, wherein the dielectric powder is a dielectric powder produced by a hydrothermal synthesis method.   3. The dielectric paste according to claim 1, wherein the dielectric powder has a half width at an X-ray diffraction peak of a (111) plane of 0.086 ° or less. A capacitor formed on a ceramic substrate, made of a dielectric sandwiched between two electrodes,
The said dielectric material is a thing formed by baking the dielectric paste as described in any one of Claims 1-4 at the temperature of 900 degrees C or less.   The electrode is obtained by firing a conductive paste at a temperature of 900 ° C. or less, and the conductive paste contains silver particles having an average particle size of 0.5 μm or more and 5 μm or less. 5. The capacitor according to 5. A capacitor made of a dielectric sandwiched between two electrodes is a multilayer ceramic substrate with a built-in capacitor disposed between two laminated ceramic substrates,
A multilayer ceramic substrate with a built-in capacitor, wherein the dielectric is obtained by firing the dielectric paste according to any one of claims 1 to 4 at a temperature of 900 ° C or lower.   8. The multilayer ceramic substrate with a built-in capacitor according to claim 7, wherein the capacitor is disposed in a cavity formed between two laminated ceramic substrates.   The electrode is obtained by firing a conductive paste at a temperature of 900 ° C. or less, and the conductive paste contains silver particles having an average particle size of 0.5 μm or more and 5 μm or less. A multilayer ceramic substrate with a built-in capacitor according to 7 or 8.

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