JP2003277044A - Method for manufacturing spherical silica - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing spherical silica synthesized with a sol-gel method suited for uses such as a filler for an IC sealant resin, a substrate, an electronic material and raw materials of highly pure silica glass used in semiconductor manufacturing devices, quartz glass and optical glass or the like, generating no caking thereof in sintering and excellent in breaking into coarse particles. <P>SOLUTION: The method for manufacturing the spherical silica is characterized in breaking spherical silica gel containing Li, Na, K of which the sum of contents is 10 ppm or less before sintering into the coarse particles by using a screen or the like and subsequently sintering at 600°C or higher. Furthermore, in the method for manufacturing the spherical silica, the spherical silica gel before breaking into the coarse particles is spherical silica gel obtained by being washed with an aqueous acid solution of ≥0.005 mass % concentration and subsequently washed with pure water. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing spherical silica by a sol-gel method. More specifically, IC
The present invention relates to a method for producing spherical silica, which is suitable for use as a filler for a resin for a sealing material, a substrate, high-purity silica glass and quartz glass for electronic materials and semiconductor manufacturing equipment, and a raw material for optical glass.

[0002]

2. Description of the Related Art In recent years, with the rapid development of the electronic industry, high-purity silica has been used for electronic materials and semiconductor manufacturing. Of course, it has become desirable to have other performance as well.

In the application of semiconductor encapsulating materials, importance has been placed on fluidity at the time of resin mixing, and spherical silica has come to be used as a filler. In recent years, flip-chip type semiconductor devices have been developed, a sealing material (underfill material) that can be poured into a narrow gap is required, and spherical silica that has good coarseness and excellent fluidity has been desired. . Here, coarse grain cutting means the maximum particle diameter with respect to the average particle diameter, and in the case of the same average particle diameter, the smaller the maximum particle diameter of spherical silica,
Shows spherical silica with good coarse grain cutting.

Conventionally, as a method for producing spherical silica, a method in which silicon tetrachloride or an alkali silicate is used as a raw material, the synthesized silica is melted into a spherical shape by a flame, a method in which silicon particles are burned and oxidized by an oxyhydrogen flame, a silicon alkoxide, and a silicic acid A sol-gel method using an alkaline aqueous solution has been proposed.

However, in the method of melt spheroidizing in the gas phase such as the flame melting method, solidification between particles is likely to occur, and spherical silica with good coarse grain cutting cannot be obtained. The sol-gel method gives spherical silica with better coarse grain cutting than the flame-melting method, but it still has the problem that solidification occurs between particles during firing and the top size of the spherical silica after firing becomes large. It was Incidentally, the solidification means that the particles of the powder are sintered at a heating temperature equal to or lower than the melting point to form a relatively large lump.

In the sol-gel method, several methods for avoiding solidification during firing have been proposed. According to JP-A-1-234318, a method of fluidized drying and fluidized firing is mentioned, but solidification between particles cannot be completely avoided, and particularly a filler for a sealing material for flip chips. Was not suitable for. It should be noted that the non-consolidated spherical silica means particles that are densified only in the particles by firing and are not sintered between the particles.

The solidified particles cause deterioration of fluidity, and become coarse particles to increase the maximum particle size. It is difficult to completely remove the solidified coarse particles once formed by classification, and it is desirable that sintering between particles does not occur during firing.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for producing spherical silica having good coarse grain breakage, which does not cause solidification during firing in the spherical silica synthesized by the sol-gel method. Especially.

[0009]

Means for Solving the Problems As a result of research to improve the problems in the conventional method, the present inventors have found that in the method for producing spherical silica produced by the sol-gel method, the spherical silica before firing is Li, Na, K included
We have found that interparticle sintering during firing can be suppressed by suppressing the content and crushing before firing, and completed the present invention.

That is, the first invention of the present invention is "Li, N
A method for producing spherical silica, characterized in that spherical silica gel having a total content of a and K of 10 ppm or less is crushed and then fired at a temperature of 600 ° C. or higher. Is the gist.

The second invention of the present invention is summarized as "a method for producing spherical silica according to the first invention, wherein the crushing is a crushing method using a screen".

A third invention of the present invention is the spherical silica gel obtained by washing the spherical silica gel before crushing with an acid aqueous solution of 0.005% by mass or more and then with pure water. 2. The method for producing spherical silica according to the invention of 2. ”
Is the gist.

Spherical silica gel having a total content of Li, Na, and K of 10 ppm or less is not particularly specified, but can be manufactured by the sol-gel method. In the method for producing spherical silica gel by the sol-gel method, any raw material such as silicon alkoxide, alkali silicate, and silica sol can be used as long as they are in solution or sol at the raw material stage. In the sol-gel method, using these raw materials, a particle growth method of growing seed particles, a method of suspending or emulsifying the raw materials and solidifying them, and the like can be mentioned. There is no problem if it is in the form of a solution or a sol at the raw material stage, and any method can be applied as long as it is a method of solidifying in a gel state in the manufacturing process. The raw material is most preferably an alkali silicate in consideration of cost. As the alkali silicate, sodium silicate is the most inexpensive and preferable in view of versatility. In addition, potassium silicate and lithium silicate can also be used.

The spherical silica gel before firing has an average particle size of 0.1.
Particles of about 100 μm are preferred. In particular, when used for the purpose of permeating a narrow gap such as an underfill material, it is preferable to use spherical silica gel having a particle size distribution in which the maximum particle size is 4 times or less of the average particle size. In general, interparticle sintering tends to occur as the particle size decreases, but the method according to the present invention is particularly effective for firing spherical silica gel particles having an average particle size of 0.1 to 20 μm.

Li contained in the spherical silica gel before firing,
The total content of each element of Na and K must be 10ppm or less. If it exceeds 10 ppm, inter-particle sintering will occur during firing, and desired flow characteristics will not be exhibited when the resin is blended.
Flowability is represented by the viscosity of the resin when blended and the time it takes to penetrate into narrow gaps. L to maximize flow characteristics
5ppm or less is preferable for each element of i, Na and K, especially 1ppm
The following shows very good flow properties. Among these alkali metals, it is particularly necessary to reduce Na.
Is preferably 1 ppm or less, and Na is 0.2 p
By controlling the pressure to be pm or less, the flow characteristics are dramatically improved.

The content of these impurities can be directly measured by an appropriate analysis means. For example, silica is heated and dissolved in an aqueous solution of hydrogen fluoride to vaporize the silica as SiF ₄ , and the residue is subjected to ICP. The impurity concentration can be measured by analyzing with MS.

When the spherical silica is mixed with the resin, the content of Li, Na and K of the raw material spherical silica gel before firing is reduced and at the same time the spherical silica gel before firing is made to exhibit good flow characteristics. Crushing is essential. The crushing can be carried out by a jet mill, a pin mill, a ball mill, a roll mill, a vibrating screen, an ultrasonic screen or the like, and the crushing method using a screen is most effective. In addition, among the methods using a screen, a method of feeding the raw material into the inside of a horizontal cylindrical screen and continuously crushing it by rotating a blade attached inside the screen at a high speed (for example, Turbo Industrial Turbo Screener) is the most preferable in terms of cost.

Although the material of the screen is not particularly specified, it is preferable that the metal content is not mixed, and a resin screen is preferable in order to satisfy this. The type of resin is not particularly limited, but polyethylene, polypropylene, nylon, carbon, acryl, polyester, polyimide, fluororesin, etc. can be used.

As the screen used for crushing the spherical silica gel, it is preferable to use a screen having an opening of 10 times or less of the maximum particle size of the spherical silica gel to be crushed, preferably 1 to 5 times. Use the screen. It is more preferable to use a screen having a mesh size of 1 to 3 times.

The calcination method after the crushing of the spherical silica gel is not particularly specified, but for example, it is put in a container such as quartz and the temperature is 600 to 1 in an electric furnace.
It can be fired at any temperature of 500 ° C. Further, as other methods, a fluidized firing furnace, a rotary kiln, a flame firing furnace, or the like can be used. In some cases, it may be extremely weakly solidified after firing, but by crushing again using a screen, spherical silica having no solidification can be obtained.

Generally, the more silanol groups on the surface of the spherical silica, the higher the resin compounding viscosity, so it is necessary to reduce the silanol content. Since the amount of silanol groups on the surface of the spherical silica changes depending on the firing temperature, the firing temperature is preferably 1000 to 1300 ° C in order to reduce the silanol content.
In particular, in order to maximize the flow characteristics when compounding resin, 11
50-1250 degreeC is preferable.

It is preferable that the spherical silica is more spherical in order to improve the flow characteristics when the resin is compounded. Since the sphericity of the spherical silica gel before firing has a great influence on the sphericity of the spherical silica after firing, the sphericity is preferably 0.9 to 1.0. The sphericity A is represented by the ratio of the major axis (D1 [μm]) and the minor axis (D2 [μm]) of the particle.

A = D2 / D1 It is preferable that the spherical silica gel before firing also reduces metal elements other than alkali metals. Particularly, it is preferable to reduce the alkaline earth metal to the same level as that of the alkali metal. The content of other metal elements is also preferably 5 ppm or less. Especially when it is desired to improve the flow characteristics, Si and O
It is preferable that all the elements except 1 are less than 1 ppm.

In the present invention, the spherical silica gel is 50 m ²
It means silica having a specific surface area of not less than / g. A large number of silanol groups remain on the surface of spherical silica gel having a specific surface area of 50 m ² / g or more, and silanol groups between particles are dehydrated and condensed, so that interparticle sintering is likely to occur. In the present invention, even when the spherical silica gel having a specific surface area of 200 m ² / g or more is fired, sintering between particles does not occur. In addition, 2p alkali metal
By reducing to pm or less and crushing before firing, sintering between particles does not occur even when firing spherical silica gel having a specific surface area of about 500 to 1000 m ² / g.

The method for producing the spherical silica gel of the present invention is not particularly limited, but it is preferably produced by a method using an aqueous solution of alkali silicate and an acid. Specifically, a water-in-oil type (W / O type) emulsion in which fine particles are dispersed as an aqueous dispersion of an alkali silicate solution is prepared, and the prepared water-in-oil type (W / O type) emulsion is treated with an acid. Mix to form spherical silica gel. The acid used is preferably a mineral acid, especially sulfuric acid. Regarding extraction of impurities, it is preferable to generate spherical silica gel with an acid concentration after the reaction of 10% by mass or more. Further, the reaction liquid containing the generated spherical silica gel is heated to extract impurities. Heating temperature is 5
It is preferably 0 ° C or higher. After heating, the obtained spherical silica gel is washed and dried to obtain spherical silica gel.

By washing with a dilute acid, the adsorption of alkali metal or the like onto the spherical silica gel can be suppressed. When the concentration of alkali metal ions in the cleaning liquid is 100 ppm or more, it is preferable to perform cleaning again with a dilute acid. As the kind of acid, mineral acid is preferable, and sulfuric acid is particularly preferable. The concentration is
0.005 mass% or more is preferable, and 0.005 to 20 mass% is used suitably. The sulfuric acid concentration is preferably diluted in consideration of the cost, and is preferably 0.1 to 3% by mass in consideration of the cleaning effect of the alkali metal.

The washing method is not particularly limited, but a method of forming a cake layer of spherical silica gel and passing a dilute acid or pure water through the cake layer to wash it (cake rinse) and making the spherical silica gel into a dilute acid or pure water. A method of dispersing and filtering spherical silica gel (repulp rinse) can be applied. Spherical silica gel having a desired purity can be obtained by a combination of these treatments and washing treatments multiple times. The amount of acid used for washing is 1 to 5 of the water content contained in the hydrous spherical silica gel.
It can be appropriately selected by about double.

[0028]

EXAMPLES The present invention will be described below based on examples.

Example 1 1> Production of spherical silica gel 1-1) Preparation of emulsion JIS No. 3 water glass was concentrated as an aqueous alkali silicate solution, and the viscosity was adjusted to about 0.4 Pa · s at 25 ° C. The SiO ₂ content was about 30 mass%, and the Na ₂ O content was about 10 mass%. Isoparaffinic hydrocarbon oil (“Isosol 400”, manufactured by Nippon Petrochemical Industry) as a liquid for forming a continuous phase, sorbitan monooleate (“Reodol SP-O10”) as an emulsifier,
Kao) was used. Concentrated water glass, Isozol 400, Rheodor SP-O10 20kg, 7.5k respectively
g, 0.18 kg was weighed. The respective raw materials were mixed and roughly stirred with a stirrer, and then emulsified with an in-line emulsifier at a rotation speed of 2980 rpm to obtain 415 g of an emulsion.

1-2) Coagulation of spherical silica gel, extraction of impurities, and washing treatment 575 g of 28% aqueous sulfuric acid solution was prepared, and 415 g of the above-mentioned emulsion was added thereto while stirring at room temperature. After the addition was completed, stirring was continued at room temperature for another 40 minutes. Then 62% by mass under stirring
40 g of industrial nitric acid was added, and the mixture was further stirred for 20 minutes, heated to 100 ° C. under stirring, and kept for 30 minutes. By this treatment, the emulsion-like reaction liquid was separated into an oil phase (upper layer) and an aqueous phase in which spherical silica gel was dispersed (lower layer).

The oil phase was removed, and the spherical silica gel in the aqueous phase was filtered with a Nutsche, and 200 g of a 1 mass% sulfuric acid aqueous solution was passed through the spherical silica gel cake layer on the Nutsche to rinse the cake. Further, the cake-rinsed spherical silica gel was repulp rinsed with 300 g of a 1% by mass sulfuric acid aqueous solution for 10 minutes, and then dewatered with a Nutsche. Furthermore, the cake was rinsed with 500 g of pure water, then dewatered, and further repulped with 500 g of pure water. The cake rinsing and the repulp rinsing with pure water were repeated until the pH of the washing and deliquoring of the repulp rinse became 4 or more. At the stage where the pH of the repulp rinse washes and dewatered was 4 or more, dehydration was performed using a Nutsche to obtain spherical silica gel.

As a result of analyzing the alkali metal content of the obtained spherical silica gel, Li, Na, and K were found to be <0.1 p, respectively.
It was pm, 0.1 ppm, and <0.1 ppm.

2> Drying / crushing / calcining step of spherical silica gel The obtained spherical silica gel is dried at a temperature of 120 ° C. for 20 hours, and 1
00 g of dry spherical silica gel was obtained. After drying, the resulting dried spherical silica gel was used as Turbo Screwer T made by Turbo Industry.
Using S250 x 200, polyester aperture 27μ
It was passed through a m screen and crushed. Dry spherical silica gel that passed through the screen was heated to 1150 ° C in a quartz beaker.
It was calcined for 2 hours to obtain spherical silica.

When the spherical silica obtained by firing was analyzed, alkali metals such as Li, Na and K, C
a, alkaline earth metals such as Mg and Cr, Fe, Cu
Concentration of each element of isotransition metal is 1ppm or less, and U
The total of radioactive elements of Th and Th was 0.1 ppb or less.
Tables 1 and 2 show the results of various measurements and observations of the obtained spherical silica. The average particle size of the obtained spherical silica is
The particle size was 4.0 μm, the maximum particle size was 12 μm, and the specific gravity was 2.19. The specific surface area measured by the BET method is 0.7 m ² / g, which is the theoretical value.
It was 1.0 times. The sphericity is 0.9 from the electron micrograph.
The content of the above particles was 99% or more, and the smoothness of the surface was good.

ICP-MS was used to measure the impurity metal content.
(Model PMS-2000 manufactured by Yokogawa Electric Corporation).

The particle size was measured using LS-130 manufactured by BECKMAN COULTER. The average particle size is the median value, and the maximum particle size is the particle size under the sieve showing 100.00%. On the 32 μm sieve, 50 g of a sample was slurried with 150 g of pure water, passed through a stainless steel sieve, and the residue on the sieve was dried and measured.

20 μm gap permeability The obtained spherical silica was uniformly mixed with Japan epoxy resin Epicoat 815 at a silica compounding ratio of 65% by mass (mixing spherical silica 26 g and Epicoat 81514 g) and heated to a temperature of 75 ° C. Width 5m
The measurement sample was hung on one side of a mold having a gap of m, a gap size of 20 μm, and a length of 18 mm, and the time it took for one end to penetrate due to a capillary phenomenon was measured and displayed in time (minutes).

The resin compounding viscosity is the viscosity when Epicoat 815 manufactured by Japan Epoxy Resin and silica are mixed at a silica compounding ratio of 70% by mass (silica particles 28 g and Epicoat 81512 g are mixed) and are measured at 50 ° C. As the viscometer, RE80R type (E type viscometer) manufactured by Toki Sangyo was used.

Example 2 Spherical silica was obtained in the same manner as in Example 1 except that the screen opening at the time of crushing was 24 μm. Tables 1 and 2 show the results of various measurements and observations of the obtained spherical silica.

Example 3 A raw material was prepared by diluting water glass as a raw material and adjusting the SiO ₂ content to 15% by mass. Otherwise in the same manner as in Example 2, spherical silica was obtained. The results of various measurements and observations on the obtained spherical silica are shown in Tables 1 and 2.

Comparative Example 1 The dried spherical silica gel obtained after drying in Example 1 was placed in a quartz beaker without crushing and was fired at 1150 ° C. in a box-type electric furnace to obtain spherical silica. Tables 1 and 2 show the results of various measurements and observations of the obtained spherical silica.

Comparative Example 2 1% by mass of spherical silica gel obtained after the reaction in Example 1
It was washed with pure water alone without using sulfuric acid. Otherwise in the same manner as in Example 1, spherical silica was obtained. Tables 1 and 2 show the results of various measurements and observations of the obtained spherical silica.

[0043]

[Table 1]

[Table 2]

[0044]

According to the method of the present invention, it is possible to obtain spherical silica with good coarse grain breakage by the sol-gel method. The spherical silica obtained by the method of the present invention has a sharp particle size and has a very small amount of coarse particles, as compared with the prior art, so that liquid sealing such as pouring into particularly narrow gaps in electronic parts is possible. It can be suitably used as a filler for materials.

Continued front page    (72) Inventor Takashi Mitsuhashi             3-10-1, Daikokucho, Tsurumi-ku, Yokohama-shi, Kanagawa             Ryo Rayon Co., Ltd., Chemical Products Development Laboratory F term (reference) 4G072 AA25 AA28 BB07 CC10 GG01                       GG03 HH19 HH21 HH22 JJ11                       JJ13 LL06 MM01 MM23 MM26                       MM31 MM35 MM36 PP05 PP17                       RR05 RR07 RR12 SS01 TT01                       TT19 TT20

Claims (8)

[Claims] 1. The total content of Li, Na and K is 10 ppm.
A method for producing spherical silica, comprising crushing the following spherical silica gel and then firing at a temperature of 600 ° C. or higher. 2. The method for producing spherical silica according to claim 1, wherein the spherical silica gel is spherical silica gel produced from an alkali silicate. 3. The average particle size of the spherical silica gel is 0.1-100 μm.
The method for producing spherical silica according to claim 1 or 2, wherein m and the maximum particle size are 4 times or less the average particle size. 4. The method for producing spherical silica according to claim 1, wherein the crushing is a crushing method using a screen. 5. The method for producing spherical silica according to claim 4, wherein the screen opening is 10 times or less the maximum particle size of the spherical silica gel. 6. The method for producing spherical silica according to claim 4, wherein the screen is made of resin. 7. The spherical silica gel before crushing is 0.005% by mass.
The method for producing spherical silica according to any one of claims 1 to 6, which is spherical silica gel obtained by washing with the aqueous acid solution and then with pure water. 8. The method for producing spherical silica gel is as follows (1) to (5)
The method for producing spherical silica according to any one of claims 1 to 7, characterized by including the step of. (1) An emulsification step for preparing a water-in-oil type (W / O type) emulsion in which fine particles are dispersed using an aqueous solution of alkali silicate as a dispersion phase (2) Water-in-oil type (W / O type) prepared in (1) Type) emulsion is mixed with acid to produce spherical silica gel. Coagulation step (3) The reaction liquid containing spherical silica gel produced in (2) is heated to extract impurities in the extraction step (4) (3). Wash the extracted spherical silica gel,
Drying process to dry