JPS6296313A - Production of high-purity spherical silica filler - Google Patents

Abstract

PURPOSE:To produce a dense high-purity spherical silica filler having a sharp grain size distribution without cracking, by slurrying fine synthetic silica particles having a specific particle size distribution, spray granulating the resultant slurry and firing or spraying and fusing the resultant grains. CONSTITUTION:Fine synthetic silica particles without containing impurities, e.g. U, Th, etc., is mixed with a binder without containing an impurity to prepare a slurry in about 5-50wt% concentration, which is then spray granulated in a spray dryer. The resultant granulated grains having about <=300mum grain size are then fired and/or sprayed and fused at about >=1,700 deg.C. The particle size distribution of the above-mentioned fine synthetic silica particles is a mixture of 40-80wt% group of maximum particle diameter having 0.5D-D particle diameter with 10-40wt% group of medium particles having 0.2D-0.5D particle diameter and 10-40wt% group of minimum particles having <=0.2D particle diameter (the maximum particle diameter is expressed by D). The value of the above-mentioned D is preferably 0.05-0.1mum. Thereby, the aimed dense and firm high-purity spherical silica filler having high roundness without cracking and breaking is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a high-purity spherical silica filler, specifically a method for producing a high-purity spherical silica filler suitable as a filler for a resin composition for encapsulating semiconductor elements. Regarding.

[Prior art and problems]

Currently, resin encapsulation methods for semiconductor devices account for about 80 of all semiconductor device encapsulation methods because they are economical and mass-producible.

Silica is mainly used as a filler in resin sealing materials, but as semiconductor devices become more highly integrated, malfunctions due to alpha rays from UXTh contained in the filler are becoming a problem. LSIs will become more integrated,
Especially 1 megabit and 4 megabit dynamic RA
It also greatly influenced the design of M.

On the other hand, as semiconductor devices become more highly integrated, there is a growing demand for improved moldability and fluidity and lower stress during resin encapsulation.

Until now, melted and crushed natural silica stone has been mainly used as filler for resin and soil, but this crushed filler has an irregular shape with many sharp corners, and not only has poor fluidity but also There is also the risk of stress being applied to the surface of the element, which may upset the characteristics of the element, and furthermore, of damaging the element during molding.

As a countermeasure to these problems, JP-A-60-1318
No. 68 proposes a method for producing high-purity spherical silica filler by granulating synthetic silica particles and then subjecting them to thermal spray melting treatment.

However, this method has the disadvantage that the spherical silica particles become misshapen during the heat treatment process such as baking or thermal spray melting.

The object of the present invention is to produce a spherical silica filler that is dense, strong, and has a sharp particle size distribution without such drawbacks.

[Means for solving the problem] In order to solve this problem, the inventors of the present invention have made extensive studies and found that by using synthetic silica fine particles that are a mixture of different particle sizes in an appropriate ratio, it is possible to achieve a dense structure. It has been found that a strong granulated spherical product can be obtained.

That is, in a method of producing a high-purity spherical silica filler by slurrying synthetic silica fine particles, spraying and granulating the slurry using a spray dryer, and then performing firing and/or thermal spray melting treatment, the synthetic silica fine particles form the largest particle group and the intermediate ladle. When the maximum particle diameter is expressed as D, the maximum particle group is Q, 5D to D,
Intermediate ladle group is 0.2D~0.5DX * Small particle group is 0.2
D or less in size, and each blending ratio is 40 to 80% by weight for the largest particle group and 10 to 40% by weight for the intermediate particle group
The above object is achieved by setting the minimum particle group to 10 to 40% by weight.

The present invention will be described in more detail below. In the present invention, synthetic silica fine particles used as a raw material are used to convert easily volatile silicon compounds such as halogenated silicon compounds, silanes, etc. into alkoxylic acids by hydrolysis, oxidative decomposition, or in the presence of alcohol. The UXTh content is preferably 10 ppb or less. What is particularly important in the present invention is that, as a result of various experiments, by setting the particle size structure of the synthetic silica fine particles as described above, a dense spherical silica filler with high sphericity and no cracking can be produced. That's what I did. In this case, the maximum particle size is 0.05 to 0.1
It was also confirmed that the densest and strongest filler can be obtained when the thickness is μm. Note that the particle size can be measured by TEM (transmission electron microscope) or SEM.

In order to produce the spherical silica filler of the present invention using synthetic silica fine particles having such a particle size structure, a slurry is prepared by mixing the synthetic silica fine particles and a binder, and the slurry is sprayed and granulated using a spray dryer. Heat treatment such as post-baking and/or thermal spray melting may be performed.

The slurry concentration is preferably 5 to 50% by weight, especially 1
5-60! It's quantity. As the binder, ethyl silicate, colloidal silica, polyvinyl alcohol, carboxymethyl cellulose, or the like is added as necessary to water or alcohol that does not substantially contain radioactive impurities such as U or Th. As for the operating conditions of the spray dryer, the amount of slurry supplied, temperature, rotation speed of the desk, etc. are controlled so that the size of powdered particles is 600 μm or less, particularly 200 μm or less. If the granulated particles are larger than 300 μm, there is a risk that the burner will become clogged during thermal spray melting, and it will be difficult to obtain spherical silica filler with a sharp particle size structure. The conditions are that after pre-firing at a temperature of 1,300°C or less, the firing is performed instantly in an atmosphere at a temperature of 700°C or more.
Or it is desirable to melt it.

[Effect]

When using synthetic silica fine particles with a relatively large and uniform particle size of, for example, about 0.1 μm, the voids between the fine particles become large during drying and kelization, so it is difficult to use a dispersion medium such as water. Since the cohesive force between the fine particles decreases, resulting in a soft del, it is susceptible to stress and easily loses its shape during the subsequent firing process or thermal spray melting process. Conversely, if synthetic silica fine powder is used that has a relatively small and uniform particle size of approximately 01 μm, the cohesive force between the fine particles will increase and a strong del will result, but compared to the fine powder Due to the increased surface area, the slurry becomes highly viscous even at a fairly low concentration, and as a result, the slurry dries and becomes viscous while the particles are dispersed at a low concentration, making the resulting gel more likely to crack.

On the other hand, if a slurry is prepared using synthetic silica fine particles having the particle size structure described above as in the present invention, intermediate particles (particle size 0. .2 to 0.5 D) is filled, and the spaces between the intermediate particles and between the largest particle and the intermediate particle are filled with the smallest particle (particle size <
0.2 D) is filled. As a result, the cohesive force between the particles is strong, and it is possible to prepare a slurry with a high concentration, so that it is possible to obtain a strong, crack-free spherical delta during delta formation.

〔Example〕

The present invention will be explained in more detail by giving Examples and Comparative Examples.

Example A total of 10 synthetic silica fine particles having the particle size and composition shown below.
9 was mixed with 34 of pure water to prepare a slurry.

Largest particle group; 6 kl for 0.06-0.1 μm? Intermediate rice grain group: 0.03-0.05 μm, 3 kg Minimum particle group: 0. ．． 01 to 0.02 μm to 1 kq of this slurry to a rotating disk spray dryer.
/ Hr speed, disk rotation speed 15,000
Spray granulation was carried out under the conditions of rpm and dry air temperature of 26,000 to obtain granulated products with a particle size of 5 to 50 μm. This granulated product was fired at a temperature of 1150°C for 2 hours, and then hydrogen was heated to 30 Nm.
3/Hr (43,9m/8), oxygen gas 15N
The silica was poured into a 7mm gas composition having a gas composition of m3/Hr (8.3 m/S), and was thermally sprayed and melted at a temperature of 1850°C to obtain spherical silica.

When the obtained spherical silica was observed by SEM, it was found to be spherical silica particles with high sphericity as shown in FIG. 1, and no cracks, breaks, or flocs were observed.

Comparative Example 1 2 kq of synthetic silica fine particles with a relatively uniform particle size of about 0.01 to 0.02 μm (TEM observation) were mixed with 2 kq of pure water.
3 and 9 were mixed to prepare a slurry. This slurry was sprayed and granulated under the same conditions as in the examples to obtain granulated products with a particle size of 10 to 60 μm. This granulated product was thermally sprayed and melted under the same conditions as in the examples to obtain spherical silica. SEM of the obtained spherical silica
Upon observation, as shown in FIG. 2, in addition to spherical particles, many cracked and shattered particles were observed.

Comparative Example 2 Synthetic silica fine particles 10 and 9 having a relatively uniform particle size of about 0.07 to 0.1 μm were mixed with 9 in pure water 23 to prepare a slurry. This slurry was treated under the same conditions as in Comparative Example 1 to obtain spherical silica. The obtained spherical silica is
Upon EM observation, as shown in FIG. 6, in addition to spherical particles, many groups of floc-like microparticles were observed.

〔Effect of the invention〕

According to the present invention, it is possible to produce a highly pure spherical silica filler that is free from cracks and breaks, is dense, has high sphericity, and has a sharp particle size distribution.

[Brief explanation of drawings]

FIG. 1 is an SEM photograph at a magnification of 1000 times of the spherical silica obtained in the example. FIG. 2 is a photograph of the spherical silica obtained in Comparative Example 1 at a magnification of 500 times. FIG. 3 is an SEM photograph of the spherical silica obtained in Comparative Example 2 at a magnification of 650 times. Patent Applicant Denki Kagaku Kogyo Co., Ltd. Figure 1 Figure 2 Procedure Supplement J1-Gi 1 (Method) % Formula % 1, Incident Display Shoq-A 1960 Patent Application No. 2 Ro6-70 2, Invention The name: High-purity spherical silica noiler manufacturing method, and its relationship with the case of the person making the amendment! (°￥Applicant address: 4-1-3, Yurakucho IJ, ChiyoEEI-ku, Tokyo 100) 1986
January 28rJ (Delivery El) 5゜Paulownia j of a brief explanation of the drawings of the specification subject to the amendment 6. Details of the amendment As shown in the attached sheet, lines 7-12 of No. 10 of the detailed schedule have been revised as follows. -1. "Figure 1 shows the structure of grains of silica obtained in Example 7".
It's a photo. FIG. 2 is a ζ warehouse M photograph obtained in Comparative Example 1 and showing the particle structure of t1/ζ spherical warping force at a magnification of 50 times white.

Claims (2)

[Claims] (1) In a method of producing a high-purity spherical silica filler by slurrying synthetic silica particles, spraying and granulating them with a spray dryer, and then performing firing and/or thermal spray melting treatment, the synthetic silica particles are the largest particle group, the middle particle group, and the like. It consists of three particle groups: a particle group and a minimum particle group, and when the maximum particle diameter is expressed as D, the maximum particle group is 0.5D to D, the intermediate particle group is 0.2D to 0.5D, and the minimum particle group is High particle size particles having a size of 0.2D or less and having a blending ratio of 40 to 80% by weight for the largest particle group, 10 to 40% by weight for the intermediate particle group, and 10 to 40% by weight for the smallest particle group. Method for manufacturing purity spherical silica filler. (2) Maximum particle diameter D of synthetic silica fine particles is 0.05 to 0
．． A method for producing a high-purity spherical silica filler according to claim 1, wherein the filler has a diameter of 1 μm.