JP2002047007A - Porous powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent silica gel being amolphous from changing into cristobalite by heat treatment. SOLUTION: The silica gel with mean grain size of 0.1-20 μm is incorporated with a compound by >=0.5 wt.% expressed in terms of oxide, containing >=1 kinds elements from between alkaline earth metal and Zr. By heat treating this mixture at 800-1100 deg.C, the porous fine particle is obtained which is excellent in heat stability, constituting amolphousness without crystallizing even under heat treatment at 800-1100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous powder produced using silica gel as a raw material and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, silica gel produced by a sol-gel method has been used as a desiccant, an adsorbent for a gas chromatography device, a catalyst carrier, and a filtering agent because of its large specific surface area and voids. Further, as a technique for further imparting functionality, a technique of combining or supporting various metals and metal oxides has been proposed and put to practical use in JP-A-10-72210 or the like. Silica gel that has been put into practical use is basically amorphous, despite differences in specific surface area, porosity, and the like.
The specific surface area and porosity of these porous silica gel materials are changed by heat treatment. Specifically, the heat treatment tends to reduce the specific surface area and the porosity. By applying a heat treatment utilizing such properties, a porous silica gel having desired characteristics can be obtained.

[0003]

Although silica gel is inexpensive and is a very useful material for various uses, it has a problem that it is difficult to handle such as slurrying because the specific surface area is too large. Although this problem can be solved by applying heat treatment, crystallization may occur due to the addition of heat history, and the characteristics may change. For this reason, various characteristics change and pose a problem. For example, when crystallized into quartz or cristobalite, the coefficient of thermal expansion becomes three times or more that before the heat treatment, and there are inflection points in the thermal expansion, causing various problems in use.

In particular, when used as a raw material of a ceramic insulating substrate in a wiring board such as a package for housing a semiconductor element, the insulating substrate is required to have a thermal expansion coefficient close to that of the semiconductor element, so that the thermal expansion coefficient is generally 4 ppm. / ℃
The degree is preferred.

When silica gel is used as a raw material, amorphous silica gel is crystallized into cristobalite when it is treated in a firing temperature frame for a ceramic insulating substrate, and the thermal expansion coefficient of the insulating substrate becomes too large. There is a problem that the mounting reliability is not sufficiently improved.

[0006]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors have carried out a specific metal oxide on silica gel and further heat treatment to reduce the specific surface area. It has been found that an amorphous porous powder having high stability is obtained.

That is, the porous powder of the present invention contains a compound containing silica as a main component and at least one element selected from the group consisting of alkaline earth metals and Zr in an oxide equivalent.
It is characterized by comprising amorphous by 5% by weight or more and does not crystallize even when heat treatment at 800 ° C. or more is applied. Further, the pore diameter in the powder is desirably 15 μm or less.

[0008] In addition, as a method for producing a porous powder, a compound containing at least one element selected from the group consisting of alkaline earth metals and Zr is added to silica gel having an average particle size of 0.1 to 20 µm. Is added at 0.5% by weight or more in terms of oxide, and the mixture is heat-treated at 800 to 1100 ° C.

According to the present invention, even when such a porous powder is used, for example, as a raw material for a ceramic insulating substrate in a wiring board, the silica gel does not crystallize in the firing step and the coefficient of thermal expansion and the like do not change. A ceramic insulating substrate can be easily manufactured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a porous powder of the present invention will be described in detail below. According to the production method of the present invention, silica gel is used as a starting material. This silica gel is produced by a so-called sol-gel method, and any production method can be used as long as it is an amorphous porous material containing silica as a main component.

However, it is necessary that the average particle diameter of the silica gel powder is 0.1 to 20 μm. When the average particle size is smaller than 0.1 μm, the additives described below are not sufficiently supported on all the silica gel particles, become non-uniform, and the stability to heat treatment is impaired. The resulting powder is larger than 20 μm and is not suitable for the purpose.

Next, a compound containing at least one element selected from the group consisting of alkaline earth metals and Zr is added to the silica gel powder in an amount of 0.5% by weight or more, especially 1.0% by weight in terms of oxide. % And mixed. The stability to heat treatment can be increased by adding the above-mentioned additional component compounds. The upper limit of the additive is not particularly limited, but the effect is not changed even if it is added in excess of 20% by weight. Therefore, the upper limit is desirably 20% by weight or less.

As the alkaline earth compound, Mg is used.
O, Mg (C ₂ H ₅ O) ₂ , Mg (CH ₃ OC ₂ H ₄ O) ₂ ,
MgF ₂ , Mg (OH) ₂ , Mg (NO ₃ ) ₂ .4H ₂ O,
SrO, Sr (CH ₃ OC ₂ H ₄ O) ₂ , SrF ₂ , Sr
_{(OH) 2 · 8H 2 O} , Sr (NO 3) 2, BaO, Ba
_{(CH 3 OC 2 H 4 O} ) 2, BaF 2, Ba (OH) 2 · 8H
_At least one selected from the group consisting of ₂ O and Ba (NO ₃ ) ₂ is used.

As the Zr compound, ZrO ₂ , Zr (O
_{CH (CH 3) 2) 4} , ZrF 4, ZrO (NO 3) 2 · 2H
_At least one selected from the group of 2O is used.

These compounds have an average particle size of 0.5-2.
It is desirable to add as a μm powder. In the case of a compound that can be easily ionized, a solution containing the above-mentioned metal ions can be prepared, silica gel can be mixed in the solution, and dried.

After the above additives are added to the silica gel powder, they are uniformly mixed by a mixing means such as a ball mill. At this time, a more uniform mixture can be obtained by using an appropriate solvent. At this time, it is desirable that organic balls or containers can be used as much as possible and decomposed and removed by heat treatment so that impurities from the mixing means are not mixed.

Next, the above mixture is heated at 800 to 1100 ° C.
At a temperature of 0.5 to 10 hours. If the temperature at this time is lower than 800 ° C., the reaction or diffusion between the silica gel and the additive does not proceed sufficiently. If the temperature is higher than 1100 ° C., the number of pores in the powder decreases. Also,
The atmosphere during the heat treatment may be an oxidizing atmosphere such as the air, a non-oxidizing atmosphere such as nitrogen, or an inert atmosphere such as argon.

The powder cooled to room temperature after the heat treatment can be appropriately pulverized and finely pulverized to an average particle size of 20 μm or less.

The prepared powder has an average pore diameter of 15 μm.
Hereafter, it has fine pores of 5 μm or less, especially 1 μm or less, and has substantially no crystal phase.
In addition, it is made of an amorphous material that does not crystallize by heat treatment and specifically does not crystallize even when heat treatment at 800 ° C. or more is applied.

For this purpose, the porous powder of the present invention comprises Si
The present invention can be applied to any application in which the property of O ₂ (amorphous) is required to be exhibited stably or fine pores are required.

In particular, by using as a ceramic filler component dispersed in glass in a ceramic insulating substrate in a ceramic wiring substrate on which a semiconductor element such as a semiconductor element housing package is mounted, -150 to
At 400 ° C., a stable thermal expansion characteristic of α = 3 to 7 × 10 ⁻⁶ / ° C. can be exhibited, and the dielectric constant of ceramics can be reduced by dispersion of pores in the porous body.

[0022]

EXAMPLE The average particle size produced by the sol-gel method was 1
For a 5 μm silica gel powder, the average particle size is 0.5 to
Various metal oxides of 2 μm were added at the ratios in Tables 1 to 4, and the mixture was mixed with isopropyl alcohol for 24 hours using urethane resin balls.

Thereafter, the powder was dried at 120 ° C., heat-treated in the air at the temperatures shown in Tables 1 to 10 for 10 hours, and allowed to cool. The powder after cooling was lightly crushed by a ball mill.

The average particle size of the obtained powder was measured by a laser sedimentation method.
The presence or absence of a crystal phase was identified by T1400V type X-ray diffraction measurement. Further, the presence or absence of a crystal phase when the heat treatment at 800 to 1100 ° C. × 10 hours was repeated 5 times was measured. Further, the average pore diameter of the powder produced by the porosimeter was measured. The results are shown in Tables 1 to 4.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

According to the results of Tables 1 to 4, No. 1 containing no metal oxide was used. 1, 27, 53, and 79 all changed to cristobalite (c) after the heat treatment. In addition, No. ₃ containing B ₂ O ₃ as a metal oxide. 2-6, 28-3
2, 54 to 58 and 80 to 84 also changed to cristobalite (c) after the heat treatment.

On the other hand, No. 1 containing 0.5% by weight or more of BaO as an alkaline earth element. 8-11, 34-3
Nos. 7, 60 to 63, 86 to 89 and No. 7 containing 0.5% by weight or more of CaO as an alkaline earth element. 13-1
6, 39 to 42, 65 to 68, and 91 to 94 did not crystallize and remained amorphous (a).

Similarly, 0.5% of ZrO ₂ is used as a metal oxide.
No. 5% by weight or more. 23-26, 49-52, 7
5 to 78 and 101 to 104 also became amorphous (a).

No. 3 containing 0.5% by weight or more of ZnO as a metal oxide. 18-21, 44-47, 70-7
3, 96-99, the crystal phase after heat treatment is quartz (q)
It became. However, in the case of No.
In Nos. 18 to 21, the amorphous (a) component remained, and the amount of crystals changed after repeated heat treatment. Other Nos. 44-47, 70-73, 96-9
In No. 9, the amorphous (a) component did not remain, and no change in the crystal phase was observed even after repeated heat treatment. In all the samples in which the content of the metal oxide was less than 0.5% by weight, the crystal phase was cristobalite (c).

From the above results, when at least 0.5% by weight of oxide containing at least one compound containing at least one element selected from among alkaline earth metals and Zr is considered, It was found that it did not crystallize and was thermally excellent in stability.

[0034]

As described in detail above, according to the present invention,
The porous granules containing silica as a main component contain at least one compound containing at least one element selected from among alkaline earth metals and Zr in an amount of 0.5% by weight or more in terms of oxide. By heat treatment at the above temperature,
It is possible to easily produce a thermally stable porous powder having an amorphous crystal phase after heat treatment.

Claims (2)

[Claims] 1. An amorphous material comprising silica as a main component and containing at least 0.5% by weight of a compound containing at least one element selected from an alkaline earth metal and Zr in terms of oxide. Porous powder. 2. A compound containing at least one element selected from the group consisting of an alkaline earth metal and Zr is added to silica gel having an average particle size of 0.1 to 20 μm in an amount of 0.5% by weight in terms of oxide. A method for producing a porous powder, comprising adding the above and heat treating the mixture at 800 to 1100 ° C.