JP2611601B2 - Method for producing spherical corundum particles and composition containing spherical corundum particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing spherical corundum particles, and high thermal conductivity using the spherical corundum particles.
Low viscosity and low coefficient of thermal expansion rubber and plastic compositions.

[0002]

2. Description of the Related Art In recent years, as electronic components have become smaller and have higher capacities, there has been an increasing demand for rubber-plastic based insulating materials having excellent heat dissipation properties, and alumina, particularly corundum, having excellent heat conductivity as a filler. (Α-alumina) has attracted attention and has been used in place of fused silica or crystalline silica. On the other hand, corundum particles have a high Mohs hardness, and are used when mixing and filling plastics, rubber, and other materials, or when molding a composite material filled with alumina particles.
It is known that the kneading / forming apparatus is significantly damaged. In particular, when attempting to use a pulverized product of fused alumina or sintered alumina, which is well known as corundum particles, as a filler for a resin sealing material for electronic components such as ICs, LSIs, and VLSIs, the sharp cutting edge is required. Grinding or abrasion is severe and may damage the bonding wires and semiconductor elements. Such a defect is not limited to the resin sealing material, but also becomes a major obstacle in applications in which alumina is widely filled into an electrical insulating resin of an electronic component or an engineering plastic for a structural material to improve thermal conductivity and wear resistance. there is a possibility.

[0003] Therefore, in a pulverized product of fused alumina or sintered alumina produced by a known method, aluminum hydroxide is used as a sphering accelerator in an amount of 5 to 100% by weight (in terms of alumina, ratio to fused alumina or sintered alumina). It is characterized in that it is added alone or in combination with another agent known as a crystallization accelerator for alumina, is heated at a temperature of 1000 to 1550 ° C., and then is crushed, and has an average particle size of 5 to 35 μm by a sedimentation method. , Maximum particle size is 150μ
There has been proposed a method for producing corundum particles having a spherical shape having no cutting edge not exceeding m. (Japanese Patent Application Laid-Open No. 62-194420)
Weight ratio of 80 to 9
Highly thermally conductive rubber / plastic compositions containing up to 2% have been proposed. (JP-A-63-20340)

[0004]

The high thermal conductive rubber / plastic composition containing the spherical corundum described above has the following problems and is therefore required to have higher performance. . JP-A-62-1
No. 91420, and the maximum particle size is 15
When spherical corundum particles having a shape of 0 μm or less, an average particle diameter of 5 to 35 μm, and having no cutting edge are used, these various problems have not been solved. All of these problems are largely caused by the particle size distribution of the spherical corundum particles, and are particularly likely to occur when particles having a size of 30 μm or more are present. Therefore, the maximum particle size of the coarse particles is 3
Although it is possible to adopt a method of cutting coarse particles with an air classifier or a vibrating sieve in order to reduce the particle size to 0 μm or less,
The problem is that the viscosity of the rubber-plastic composition which is rich in fluidity (hereinafter referred to as a liquid rubber-plastic composition) tends to be high, or the flow characteristics represented by spiral flow deteriorate for resin sealants. There is a point.

In a liquid rubber / plastic composition,
Since sedimentation during storage from the end of production until use is large, re-stirring treatment before use is essential. Therefore, low viscosity, good workability, less sedimentation during storage from the end of production to use, and the homogenization work by re-stirring before use can be omitted, and excellent workability is required. Easy to settle and separate. In a sheet-like composition used as an electrical insulating material,
For example, several mm to 0.5
mm, which reduces the adhesion,
Heat dissipation is reduced. What has excellent surface smoothness, good adhesiveness with a semiconductor element, and excellent heat dissipation is required. In the case of a composition for a semiconductor insulating sealing material, as the integration becomes higher and the wiring becomes finer than before, the wiring is likely to be damaged at the time of molding, and it is required that the composition hardly occur. Accordingly, an object of the present invention is to provide a method for producing spherical corundum particles which can solve the above various needs, and a highly heat-conductive rubber / plastic composition containing the spherical corundum particles.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned situation, and as a result, have found that the problem can be solved by improving the method for producing spherical corundum particles, and have completed the present invention. . That is, the gist of the present invention is as follows: (1) One or more of a halogen compound, a boron compound, and an alumina hydrate are added to a pulverized product of fused alumina and / or sintered alumina, and heat treatment is performed. And
Next, in the method for producing spherical corundum particles to be crushed, the amount of alumina hydrate added to electrofused alumina and / or sintered alumina is 100 to 30 in terms of alumina.
0 wt%, the maximum diameter of a single particle is 35
This is a method for producing spherical corundum particles having an average particle diameter of 5 to 15 μm or less. (2) A highly thermally conductive rubber / plastic composition containing the spherical corundum particles described in (1) in an amount of 80 to 92% by weight. Hereinafter, the present invention will be described in detail.

The alumina coarse particles used as a starting material in the present invention may be either electrofused alumina or sintered alumina produced by a known method. Has a mean particle size of 5 μm to 35 μm, preferably 10 μm to 25 μm, and the maximum particle size does not exceed 150 μm, and is preferably 74 μm or less. Average diameter is 5μm
In the following cases, it is not necessary to apply the present invention since a rounded particle shape can be obtained by a known method of adding a crystal growth agent to aluminum hydroxide. Further, it is not preferable that the number of particles having an average diameter of the raw material of 35 μm or more or larger than 150 μm increases, because the cutting edge of coarse particles is insufficiently reduced.

Further, in order to promote the spheroidization of coarse particles, alumina hydrate, particularly aluminum hydroxide, alumina gel or fine alumina having good thermal reactivity is mixed with electrofused alumina or sintered alumina in advance and heat-treated. Has been found to be effective. From the economical viewpoint, the Bayer method aluminum hydroxide (gibbsite crystal) is preferable, and the one having an average particle diameter of 10 μm or less is optimal. According to the observations of the present inventors, such a spheroidizing agent acts on the coarse-grained alumina synergistically with the below-described agent, and a surprising phenomenon that the spheroidizing agent is selectively absorbed by an irregular sharp cutting edge to be spheroidized. Admitted. As a secondary effect, the addition of alumina hydrate such as aluminum hydroxide or alumina gel in particular reduces the cohesive force of the agglomerates of the heat-treated product, making it easier to disintegrate it into primary particles. Features were observed.

The optimum amount of the sphering accelerator varies depending on the particle size of the pulverized product of fused alumina or sintered alumina, but when aluminum hydroxide is added, 100 wt.
% To 300 wt% (in terms of alumina, the ratio to fused alumina and / or sintered alumina) is preferred. 1
When the content is less than 00 wt%, most of the aluminum hydroxide is absorbed by the coarse-grained alumina, so that the ratio of the alumina constituting the fine-grained portion is small and the particle size distribution is narrow. . Also 300
If the content exceeds wt%, the ratio of free fine alumina remaining without being absorbed is too large, which is not preferable because it has the effect of increasing the viscosity of the liquid composition and hardening the rubber composition.

The chemicals to be added at the time of heat treatment include halogen compounds known alone or in combination as alumina crystal growth promoters, especially fluorine compounds such as NaF and CaF ₂ and / or MgF ₂ , Na ₃ AlF ₆ , B ₂ O
_{3, H 3 BO 3, mNa} 2 O · nB 2 O 3, good boron compounds such硼弗containing compounds, especially the combination of fluoride and a boron compound, or硼弗containing compounds are preferred. The addition amount of the chemical varies depending on the heating temperature, the residence time in the furnace, and the type of the heating furnace, but the effective addition concentration is 0.1 to the total alumina content.
４4.0% by weight. As the type of the heating furnace, known means such as a single kiln, a tunnel kiln, and a rotary kiln may be used, and the heating temperature is a temperature at which alumina hydrate such as aluminum hydroxide is substantially added to α-alumina, that is, about 1150 ° C or more. If so, the object of the invention is achieved.

A particularly preferred heat treatment temperature range is 1350.
C. or more and 1550 ° C. or less. At a temperature of 1550 ° C. or higher, the agglomeration of the agglomerates becomes stronger in the presence of aluminum hydroxide, and crushing into primary particles does not proceed easily.
The residence time of the heating furnace varies depending on the heating temperature, but a residence time of at least 30 minutes, preferably about 1 to 3 hours is required for the particle diameter to be spherical. According to such a method, the spherical alumina particles produced are in the form of secondary aggregated particles, and are crushed for a short time by a known pulverizing means, for example, a ball mill, a vibration mill, a jet mill, or the like. Is obtained.

The spherical alumina obtained in the present invention is composed of substantially spherical single particles, and the particle size distribution is controlled to a maximum particle size of 35 μm. When particles larger than this are mixed, when rubber and plastic are filled, the liquid composition tends to settle and separate during storage, etc., and the sheet-like composition has poor surface smoothness, resulting in poor adhesion. This is not preferable because it lowers the heat radiation. The average particle diameter is controlled so as to be in the range of 5 to 15 μm. If it exceeds 15 μm, the hardness of the corundum particles is too high, so that the molding machine for forming the composition wears hard, and the composition used for the insulating sealant increases the damage of the semiconductor element. On the other hand, when the particle size is 5 μm or less, the viscosity of the liquid composition becomes high and molding becomes difficult, which is not preferable.

The polymer to be blended with the spherical corundum particles includes thermoplastic engineering plastics such as polyethylene, polypropylene, nylon, polycarbonate, and polyphenylene sulfide, and thermosetting resins such as epoxy resin, unsaturated polyester resin, and phenol resin. Curable plastics and elastomers such as silicone rubber are suitable. In particular, IC, L
Epoxy resin used for sealing the SI, such as phenol novolak epoxy, cresol novolak epoxy or silicone resin, or heat resin
Silicone rubber for sink applications is the preferred polymer.

The range of the filling amount of the spherical alumina is desirably up to 80 to 92% by weight. If less than 80%, 6
This is because a thermal conductivity of 0 × 10 ⁻⁴ cal / cm · sec · ° C. or more cannot be obtained, and if it exceeds 92%, the plastic fluidity of the compound becomes insufficient and molding becomes difficult. In the formulation,
It is free to add a flame retardant, a filler other than alumina, a lubricant, a release agent, and a colorant within a range that does not impair the gist of the present invention.

[0015]

EXAMPLES Next, the contents of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. [Example] Commercially available pulverized sintered alumina (SRW- manufactured by Showa Denko KK)
3058 g (weight ratio in terms of alumina, 200 μm in terms of alumina) of fine aluminum hydroxide (H-42M, manufactured by Showa Denko KK, average particle diameter: 1 μm) was added to 1000 g of 1500F (average particle diameter: 10 μm).
wt%), and 60 g each of anhydrous aluminum fluoride and boric acid (2 wt% relative to the total alumina content).
%), Mixed well, and baked at 1450 ° C. for 3 hours to obtain a baked product. This was shaken with a vibration ball mill (SM0.6 alumina ball manufactured by Kawasaki Heavy Industries, Ltd. and alumina in a ratio of 1).
0) crushed 30 times, the particle size of the obtained crushed product was measured. The average particle size was 8 μm, and particles larger than 30 μm accounted for 0.03% of the whole. In addition, the shape was observed by an electron micrograph, but there was no sharp cutting edge, and it was spherical. 5 g of this pulverized powder was added to 100 g of silicone oil (KF-96, 50 cp, manufactured by Shin-Etsu Chemical Co., Ltd.).
The mixture was mixed at a ratio of 00 g to prepare an oil compound (liquid composition). As shown in Table 1, the viscosity of the compound at this time was 35 poise. The compound was transferred to a glass container and kept at room temperature for 20 days, but no sedimentation at the bottom was observed.

[Comparative Example 1] The same finely divided aluminum hydroxide 5 as in the example was added to 1000 g of the same sintered alumina as in the example.
10 g (weight ratio in terms of alumina: 30 wt%) were mixed, and the same chemicals as in the example were added in 27 g increments (weight ratio to total alumina content: 2 wt%), followed by firing in the same manner.
Crushed to obtain a powder. The average particle size of this powder is 11 μm
The ratio of particles having a particle size of 30 μm or more was 2.5%. The shape was observed by an electron micrograph, and it was found to be spherical without sharp cutting edges. The obtained powder was used as a silicone oil compound in the same manner as in the example, the viscosity of the compound was measured, and the compound was transferred to a glass container and allowed to stand at room temperature, and the number of days until sedimentation at the bottom occurred was measured. The results are as shown in Table 1.

Comparative Example 2 The powder obtained in Comparative Example 1 was further pulverized for 30 minutes to obtain a powder. The average particle size is 7 μm and 3
0.5% or more of the particles having a particle size of 0 μm or more accounted for 0.5% of the whole. The obtained powder was used as a silicone oil compound in the same manner as in the example, the viscosity of the compound was measured, and the compound was transferred to a glass container and allowed to stand at room temperature, and the number of days until sedimentation at the bottom occurred was measured.
The results are as shown in Table 1.

Comparative Example 3 The same finely divided aluminum hydroxide 8 as in the example was added to 1000 g of the same sintered alumina as in the example.
000 g (weight ratio in terms of alumina: 520 wt%) and 125 g of the same chemicals as in the example were mixed, baked and crushed under the same conditions. The average particle size of the powder is 3 μm and 30 μm
The above particles accounted for 0.02% of the whole. The obtained powder was used as a silicone oil compound in the same manner as in the example, the viscosity of the compound was measured, and the compound was transferred to a glass container and allowed to stand at room temperature, and the number of days until sedimentation at the bottom occurred was measured. The results are as shown in Table 1.

Comparative Example 4 The powder obtained in Comparative Example 1 was passed through an air classifier (Turbo Classifier, manufactured by Nisshin Engineering Co., Ltd.) to 30 μm.
The operation was carried out to remove particles of m or more to obtain a powder. Profit rate is 7
8%, the average particle size of the obtained powder was 8 μm,
The ratio of particles having a size of 0 μm or more was 0.01% or less.
The obtained powder was used as a silicone oil compound in the same manner as in the example, the viscosity of the compound was measured, and the compound was transferred to a glass container and allowed to stand at room temperature, and the number of days until sedimentation at the bottom occurred was measured. The results are as shown in Table 1.

[0020]

[Table 1]

[0021]

As is evident from the above, the compounding of the spherical corundum particles of the present invention causes the problem of sedimentation and separation of the liquid rubber / plastic composition and the problem of lowering the heat radiation of the thin sheet-like rubber / plastic composition. Disappears,
A rubber / plastic composition which was much more practical was obtained.

Claims (2)

(57) [Claims] 1. A halogenated compound, a boron compound, and / or an alumina hydrate are added to a pulverized product of fused alumina and / or sintered alumina, and heated at a temperature of 1000 to 1550 ° C. A method for producing spherical corundum particles to be treated and then crushed, wherein the amount of alumina hydrate added to the fused alumina and / or sintered alumina is 100 to 300 wt% in terms of alumina. Manufacturing method. 2. A single particle having a maximum diameter of 35 μm or less, an average particle diameter of 5 to 15 μm, a shape having no cutting edge, and the spherical corundum particles according to claim 1 in a weight ratio of 80 to 92%. Highly heat-conductive rubber / plastic composition characterized by containing.