JP2000063182A - Production of ceramic raw material capable of being sintered at low temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a ceramic raw material which can be sintered at a low temperature and is useful as a precursor for a sintered product, to provide a method for producing the ceramic sintered product using the same, and to provide a method for producing a multi-layered ceramic circuit board. SOLUTION: This method for producing a ceramic raw material comprises preparing starting raw materials satisfying the below conditions (1), (2) and (3), and subsequently calcining the starting raw materials in a temperature range of 800-900 deg.C. (1), The starting raw materials comprises (a) kaolinitic or halloysitic clay powder, (b) calcium carbonate powder, and (c) silica powder. (2), The mixture composition ratio (converted into the oxides after calcination) of the above raw materials (a), (b) and (c) is expressed by the inequalities: 0.15<=(x)<=0.45, 0.05<=(y)<=0.20, 0.45<=(z)<=0.75 [(x)+(V)+(z)=1.00], when a mol composition formula is xCaO.yAl2O3. zSiO2. (3). The starting raw materials are a fine particle mixture having an average particle diameter of <=2.0 μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a ceramic raw material, a ceramic sintered body and a multilayer ceramic wiring board, and is particularly useful as a low temperature fired ceramic substrate for electric parts, especially as a ceramic for a multilayer wiring board or a microwave dielectric substrate. , A method for producing a ceramic raw material containing almost no alkali, boron oxide or lead oxide and capable of being sintered and densified at a low temperature of 1000 ° C. or lower.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices represented by mobile phones, a multilayer wiring board in which a plurality of porcelain sheets are laminated is used as a board on which electronic components are mounted. In addition, miniaturization is also required for individual parts that make up the equipment,
In addition to the conventional multilayer chip capacitors, small multilayer components such as high frequency chip inductors and chip LC filters have been developed.

Conventionally, alumina ceramics have been generally used as the material for the multilayer wiring board as described above. However, since the sintering temperature of alumina ceramics is as high as 1500 ° C. or higher, it is necessary to use W or Mo as a conductive material for co-firing circuit wiring. In this case, high temperature firing in a non-oxidizing atmosphere is required, and there is a drawback in that loss due to electric resistance of circuit wiring is high.

Therefore, in order to solve these problems,
A porcelain composition for substrates that can be sintered at low temperatures has been developed. One of them is a ceramic raw material that can be sintered at a low temperature of 900 ° C. or lower. When this low-temperature sintered ceramic raw material is used for a multilayer wiring board, highly conductive silver can be used as a metal for internal wiring. For this reason, firing in an oxidizing atmosphere is possible and loss due to the electrical resistance of the metal wiring is greatly reduced.

Such low-temperature sinterable ceramic materials can be roughly classified into two types, that is, a crystallized glass type and a glass ceramic composite type. A typical method for producing a crystallized glass-based ceramic raw material is to add P ₂ O ₅ or B ₂ O ₃ to a raw material having a composition close to cordierite, melt the mixture at high temperature to prepare the glass, and then use this glass. It is a method of finely pulverizing to powder, followed by molding, firing and crystallization.

Further, a method for producing a glass-ceramic composite system is, for example, to mix alumina fine particles and glass powder,
This is a method of forming and firing. Borosilicate glass and lead-based glass are generally used as this glass.

[0007]

However, although all of these ceramic raw materials can be sintered at low temperature, they have the following problems. First of all, in any of the methods, it is necessary to vitrify, so the raw material must be melted at a high temperature, and the obtained glass is difficult to crush, resulting in high cost.

Next, the ceramic raw material generally contains a large amount of monovalent metal ions, boron oxide and lead oxide. These compounds often evaporate during firing, react with conductive materials, or damage the furnace.
In addition, when a ceramic wiring board is manufactured using a ceramic raw material that contains a large amount of monovalent metal ions, the insulation resistance of the ceramic substrate decreases and the withstand voltage decreases,
It is also a problem in terms of reliability.

Then, as a result of earnest research, the inventors have obtained a completely new idea and completed the present invention. That is,
In view of such conventional problems, the present invention is capable of sintering at a low temperature, does not contain monovalent alkali metal ions, boron oxide and lead oxide, does not react with a conductive material, and does not damage the furnace. A method of manufacturing a ceramic raw material as a precursor of a body, a method of manufacturing a ceramic sintered body using the same, and a method of manufacturing a multilayer ceramic wiring board.

[0010]

The present invention comprises (1) (a) kaolinite or halosite clay powder, (b) calcium carbonate powder, and (c) silica powder, and (2)
The mixed composition ratios of (a), (b), and (c) above have a molar composition formula of xCaO · yAl ₂ O _{3 in} terms of oxides after burning.
・ When expressed by zSiO ₂ , 0.15 ≦ x ≦ 0.45
0.05 ≦ y ≦ 0.20, 0.45 ≦ z ≦ 0.75 (x
+ Y + z = 1.00), and (3) prepare a starting material satisfying the conditions (1), (2), and (3) that is a mixture of fine particles having an average particle size of 2.0 μm or less. A method for producing a ceramic raw material, which comprises a step and a step of calcining the starting material within a temperature range of 800 to 900 ° C.

What is most noticeable in the present invention is that the predetermined starting material is calcined at the predetermined temperature. By this calcination, (a) component clay and (b)
Decomposition of calcium carbonate proceeds at the same time, resulting in highly reactive decomposition products. Then, the decomposition products react with each other to form amorphous fine particles in a state close to a solid solution. As a result, a low temperature sinterable ceramic raw material is obtained.

The ceramic raw material obtained by the present invention can be easily pulverized into fine particles by mechanical pulverization. The fine particles are mainly composed of an amorphous phase. Therefore, the sintering activity is extremely high. Therefore, the ceramic raw material can be densified by low-temperature firing at 1000 ° C. or less to form a ceramic sintered body. In addition, since the above ceramic raw material does not contain monovalent alkali metal ions, boron oxide and lead oxide, it does not react with the conductive material by firing and does not damage the firing furnace. The property is improved.

Next, details of the present invention will be described. (Starting Material) The starting material is composed of (a) kaolinite or halosite clay powder, (b) calcium carbonate powder, and (c) silica powder.

The x in the above composition formula represents the molar ratio of CaO in the oxide of the starting material after burning. The range of x is 0.
15 ≦ x ≦ 0.45. As a result, in the ceramic raw material obtained by calcination, fine particles are densified and sintered even by low temperature firing at 1000 ° C. or less. Therefore, it is possible to obtain a ceramic raw material that can sufficiently exert the effect as a low temperature firing precursor.

On the other hand, when x is less than 0.15,
The effect of the ceramic raw material as a precursor for low temperature firing is not sufficient, and the firing temperature at which it becomes dense becomes higher than 1000 ° C. If x is greater than 0.45,
Calcium silicate (2
CaO.SiO ₂ ) precipitates and the sinterability deteriorates, and the water resistance also deteriorates significantly.

In the above composition formula, y represents the molar ratio of Al ₂ O ₃ in the oxide of the starting material after burning. The range of y is 0.05 ≦ y ≦ 0.20. As a result, the sinterability when firing the ceramic raw material is improved and the water resistance is increased. On the other hand, when y is less than 0.05, calcium silicate (2CaO.SiO ₂ ) precipitates during firing, resulting in poor sinterability and poor water resistance. Also, y
When the value exceeds 0.20, the effect as a firing precursor of the ceramic raw material is low, and even if firing is performed at a temperature higher than 1000 ° C., the densification is not sufficient.

In the above composition formula, z represents the molar ratio of SiO ₂ (silica) in the oxide of the starting material after burning. The range of z is 0.45 ≦ z ≦ 0.75. As a result, a ceramic raw material having high sinterability and easily densified can be obtained. On the other hand, if z is less than 0.45, amorphous grains after calcination, that is, crystals of gerenite are precipitated from the ceramic raw material. Therefore, even if such a ceramic raw material is fired, a sufficiently dense sintered body cannot be obtained.
Further, when z is more than 0.75, many silica crystal particles are present in the product after calcination in addition to the non-crystalline fine particles. Therefore, viscous flow during sintering becomes insufficient, and
A dense sintered body cannot be obtained even at a temperature higher than 00 ° C.

The starting material is a fine particle mixture having an average particle size of 2.0 μm or less. As a result, solid solution between decomposition products during calcination is completed in a short time, and a ceramic raw material mainly composed of amorphous fine particles, which can be sintered at low temperature, is obtained. On the other hand, when it exceeds 2.0 μm, it takes an extremely long time to complete the solid solution between the decomposition products during calcination,
During that time, crystallization starts from the generated amorphous fine particles.
Therefore, the viscous flow of the fine particles becomes insufficient in the firing process, and it becomes difficult to sinter, and the effect as a precursor for low temperature firing becomes low.

In order to make the average particle size of the starting material 2.0 μm or less, for example, the three components (a), (b) and (c) may be mixed and pulverized with a ball mill or the like. It is also possible to use a mixture of the above three components having such a size that the above average particle diameter is obtained.

(Calcination) Next, the above starting materials are added in the range of 800 to 9
Calcination is performed within a narrow temperature range of 00 ° C. As a result, the decomposition and solid solution of the starting material are sufficiently performed. Therefore, when the ceramic raw material obtained by calcination is fired, the firing shrinkage is small and cracks and defects can be suppressed. On the other hand, when the calcination temperature is lower than 800 ° C., the decomposition and solid solution of the starting materials become insufficient even after a long time calcination. For this reason, the firing shrinkage rate of the ceramic raw material becomes high, and the components are often decomposed during firing to cause cracks and defects in the sintered body. Actually, in order to prevent such a problem from occurring, the ratio of undecomposed material in the ceramic raw material obtained by calcination is set to 10
Must be less than or equal to%. In the manufacturing method of the present invention, the ratio of the undecomposed material of the ceramic raw material is 10% or less, so that defects such as cracks in the sintered body are hard to occur. Further, when the calcination temperature is higher than 900 ° C, crystallization of anorthite and grenite starts at the calcination stage, and the ceramic raw material after the calcination does not play the role of the precursor.
It does not densify at low temperatures below 000 ° C (see Fig. 1).

(Manufacturing Method of Ceramic Sintered Body) In manufacturing a ceramic sintered body using the above-mentioned ceramic raw material, for example, functional oxide powder is added to and mixed with the above-mentioned ceramic raw material at a ratio of 5 to 35 wt%. Then, there is provided a method for producing a ceramic sintered body, which comprises a step of molding and obtaining a molded body and a step of firing the molded body at a low temperature of 1000 ° C. or lower.

In the present invention, a predetermined amount of the functional oxide powder is added to the ceramic raw material and the ceramic raw material is fired. Therefore, it is possible to improve and impart mechanical properties, thermal properties, or electrical properties of the ceramic sintered body while maintaining the property of sintering at a low temperature. In addition, the mechanical strength increases and the thermal conductivity also increases. According to the invention, 10
By firing at a temperature below 00 ° C, a stable and homogeneous functional ceramic sintered body can be easily manufactured at low cost,
Mass production can be realized. In addition, since the ceramic raw material does not contain monovalent alkali metal ions, boron oxide and lead oxide, the firing does not react with the conductive material and does not damage the firing furnace.

Further, the ceramic raw material is a reaction-active amorphous sintering precursor as described above. Therefore, when the functional oxide powder is added to the ceramic raw material and mixed and fired, crystallization of the amorphous precursor starts from the surface of the functional oxide particles, and the amorphous phase behaves like a liquid phase. . Therefore, the effect that the liquid phase sintering proceeds at a low temperature of 900 ° C. or lower and becomes denser is obtained.

On the other hand, if it is less than 5 wt%, the sintered body will have a large amount of glassy phase and become brittle, and a ceramic sintered body that fully exhibits the above-mentioned properties cannot be obtained. Also, 35
When it exceeds wt%, it becomes difficult to densify at low temperature.

The above-mentioned functional oxide powder is, for example, one kind or two or more kinds selected from the group of low dielectric constant oxide, high thermal conductivity oxide, ferroelectric oxide, and ferromagnetic oxide. Examples of the low dielectric constant oxide include silica, cordierite, steatite, and forsterite. Further, examples of the high thermal conductive oxide include alumina. The ferroelectric oxide may be barium titanate, for example. The ferromagnetic oxide may be ferrite, for example.

Next, the ceramic raw material to which the functional oxide powder is added is molded to obtain a molded body. Examples of the molding method include, but are not limited to, a slip casting method and a doctor blade method.

Next, the compact is fired at a low temperature of 1000 ° C. or lower. As a result, the compact is densified and sintered to obtain a ceramic sintered body. Firing temperature is 1000
If the temperature exceeds ℃, the energy required for firing becomes large and it becomes difficult to save energy. In addition, since materials with high conductivity such as Ag and Cu have low melting points, they cannot be used as electrodes at high firing temperatures. Also,
The lower limit of the firing temperature is preferably 800 ° C. 8
If the temperature is lower than 00 ° C, the densification of the ceramic raw material becomes insufficient.

(Use of Ceramic Sintered Body) The manufacturing method of the present invention is extremely useful as a novel manufacturing method for low-temperature fired ceramic substrates for electric parts, particularly ceramics for multilayer wiring substrates and microwave dielectric substrates. There are other uses such as plates, figurines, and coating materials.

(Manufacturing Method of Multilayer Ceramic Wiring Board) A multilayer ceramic wiring board can also be manufactured by utilizing the above-mentioned manufacturing method of the ceramic sintered body. For example, 5 to 35w of functional oxide powder is added to the above ceramic raw material.
A step of adding and mixing at a ratio of t% to obtain a raw sheet by molding into a sheet shape, a step of printing a conductor circuit on the surface of the raw sheet, and laminating and pressing a plurality of the raw sheets to form a laminated body. There is a method for producing a multilayer ceramic wiring board, which comprises the steps of obtaining and the step of firing the laminate at a low temperature of 1000 ° C. or lower.

In the present manufacturing method, 1000 sheets of green sheet made of the above ceramic raw material and functional oxide powder are used.
It can be sintered at low temperature below ℃. Therefore, it is possible to use an inexpensive conductive material having a high electric conductivity, such as Ag or Cu, as an electrode. Therefore, it is possible to simultaneously sinter the green sheet and the conductor circuit material by firing at a low temperature of 1000 ° C. Therefore, it is possible to obtain a multilayer ceramic wiring board in which the ceramic substrate and the conductor circuit are integrated.

The lower limit of the firing temperature is preferably the same as in the case of the above-mentioned method for producing a ceramic sintered body. Also,
It is preferable to use the same functional oxide powder as that described above. The conductor circuit is preferably made of Ag or Cu, for example. These are because the conductivity is very high. In addition, as a conductor circuit, Ag /
There are also conductive materials such as Pd and Ag / Pt.

In addition to the conductor circuits, various functional circuits such as via holes can be formed on the green sheet. When the Ag conductive material is used, the firing conditions are preferably degreasing, gradual heating, and firing at 850 to 900 ° C. On the other hand, when Cu is used as a conductive material, firing must be performed in a reducing atmosphere.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 (Production of Ceramic Raw Material) New Zealand kaolin, commercially available calcium carbonate and commercially available finely divided silica were used as starting materials. When the composition formula is xCaO · yAl ₂ O ₃ · zSiO _{2 in} terms of oxide after burning, x is
= 0.25, y = 0.15 and z = 0.60.
Pulverize and mix the above mixture in a wet ball mill for 24 hours,
The average particle size of the obtained pulverized product was 1.4 μm. After drying this, it was calcined at each temperature within the temperature range of 700 to 1000 ° C. As a result, a ceramic raw material was obtained.

According to the X-ray diffraction result of the calcined product, 850 ° C.
Below, calcium carbonate remains, and above 920 ° C,
Anorthite crystallized. However, from 820 ℃ to 90
In the sample calcined within the temperature range of 0 ° C., no crystal phase was observed except the crystals of silica in the starting material.

(Manufacturing Method of Ceramic Sintered Body) 5 to 50 wt% of α-Al ₂ O ₃ fine particle powder is added to the ceramic raw material calcined at each of the above temperatures, mixed and pulverized, and dry pressure molding ( Molding pressure 120MPa), 850 each
Baking was performed at 0 ° C and 900 ° C for 1 hour. By this,
A ceramic sintered body was obtained.

FIG. 1 shows changes in the molding density and firing density depending on the calcination temperature of the ceramic raw material when the amount of α-Al ₂ O ₃ added was kept constant at 20 wt%. The compacting density is determined from the weight and volume of the compact, and the firing density is determined from the weight and volume of the sintered compact. Their weight and volume were measured with a balance and a micrometer, respectively. The amount of undecomposed starting material remaining in the ceramic raw material after calcination was measured and calculated by thermogravimetric analysis.

As a result of measuring these changes in density, 90
At a calcination temperature higher than 0 ° C, anorthite was crystallized from the ceramic raw material and a sufficiently densified sintered body could not be obtained. When it was calcined at a temperature between 800 ° C and 900 ° C, it was sufficiently densified.

With respect to the ceramic raw material which was calcined at 850 ° C., the amount of α-Al ₂ O ₃ added was changed to prepare a molded body in the same manner as described above, and 850 ° C. and 900 ° C., respectively.
It was baked in. Fig. 2 shows changes in the firing bulk density of the obtained sintered body.
It was shown to. The densification was insufficient in the composition in which the amount of alumina added exceeded 35 wt%.

20 wt% of alumina is added, and the temperature is 900 ° C.
The sintered body fired at No. 1 had a water absorption of almost 0 and a coefficient of thermal expansion of 5.2 × 10 ⁻⁶ / ° C., which was close to that of silicon.
When the characteristics in the microwave band were evaluated, the dielectric constant was 7.
8. The Q · f value was 10,000 or more, which was a very excellent characteristic as a microwave dielectric laminated substrate.

Embodiment 2 As in Embodiment 1, New Zealand kaolin, commercially available calcium carbonate and commercially available finely divided silica were used as starting materials for the ceramic raw materials. The composition of the compound is xCaO · yAl ₂ O ₃ · zSiO _{2 in} terms of oxide after burning.
, X = 0.30, y = 0.05 and z = 0.
It was 65. The above mixture was ground and mixed in a wet ball mill for 24 hours. The average particle size of the obtained pulverized product is 1.5μ.
It was m. This was dried and then calcined at 850 ° C.
5 to 50 wt% of CaZrO ₃ fine powder was added to the calcined ceramic raw material, mixed and pulverized, a binder was added, and a sheet was formed by a slip casting method.

The results of firing the above green sheet at 850 ° C. and 900 ° C. are shown in FIG. The densification was insufficient in the composition in which the addition amount of CaZrO ₃ fine powder exceeded 35 wt%. A raw sheet having a composition containing 30 wt% of CaZrO ₃ was fired at 900 ° C. The CaZrO ₃ -based substrate had a bulk density of 2.8 g / cm ³ and a water absorption rate of 0.01% or less,
The surface roughness Ra was as smooth as 0.2 μm, and the deformation and warpage were small, and it was suitable as a circuit board.

Embodiment 3 In this embodiment, a multilayer ceramic wiring board was manufactured using the method of Embodiment 2. That is, a ceramic raw material was obtained in the same manner as in Embodiment 2 above, while CaZrO
₃ % by weight of fine powder was added, mixed and pulverized, a binder was added, and a sheet was formed by a slip casting method. After forming the green sheets, as shown in FIG. 4 (a), a plurality of green sheets 11 are provided with via holes 21,
The conductor circuit 22 was formed by filling the inside with Ag conductor paste by a printing method and printing the conductor paste made of Ag or Cu on the surface of the green sheet.

Next, the green sheet 11 was laminated and pressure-bonded to obtain a multilayer sheet 1 (FIG. 4 (b)). Then, the multilayer sheet 1 was fired at a low temperature of 900 ° C. (FIG. 4).
(C)). Thereby, as shown in FIG. 4D, a multilayer ceramic wiring board 5 including the ceramic sintered body 10, the conductor circuit 2, and the via hole 21 was obtained.

In this example, a green sheet made of the ceramic raw material and the functional oxide powder is fired at a low temperature of 900 ° C. In addition to Ag, C is used as the material for the conductor circuit.
u can also be used. When using Cu, it is necessary to perform firing in a reducing atmosphere. By firing at a low temperature of 1000 ° C., the green sheet and the conductor circuit material are simultaneously sintered, and a multilayer ceramic wiring board in which the ceramic substrate and the conductor circuit are integrated can be obtained. Also, since it is fired at a low temperature,
It also saves energy.

[0045]

According to the present invention, it is possible to sinter at a low temperature, does not contain monovalent alkali metal ions, boron oxide and lead oxide, does not react with the conductive material, and does not damage the furnace.
A method for producing a ceramic raw material as a precursor of a sintered body,
It is also possible to provide a method for producing a ceramic sintered body using the same, and a method for producing a multilayer ceramic wiring board.

[Brief description of drawings]

FIG. 1 is an explanatory view showing changes in a molding density and a firing density according to a calcination temperature of a ceramic raw material according to a first embodiment.

[FIG. 2] α-Al in a starting material in Embodiment 1
Content and baking temperature ₂ O ₃ is an explanatory diagram showing the effect of the bulk density of the ceramic sintered body.

FIG. 3 is an explanatory view showing the influence of the addition amount of CaZrO ₃ added to the ceramic raw material and the firing temperature of the green sheet on the bulk density of the ceramic sintered body in the second embodiment.

FIG. 4 is an explanatory view showing a method for manufacturing a multilayer ceramic wiring board according to the third embodiment.

[Explanation of symbols]

1. ． ． Laminated sheet, 10. ． ． Ceramic sintered body, 11. ． ． Raw sheet, 21. ． ． Beer hall, 22. ． ． Conductor circuit, 5. ． ． Multilayer ceramic wiring board,

Continued front page    (72) Inventor Masato Nakata             3 2232 2352 Kakino Hirohata, Tsuruzato-cho, Toki City, Gifu Prefecture               Maruwa Ceramic Co., Ltd. Toki Factory (72) Inventor Toshinori Akimatsu             3 2232 2352 Kakino Hirohata, Tsuruzato-cho, Toki City, Gifu Prefecture               Maruwa Ceramic Co., Ltd. Toki Factory F-term (reference) 5G303 AA05 AB15 BA12 CA01 CB01                       CB06 CB30 CB39 DA04 DA06

Claims (3)

[Claims] 1. (1) (a) Kaolinite or halosite clay powder, (b) calcium carbonate powder,
And (c) silica powder, (2) above (a),
The mixed composition ratios of (b) and (c) are calculated as oxides after burning, and the molar composition formula is xCaO · yAl ₂ O ₃ · zSiO ₂
Is expressed as 0.15 ≦ x ≦ 0.45, 0.05 ≦ y
≦ 0.20, 0.45 ≦ z ≦ 0.75 (x + y + z =
1.00) and (3) the average particle size is 2.
A step of preparing a starting material satisfying the above conditions (1), (2) and (3) that is a fine particle mixture of 0 μm or less, and a step of calcining the starting material within a temperature range of 800 to 900 ° C. A method for producing a ceramic raw material, comprising: 2. A step of adding a functional oxide powder to the ceramic raw material according to claim 1 at a ratio of 5 to 35 wt% and molding the mixture to obtain a compact, and the compact at a low temperature of 1000 ° C. or lower. A method for producing a ceramic sintered body, which comprises a step of firing. 3. A step of adding a functional oxide powder to the ceramic raw material according to claim 1 at a ratio of 5 to 35 wt% and mixing the mixture to obtain a raw sheet, and a conductor on the surface of the raw sheet. A step of printing a circuit, a step of stacking a plurality of the above-mentioned green sheets and press-bonding to obtain a stack, and a step of stacking the stack 10
And a step of firing at a low temperature of 00 ° C. or lower.