JPH062569B2 - Silica fine powder - Google Patents

Description

Detailed Description of the Invention

[0001]

[Industrial applications]

The present invention relates to a fine powder used in a synthetic resin composition for sealing electronic parts such as semiconductors. More specifically, it relates to silica fine powder particles with rounded corners, which are suitable as a filler for the composition.

[0002]

[Problems to be Solved by Conventional Techniques and Inventions]

Semiconductors and electronic parts are sealed with a ceramic package or resin to protect them from the external environment, but this sealing material is a synthetic material containing an inorganic filler in terms of cost, productivity, etc. Resin compositions are widely used. This synthetic resin composition is composed of a thermosetting 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 and low moisture permeability. Since it is desirable that the inorganic wet filler has excellent mechanical properties and the like and that the cost is low, it is necessary to blend the inorganic wet filler as much as possible, as long as the moldability thereof allows.

However, since the inorganic powder used as a filler mainly pulverizes the lumps thereof into powder having a proper size and distribution, its shape generally has corners, and this and thermosetting of epoxy resin or the like. When a resin mixture is used as a sealing material, the fluidity is not sufficient, the filling property and the workability are poor, and the devices in the molding process are significantly worn. It has also been reported that the sharp and sharp corners of the filler particles damage the surface of the semiconductor device, which causes a soft error.

In general, when the thermosetting resin is contracted when it is cured, stress is generated, and in addition to this stress, the heat generated from the semiconductor causes a large difference in thermal expansion coefficient between the semiconductor element and the encapsulating resin composition. There is a stress that occurs in.
Of these internal stresses, in order to relieve the latter stress, it is usually desirable to fill an inorganic filler having a small coefficient of thermal expansion as much as possible. However, in this respect as well, if the filling amount of the angular filler produced by pulverization is increased, the fluidity is extremely reduced, so that there is no choice but to be limited by the amount, and it is not useful for relaxing internal stress. .

In order to solve such problems, for example, JP-A-58-145613 or JP-A-6-
According to Japanese Patent Laid-Open No. 1-118131, crystalline fine powder silica is ejected from a nozzle together with a gas flow to disperse and melt particles.
A method has been proposed in which spherical fused fine powder silica is suspended by controlling appropriate conditions such as cooling. However, this method has the drawback of being costly.

On the other hand, no production example of crystal-type spherical silica has been proposed so far. In view of such a situation, the present inventors have investigated a method for producing roundish silica fine powder particles, and disclosed in JP-A-63-63
The application was filed on May 13, 1987 as Japanese Patent No. 282109 (method for producing fine silica powder particles). JP-A-63-2
The fine silica powder obtained by the method of Japanese Patent No. 82109 is a rounded particle having a maximum particle diameter of 300 μm or less, and is an excellent filler for a synthetic resin composition for encapsulating a semiconductor element.

[0007] The inventors of the present invention then continued to make a thorough study, and found that the maximum particle diameter was 200 μm or less and the average particle diameter was 7 μm.
A fine silica powder containing 12% by weight or more of particles having a fine silica content of 3 μm or less and 2% by weight or more of particles having a fine silica content of 3 μm or less has excellent properties as a filler or the like. Knowing, I arrived at the present invention.

[0008]

[Means for Solving the Problems]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have completed the present invention. That is, the gist of the present invention is a finely powdered silica having rounded corners, which is obtained by grinding particles of each other in the presence of an aqueous medium while applying a pressing force to the ground silica from the outside. A fine silica powder having a maximum particle diameter of 200 μm or less, an average particle diameter of 7 μm or more and 35 μm or less, and a fine particle silica of 3 μm or less having a particle size distribution of 12% by weight or more and 1 μm or less of 2% by weight or more. The present invention provides good flowability when the silica fine powder of the present invention is blended with a thermosetting resin, and enables high blending.

The crushed silica used in the present invention may be either crystalline silica or fused silica. As the crystalline silica, natural high-purity silica stone, silica sand, quartz or the like is generally used. Is an ingot obtained by melting at a high temperature. Usually, these are roughly crushed with a jaw crusher, a roll crusher, etc., and these coarsely crushed products are further finely crushed with a ball mill etc., and used as crushed silica in the present invention. The average particle size of the crushed finely pulverized silica obtained here needs to be slightly larger than that of the fine silica powder having the rounded corners of the final product.

When the silica fine powder of the present invention is blended with a thermosetting resin, the fluidity is remarkably improved, but its action mechanism is not clear. However, in addition to the rounded corners of the particles, fine particles containing sub-micron-order particles generated as a result of grinding adhere to particles of the order of tens of microns, improving the fluidity, which results in an optimal particle size distribution. It is believed that they have made a great contribution to the formation of.

In the present invention, the chamfering treatment grinds particles together in the presence of an aqueous medium while applying a pressing force from the outside to the crushed silica, but the pressing force is smoothly transmitted to the powder in the absence of the aqueous medium. Not being done, the efficiency of milling is very low. The presence of 0.5-18% by weight, preferably 3-13% by weight, of the aqueous medium, relative to the normally crushed silica, effectively acts on the attrition. As the aqueous medium to be used, it is sufficient that the silica fine particles interact with each other and the pressure from the outside is easily transmitted to the powder, and water, alcohols, liquid substances such as mineral oil can be advantageously used, but the medium Cost, ease of handling, etc.,
From the viewpoint of ease of separation after the operation, water alone or a medium in which alcohols such as ethanol and methanol are dissolved in water can be industrially most advantageously used.

Further, the pressing force applied to the roller from the outside cannot be numerically limited because the pressing method differs depending on the machine, but when the pressing force is too strong, not only the chamfering but also the volume destruction of the particles occurs, The crushing progresses and the chamfering process is hindered. If it is too weak, the efficiency of chamfering will decrease, so it may be appropriately determined according to the equipment, raw material, product type (crystalline or amorphous), and the like. Further, it is also possible to send a coarsely crushed product having a size of several mm or less directly to this chamfering step, and perform the chamfering operation simultaneously with the pulverization to a desired particle size. As described above, there are various methods for grinding the particles while applying a pressing force from the outside, but the roller mill can be most effectively used from the viewpoint of cost such as energy or efficiency.

The fine silica powder of the present invention has a maximum particle size of 2
00 μm or less, preferably 100 μm or less, 20
If it is 0 μm or more, it cannot be used because it occurs in the step of resin sealing the semiconductor. Further, the average particle size is 7 μm or more and 35 μm or less, preferably 12 μm or more and 20 μm or less, and 7 μm or less or 35 μm or more,
In either case, the good fluidity of the resin composition is impaired.

Next, regarding the particle size distribution of fine particle silica,
Those having a thickness of 3 μm or less are 12% by weight or more, preferably 14% by weight or more, and those having a thickness of 1 μm or less are 2% by weight or more, preferably 3
When it is present in an amount of not less than wt%, good fluidity can be obtained. However, fine particles of 3 μm or less do not necessarily have to be rounded to have roundness, and may be crushed fine particles. In any case, if the amount is less than the lower limit, the fluidity of the resin composition will decrease. The above-mentioned silica fine powder having an average particle diameter of 7 to 35 μm and fine particles present in a desired ratio can be obtained by appropriately adjusting the pressing force, the rotation speed, the amount of the aqueous medium, or the like. It can also be obtained by adding crushed silica of 3 μm or less before or during the main treatment or after the treatment.

The silica fine powder of the present invention can be used by being mixed with a thermosetting resin. As the thermosetting resin, any resin such as epoxy resin, phenol resin, polyester resin, silicone resin can be used,
Of these, epoxy resins can be industrially advantageously used. A desired resin composition can be obtained by blending 100 parts by weight of these thermosetting resins with the fine silica powder of the present invention in the range of 60 to 600 parts by weight. If it is 60 parts by weight or less, the effect of reducing the internal stress is not observed, and if it exceeds 600 parts by weight, the fluidity of the resin is lowered, which is not preferable. As a method of kneading the fine powder with the thermosetting resin, a kneader, a roll mill, a mixer or the like may be usually used.

[0016]

【Example】

Next, the present invention will be described in detail with reference to examples. Example 1 The coarsely crushed crystalline silica was finely crushed by a ball mill to obtain 500 g of crushed crystalline silica having an average particle diameter of 23.2 μm. This was charged into a roller mill (MPV-0.5 type Matsumoto Foundry Iron Works), and 60 ml of water was added at the same time. The pressing force of the roller was 40 kg / cm ² (linear pressure), the clearance between the roller and the bottom plate was 3 mm, and the number of rotations of the bottom plate was 42 rpm. As a result of drying and pulverizing the obtained treated product, the average particle diameter was 19.4 μm, and the particle size distribution of the fine particles was 3 μm or less 22.1% by weight and 1 μm or less 4.4% by weight. The particle size distribution was measured using a laser diffraction type particle size distribution measuring device (CILAS, model 715). An electron micrograph of the silica fine powder produced by performing the chamfering treatment in this manner is shown in FIG.

Example 2 By changing the average particle size of the crushed crystalline silica used in Example 1 and the treatment conditions of the roller mill, the silica fine powders shown in Tables A, B, and C and subjected to the chamfering treatment were used. Manufactured.

[Table 1]

Comparative Example 1 In the same manner as in Example 2, finely powdered silica shown in D and E of Table 2 was produced by subjecting the crushed crystalline silica to a chamfering treatment.

[Table 2]

Comparative Example 2 A coarsely crushed silica stone was finely pulverized with a ball mill to give an average particle diameter of 1
Crushed crystalline silica of 9.2 μm was obtained. Since this one is not processed with a roller mill, the particles have corners,
The electron micrograph was as shown in FIG. The particle size distribution of the fine particles was 3 μm or less, 12.4% by weight, and 1 μm or less, 2.0% by weight.

Example 3 Coarse crushed fused silica was finely crushed with a ball mill to obtain 500 g of crushed fused silica having an average particle diameter of 24.6 μm. After that, the chamfering treatment was performed in the same manner as in Example 1 except that the pressing force of the roller was changed to 20 kg / cm ² (linear pressure), and the average particle size was 1
A silica fine powder having a particle size distribution of 8.6 μm and a fine particle size distribution of 3 μm or less and 23.2% by weight and 1 μm or less and 4.1% by weight was obtained.

Comparative Example 3 In the same manner as in Comparative Example 2, the fused silica coarsely crushed product was not finely chamfered by a roller mill but was simply finely pulverized by a ball mill to obtain crushed fused silica having an average particle diameter of 18.5 μm. . The particle size distribution of fine particles of this product is 3 μm or less 16.2% by weight, 1
It was 3.1% by weight or less of μm.

Test Examples 1 to 5 The fine powder (obtained by treating crushed crystalline silica with a roller mill) produced in Examples 1 and 2 was used as an epoxy resin 10.
To 0 part by weight, the parts by weight shown in Table 3 were blended, kneaded in a kneader for 15 minutes, cooled and pulverized to obtain an epoxy resin composition. To see the flowability of these compositions, spiral flow was measured according to EMMI standard 1-66.

[Table 3]

Comparative Test Examples 1 to 3 Epoxy resin compositions were obtained in the same manner as in Test Examples 1 to 5 using the crystalline silica fine particles obtained in Comparative Examples 1D, 1E and Comparative Example 2 as a filler (Table 4). ). It was clarified that the fluidity was deteriorated under the condition that the silica fine powder having a particle size of 1 μm or less was 2% by weight or less, the average particle size was too small, or the filler was angular.

[Table 4]

Examples 6 and 7 Blended with an epoxy resin in the same manner as in Test Examples 1 to 5 using the fused silica fine particles obtained by the method of Example 3 in which the crushed fused silica is cut off with a roller mill as a filler. Then
The epoxy resin compositions shown in Table 5 were obtained, and at the same time, the spiral flow was measured.

Comparative Test Example 4 Comparative Test Example 4 is the same as the case of Comparative Test Examples 1 to 3 in the case of fine crystalline silica particles, in which crushed fused silica was used as a filling without being chamfered by a roller mill. Similarly, when the fused silica fine particles are used, Table 5
As shown in, the liquidity was reduced.

[Table 5]

Reference Example An epoxy resin composition containing 70% by weight of each of the fine powders obtained in Example 1, Comparative Example 2, Example 3, and Comparative Example 3 was produced, and these were molded in a mold of 50 mmφ. Was filled in and was pressure-molded to produce a tablet having an outer diameter of 50 mm and a height of 10 mm. A wear test was carried out using this. The results are shown in FIGS. 3 and 4. When the rounded and rounded silica fine particles of the present invention were used as the filler, the wear property was clearly improved.

[0027]

【The invention's effect】

The silica fine powder of the present invention, when mixed with a heat-effective resin and used for sealing electronic components such as semiconductors, improves the fluidity and abrasability in the transfer molding process, and also increases the internal stress of the sealed product. It is also useful in reducing workability and improving workability and performance.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a crystal structure of crushed crystalline silica fine particles having rounded corners and roundness according to the present invention.

FIG. 2 is a photomicrograph showing the crystal structure of crushed crystalline silica fine particles with corners before treatment.

FIG. 3 shows the results of a taber abrasion test of an epoxy resin composition obtained by blending the fine powder obtained in Example 1 or Comparative Example 2.

FIG. 4 shows the results of a taber abrasion test of an epoxy resin composition obtained by blending the fine powder obtained in Example 3 or Comparative Example 3.

Claims (3)

[Claims] 1. A finely powdered silica having rounded corners, which is obtained by grinding particles together in the presence of an aqueous medium while applying a pressing force to the crushed silica from the outside. Particle size is less than 200 μm and average particle size is 7
A fine silica powder having a particle size distribution of 12% by weight or more and 2% by weight or more of 12% by weight or more of finely divided silica having a size of 3 μm or less and 3 μm or less. 2. The silica fine powder according to claim 1, wherein the method of grinding the particles in the presence of an aqueous medium while applying a pressing force from the outside of the crushed silica is a method using a roller mill. 3. The fine silica powder according to claim 1, wherein the crushed silica is crystalline silica and / or fused silica.