JP2829882B2 - Fiber filler material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fiber filler material composed of fibers containing 40 to 95% by weight of alumina and having silica as the remaining main component.

[Prior art] Fibers having an alumina content of 40 to 95% by weight and the remaining main component consisting of silica are generally used as high-temperature insulating materials because of their high heat resistance. Mixed with the matrix of
It is used as a means for achieving hardness and dimensional stability.

Generally, such fibers are classified into amorphous fibers and crystalline fibers in terms of material.

Amorphous ones have an alumina content of approximately 40-65% by weight, with the balance being silica. The crystalline one has an alumina content of 60-95% by weight with the balance being silica.

Each of the fibers has the above-described composition as a basic composition, and it is known to add tens of percent to several percent of subcomponents such as chromium oxide, zirconium oxide, and boron oxide. Fibers to which these subcomponents are added have improved heat resistance and improved ease of fiberization.

Fibers having an alumina content of 40 to 95% by weight and the remaining main component consisting of silica are classified into continuous fibers and short fibers according to the fiber length. The continuous fiber is handled in a state of being wound on a bobbin, and the short fiber is handled in an aggregate of about 50 to 100 mm.

When used as a fiber filler material for semiconductor encapsulation, continuous fibers are used after being cut short. Short fibers as they are,
Or, it is used after being cut short.

[Problems to be Solved by the Invention] However, when these fibers are subjected to the cutting process, the cut area increases accordingly, and as a result, the surface area increases.

This increase in surface area becomes more pronounced as the material is cut into smaller pieces.

For example, when a fiber having a diameter of 3 μm and a length of 100 mm is cut to 50 μm, the surface area increases by 3%, when cut to 10 μm, it increases by 15%, and when cut to 3 μm, it actually increases by 50%.

Originally, these fibers have a smaller fiber diameter and a larger specific surface area than glass fibers or the like.

Therefore, when a component soluble in the matrix is present in the fiber when mixed with the fiber matrix, the amount of the soluble component eluted into the matrix through the fiber surface increases.

In particular, the cut new fiber surface is very active. Such active surfaces are generally highly reactive and are prone to react with and adsorb other substances. Such cut surface properties accelerate the dissolution of the soluble components in the fibers into the matrix.

Soluble components are particularly easy to elute in the water present in the matrix.

By way of components eluted in water, Na ^+, K ^+, or an alkali metal ion Li ⁺ and the like, F ^-, Cl ^- halogen ion such as is typical.

Soluble components are often derived from unavoidable impurities in raw materials for producing fibers.

Soluble components that elute into the matrix may not be a problem in some cases, but may be very problematic. It is particularly the Na ⁺ ion that has a large amount and a large effect.

For example, a filler material for semiconductor sealing dislikes the presence of an alkali metal even in a very small amount. This is because the characteristics of the semiconductor are impaired.

Therefore, a filler material having a large amount of alkali elution into the matrix resin cannot be used as a semiconductor sealing material.

On the other hand, strength can be raised as a basic property required for the fiber filler material.

When the above-mentioned fibers are used as a reinforcing material in a matrix such as a metal, the fibers are subjected to a high temperature close to the melting temperature or the sintering temperature of the metal during molding.

In such a case, once the conventional fiber filler material was exposed to a high temperature, the strength characteristics were significantly reduced.

A first object of the present invention is to provide a fiber filler material in which alkali metals are less eluted into a matrix.

A second object of the present invention is to provide a fiber filler material that has a small decrease in strength at high temperatures.

[Means for Solving the Problems] The present invention has the following configuration to achieve the above object. That is, the present invention, the content of alumina is 40
In a fiber filler material composed of fibers whose main component is silica, the total of Na and K contained in the whole fibers is 250 ppm or less, and Fe is 50% by weight.
0 ppm or less, and the average fiber length of the fiber is 200 μm
The gist is a fiber filler material characterized by the following. For example, the filler material for semiconductor encapsulation is composed of fibers, and the total of Na and K contained in the fibers is 250 ppm.
Hereinafter, Fe contained in the fiber is 500 ppm or less, and the average fiber length is 200 μm or less. Moreover, the fibers are
Amorphous fiber having an alumina content of 40 to 65% by weight and the remaining main component being silica (hereinafter, the amorphous fiber is referred to as an amorphous fiber), and an alumina content of 60 to 95% Polycrystalline fibers of which the main component is silica in weight%, or polycrystalline fibers having an alumina content of 95% by weight (hereinafter, crystalline fibers are referred to as polycrystalline fibers).

[Action] The average fiber diameter is about 3 μm, and if the length is less than 3 μm, the characteristics as a fiber are lost.

If the average fiber length is 200 μm or less, the average fiber length is 2
This is because if it exceeds 00 μm, it is difficult to disperse in the matrix. The most preferred average fiber length is 150 μm or less.

The mixing of Na, K and Fe can be minimized under sufficient consideration, but it is not preferable to exceed a certain amount.

The total content of Na and K should not exceed 250 ppm.
If it exceeds 250 ppm, the amount of Na or K eluted in water becomes too large. If the amount is less than 10 ppm, the raw materials become too expensive and the production takes too much time.

The Fe content should be below 500 ppm. If it exceeds 500 ppm, a decrease in tensile strength and a decrease in tensile modulus at high temperatures are observed.

In any case, if the fiber filler material contains only a small amount of the alkali metal as described above, the strength and the like do not decrease at high temperatures.

[Example] The fiber filler material according to the present invention is characterized in that the content of Na, K, and Fe is remarkably low as compared with the conventional alumina siliceous fiber. The contents of Na, K and Fe are about 1/10 or less as compared with the conventional products.

The amorphous fiber filler material is produced by cutting high-purity amorphous fibers so that the average fiber length is 200 μm or less.

At the time of cutting, care must be taken to maintain high purity. When processing a small amount, a high-purity alumina mortar is suitable. In the case of treating a large amount, it is appropriate to use a pulverizer such as a ball mill composed of high-purity alumina or alumina-silica or zirconia.

High-purity amorphous fibers are made from high-purity alumina and silica raw materials. In addition, a high-purity alumina silica compound may be used as a raw material.

Even in conventional amorphous fibers, relatively high-purity ceramic materials have been used. For example, Bayer method alumina with relatively high purity is used as the alumina raw material,
Silica sand and the like have been used as silica raw materials. Also, clay such as kaolin has been used as the alumina-silica compound.

Although such raw materials have relatively few impurities, they each contain oxides of Na, K, and Fe in the range of 0.01 to 0.2%.

Raw materials containing impurities in such a range are not preferable as raw materials for the amorphous fiber filler material according to the present invention. As the raw material of the amorphous fiber filler material according to the present invention, those having a lower content of alkali metal oxides and Fe oxides are desired.

As will be described later, it is difficult to reduce the amount of impurities newly mixed in the manufacturing stage to zero, even if a raw material having less impurities is used in the present technology.

Unfortunately, the amount of impurities expected to be incorporated during the manufacturing stage does not differ much from the amount of impurities allowed in the amorphous fibers according to the present invention.

Therefore, when the target is an amorphous fiber in which impurities are almost reduced to the limit, the amount of impurities in the raw material is required to be almost zero.

Raw materials satisfying such requirements are difficult to find in natural raw materials.

Usually, a synthetic raw material is used for both the alumina raw material and the silica raw material. As the alumina raw material, a synthetic alumina of the Bayer method has been used in the past, but the alumina of the Bayer method contains Na ₂ O in the range of 0.1 to 0.2 due to the production method.

Therefore, in order to produce the amorphous fiber filler material of the present invention, it is preferable to select an alumina raw material to be used by a method other than the ordinary Bayer method. For example, it is preferable to use alumina made by the ammonium alum method, the organometallic hydrolysis method, or another method.

However, it does not deny the use of raw materials containing many impurities. Even if a raw material containing many impurities is used, the fiber filler material of the present invention can be manufactured by adding a step of removing impurities.

As for the silica raw material, natural silica sand is difficult to use in the present invention because of its high content of impurities, particularly alkali metal oxides.

Therefore, it is preferable to use a synthesis raw material as the silica raw material. Examples of such a raw material include synthetic silica starting from silicon tetrachloride or various alkyl silylate.

Table 1 shows examples of chemical analysis values of impurities in the raw materials used for producing the above-mentioned amorphous fibers. For comparison, the analytical values of impurities of the Bayer method alumina and natural silica sand (flatary sand), which are often used in the past, are shown.

Both ACL-27 and CAH-501 in Table 1 are examples of high-purity alumina raw materials. These aluminas have an impurity content of 100 ppm or less by weight for any element.

With this degree of purity, it can be used in the present invention. P-
3 is an example of a high-purity silica raw material, and the impurity element is almost zero. This can likewise be used in the present invention.

A-H is an example of the Bayer method alumina which has been used in a larger amount than before. In this example, the contents of Na and Fe are large. In the case of the flattery sand, Fe, Na, and K are considerably small, but significantly higher than that of P-3. Raw materials with many impurities cannot be used in large amounts, but they can be used by mixing them with high-purity products.

In order to produce the amorphous fiber filler material for semiconductor encapsulation according to the present invention, first, a high-purity raw material is blended in a predetermined blending ratio and melted in an electric furnace. The type of the electric furnace used for melting may be any type, but in any case, unnecessary impurities from portions other than the raw materials are prevented from entering the melt as much as possible. Sources of impurities extend to all materials that are in direct contact with the raw material and the melt. For example, there are a raw material storage tank, a raw material mixer, a raw material transport system, a furnace shell, an orifice, an electrode, a high-speed gas body, a cotton collection room, and the like.

As undesirable impurities, other than oxides of Na and K,
An oxide of Fe may be used. It is desirable that these impurities be as small as possible.

The impurities finally taken into the fibers are divided into those coming from the raw materials and those coming from other routes as described above.

As an example of impurities entering through the latter route, Fe and its oxides are particularly prominent. Na and many of its oxides also enter via the latter route.

Therefore, what should be noted in practicing the present invention is not only to examine the purity of the raw material, but also to check the content of Na and Fe in the fiber as a product.

[Experimental Example] The present invention will be described in more detail with reference to experimental examples.

High-purity alumina and high-purity silica shown in Table 1 were blended in a predetermined ratio. The formulation was melted in an electric arc furnace and the melt was directed as a thin stream outside the furnace. High-speed air was applied to the fine stream to form fibers. Table 2 shows the target composition.

In Experimental Example 1 in Table 2, the alumina raw material was ACL-27,
The silica raw material was designated as P-3.

In Experimental Example 2, the alumina material was ACL-27 and CAH-501 at 50.
% And the mixture was used, and the silica raw material was designated as P-3.

In Experimental Example 3, the alumina raw material was CAH-501, and the silica raw material was P-3.

In Comparative Example 1-a, AH was used as the alumina raw material and silica raw material was used as the flattery sand. This is a combination conventionally used conventionally. The obtained fiber was ground to about 50 μm in a high-purity alumina mortar. Table 3 shows the chemical analysis values of impurities performed on the pulverized material.

According to Table 3, in all of the fibers of Experimental Examples 1, 2, and 3, an impurity amount larger than the amount expected from the composition of the raw materials was observed. In particular, the increase of Na and Fe was remarkable.

Experimental Example 4 is another example of the fiber filler material according to the present invention. This is an example of a polycrystalline fiber filler material, which is a mullite fiber produced according to the invention of Japanese Patent Publication No. 62-12321 of the present applicant. In particular, it is a high-purity mullite fiber which is fired through high-purity basic aluminum chloride, colloidal silica, and lactic acid as a starting material and a precursor fiber. During firing, steam treatment was performed for the purpose of reducing residual chlorine.
The obtained fiber was ground to about 50 μm in a high-purity mortar, and it was chemically analyzed.

The crystalline fiber filler material according to the present invention can be obtained by other methods. For example, using a sol obtained by hydrolyzing an organic metal as a starting material, a high-purity starting material is used, and a process in which impurities are not mixed is employed.

Extracted water characteristics of the fiber filler materials shown in Table 3 were measured. The measuring method will be described below.

8 gr of the fiber filler material was placed in 80 gr of distilled water contained in a polyethylene container, and the whole container was placed in a thermostat at 95 ° C. Two
After 0 hour, the container was taken out and cooled to room temperature.
The supernatant in the container was subjected to chemical analysis, measurement of acidity, and measurement of electric conductivity. Table 4 shows the results.

According to Table 4, all of Experimental Examples 1, 2, 3, and 4 were Na
⁺ , K ⁺ ions show a small value of 5 ppm or less. Also, the electric conductivity shows a small value of about 10 μS / cm. On the other hand, in Comparative Example 1, the concentration of Na ⁺ ions was as large as 13 ppm, and the electric conductivity was as large as 22.7 μS / cm.

For example, in view of the conditions required as a filler material for semiconductor encapsulation, it is preferable that the amount of Na ⁺ , K ⁺ , and CL ⁻ eluted in water be small. In particular, it is desired that the amount of Na ⁺ ions is small. The concentration of Na ⁺ ions is preferably 0, but up to 5
Up to ppm is acceptable. If it exceeds 5 ppm, it has an adverse effect on semiconductors. Electrical conductivity is proportional to the concentration of Na ⁺ , K ⁺ and other cations. Therefore, the small amount of impurity cations is supported by the low electric conductivity.

Next, the strength of the fiber filler material according to the present invention will be described.

Tensile strength tests were performed on the amorphous fibers shown in Table 3. The test conditions are as follows: when performing a tensile test at room temperature, and in advance.
It was divided into two types when a heat treatment was performed at 800 ° C. for 30 minutes to perform a tensile test. The test method was performed according to JIS R7601. 1
For 50 fibers per sample, distance between chucks 25 mm,
The test was performed at a pulling speed of 2 mm / min. The fiber diameter was measured with a microscope for the broken part. Table 5 shows the results.

According to Table 5, the tensile strengths without heat treatment in Experimental Examples 1, 2, and 3 are slightly higher or comparable to those in Comparative Example 1. The same can be said for the tensile modulus. However, in the case of Experimental Examples 1, 2, and 3, the tensile strength when heat-treated at 800 ° C. is maintained at an average of 170 kg / mm ² , but the tensile strength of the comparative example is reduced to 96 kg / mm ² .

Comparing the tensile elastic moduli of the two, in the case of the experimental example of the present invention, no decrease was caused by the heat treatment. That is, about 1300
It has maintained a 0Kg / mm ^2. In comparison, the tensile modulus of Comparative Example 1 was reduced to about 7000 kg / mm ² by the heat treatment. That is, in the case of Comparative Example 1, both the tensile strength and the tensile modulus were significantly reduced by the heat treatment.

Various methods can be applied to the analysis of the trace components.
For example, the quantification of Na ⁺ and K ^{+ in} the extraction water shown in Table 4 was performed by flame photometry. Cl ^- The quantitative spectrophotometric method was used.

[Effects of the Invention] As described above, the fiber filler material according to the present invention has a small amount of alkali metal eluted in water in the matrix, and has a small decrease in tensile strength and tensile modulus even when exposed to high temperatures.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeo Endo 4-4 Nihonbashi Hisamatsucho, Chuo-ku, Tokyo Itoishi Building Inside Toshiba Monoflux Co., Ltd. (72) Inventor Kimio Hirata 4th Nihonbashi Hisamatsucho, Chuo-ku, Tokyo No. 4 Itoshige Building Toshiba Monoflux Co., Ltd. (72) Inventor Yu Shinbo 30 Soya, Hata-shi, Kanagawa Pref. Toshiba Ceramics Co., Ltd. (72) Inventor Koichi Shiraishi 30 Soya, Hata-shi, Kanagawa Toshiba Ceramics Central Research Institute, Inc. (56) References Patent 2673142 (JP, B2) Patent 2743214 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 9/08

Claims (1)

(57) [Claims] 1. A fiber filler material having an alumina content of 40 to 95% by weight and a residual main component composed of silica, wherein a total of Na and K contained in the entire fiber is 250 ppm or less. In, Fe is 500ppm or less,
And a fiber filler material having an average fiber length of 200 μm or less.