JPH0550447B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a hollow spherical silica glass suitable for use as a filler in a sealing material for semiconductor devices, and a method for manufacturing the same. (Prior art) Conventionally, fillers for this type of semiconductor element encapsulant have been used to help dissipate heat from the semiconductor element and further reduce stress due to thermal cycles, so fillers with high thermal conductivity and low coefficient of thermal expansion have been used. In addition, spherical silica glass is used due to its mechanical strength.
It has been desired to propose a filler for a semiconductor element encapsulant that can further reduce the heat generated when a semiconductor element is used in a high frequency range such as in a computer. (Problems to be Solved by the Invention) An object of the present invention is to provide a filler for a semiconductor element sealing material that satisfies the above-mentioned needs, and a method for producing hollow spherical silica glass used as the filler. (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors have conducted intensive research and found that by making conventional solid spherical silica glass (spherical silica glass filled with a substance) hollow. It has now been discovered that a filler for a semiconductor device encapsulant that satisfies the above requirements can be obtained. The present invention has been made based on the above findings, and the filler for semiconductor element encapsulant is obtained by hydrolysis of silicate ester having a particle size comparable to that of conventional solid spherical silica glass. It is hollow spherical silica glass. In addition, the method for manufacturing hollow spherical silica glass involves dispersing a sol obtained by hydrolyzing a silicate ester raw material solution in a dispersion medium to generate a gel, separating the resulting gel, It is characterized by being dried at a temperature of 40 to 90°C and then fired. Examples of the silicic acid ester used in the production method of the present invention include methyl silicate, ethyl silicate, propyl silicate, and the like. In addition, for hydrolysis of silicate ester, it is sufficient to mix and stir silicate ester, water, and a catalyst such as aqueous ammonia to suspend the silicate ester, and the mixing ratio is about 3 to 10 moles of water to 1 mole of silicate ester. When aqueous ammonia is used as a catalyst, it is preferably used in an amount of about 5 x 10 ^-5 to 5 x 10 ^-3 mol per 1 mol of silicate ester. Further, the dispersion medium used in the production method of the present invention may be any liquid that is incompatible with the raw material solution or has extremely small size, and examples thereof include butanol, hexanol, octanol, and toluene. Further, the amount of dispersion medium is generally about 1 to 3 times the volume of the silicate ester raw material solution. In addition, the generated and separated gel is dried at a humidity of 50%.
% or more, and the temperature was set at 40 to 90°C because if the drying speed is too fast, the hollow form of the granular gel will occur too quickly, and the skin of the hollow gel will become thin and easily damaged. If the drying speed is too slow, the hollow shape of the granular gel will slow down and only a granular gel with a thick skin or a solid granular gel will be obtained, making it impossible to obtain hollow spherical silica glass suitable as a filler for sealants. This is because of the following reasons. Regarding firing after drying, for example, after the above-mentioned firing is heat-treated at a temperature of 900°C or less,
If the heat treatment is performed in a floating state at 1700°C, a good hollow spherical silica glass can be obtained. In addition, it is better to perform the heat treatment at a temperature of 900°C or lower as slowly as possible to increase the rate of temperature rise to the desired temperature in order to sufficiently vitrify the silica in a dry state without causing foaming or bursting of the gel particles. The rate of temperature rise is generally about 100°C/1 hour. Further, for heat treatment in a floating state at a temperature of 1000 to 1700°C, the gel powder may be fed into an electric furnace from one side of the furnace, heat treated in a floating state, and then recovered from the other side of the furnace. In addition, if the gel powder is heat-treated in a static state rather than in a floating state, the spherical silica glasses will more easily fuse together, and a hollow spherical silica glass with a dense glassy skin and a predetermined thickness will be obtained. I don't like it because it disappears. (Example) Next, specific examples of the manufacturing method of the filler for semiconductor element sealing material and hollow spherical silica glass of the present invention will be described together with comparative examples. Example First, in a 500 c.c. beaker, 1 mole of methyl silicate purified by distillation and 5 moles of distilled water, purity 99.5%.
1 x 10 ^-4 mol of ammonia water and stirred vigorously for 10 minutes at 25°C using a magnetic stirrer until the viscosity of about 250 c.c. was 10 poise (Tokyo Keiki B-type viscometer). Adjusted Sol. Next, the sol 250 c.c.
The sol was poured into a dispersion medium consisting of butanol with a purity of 98%, which was twice the volume of the sol in the CC beaker, and the temperature was raised to 25°C using a magnetic stirrer.
The mixture was vigorously stirred for 5 hours to form a wet gel. The produced wet gel was cloudy and suspended in the dispersion medium. Subsequently, the produced wet gel dispersion medium was filtered under reduced pressure using a filter paper with a pore size of 3 μm to separate the wet gel and the filtrate, and the wet gel on the filter paper was purified to a purity of 98%.
% butanol 500 c.c. twice, then distilled water 300 c.c.
Washed once with After washing, the wet gel was examined under a transmission microscope (magnification
When observed under a magnification of 100 times, it was found to be a transparent gel with a particle size of 5 to 80 μm. Next, the wet gel separated from the gel dispersion medium by the above method was heated to 40% humidity and 50% humidity in a constant temperature and humidity chamber.
%, 60%, 70%, 80%, 90%, 95%, temperature 25℃, 40℃, 60℃, 80℃, 90℃, 100℃
Dry for 24 hours at ℃. After drying, the granular gel is heated at a heating rate of 100% in an electric furnace.
After raising the temperature to 800°C at a rate of 1 hour, it was fired at this temperature for 2 hours to produce spherical silica having a particle size of 3 to 60 μm. The hollow state of each of the spherical silica particles was examined using a transmission microscope (200x magnification), and the results are shown in the table.

【table】

[Table] As is clear from the table, when drying the gel separated from the dispersion medium, the lower the humidity and higher the temperature, the larger the cavity of the spherical silica, and the higher the humidity and lower the temperature, the smaller the cavity of the spherical silica. It approaches a solid spherical body. Therefore, it was confirmed that the optimum conditions for drying the gel separated from the dispersion medium are a humidity of 50% or more and a temperature of 40 to 90°C. In addition, 1 of the spherical silicas with different sizes of hollow parts.
An example is shown in Figure 1. Next, in the above method, the wet gel was dried at a humidity of 90% and a temperature of 60°C, and after drying, the spherical silica obtained by heat treatment at a temperature of 800°C was placed in a vertical electric furnace with an inner diameter of 10 cm and a length of 200 cm. Inner diameter 8 arranged in
cm, and a length of 150 cm, is fed together with air at a rate of 100g/min from the bottom of the heating tube into a heat-resistant heating tube made of alumina material, and after heat treatment for several seconds in a floating state, A filler for semiconductor device encapsulant made of spherical silica glass was recovered. The heat treatment temperature using the heating tube was 900°C to 1800°C in 100°C increments. When we investigated the cavity state and glass quality of the obtained filler for semiconductor device encapsulant made of hollow spherical silica glass, we found that when the heat treatment temperature was 1000 to 1700°C, the obtained hollow spherical silica glass remained hollow and became glass. The silica glass was becoming more densified, and the silica glass was transparent. However, the heat treatment temperature is 1800℃
The spherical silica glass obtained above was in a solid state with no cavity maintained. Further, when the heat treatment temperature was 900°C or lower, the obtained spherical silica glass did not become densified and was porous. Comparative Example A dry gel was prepared in the same manner as in the previous example except that the wet gel was dried at a humidity of 90% and a temperature of 60°C. The created dry gel was directly heated to a temperature of 800°C without being subjected to heat treatment at a temperature of 800°C, and was placed in a vertical electric furnace with an inner diameter of 10 cm and a length of 200 cm.
It was fed with air at a rate of 100 g/min into a 150 cm heat-resistant heating tube made of alumina material from the bottom of the heating tube, heat-treated for several seconds in a floating state, and then recovered from the top of the heating tube. The heat treatment temperature using the heating tube was 900°C to 1800°C in 100°C increments. When we investigated the hollow state and glass quality of each spherical silica glass obtained, we found that the heat treatment temperature was 1000℃.
At ~1500°C, the obtained spherical silica glass was glassy but foamed. Also, the heat treatment temperature
At temperatures above 1600°C, the obtained spherical silica glass became transparent, but remained solid without forming cavities. Furthermore, if the heat treatment temperature is below 900℃, the obtained spherical silica glass will not be densified.
It was porous. As is clear from the Examples and Comparative Examples, the gel separated from the gel dispersion medium was heated at a humidity of 90% and a temperature of 60%.
After drying at ℃, hollow spherical silica glass was obtained by the method of the embodiment of the present invention, in which heat treatment was performed at a temperature of 800℃ and further heat treatment in a suspended state at a temperature of 1000 to 1700℃. In the method of the comparative example, in which the gel separated from the medium and dried is directly subjected to high-temperature firing, only spherical silica glass in a foamed state or solid spherical shape could be obtained. (Effects of the Invention) As described above, the filler for a semiconductor element sealing material of the present invention is a hollow spherical silica glass obtained by hydrolyzing a silicate ester. Therefore, since the inside is hollow, when used as a filler for a semiconductor element encapsulant, the dielectric constant of the encapsulant filler itself can be reduced, reducing the dielectric loss of the semiconductor element and reducing heat generation. It has the effect of In addition, the method for manufacturing hollow spherical silica glass involves dispersing a sol obtained by hydrolyzing a silicate ester raw material solution in a dispersion medium to generate a gel, separating the resulting gel, and dispersing the gel at a humidity of 50%. Above, temperature 40~
Since the glass is dried at 90°C and then fired, it has the advantage that hollow spherical silica glass, which could not be obtained by conventional methods, can be produced extremely easily without agglomeration of the spheres. Further, the firing is performed by heat treatment at a temperature of 900°C or less,
Then, by heat treatment in a floating state at a temperature of 1000 to 1700°C, a good hollow spherical silica glass can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the size of a hollow portion of hollow spherical silica.

Claims (1)

[Claims] 1. A filler for a semiconductor device encapsulant comprising hollow spherical silica glass obtained by hydrolyzing a silicate ester. 2 Disperse the sol obtained by hydrolyzing the silicate ester raw material solution in a dispersion medium to generate a gel,
Separate the resulting gel and keep it at a humidity of 50% or more and a temperature of 40~
A method for producing hollow spherical silica glass, which comprises drying it at 90°C and then firing it. 3 After the firing is heat treated at a temperature of 900°C or less,
3. The method for producing hollow spherical silica glass according to claim 2, wherein the process is then carried out by heat treatment in a floating state at a temperature of 1000 to 1700°C.