JPH057331B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a method for manufacturing spherical silica glass used as a filler in a sealing material for semiconductor elements, for example. More specifically, the present invention relates to a method for producing spherical silica glass using a sol-gel method. (Prior art) Silica glass powder, which has material properties such as electrical insulation, low coefficient of thermal expansion, high thermal conductivity, high strength, and low dielectric constant, is currently used for fillers in encapsulating materials for semiconductor devices. . Additionally, with the recent increase in the memory capacity of semiconductor devices, in addition to the above characteristics, the filler is also required to have high purity with less soluble impurities that corrode the Al lead frame and α-ray emitting impurities that cause memory soft errors. Silica glass having a spherical shape and a wide particle size distribution is required in order to prevent damage to the lead frame, increase the filling rate of the filler, and improve the fluidity, that is, the moldability, of the sealing material. Conventionally, as a method for producing this type of spherical silica glass, it is known to produce spherical silica glass by crushing natural silica stone and crystal and remelting it to make it spherical. Due to the demand for high purity, SiCl ₄ was replaced with O ₂ −H ₂
Glass powder is created by hydrolysis in a flame, which is sintered and crushed at a temperature of 1800-2000℃, and then O ₂ − _{H 2}
A so-called gas-phase method has been adopted in which spherical silica glass is produced by heating it in a flame to make it spherical. However, this gas phase method requires hydrolysis of _SiCl4 , sintering, and remelting of the powder at a temperature of 1800-2000℃.
Since the process is carried out in an O ₂ −H ₂ flame, a large amount of thermal energy is required, which causes a problem in that the proportion of energy costs in the manufacturing cost becomes extremely high, making the product expensive. Therefore, assuming that the above-mentioned problem does not exist, JP-A-58-
As disclosed in Japanese Patent No. 176136, a mixed solution of silicate ester, water, and alcohol is dispersed and suspended in a liquid that is substantially incompatible with these to form a granular gel, and the resulting powder is The so-called sol-gel method, in which spherical silica glass is formed by separating and firing particulate gel, is attracting attention. However, the sol-gel method is a method of obtaining a powder-like gel by dispersing a mixed solution of silicate ester, water, and alcohol in a liquid that is substantially incompatible with the solution; There is a problem in that the shape of the gel is crushed into angular shapes, or the gel particles aggregate with each other, making it impossible to obtain a spherical gel. Therefore, the applicant previously filed Japanese Patent Application No. 1-43940.
In the method for producing spherical silica glass by a sol-gel method, the sol obtained by hydrolyzing a silicate ester raw material solution is dispersed in a dispersion medium to form a gel, and the resulting gel is separated and fired. We proposed a method for manufacturing spherical silica glass using butanol as a dispersion medium. (Problems to be Solved by the Invention) However, since the method described above is a method in which a sol is poured into a dispersion medium and dispersed while stirring the dispersion medium to obtain a spherical gel, the resulting gel is not a spherical gel. However, it is difficult to separate the spherical gel from the amorphous gel, and it is also difficult to control the particle size of the powdery gel that is produced. The problem is that you can't get it. The present invention solves the above-mentioned problems and provides a method for manufacturing spherical silica glass using a sol-gel method, which can disperse gel well without breaking or agglomerating it, and can produce spherical gel with uniform particle size. The purpose is to provide. (Means for Solving the Problem) As a result of intensive studies to achieve the above object, the present inventors have discovered that, in the sol-gel method, when dispersing the sol in a dispersion medium, the gel is dispensed using a nozzle. It has been found that the particle size of the gel can be uniformly controlled by The present invention has been made based on the above findings, and the method for producing spherical silica glass comprises dispersing a sol obtained by hydrolyzing a silicate ester raw material solution in a dispersion medium to generate a gel. A method for producing spherical silica glass by a sol-gel method in which the gel obtained is separated and fired is characterized in that when the sol is dispersed in a dispersion medium, the sol is dispensed through a nozzle hole. Examples of the silicic acid ester used in the present invention include methyl silicate, ethyl silicate, propyl silicate, and the like. In addition, for hydrolysis of silicate ester, silicate ester, water, and a catalyst such as aqueous ammonia may be mixed and suspended by stirring, and the mixing ratio is 4 to 10 mol of water to 1 mol of silicate ester. When aqueous ammonia is used as a catalyst, the amount is about 1×10 ⁻⁴ to 1×10 ⁻³ mol per 1 mol of silicate ester. Further, examples of the dispersion medium include butanol, hexanol, and the like. The amount of dispersion medium is generally about 1 to 3 times the volume of the silicate ester raw material solution. (Example) Next, an example of the method of the present invention will be described. 1 and 2 show one embodiment of a nozzle used to carry out the method of the present invention,
In the figure, 1 indicates a nozzle. The nozzle 1 has an inner diameter of 80mm
A nozzle in which a plurality of nozzle holes 3 having a diameter of about 0.5 to 4 mmφ are removably inserted into the lower part of the main body 2 with a hole interval A of about 1 to 20 times the hole diameter. It consists of a plate 4, a lid 5 that is removably fitted above the main body 2, and a supply pipe 7 that is attached to the side wall of the main body 2 and supplies compressed air into the main body 2 through a control valve 6. Filled with Sol S, air pressure 0.5~
Compressed air of about 2 kg/cm ² was supplied into the main body 2 through the supply pipe 7, and the sol S was dispensed into the dispersion medium through the nozzle hole 3. A specific example of a method for manufacturing spherical silica glass using the above nozzle will be described together with a comparative example. Example 1 First, 5 moles of distilled water and 5 x 10 ^-4 moles of ammonia water with purity of 99.5% were added to 1 mole of distilled methyl silicate in a 500 c.c. beaker, and a magnetic stirrer was added. At a temperature of 25℃, 3
The mixture was vigorously stirred for a minute to prepare a sol with a viscosity of about 250 c.c. and a viscosity of 0.5 poise (Tokyo Keiki B-type viscometer). Next, 32 nozzle holes 3 with a diameter of 3 mmφ (hole spacing A is
2.5 times) After filling the body 2 of the nozzle 1 with the nozzle plate ⁴ drilled with 250 c.c. of the sol, 1000 c.c. Dispense the sol into a butanol dispersion medium whose volume is twice the volume of the sol in a beaker, and increase the rotation speed using a magnetic stirrer at a temperature of 25°C.
A gel was formed by vigorous stirring at 3000 rpm for 60 minutes. The average particle size and particle size (0.1 to 200 .mu.m) distribution of the resulting gel was measured immediately after stirring, and the average particle size was 35.0 .mu.m, and the particle size distribution n was 1.97. Further, the generated gel was observed with an optical microscope (magnification: 50 times), and the observation results are shown in FIG. Further, the average particle size and particle size distribution of the gel were measured using a laser diffraction particle size distribution analyzer LA-500 (manufactured by Horiba, Ltd.). The particle size distribution n (a constant indicating the width of the distribution) is calculated using the Rosin-Rammler formula "R=
exp(-p/D _36.8 ) ^n' ' using the following formula. n=lnlnR/ln(-p/D _36.8 ) In the formula, R is the cumulative % on the sieve, exp is the base of the natural logarithm,
Dp represents the particle size when R is %, and D _36.8 represents the particle size when R is 36.8%. Therefore, the smaller the value of n, the wider the particle size distribution, and the larger the value of n, the narrower the particle size distribution. Next, the generated gel dispersion is separated into a gel and a filtrate by decantation, and then the gel is purified.
2 x 500 c.c. of 95% butanol, then 300 c.c. of distilled water
After washing once with CC, it was dried for 24 hours in a constant temperature and humidity chamber at a temperature of 40°C and a humidity of 95%. After drying, the granular gel is heated at a heating rate of 100% in an electric furnace.
℃ / 1 hour to raise the temperature to 800℃, and at that temperature 2
After firing for a period of time, it was further fired in a suspended state in air at a temperature of 1700°C to obtain spherical silica glass. Comparative Example 1 Spherical silica glass was produced in the same manner as in Example 1 except that the sol was directly dispersed in the dispersion medium without using a nozzle. Further, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured, and the average particle size was 37.9 μm, and the particle size distribution n was 1.74. . In addition, the generated gel was observed using an optical microscope (50x magnification).
The observation results are shown in Figure 5. As is clear from FIGS. 4 and 5, in the method of Example 1 of the present invention, the gel was monodispersed as spherical particles with a particle size of about 2 to 200 μm. On the other hand, in the method of Comparative Example 1, in which the sol is directly dispersed in the dispersion medium without using a nozzle, gel dispersion is good, but irregularly shaped fibrous gel was generated within the spherical gel. . It is thought that this fibrous gel was formed because the sol was gelatinized into a fibrous state that was stretched by the flow of the dispersion medium while the sol was being fragmented by stirring. Example 2 Spherical silica glass was produced in the same manner as in Example 1, except that a spray nozzle as shown in Figure 3 was used instead of the nozzle in Example 1, and the air pressure supplied to the nozzle was 3 kg/cm ² . Created. Further, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured, and the average particle size was 15.3 μm, and the particle size distribution n was 1.87. . Further, when the produced gel was observed with an optical microscope, it was found to be monodispersed as spherical particles with a particle size of about 1 to 50 μm. When dispersing the sol in a dispersion medium in this way, if the nozzle used is a spray nozzle, the average particle size of the resulting gel can be reduced. The spray nozzle shown in the third figure used in this example will be explained. The spray nozzle 11 includes a sol nozzle 13 having a hole 12 with a diameter of about 1 to 3 mmφ bored at its tip, an air nozzle 14 surrounding the outside of the sol nozzle 13, and a supply pipe 15 that supplies compressed air to the air nozzle 14. Compressed air with an air pressure of about 1 to 5 kg/cm ² is supplied to the air nozzle 14 from the supply pipe 15, and the jet energy of the compressed air from the air nozzle 14 is used to generate the sol S.
was atomized and sprayed from the tip of the spray nozzle 11. Examples 3, 4, 5, 6 Spherical silica glasses were prepared in the same manner as in Example 1 except that the amount of water added to 1 mole of methyl silicate was 4 mol, 6 mol, 7.5 mol, and 10 mol. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 1 together with the results of Example 1. Comparative Examples 2 and 3 Spherical silica glasses were prepared in the same manner as in Example 1 except that the amount of water added was 3 mol and 15 mol per mol of methyl silicate. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 1.

[Table] As is clear from Table 1, the amount of water added per 1 mol of methyl silicate was 4 to 10 mol.
Method No. 6 was able to disperse spherical gel in the dispersion medium. Furthermore, even if the amount of water added per mole of methyl silicate was increased from 4 to 10 moles, the average particle size of the gel obtained tended to remain almost constant; It was found that the particle size distribution constant tends to become smaller, that is, the particle size distribution tends to become wider. On the other hand, in the method of Comparative Example 2 in which the amount of water added was 3 moles, the reaction rate was fast, and the viscosity of the sol rapidly increased, gelation occurred, and the sol could not be dispersed in the dispersion medium. In addition, in the method of Comparative Example 3 in which the amount of water added was 15 moles, the reaction rate was slow, the viscosity of the sol increased slowly, and only gel with broken particles was produced. Therefore, in order to produce a uniform spherical gel, the amount of water added to methyl silicate should be about 4 to 10 moles per mole of methyl silicate. Examples 7, 8, 9 The same method as in Example 1 except that the amount of ammonia water added to 1 mole of methyl silicate was 2 x 10 ^-4 mol, 3 x 10 ^-4 mol, and 3 x 10 ^-3 mol. A spherical silica glass was created. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 2 together with the results of Example 1. Comparative Examples 4 and 5 Spherical silica glasses were prepared in the same manner as in Example 1, except that the amount of ammonia water added to 1 mole of methyl silicate was 5×10 ⁻⁵ mol and 3×10 ⁻³ mol. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 2.

【table】

[Table] As is clear from Table 2, the amount of ammonia water added to 1 mole of methyl silicate is 1×10 ^-4 to 1×
The methods of Examples 7 to 9 in which the amount was 10 ^-3 mol were able to disperse spherical gels in the dispersion medium. Furthermore, as the amount of ammonia water added per mole of methyl silicate increases from 1 x 10 ^-4 mol to 1 x 10 ^-3 mol, the average particle size of the gel obtained tends to increase; It was found that the distribution constant of particles tends to become smaller, that is, the particle size distribution tends to become wider. In contrast, the amount of ammonia water added was 5×10 ^-5
In the method of Comparative Example 4, the reaction rate was fast and the gel was not dispersed but was in an aggregated state. In addition, in the method of Comparative Example 5 in which the amount of ammonia water added was 1×10 ^-3 mol, the reaction rate was slow and only a gel with broken particles was produced. Therefore, in order to produce a uniform spherical gel, the amount of ammonia water to be added to methyl silicate is 1 x 10 ^-4 to 1 mol of ammonia water per 1 mole of methyl silicate.
The amount may be approximately ×10 ⁻³ mol. Examples 10, 11, 12, 13, 14 The above examples except that the viscosity of the sol obtained by adding water and aqueous ammonia to methyl silicate was 1.0 poise, 3.2 poise, 5.7 poise, 9.0 poise, and 10.0 poise. Spherical silica glass was created in the same manner as in Example 1. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 3 together with the results of Example 1. Comparative Example 6 A spherical silica glass was prepared in the same manner as in Example 1 except that the viscosity of the sol obtained by adding water and aqueous ammonia to methyl silicate was set to 20 poise. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 3.

[Table] As is clear from Table 3, methyl silicate and water,
The viscosity of the sol obtained by adding ammonia water is
The methods of Examples 10 to 14 in which the poise was set to 0.5 to 10.0 poise were able to disperse spherical gels in the dispersion medium.
Furthermore, as the viscosity of the sol obtained by adding water and aqueous ammonia to methyl silicate increases from 0.5 poise to 10.0 poise, the average particle size of the gel obtained tends to increase. It was found that even if the viscosity of the sol increased, the particle size distribution constant remained almost unchanged. On the other hand, in the method of Comparative Example 6 in which the viscosity of the sol obtained by adding water and aqueous ammonia to methyl silicate was 20 poise, the sol was gelled before being dispersed in the dispersion medium, and the gel was several hundred It was in the form of a lump of μm to several mm. Therefore, in order to produce a uniform spherical gel, the viscosity of the sol obtained by adding methyl silicate water and ammonia water should be about 0.5 to 10.0 poise. Examples 15, 16, 17, 18 The diameter of the nozzle holes 3 of the nozzle plate 4 was set to 0.5 mmφ (hole spacing A
20 times), the hole diameter was 1 mmφ (the hole spacing A was 10 times), the hole diameter was 2 mmφ (the hole spacing A was 4 times), and the hole diameter was 4 mmφ (the hole spacing A was 1.5 times). Spherical silica glass was produced in the same manner as in Example 1. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 4 together with the results of Example 1. Comparative example 7 The diameter of the hole 3 of the nozzle plate 4 is 5 mmφ (the hole interval A is 1 times)
A spherical silica glass was produced in the same manner as in Example 1 except that the nozzle 1 was used. In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 4.

[Table] As is clear from Table 4, the methods of Examples 15 to 18 using the nozzle 1 in which the diameter of the nozzle hole 3 of the nozzle plate 4 is 0.5 mmφ to 4 mmφ disperse spherical gel in the dispersion medium. was completed. In contrast, the diameter of the nozzle hole 3 of the nozzle plate 4 is 4 mm.
In the method of Comparative Example 7 using the nozzle 1 having a diameter of φ, the gel was well dispersed, but irregularly shaped fibrous gel was formed in the spherical gel. Therefore, in order to generate a uniform spherical gel, the diameter of the nozzle hole 3 of the nozzle plate 4 should be approximately 0.5 to 4 mmφ.
Further, the hole interval A may be approximately 1.5 to 20 times the hole diameter. Examples 19, 29, 21, 22 The rotation speed when dispersing the sol in the dispersion medium and stirring it with a magnetic stirrer was 2900 rpm and 3300 rpm.
(all stirring times are 60 minutes), or
10 minutes, 180 minutes (both stirring speeds are
A spherical silica glass was produced in the same manner as in Example 1 except that the speed was changed to 3000 rpm). In addition, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured. The results are shown in Table 5 together with the results of Example 1.

[Table] As is clear from Table 5, the methods of Examples 18 to 21, in which the rotational speed during stirring with a magnetic stirrer was 2900 rpm to 3300 rpm, were able to disperse spherical gels in the dispersion medium. However, as the stirring time becomes longer, the stirring becomes excessive and the gel is more likely to be destroyed, so the stirring time is preferably up to 60 minutes. Example 23 When dispersing the sol in a dispersion medium and stirring it with a magnetic stirrer, first use an ultrasonic cleaner (product name
A spherical silica glass was prepared in the same manner as in Example 1, except that the mixture was stirred for 10 minutes at a frequency of 45 KHz using a BRANSON 1200 (manufactured by Yamato Scientific Co., Ltd.), and then stirred for 50 minutes at a rotational speed of 3000 rpm using a magnetic stirrer. Further, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured, and the average particle size was 24.3 μm, and the particle size distribution n was 2.06. Example 24 When dispersing a sol in a dispersion medium and stirring it with a magnetic stirrer, first a mixer (trade name MX-
915C, manufactured by Matsushita Electric Industrial Co., Ltd.)
After stirring at 5000 rpm for 10 minutes, spherical silica glass was produced in the same manner as in Example 1 except that the mixture was stirred for 50 minutes at 3000 rpm using a magnetic stirrer. Further, in the same manner as in Example 1, the average particle size and particle size distribution of the gel produced by allowing it to stand immediately after stirring were measured, and the average particle size was 18.5 μm, and the particle size distribution n was 2.19. When a sol is dispersed in a dispersion medium and stirred as in the methods of Examples 23 and 24, if different stirring methods are used in combination, the average particle size of the resulting gel can be reduced. (Effects of the Invention) As described above, according to the method for producing spherical silica glass of the present invention, when dispensing the sol into the dispersion medium, the sol is passed through the nozzle hole. The resulting gel is dispersed in the dispersion medium without agglomerating or being destroyed, and gels with the desired particle size can be produced uniformly without the presence of irregularly shaped gels. It has effects such as easy production of silica glass.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of the nozzle used in the method of the present invention, with Figure 1 being a cross-sectional view thereof, Figure 2 being a plan view of the nozzle plate, and Figure 3 showing the nozzle used in the method of the present invention. 4 is a photograph showing the structure of gel particles dispersed in a dispersion medium in an example of the present invention, and FIG. 5 is a photograph showing a structure of gel particles dispersed in a dispersion medium in a comparative example. This is a photograph showing the structure of.

Claims (1)

[Claims] 1 Disperse the sol obtained by hydrolyzing the silicate ester raw material solution in a dispersion medium to generate a gel,
A method for producing spherical silica glass by a sol-gel method in which the obtained gel is separated and fired, characterized in that the sol is dispensed through a nozzle hole when the sol is dispersed in a dispersion medium. Method for manufacturing silica glass.