JPS63282109A - Production of silica fine powder particle - Google Patents

Abstract

PURPOSE:To inexpensively produce edgeless silica fine powder especially suitable for making a sealing synthetic resin composition for semiconductor element by scouring silica fine powder particle with strongly pushing one to another and by making edgy powder particle round. CONSTITUTION:Crystalline silica or amorphous silica fine powder particle is scoured without breaking its body while strongly pushing one to another from the outside e.g. with rotary roller in the presence of aq. medium to make edgy powder particle round. Liquid substance such as water, alcohols, mineral oil, etc., can be advantageously used as the aq. medium, but water alone or medium dissolving alcohols such as ethanol, methanol, etc., in water can be advantageously and industrially used, because of the cost and easiness of handling in the procedure and separation after the procedure. Roller mill is given as an equipment suitable for the titled production.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for producing fine silica powder particles with rounded corners;
In particular, the present invention relates to a method for producing fine silica powder particles suitable as a filler for synthetic resin compositions for encapsulating semiconductor devices.

(Prior Art) (Problem to be Solved by the Invention) Semiconductor elements are sealed with ceramic packages or resin to protect them from the external environment. For these reasons, synthetic resin compositions containing inorganic fillers have become popular.

This synthetic resin composition is composed of a synthetic resin such as an epoxy resin and an inorganic filler such as silica, but these compositions have a small coefficient of thermal expansion, good thermal conductivity, low moisture permeability, and mechanical properties. In order to have excellent properties and low cost, it is necessary to incorporate this inorganic filler in as much amount as possible, as long as its moldability allows.

In particular, silica-based fillers are considered to be most suitable as inorganic fillers, and are used in most synthetic resin sealing fillers. There are two types of silica fillers: crystalline and amorphous.
There are different types. Crystal type silica is manufactured by crushing and refining highly pure natural white silica or crystal. This type has excellent thermal conductivity.

Amorphous silica includes fused silica, which is produced by melting crystalline silica at high temperatures, and dry and wet synthetic silica.

This fused amorphous silica has excellent thermal expansion properties, so
It is also used in large quantities industrially. However, as the integration of semiconductor devices progresses, there is a tendency to emphasize thermal conductivity, and the need for crystalline silica is also increasing.

The finely divided silica particles commonly used as fillers are obtained through a conventional crushing process, and the particles have corners as shown in the photographs in FIG. 2 or 4. If the particles have corners, the viscosity will increase when mixed with resin and encapsulated semiconductor elements, causing a lot of wear on the mold, not only reducing workability but also causing impurities due to wear on the mold. There are adverse effects such as contamination, and therefore, the amount of filler mixed cannot be increased, which limits the ability to improve performance.

Regarding amorphous type fused silica, attempts have been made to produce spherical silica. For example, JP-A-58-1456
According to Publication No. 13 or Japanese Unexamined Patent Publication No. 1981-8131, finely crystalline powdered silica is jetted out from a nozzle along with a gas flow, and particle dispersion, melting, cooling, etc. are controlled under appropriate conditions to form spherical non-silica particles. Create crystalline fine powder silica particles. However, this method is expensive and is limited to use in some special cases.

On the other hand, no example of producing crystalline type spherical silica has been proposed to date.

(Means for Solving the Problems) As a result of intensive study on a low-cost manufacturing method for silica fine powder particles having no corners, the present inventors have discovered that crystalline silica or amorphous silica fine powder particles are heated by a rotating roller from the outside. It has been discovered that angular silica fine particles can be rounded industrially advantageously by rubbing the fine particles of fine powder against each other in the presence of an aqueous medium while applying a pressing force, etc., and this has led to the present invention. It is.

The present inventors focused on the process of generating singing sand, in which the sand particles are rubbed together by the force of waves under a certain water pressure, and the corners are ground, resulting in a shape close to a perfect sphere. We thought that we could create fine particles with rounded edges by rubbing them together, and as a result of our extensive research, we decided to apply an appropriate pressing force to the silica fine powder from the outside, and to make sure that this pressing force effectively reaches the silica fine particles. Therefore, I learned that adding an aqueous medium is very effective.

The aqueous medium used in the present invention may be any liquid that allows fine silica particles to interact with each other and easily transmits pressure from the outside to the powder, and liquid substances such as water, alcohols, and mineral oil can be advantageously used. However, due to the cost of the medium, ease of handling during operation, and ease of separation after operation, water alone or water and ethanol are used.

A medium in which an alcohol such as methanol is dissolved can be most advantageously used industrially.

When carrying out the present invention, equipment suitable for the method of the present invention is firstly a roller mill. A roller mill has a grinding bowl rotated by a roller, and at least two grinding rollers rotating on a rotating track inside the grinding bowl. It is possible to apply pressure such as

When carrying out the invention using a roller mill, if
If only the fine powder is charged into a roller mill and rounded without adding an aqueous medium, the fine powder will escape from the roller and the efficiency will be low. Adding an appropriate amount of a medium such as water allows the pressing force of the roller to be smoothly transmitted to the powder, allowing efficient cornering operations.

The present invention can be applied equally advantageously to crystalline and amorphous silica fine powder particles.

The size of the fine silica powder used as a raw material in the present invention is usually 500 microns or less, and when the fine powder of such a size is rounded with a roller mill, the amount of the aqueous medium to be added is 0. .5-18%, preferably 3
~13% is suitable.

If the amount added is less than 0.5%, the pressing force of the roller will not reach the fine silica powder sufficiently, and the powder will escape from the roller, so that the frictional force between the particles will not work and the effect will be degraded. Furthermore, if the amount of liquid added is more than 18%, the object will become lump-like or slurry-like, making the cornering operation difficult.

Also, the pressing force applied to the roller from the outside is ad
Although it cannot be numerically limited because the method of pressing differs depending on the type of pressure, if the pressing force is too strong, not only the corners are removed but also the volume of the particles is crushed, the crushing progresses and the cornering is inhibited. Also,
If it is too weak, the efficiency of cornering will decrease, so it should be determined appropriately depending on the equipment, raw materials, type (crystalline, amorphous), etc. Moreover, it is also possible to directly send a coarsely crushed product of several nanometers or less to this squaring process, and perform the squaring operation at the same time as the crushing to a desired particle size.

An example of implementing the present invention will be explained using FIG. 1.

First, the high-purity silica block or high-purity fused silica ingot block (2) is coarsely crushed using a crusher such as a show crusher (2). In this case, to prevent contamination, the crusher liner is preferably made of high-purity alumina or the like. Next, the mixture is further coarsely crushed using a roll crusher (2). In this case as well, the rolls etc. may be made of high purity alumina or the like.

Normally, at the exit of ■, the silica is crushed to less than the number 1),
Further, this is usually finely pulverized using a ball mill or the like (3) to obtain a fine silica powder of 500 microns or less.

The finely powdered silica thus obtained is sent to a cornering process according to the present invention, such as a roller mill. When using a roller mill, parts such as rotating bowls and rollers that come into contact with fine silica powder particles are made of ceramic or lined with polyurethane resin or the like to prevent contamination due to abrasion.

In some cases, by sending the coarsely pulverized product such as the roll crusher 7 shear (2) directly to the chamfering step (2) and appropriately controlling the operating conditions, the fine pulverization and chamfering operations can be carried out simultaneously. The fine silica powder after the corner removal operation is
The product is dried through the drying process.

When carrying out the present invention, it is advantageous that an ordinary roller mill or the like can be used as is or with only a slight modification such as making the part that comes into contact with the fine silica powder a ceramic material or lining it with a polyurethane resin. Running costs are also very low, as most of them are mechanical power costs such as rotation.

The method of the invention can be carried out either in a bunch operation or in a continuous operation.

(Example) The present invention will be specifically explained below using Examples.

Example 1 0-lar mill (MPV-Q, type 5 Matsumoto casting ironwork fracture)
Average particle size 2 finely pulverized using a ball mill in advance
500 g of 3.2 micron crystalline silica was charged and at the same time 60I1)7 of water was added. Roller pressing force 40k
g/cm (linear pressure), the clearance between the roller and the bottom plate is 3fi, and the rotation speed of the bottom plate is set to 42rp+*.As a result of processing for 1 hour, the average particle diameter of the processed material obtained is 19.
It was 4 microns. The electron micrographs are shown in Figure 3 (200x magnification) compared with Figure 2 (100x magnification) of the raw material, and the shape of the treated silica particles was considerably rounder than that of the raw material.

Example 2 500 g of crushed fused silica with an average particle diameter of 24.6 microns finely pulverized by a ball mill was charged in advance into a 0-lar mill (MPV-0,5 type Matsumoto Cast Iron Works), and 60 g of water was added at the same time. did.

The treatment was carried out for 1 hour at a roller pressing force of 20 kg/port (linear pressure), a clearance between the roller and the bottom plate of 3.5 mm, and a rotation speed of the bottom plate of 42 rpm. The average particle diameter of the obtained treated product was 18.6 microns, and its electron micrographs are shown in Figure 5 (250x magnification) compared with Figure 4 (100x magnification) of the raw material, but compared to the raw material silica. The particle shape of the treated silica was considerably rounded.

Example 3 - The same treatment as in Example 1 was carried out except that 50% ethanol aqueous solution 60 was used instead of water 60. The average particle size of the obtained treated product was 19.7 microns. can be,
The electron micrograph was exactly the same as Figure 2, and the treated product was considerably rounder than the raw material.

(Effects of the Invention) By carrying out the present invention, it is possible to make angular and crushed silica rounded, whether crystalline silica or amorphous silica, and the silica obtained by the present invention can be used for semiconductor devices. When used as a filler for resin sealing, workability in the fat sealing transfer molding process can be improved.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the present invention, FIGS. 2 and 3 are electron micrographs showing the shape of the crystalline silica of Example 1 before and after treatment, and FIGS. 4 and 5 These are electron micrographs showing the shape of fused silica before and after treatment in Example 2.

Claims (4)

[Claims] (1) While applying a pressing force to the crystalline silica or amorphous silica fine powder particles from the outside using a rotating roller, etc., the fine powder particles are rubbed against each other in the presence of an aqueous medium without causing volume destruction to produce angular particles. A method for producing fine silica powder particles characterized by giving a rounded appearance. (2) The method according to claim (1), wherein the aqueous medium is water or a mixture of water and alcohol. (3) Claim No. 1 in which the operation of applying pressing force from the outside with a rotating roller or the like is performed using a roller mill.
The method described in section. (4) The method according to claim (1), wherein the fine silica powder particles obtained are 300 microns or less.