JPH05283274A - Paste composition for copper-based conductor and manufacture of laminated ceramic element - Google Patents

Abstract

PURPOSE:To control the contraction of a volume when a copper internal electrode for a laminated capacitor element is reduced, to prevent a crack from being caused, to perfectly perform a binder-removing treatment and to prevent the insulation resistance of a dielectric from being deteriorated. CONSTITUTION:In the manufacturing method of a laminated capacitor element, a lead composite perovskite-based oxide dielectric is used and copper is used as an internal electrode. In the manufacturing method, a mixture of metallic copper and a copper oxide is used as the starting material of the copper internal electrode, and, when the ratio of the atomic number of copper (Ac) to the atomic number of oxygen (Ao) is expressed as Ac/Ao, it is used in the mixture ratio within the range of the following formula: 2.0<=(Ac/Ao)<=15.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a copper-based conductor, and to a method for producing a laminated ceramic element having a ceramic derivative such as a multilayer capacitor element and a copper-based internal conductor.

[0002]

2. Description of the Related Art In recent years, in the technical field of multilayer capacitor elements, attempts have been made to use single metals such as copper for internal conductors and internal electrodes in order to achieve high performance and low cost.

However, when metallic copper particles are used as the conductor component material of the internal electrode paste, copper of the internal electrode is removed during the thermal decomposition / removal process (debinding process) of the dielectric green sheet and the binder component of the internal electrode paste. Oxidation occurs, and there are problems that the capacitance of the capacitor is reduced, dielectric loss is increased at high frequencies, and the like. If the binder removal treatment is performed in a low oxygen partial pressure atmosphere to prevent oxidation of the internal electrodes, the removal of the binder component will be incomplete and carbon will remain in the dielectric, reducing the insulation resistance of the capacitor and sintering. There is a problem that the density tends to decrease.

On the other hand, instead of using metallic copper powder as the conductor component material of the internal electrode paste, copper oxide (Cu
Many proposals using particles of O, Cu ₂ O or a mixture thereof have been made (JP-A-62-203321, JP-A-63-15407, JP-A-63-15408, etc.).

In these methods, copper oxide is used as a starting material for the internal electrode, so that debinding is sufficiently performed in air to prevent carbon from remaining, and then copper oxide is reduced to metallize the internal electrode. Because.

[0006]

However, these materials are accompanied by volume shrinkage of 41.3% for CuO and 23.8% for Cu ₂ O when reducing copper oxide to metallic copper.

Therefore, as long as CuO, Cu ₂ O, or a mixture thereof is used as the starting material, the amount of 23.8-
A large volume shrinkage of 41.3% occurs.

That is, when the laminated ceramic capacitor element is fired, the electrodes are significantly shrunk as compared with the dielectric,
There is a problem that large distortion is accumulated inside the capacitor element.

Recent monolithic ceramic capacitors have a tendency to have a larger capacity and a smaller size, the number of dielectric layers has increased dramatically, and the thickness of the dielectric layers has been reduced from the conventional 20 μm to 10 μm or less.

When distortion is accumulated in such a situation,
There is a problem that cracks are easily generated, which causes a decrease in yield.

The present invention solves the problems of the conventional monolithic ceramic capacitor element and the like, completes the debinding process to reduce the amount of residual carbon, and prevents the insulation resistance from decreasing. An object of the present invention is to provide a copper-based conductor paste composition capable of controlling volume contraction due to reduction of a conductor and preventing the occurrence of cracks, and a method for producing a multilayer capacitor element.

[0012]

Means for Solving the Problems The present inventors have conducted various studies to develop a copper-based conductor paste composition having the above-mentioned preferable characteristics, particularly as to control of volume shrinkage during reduction. , The following findings were obtained.

That is, the volume change during reduction is considered to be due to the inflow and outflow of copper atoms and oxygen atoms in the inner conductor, but when conventional copper oxides (CuO, Cu ₂ O) are used as the inner conductor component material. Since the ratio of copper atoms to oxygen atoms is fixed to 1: 1 for CuO and 2: 1 for Cu ₂ O, the volume change cannot be adjusted.

However, the volume contraction is controlled by using a mixture of metallic copper and copper oxide as the material of the inner conductor and adjusting the number of copper atoms and the number of oxygen atoms in the material to be within a certain range. However, they have found that it is possible to prevent the occurrence of cracks, and have completed the present invention based on this finding.

That is, the present invention is as follows.

(1) In the copper-based conductor paste composition, a conductor component material comprising a mixture of copper metal particles and copper oxide particles, and a binder component, wherein the metal copper particles and copper in the conductor component material are used. When the mixing ratio of the oxide particles is represented by the ratio (Ac / Ao) of the number of copper atoms (Ac) and the number of oxygen atoms (Ao) in the mixture [Formula 1]: 2.0 ≦ (A
c / Ao) ≦ 15.0 The copper-based conductor paste composition is characterized in that it is within the range.

(2) Further, the average particle diameter (D) of the metallic copper particles and the average particle diameter (d) of the copper oxide particles are 0.005 to.
It is in the range of 3 μm, and the ratio of the average particle diameter (D) of the metallic copper particles to the average particle diameter (d) of the copper oxide particles (D /
d) is a copper-based conductor paste composition satisfying the formula [2]: 0.001 ≦ (D / d) ≦ 20.

(3) Further, in the present invention, in the method for producing a laminated ceramics element having a ceramics dielectric and an internal conductor, the above-mentioned copper-based conductor paste composition is provided between the ceramics dielectric material layers. A laminated ceramics element characterized in that after the inner conductors are alternately formed, the binder component is debindered in an oxygen-containing atmosphere, then the inner conductor is reduced in a temperature range lower than the firing temperature, and further fired. Is a manufacturing method.

Further, in the above-mentioned method for manufacturing a laminated ceramics element, the following are preferable embodiments.

(4) The ceramic dielectric is a lead composite perovskite oxide.

(5) The above-mentioned debinding process is carried out in an atmosphere of oxygen partial pressure (P ₁ (atmospheric pressure)) of [Formula 3]: −5 ≦ log ₁₀ P ₁ ≦ 0.

(6) 200 to 200 times the binder removal treatment
Performed in the temperature range of 650 ° C.

(7) The reduction treatment is carried out in an atmosphere within the oxygen partial pressure (P ₂ (atmospheric pressure)) range of the following [Formula 4].

[Formula 4]: 0 ≦ log ₁₀ (P ₂ / P ₀ ) ≦ 4 where P ₀ represents the oxygen partial pressure at which Cu ₂ O starts reduction.

(8) The reduction treatment is performed at 200 to 650 °
What is done in the temperature range of C.

(9) The ceramic element is a multilayer ceramic capacitor having a copper internal electrode.

[0027]

In the composition and method of the present invention, since a mixture of metallic copper and copper oxide is used as the internal conductor component material (starting material) in the paste composition for copper-based internal conductors, copper atoms and oxygen are used. Volume contraction due to reduction can be reduced by arbitrarily selecting the atomic ratio and adjusting the composition within the range of the atomic number ratio of the above [Formula 1].

Further, when the binder removal treatment is carried out in air, the metallic copper is oxidized, and as a result, the conventional method causes volume expansion and causes cracks. In the composition and method of the present invention, however, metallic copper and copper oxide are used. Therefore, within the range of the atomic number ratio, the volume increase of the metallic copper can be canceled to some extent by the decrease of the resin amount due to the decomposition of the binder,
Generation of cracks due to oxidative expansion can be prevented.

[0029]

[Specific Configuration] The specific configuration of the present invention will be described below.

[Copper-based conductor paste composition] The copper-based conductor paste composition used in the present invention is formed by mixing a conductor component material (starting raw material), a binder component, and optionally a solvent and various additives.

In the present invention, a mixture of metallic copper particles and copper oxide (copper oxide, etc.) particles is used as the conductor component material, and the mixing ratio of the two is defined as the number of copper atoms (Ac) in the mixture. When represented by the ratio (Ac / Ao) of the number of oxygen atoms (Ao), it is within the range of the following [Formula 1].

[Formula 1]: 2.0 ≦ (Ac / Ao) ≦ 15.0 In the case where the above ratio is too large (when the number of copper atoms is large), the oxidative expansion of copper is large during the binder removal treatment. Too much
This is because cracks occur, and conversely, even when the above ratio is too small (when the number of oxygen atoms is large), volume contraction during reduction of the internal conductor cannot be effectively reduced, and cracks occur. is there.

The adjustment within the range of the above [Formula 1] is performed by adjusting the mixing ratio of metallic copper (Cu) and copper oxide (CuO.Cu ₂ O).

The number of copper atoms (Ac) in the conductor paste
And the number of oxygen atoms (Ao) can be analyzed, for example, by the following method. Metallic copper (Cu) and copper oxide (Cu
Ammonium chloride mixed particles of O · Cu ₂ O) - ammonium carbonate - is added to a mixed solution of aqueous ammonia. Thereby, copper oxide (CuO, Cu ₂ O) is dissolved, and the number of copper atoms in this solution is quantified by ICP (high frequency inductively coupled argon plasma method), atomic absorption method, etc.
The number of copper atoms in O, Cu ₂ O) is calculated.

Next, the CuO component is dissolved in the solution in which the copper oxide is dissolved by the bathocuproine-chloroform extraction method, and the number of copper atoms in the CuO component is quantified by the absorptiometry.

Separately, metallic copper (Cu) and copper oxide (C
All the mixed particles of (uO, Cu ₂ O) are dissolved with hydrochloric acid, and the number of copper atoms in the total amount of metal and oxide is quantified by the ICP method atomic absorption method as described above.

The number of oxygen atoms can be measured from the relationship between the numbers of copper atoms.

Here, as the copper oxide, CuO and / or Cu ₂ O, a mixture containing these and other components, and the like can be used. As the metallic copper, not only copper but also copper-silver, Various copper alloys such as copper-silver-palladium can also be used. Further, various additive components may be contained within a range that does not impair the characteristics.

Regarding the particle size of the conductor component material, the average particle size (D) of metallic copper and the average particle size (d) of copper oxide are in the range of 0.005 to 3 μm, and the metallic copper particles are The ratio (D / d) of the average particle diameter (D) to the average particle diameter (d) of the copper oxide particles is preferably within the range of the following [Formula 2].

[Equation 2]: 0.001 ≦ (D / d) ≦ 0 When the average particle size of metallic copper exceeds 3 μm, coarse particles of metal locally oxidatively expand at the time of debinding to cause cracking. Because it will be. Further, even if the ratio of the average particle diameter is out of the above range, it is difficult to uniformly disperse the metallic copper, and as a result, volume expansion locally occurs due to oxidation, which also causes the generation of cracks.

Incidentally, the average particle size of the granular material is the particle size (D50) at the point where the weight is 50% by sequentially integrating from the fine particles.
Determined by

From the viewpoint of printability, the shape of the internal electrode particles is spherical, preferably spherical.

As the binder component to be mixed with the conductor component material and the later-described dielectric material, an acrylic resin binder having high burnout property is preferable, and as the solvent, a high boiling point solvent such as terpineol having good printability is preferable.

[Manufacturing Method of Multilayer Ceramics Element] Next, in the manufacturing method of the multilayer ceramic capacitor element of the present invention, metal oxide particles (eg PbO, MgO, Nb ₂ O ₃ , TiO, CaO, PbSi
The O prescribed oxide such _3), firing the compound particles capable of producing these oxides finally mixed in a ratio desired composition is obtained, calcined, and Konaiki the calcined product, the binder , Paste together with solvent. This paste is used to form a desired shape such as a sheet or print it to form a ceramic dielectric material layer.

The internal electrode is formed by printing the above-mentioned internal conductor paste composition on the dielectric layer.

Next, a binder removal treatment is performed in an oxygen-containing atmosphere, and then a reduction treatment and firing of the internal electrodes are performed in a temperature range lower than the firing temperature.

Here, as a method for laminating the dielectric layer and the internal electrode, a large number of unfired dielectric sheets (green sheets) are used.
It is possible to use a green sheet laminating method in which an internal electrode is formed by printing on each sheet and then laminated and integrated, or a printing multilayer method in which a dielectric paste and an internal electrode paste are alternately printed to form a multilayer.

The printing multilayer method is preferable in order to make the thickness of the dielectric layer thin in order to increase the capacity, but the green sheet laminating method is preferable in order to enable uniform lamination without a short circuit with a high number of laminations. ..

[Dielectric Material] As the dielectric material used in the present invention, various ceramic dielectric materials can be used, but a lead perovskide-based oxide material having a high dielectric constant and capable of low temperature firing, particularly lead. It is preferable to use a composite perovskite material.

Particularly preferable material system is Pb (M
The composition such as g _1/3 · Nb _2/3 ) O ₃ -PbTiO ₃ can be cited. In addition to this, one having Ca atoms introduced into a part of Pb atoms in the A site component of the composition, and Ni, W, Mg, Nb, and Mn in the B site component have an average atomization of tetravalent. It is also possible to use a combination of the above, or a combination of these and an alkaline earth metal oxide, copper oxide, lead silicate or the like.

[Debinding Treatment] In the production method of the present invention, it is necessary to heat the binder components in the internal conductor paste and the dielectric material in a controlled atmosphere to remove them by thermal decomposition (debinding treatment). ..

The atmosphere for the binder removal treatment is preferably an oxidizing atmosphere, particularly an air atmosphere, from the viewpoint of the burning property of the binder.

Oxygen partial pressure of the atmosphere (P ₁ (atmospheric pressure))
Is preferably controlled within the range of the following [Formula 3].

[Formula 3]: −5 ≦ log ₁₀ P ₁ ≦ 0 That is, in the above range, the debinding rate (decomposition / removal rate of the binder) is appropriate and cracks are less likely to occur. When it exceeds the above range, the oxidation reaction rate becomes too rapid, and as a result, cracks are likely to occur.

Further, in order to enhance the burnout property of the binder, steam may be introduced into the debinding treatment atmosphere.

The debinding process temperature is 200 to 650.
It is suitable to carry out in the temperature range of ° C, and preferably,
The temperature range is 580 to 600 ° C.

If the temperature is lower than 200 ° C, the binder removal rate is remarkably slowed, and if the temperature exceeds 650 ° C, unreacted copper oxide diffuses into the dielectric material, and a part of the dielectric is sintered at a low temperature. This is because cracks occur.

This copper oxide diffusion also causes a decrease in the dielectric constant of the dielectric, a defect in the insulation resistance characteristic (IR defect), a break in the electrode, and the like.

The debinding process time is usually 20 to 1
The time is 50 hours, preferably 20 to 80 hours.

[Reduction Treatment] In the production method of the present invention, it is necessary to reduce the copper-based conductor component material containing copper oxide to metallize the inner conductor.

The reduction treatment is carried out in an atmosphere containing a reducing gas such as hydrogen or carbon monoxide.

The reduction treatment is performed in an atmosphere in which copper oxide becomes metallic copper and lead oxide (PbO) is not reduced.

Preferably, the oxygen partial pressure (P
_It is preferable to carry out in a controlled atmosphere within the range of ₂ (atmospheric pressure).

[Equation 4]: 0 ≦ log ₁₀ (P ₂ / P ₀ ) ≦ 4 (where P ₀ is the oxygen partial pressure at which Cu ₂ O starts reduction). In this range, PbO is reduced. It is known that the lead composite perovskite-based dielectric material is superior in reduction resistance to PbO alone, although the above range is based on equilibrium theory. Since the kinetics dominate, and the reduction reaction of copper oxide is sufficiently faster than the reduction reaction of lead-based composite perovskite, the lead composite perovskite-based dielectric material does not undergo reduction and does not react with copper oxide at a sufficient reaction rate. Can be reduced to copper.

The temperature of the reduction treatment is lower than the firing temperature of the ceramic dielectric material. The preferred temperature range is 2
It is in the range of 00 to 650 ° C, and more preferably 3
It is in the range of 00 to 600 ° C.

When the temperature is lower than 200 ° C, the reaction rate is slow, and when the temperature is higher than 650 ° C, unreacted copper oxide diffuses into the dielectric, and similarly to the above, cracks are generated due to local sintering.
This is because it causes a decrease in the dielectric constant of the dielectric, a defect in the insulation resistance characteristic (IR defect), and a break in the electrode.

The reduction treatment time is usually 30 minutes to 20 hours.

[Firing] The reduction-processed laminated ceramic material is then fired.

This firing step can also be performed as a series of steps including the binder removal treatment and reduction treatment that are performed before.

The firing temperature in this case is usually 800 to 10
The temperature is in the range of 80 ° C, preferably 900 to 1000 ° C.

This is because if the firing temperature is too high, the copper will melt, and conversely if it is too low, the sintering of the ceramics will not proceed.

Firing is usually carried out in a non-oxidizing atmosphere and N ₂
Alternatively, it is performed in a neutral atmosphere such as vacuum.

The firing time is usually in the range of 30 minutes to 10 hours.

[0074]

The present invention will be described in more detail with reference to Examples.

0.95 Pb (Mg _1/3 Nb _2/3 ) O ₃ −
Mixing a polymethacrylate resin-based binder and a terpineol-based solvent into a material having a dielectric composition in which MgO is added in an excess of 1 mol% with respect to 0.05 PbTiO ₃ lead composite perovskite to form a paste, which is a green sheet by the doctor blading method. Molded into.

The internal electrode material powder has an average particle size of 0.5 μm.
Copper oxide (CuO) particles and metallic copper (Cu) particles (particle size ratio 1: 1) were used to form a paste with the same binder and solvent as the dielectric, and printed on the dielectric green sheet.

The lamination was carried out by the green sheet laminating method so that the dielectric had a thickness of 10 μm and the number of layers was 100.

The atmosphere for the binder removal treatment is an oxygen partial pressure P ₁
(Atmospheric pressure) is set to log ₁₀ p ₁ = -0.68, and the temperature is 55
It was carried out at 0 ° C for 60 hours.

The atmosphere for the reduction treatment is nitrogen and hydrogen, and the oxygen partial pressure P ₂ (atmospheric pressure) is set to log ₁₀ (P ₂ / P ₀ ) = 2.
It was carried out at a temperature of 600 ° C. for 2 hours.

For the main firing, a sealed magnesia container was used for N ₂
-H ₂ O-H ₂ Atmosphere partial pressure P ₃ (atmospheric pressure) log
_The temperature was controlled to ₁₀ P ₃ = −8.7 and the temperature was 950 ° C. for 2 hours.

[Examples 1 to 5] In the above, the conductor component material of the internal electrode was implemented by changing the mixing ratio of metallic copper and copper oxide, and the crack generation rate and the residual carbon amount were measured. The mixing ratio is shown in Table 1 with the results expressed by Ac / Ao.

The crack occurrence rate was 10,000 samples.
Measured in pieces.

[0083]

[Table 1]

[Examples 6 to 12] In the above-mentioned examples, the internal conductor component material was expressed as (number of copper atoms / number of oxygen atoms) = (Ac / A
o) = 4, the atmosphere and temperature of the debinding process were changed, the other conditions were the same as in Example 1, and the crack generation rate and the residual carbon amount were measured in the same manner. The results are shown in Table 2.

[0085]

[Table 2]

[Examples 13 to 27] Internal electrode paste in which the same dielectric material as in Example 1 was used and the internal conductor component material was (number of copper atoms / number of oxygen atoms) = (Ac / Ao) = 4. Is printed, and the dielectric thickness is 8 by the green sheet lamination method.
A layered product having a thickness of 150 μm and a thickness of 150 μm is formed.
It was divided into 2 mm and 1.6 mm wide green chips. Oxygen partial pressure P ₁ (atmospheric pressure) of this green chip is log ₁₀ P
₁ = −0.68, the temperature was 550 ° C., the binder was removed for 60 hours, the reduction treatment was performed, and the main firing was performed.

The conditions for the reduction treatment are N ₂ --CO--C.
Various operations were performed in O ₂ gas while changing the oxygen partial pressure P ₂ (atmospheric pressure) and the temperature.

As the internal conductor component material, the average particle diameter (D) of the metal copper particles and the ratio (D / d) of the average particle diameters of the metal copper particles and the copper oxide particles were changed.

Other firing conditions were the same as in Example 1.

In this example, the crack occurrence rate and the insulation resistance (specific resistance) of the dielectric were measured, and the results are shown in Table 3.

The specific resistance was measured on the laminated ceramic capacitor element after firing, and after the internal electrode was exposed at the terminal portion of the sample, the In--Ga alloy was applied to form the terminal electrode, and then the resistance value was measured. Was measured and calculated according to the dimension and shape.

[0092]

[Table 3]

[0093]

As can be seen from Tables 1 to 3, according to the method of the present invention, the volume contraction due to the reduction of the internal electrodes can be reduced and the generation of cracks can be effectively prevented.

Further, by properly adjusting the burnout conditions, the burnout of the binder is completely made to reduce the residual carbon, and by adjusting the reduction treatment conditions, the diffusion of copper oxide into the dielectric material is prevented. It is possible to prevent deterioration of insulation resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01G 4/12 364

Claims (9)

[Claims] 1. A copper-based conductor paste composition comprising a conductor component material composed of a mixture of metal copper particles and copper oxide particles and a binder component, wherein the metal copper particles and copper oxide in the conductor component material. The mixing ratio of the particles is defined as the ratio of the number of copper atoms (Ac) to the number of oxygen atoms (Ao) in the mixture (Ac /
A paste composition for a copper-based conductor, wherein the paste composition is within the range of the following [Formula 1] when represented by Ao). [Formula 1]: 2.0 ≦ (Ac / Ao) ≦ 15.0 2. The average particle diameter (D) of the metallic copper particles and the average particle diameter (d) of the copper oxide particles are in the range of 0.005 to 3 μm, and the average particle diameter (D) of the metallic copper particles. ) And the average particle diameter (d) of the copper oxide particles (D / d) is within the range of the following [Formula 2]. [Formula 2]: 0.001 ≦ (D / d) ≦ 20 3. A method for manufacturing a laminated ceramic element having a ceramics dielectric and an internal conductor, wherein an internal conductor made of the copper-based conductor paste composition according to claim 1 is alternately provided between the ceramics dielectric material layers. After the formation, a binder removal treatment is performed on the binder component in an oxygen-containing atmosphere, then the internal conductor is reduced in a temperature range lower than the firing temperature, and the firing is further performed. 4. The method for manufacturing a laminated ceramic element according to claim 3, wherein the ceramic dielectric is a lead composite perovskite oxide. 5. The production of a laminated ceramic element according to claim 3, wherein the debinding treatment is carried out in an atmosphere having an oxygen partial pressure (P ₁ (atmospheric pressure)) of the following [Formula 3]. Method. [Formula 3]: −5 ≦ log ₁₀ P ₁ ≦ 0 6. The binder removal treatment is performed at 200 to 650 °.
The method for producing a laminated ceramic element according to claim 3, wherein the method is performed in a temperature range of C. 7. The method for producing a laminated ceramic element according to claim 3, wherein the reduction treatment is performed in an atmosphere of oxygen partial pressure (P ₂ (atmospheric pressure)) of the following [Formula 4]. .. [Formula 4]: 0 ≦ log ₁₀ (P ₂ / P ₀ ) ≦ 4 where P ₀ represents the oxygen partial pressure at which Cu ₂ O starts reduction. 8. The method for manufacturing a laminated ceramic element according to claim 3, wherein the reduction treatment is performed in a temperature range of 200 to 650 ° C. 9. The method for producing a laminated ceramic element according to claim 3, wherein the ceramic element is a laminated ceramic capacitor having a copper internal electrode.