JP2002117738A - Method for manufacturing dielectric ceramic thick film using polymer matrix - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a dielectric ceramic thick film using a polymer matrix, more specifically, a method of manufacturing the dielectric ceramic thick film using the polymer matrix, by which a dielectric thick film in which ferroelectric ceramic fine particles are uniformly dispersed in a matrix made from a polymer material can be manufactured without using a sintering process. SOLUTION: The method for manufacturing the dielectric ceramic thick film using the polymer matrix is composed of a step of crushing the dielectric ceramic into fine particles; a step of melting the polymer material to be used as the matrix; a step of adding the dielectric particles to the melted polymer matrix and uniformly mixing them; and a step of forming the thick film on a substrate with the melted mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dielectric ceramic thick film using a polymer matrix, and more particularly to a method of uniformly dispersing a ferroelectric ceramic powder in a fine particle state in a matrix made of a polymer substance. The present invention relates to a method for producing a dielectric ceramic thick film using a polymer matrix, which can produce a dielectric thick film without a sintering process.

[0002]

2. Description of the Related Art In general, multilayer ceramic capacitors (MLCCs) are indispensable manual elements in forming small and light electronic circuits. In recent years, with the trend of miniaturization of components due to the lightness and size reduction of various electronic devices and the high integration of electronic circuits, the necessity for the development of ultra-small elements for multilayer ceramic capacitors has also increased rapidly.

In order to manufacture an ultra-compact laminated ceramic capacitor meeting the above conditions, the thickness of one layer of the dielectric ceramic after firing must be preferably 1 μm or less.

In order to manufacture an ultra-compact and reliable multilayer ceramic capacitor made of a dielectric ceramic having such a thickness, the average particle size of the dielectric ceramic after sintering is desirably one layer. It should be 1/10 or less, ie, 0.1 μm or less, but have a high density.

On the other hand, up to now, dielectric ceramics for multilayer ceramic capacitors include BaTiO.
Titanate systems centered on ₃ have been mainly used. However, such materials are generally 13
Since it is manufactured at a high sintering temperature of 00 ° C. or more, an expensive noble metal such as palladium (Pd) or platinum (Pt) that can withstand high temperatures is required as an internal electrode.

In order to reduce the cost due to the use of expensive electrodes as described above, a dielectric ceramic composition which can be fired at such a low temperature that expensive metals such as Pd and Pt are not required as internal electrodes. The necessity for the development of a low-temperature sintering technique for articles or dielectric ceramics has been indispensable.

For this reason, Pb, Cd, Bi, B, Li, Cu, and other titanates based on BaTiO _3, which have been used as dielectric ceramics for multilayer ceramic capacitors until now, have been used. Attempts have been made to produce ultrafine dielectric ceramics by adding a sintering preparation such as a system and lowering the sintering temperature (see Japanese Patent Application Laid-Open Nos. 1-192762 and 5-192).
120915, Japanese Patent Application Laid-Open No. 8-203702).

However, the average particle diameter of the raw material powder for BaTiO ₃ -based dielectric ceramics used in the production of ultra-small multilayer ceramic capacitors has already become 0.05 to 0.1 μm.
m, and of course, in the current state of the art, and in the future, through the sintering process, a dielectric ceramic thick film with an average grain size of 0.1 μm or less and a thickness of 1 μm or less will be densely and highly reliable. There is a problem that it is extremely difficult to manufacture.

The sintering preparations are all toxic substances, are not environmentally friendly, and have various problems such as reacting with water used as a solvent in the water.

Further, even if the above-mentioned sintering preparation is added, it is extremely difficult to lower the sintering temperature to 900 ° C. or less, and it is necessary to use an Ag-Pd-based noble metal internal electrode.

On the other hand, Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb
(Fe _1/2 Nb _1/2 ) O ₃ and Pb-based relaxed ferroelectric ceramics (Relaxer Ferroelectric Ceramic). Since its initial synthesis in the early 1960's, a huge amount of research has been carried out worldwide until now (GASmolenskii et al., "Ferroele
ctrics with DiffusePhase Transitions ", Sov. Phys.-
Solid State, 2 (11), 2584-2594 (1961)).

The Pb-based relaxed ferroelectric ceramics as described above can be fired at 900 to 1200 ° C., and the firing temperature is about 100 to 400 ° C. lower than that of BaTiO ₃ .
Since the dielectric properties are remarkably excellent, utilization in dielectric ceramic compositions for multilayer ceramic capacitors is expected.

However, due to problems such as volatilization of toxic Pb-based compounds, reactivity with internal electrode materials, and difficulty in establishing dispersion conditions, the dielectric ceramic composition for a multilayer ceramic capacitor is actually used. It is not widely used.

[0014]

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the above-mentioned problems of the prior art.
The aim is to produce a dielectric ceramic thick film without sintering process by uniformly dispersing dielectric ceramic powder in ultra-fine state in a matrix made of polymer material and subjecting the substrate to thick film treatment. It is an object of the present invention to provide a method for producing a dielectric ceramic thick film using a polymer matrix that can be used.

[0015]

In order to achieve the above object, the present invention provides a method for pulverizing ferroelectric ceramics into fine particles; a step of melting a polymer substance used as a matrix; Adding a ferroelectric ceramic powder to the polymer matrix melted in the above, and uniformly mixing the mixture; and forming the mixture into a thick film on a substrate. Provided is a method for manufacturing a dielectric ceramic thick film.

According to the present invention, as described above, a ferroelectric ceramic powder is uniformly dispersed in a matrix made of a polymer substance, and the substrate is subjected to a coating treatment.
While making the dielectric thick film dense and reliable without a high-temperature sintering process, it can be used to manufacture a very small dielectric thick film for a multilayer ceramic capacitor.

Further, according to the present invention, it is possible to manufacture an ultra-thin dielectric thick film for a multilayer ceramic capacitor without a sintering process, so that an expensive thin film is indispensable for manufacturing an existing multilayer ceramic capacitor. Since there is no need to use a noble metal internal electrode material, there is provided an advantage that the manufacturing cost can be reduced.

The ferroelectric ceramic of the present invention is made of BaT
Examples include an iO ₃ -based ferroelectric ceramic and a Pb-based relaxed ferroelectric ceramic, and the Pb-based relaxed ferroelectric ceramic includes Pb (B ′ ₂ ⁺ _1/3 B ″ ⁵⁺ _{2 / 3} ) O
'Any one of the ^{_{(3+ 1/2 B "5+ 1/2 O}} 3 system (however, the B ₃ system and Pb B)' ²⁺ is Mg ^2+, Ni ^2+, Zn ²⁺ , Cd ²⁺ , B ″ ⁵⁺ is one of Nb ⁵⁺ , Ta ⁵⁺ , and B ′ ³⁺ is Fe ³⁺ , Sc ³⁺ , In ³⁺ Is one of them).

[0019]

Embodiments of the present invention will be described below.

First Embodiment In order to manufacture a ferroelectric thick film using a matrix made of a polymer material according to the present invention, first, a matrix made of a ferroelectric ceramic powder and a polymer material is used. , Ie, a mixture of a ferroelectric ceramic and a polymer material.

As a starting material for producing the same, polypropylene pellets (polypropylen) which is a polymer substance are used.
e pellet) and BaTiO which is a ferroelectric ceramic
_{Use 3} .

First, the polypropylene pellets were
Maintain at a temperature of 0 to 220 ° C. for about 1 hour to melt.

To the molten polypropylene prepared as described above, 10 to 90% by weight of BaTiO ₃ powder pulverized into ultrafine powder is added.

The mixture of the molten polypropylene and the ultrafine BaTiO ₃ powder prepared as described above is continuously added to the mixture for 180 to 180 minutes.
Stir mechanically at a speed of 20-40 rpm for 20-40 minutes while maintaining the temperature at 220 ° C.

The mixture of the molten polypropylene and the ultrafine BaTiO ₃ powder prepared as described above is spin-coated on a copper substrate.

The thick film made of the ferroelectric ceramic powder and the polymer matrix manufactured by the method of the present invention has a thickness of about 0.50 to 0.97 μm and a dielectric constant of room temperature of 15 to 189. In the temperature range of −55 to 125 ° C., the amount of change in the dielectric constant is −14 to 19%. In particular, a ferroelectric thick film can be manufactured without a sintering process.

The following processes were performed to measure the performance of the composite of the ferroelectric ceramic powder having the above-mentioned characteristics and the polymer according to the composition and mixing conditions, and the results are shown in Table 1. Was.

First, the melting point is about 157 ° C. and the density is about 0.
A 90 g / cm ³ polypropylene having a molecular weight of about 12,000 (a product of Aldrich, USA) is placed in a 500 ml Pyrex separatory funnel and heated at a temperature of 180 to 220 ° C. It was melted by holding for 1 hour.

The polypropylene used herein has a molecular weight of 12,000. If the molecular weight exceeds 10,000, the viscosity is too high to prevent the formation of a thin thick film. It is preferred to use

If the melting temperature of the polypropylene is lower than 180 ° C., it is difficult to maintain the molten state,
If the temperature exceeds 220 ° C., there is a concern that the molecular structure of polypropylene may be destroyed by high heat.

The melted polypropylene was mixed with 2
Purity of about 9 while mechanically stirring at a speed of 0 to 40 rpm
9.9% or more of ultrafine BaTiO ₃ powder (specific surface area =
8.65 m ² / g, US Cabot BT-8 product) 10-9
0% by weight was added.

Here, the reason why the stirring speed is specified to be 20 to 40 rpm is that if the mixing speed is excessively lower than 20, the mixing does not proceed well, and if the mixing speed is higher than 40, the ceramic powder is separated by centrifugal force.

Then, the ceramic powder is mixed with 10 to 9
The reason for mixing in the range of 0% by weight is that if the addition amount is too small, the dielectric constant is too low, and if the addition amount is too large, the thickness of the thick film becomes too thick.

The mixture of the molten polypropylene prepared as described above and the ultrafine BaTiO ₃ powder was continuously added to the mixture for 180 to 180 minutes.
While maintaining at 220 ° C., 20 to 40 minutes, 20 to 40
The mixture was mechanically stirred at a speed of rpm and mixed to a uniform state.

The mixture of the molten polypropylene and the ultrafine BaTiO ₃ powder prepared as described above was used to prepare a mixture having a diameter of about 15 m.
m, and spin-coated on a copper substrate having a thickness of about 1 mm. At this time, the conditions of the spin coating are as follows.

The mixture was adjusted so that the lower cock of the separatory funnel was opened and dropped at a rate of 1 to 3 drops per second. Then, while rotating the copper substrate at a rate of 300 to 500 rpm, a total of 10 to 20 drops was added. It was dropped.

On the other hand, in the present embodiment, the spin coating method is described as the coating technique. However, in some cases, the extrusion coating method may be a more effective coating method.

The extrusion coating method that can be used in the present invention is a method in which the mixture is applied to a substrate, and the mixture applied to the substrate is pressed to a uniform thickness using an extrusion ruler to form a thick film. is there.

One section of the thick film formed of the composite of the dielectric ceramic powder and the polymer obtained as described above was observed by an optical microscope to measure its thickness.

On the other hand, a thick copper substrate was used as a lower electrode to investigate the dielectric characteristics of a thick film formed of a composite of the obtained dielectric ceramic powder and a polymer, and a thick film was formed on the upper portion of the thick film. After the room temperature silver paste is applied and dried, the prepared specimen is placed in a temperature control chamber (Delta, USA).
LCR meter (Hewlett Packard model name 4263B) in the temperature range of -55 to 125 ° C.
The results were shown in Table 1 (provided that the measurement conditions of the LCR meter were V _rms = 1.0,
1 kHz).

[0041]

[Table 1] From the results in Table 1, the thickness was 0.50 to 0.97 μm
A thick film made of a ferroelectric ceramic powder having a normal temperature dielectric constant of 15 to 189 and a dielectric constant change of −14 to 19% at −55 to 125 ° C. and a polymer matrix without a sintering process. It can be seen that it was obtained.

Second Embodiment As a starting material for producing a composite of a Pb-based relaxed ferroelectric ceramic and a polymer according to the present invention, PbO, MgO, TiO ₂ having a purity of about 99.9% or more is used. , Fe ₂
Pb (Mg) synthesized using O ₃ , Nb ₂ O ₅ powder, etc.
_1/3 Nb _2/3 ) O ₃ -PbTiO ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ -Pb (Di _1/3 Nb
_2/3 ) O ₃ (where Di is Ni, Zn or Cd), Pb (Fe _1/2 Nb _1/2 )
Use relaxed ferroelectric ceramics such as O ₃ and polypropylene pellets.

First, the relaxed ferroelectric ceramic is pulverized by ball milling and attrition milling to produce fine relaxed ferroelectric ceramic powder.

On the other hand, polypropylene pellets
Melt by maintaining at 220 ° C. for about 1 hour.

10 to 90% by weight of the fine relaxed ferroelectric ceramic powder prepared above is added to the molten polypropylene prepared as described above.

Then, the mixture made of the molten polypropylene and the relaxed ferroelectric ceramic powder is continuously added to the mixture.
Stir mechanically for 20-40 minutes while maintaining at 0-220 ° C.

The mixture of the molten polypropylene and the relaxed ferroelectric ceramic powder prepared as described above is spin-coated on a copper substrate.

The composite thick film of the relaxed ferroelectric ceramic and the polymer produced by the above method has a thickness of about 1.32 to 2.90 μm and a dielectric constant of room temperature of 78 to 190.
5, the change in the dielectric constant in the temperature range of -55 to 125 ° C is-
With a ratio of 85 to 37%, a dielectric thick film can be manufactured without a sintering process using a composite of a relaxed ferroelectric ceramic and a polymer.

Relaxed ferroelectric material having the above characteristics
Depends on composite composition of ceramics and polymer and mixing conditions
In order to measure the performance of Pb (Mg_1/3N
b_2/3) O _Three-PbTiO_Three, Pb (Mg_1/3Nb_2/3) O_Three
−Pb (Di_1/3Nb_2/3) O_ThreeAnd Pb (Fe_1/2Nb
_1/2) O_ThreeRelaxed ferroelectric ceramic powder in agate mortar
Crushed and sieved through # 50 sieve.

The relaxed ferroelectric ceramic powder prepared as described above is ball-milled with ZrO ₂ balls and ethanol, dried, and ground in an agate mortar to # 10.
0 sieve.

The relaxed ferroelectric ceramic powder prepared as described above was mixed with ZrO ₂ balls and an impeller made of ethanol and polyurethane at a speed of 600 rpm.
Attrition milling for 0 minutes and drying were performed to obtain fine relaxed ferroelectric ceramic powder.

The specific surface area of the relaxed ferroelectric ceramic powder prepared as described above was measured using a BET specific surface area analyzer (Quan).
1. Measured with Tachrome's product, model name Autosorb-1).
A specific surface area of 6 to 2.9 m ² / g was obtained. This is a fine relaxed ferroelectric ceramic powder having an average particle size of about 0.24 to 0.29 μm, assuming ideal spherical particles.

On the other hand, the melting point is about 157 ° C. and the density is about 0.
A 90 g / cm ³ polypropylene having a molecular weight of about 12,000 (Aldrich, USA) is melted by placing it in a 500 ml Pyrex separatory funnel, heating at 180-220 ° C. and maintaining for about 1 hour. I let it.

The melted polypropylene was mixed with 2
Fine mechanical relaxation type ferroelectric ceramic powder prepared by mechanical stirring at a speed of 0 to 40 rpm was added in an amount of 10 to 90% by weight.

The mixture composed of the molten polypropylene and the relaxed ferroelectric ceramic powder prepared as described above is mechanically stirred at a speed of 20 to 40 rpm for 20 to 40 minutes while maintaining the mixture at 180 to 220 ° C. After that, a mixture of molten polypropylene and a relaxation type ferroelectric ceramic powder was spin-coated on a copper substrate having a diameter of about 15 mm and a thickness of about 1 mm.

At this time, the lower cock of the separating funnel was opened, and the mixture was adjusted so that the mixture was dropped at a rate of 1 to 3 drops per second. ６０60 drops were added dropwise.

On the other hand, in the present embodiment, the spin coating method is described as the coating technique, but in some cases, the extrusion coating method may be a more effective coating method.

The extrusion coating method usable in the present invention is a method in which the mixture is applied to a substrate and then the mixture applied to the substrate is pressed to a uniform thickness using an extrusion roller to form a thick film. is there.

The thickness of the composite thick film of the relaxed ferroelectric ceramics and the polymer obtained through the above-described process was measured by observing one section of the composite thick film with an optical microscope.

On the other hand, a thick copper substrate was used as a lower electrode in order to investigate the dielectric properties of the obtained composite film of the relaxed ferroelectric ceramics and the polymer, and a room temperature room temperature A sample prepared by applying and drying silver paste (Ag paste) was mounted in a temperature control chamber (a product of Delta Design, USA), and an LCR meter (a product of Hewlett Packard) in a temperature range of −55 to 125 ° C. , Model name 4
263B) was used to measure the permittivity (provided that the measurement condition of the LCR meter is V _rms = 1.0,1 kHz).

Table 2 shows the results measured under the above conditions.

[0062]

[Table 2] From the results in Table 2, the thickness was 1.32 to 2.90 μm.
And a normal temperature dielectric constant of 78 to 1905 and -55 to 125 ° C.
It can be seen that a composite thick film of a relaxed ferroelectric ceramic and a polymer having a dielectric constant change of -85 to 37% was obtained without a sintering process.

Considering the results of the first and second embodiments, the composite of thinner dielectric ceramic powder and polymer becomes thinner as the amount of ferroelectric ceramic powder added decreases or as the melting temperature increases. Although it was possible to obtain a thick film made of a body, the current situation is that as the amount of ceramic powder added decreases or the melting temperature increases, the molten polypropylene that is spin-coated and the ferroelectric powder in the ultrafine state This is probably due to the low point of the mixture clay.

On the other hand, the room temperature dielectric constant increased as the amount of ceramic powder added increased and was not significantly affected by the melting temperature. That is, the room temperature dielectric constant increased as the amount of ceramic powder added and the thickness of the thick film increased when the melting temperature was the same, but when the amount of ceramic powder added was the same, the melting temperature increased and the thickness increased. The decrease in film thickness was not significantly affected.

As described above, at present, the room temperature dielectric constant is determined only by the addition amount of the ferroelectric ceramic powder constituting the thick film formed of the composite of the ferroelectric ceramic powder and the polymer. The matrix made of the polymer material in the composite of the body ceramic powder and the polymer is due to the fact that the ferroelectric ceramic powder only serves as a matrix to maintain the space between both electrodes Which also means that the ceramic ferroelectric powder is uniformly dispersed within the polymer matrix.

The change in the dielectric constant at a temperature of -55 to 125 ° C. was not significantly affected by the amount of the ceramic powder added and the melting temperature. Under such circumstances, the change in dielectric constant of a thick film made of a composite of dielectric ceramic powder and polymer is
This is considered to be determined not by the polymer matrix nor by the amount of the dielectric ceramic powder to be added, but by the inherent characteristics of the dielectric ceramic powder itself, such as the particle size of the dielectric ceramic powder.

[0067]

As described above, according to the present invention, the ferroelectric ceramic powder is uniformly dispersed in a matrix made of a polymer material and the substrate is coated. While making the dielectric thick film high in density and high in reliability, it can be used to manufacture a very small dielectric thick film for a multilayer ceramic capacitor.

According to the present invention, an ultra-thin dielectric thick film for a multilayer ceramic capacitor can be manufactured without a sintering process, so that an expensive noble metal which is indispensable for manufacturing an existing multilayer ceramic capacitor is used. Since there is no need to use an internal electrode material, an effect of reducing the manufacturing cost can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H01B 3/12 302 H01B 3/12 302 313 313Z 313K (72) Inventor He Joon Jae South Korea, Seoul, Nowon-k, Junge-dong, Jong-sard apartment 108-204 (72) Inventor Je-hwang Park South Korea, Seoul, Mapok, Yongnam-dong 246-15 F-term (reference) 4J002 BB121 DE046 DE186 5G303 AA01 AB15 AB20 BA03 CA01 CA09 CB03 CB07 CB13 CB17 CB21 CB23 CB25 CB33 CB35 CB38 CB43 DA01 DA02 DA06 5G333 AA03 AB12 CB17 DA01 DA03 DB04

Claims (13)

[Claims] 1. a step of pulverizing ferroelectric ceramics into fine particles; a step of melting a polymer substance used as a matrix; and adding a ferroelectric ceramic powder to the molten polymer substance and mixing uniformly. To do;
Forming the mixture into a thick film on a substrate. A method for producing a dielectric ceramic thick film using a polymer matrix. 2. The method as claimed in claim 1, wherein the polymer material is polypropylene having a molecular weight of 10,000 or less. 3. The polymer material has a melting temperature of 180-2.
The method for producing a dielectric ceramic thick film using a polymer matrix according to claim 1 or 2, wherein the temperature is 20 ° C. 4. The ferroelectric ceramic is BaTiO.
_{3. The} method for producing a dielectric ceramic thick film using a polymer matrix according to claim 1, wherein the thickness is 3. 5. The method of claim 1, wherein the ferroelectric ceramic is a Pb-based relaxed ferroelectric ceramic. 6. The Pb-based relaxed ferroelectric ceramic comprises Pb (B ′ 2 ⁺ _1/3 B ″ ⁵⁺ _2/3 ) O ₃ and Pb (B ′ ³⁺ _1/2 B ″).
⁵⁺ _1/2 ) O ₃ system (where B ′ ²⁺ is M
g ²⁺ , Ni ²⁺ , Zn ²⁺ , Cd ²⁺ , and B ″
⁵⁺ is one of Nb ⁵⁺ and Ta ⁵⁺ , and B ′ ³⁺ is F
e ³⁺ , Sc ³⁺ , or In ³⁺ ). The method for producing a dielectric ceramic thick film using a polymer matrix according to claim 5, wherein 7. An addition amount of the ferroelectric ceramic is 1
The method for producing a dielectric ceramic thick film using a polymer matrix according to claim 1, wherein the amount is 0 to 90% by weight. 8. The dielectric ceramic using a polymer matrix according to claim 1, wherein the temperature of maintaining the molten state of the mixture of the polymer substance and the ferroelectric ceramic is 180 to 220 ° C. Thick film manufacturing method. 9. The polymer according to claim 1, wherein the speed of mechanically stirring the mixture of the polymer material and the ferroelectric ceramic is 20 to 40 rpm, and the mixing is performed for 20 to 40 minutes. A method for producing a dielectric ceramic thick film using a matrix. 10. The method according to claim 1, wherein the method of forming the mixture of the polymer material and the ferroelectric ceramic on the substrate in a thick film is a spin coating method. Dielectric ceramic thick film manufacturing method. 11. The method according to claim 10, wherein the spin coating method comprises coating the mixture by dripping the mixture onto the substrate while rotating the substrate. 12. The method according to claim 1, wherein the method of forming the mixture into a thick film on a substrate comprises extruding the mixture onto a substrate to form a thick film. Film manufacturing method. 13. The thickness of a dielectric using a polymer substance according to claim 1, wherein the substrate is a copper substrate. Film manufacturing method.