JP2017036183A - Manufacturing method of high filling spherical aluminum nitride filler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical aluminum nitride filler having enhanced filling property.SOLUTION: Fusion of spherical aluminum nitride granules each other can be suppressed by mixing the spherical aluminum nitride granules with boron nitride powder when the spherical aluminum nitride granules containing rare earth oxide is heat treated at 1700 to 1900°C under nitrogen atmosphere. Filling property can be enhanced by controlling added amount of the used boron nitride powder to 0.2 pts.wt. or more and less than 1 pts.wt. based on 100 pts.wt. of the spherical aluminum nitride granules at that time. Also a high filling spherical aluminum nitride filler can be obtained by inputting only the spherical aluminum nitride granules and the boron nitride powder into a vessel rotary type mixer, mixing them and suppressing breakage of an aluminum nitride particle.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a spherical aluminum nitride filler.

Aluminum nitride is known as a ceramic material having excellent thermal conductivity, and its sintered substrate is widely used in electronic devices that require heat dissipation performance. Moreover, it has come to be utilized also as a filler which mixes aluminum nitride powder with resin etc.

Moreover, when manufacturing a spherical aluminum nitride filler, spherical aluminum nitride fillers may seize each other. As a solution to this problem, for example, as disclosed in JP-A-11-269302, a spherical aluminum nitride sintered body to which boron nitride (BN) powder is added has been reported.

Japanese Patent Laid-Open No. 11-269302

However, as in the case of spherical aluminum nitride filler made by a conventional manufacturing method, if the amount of boron nitride powder added is large, the filling rate cannot be increased during kneading with the resin, so the step of removing boron nitride powder Was necessary. That is, the spherical aluminum nitride filler cannot be sufficiently filled in the resin, and the mixed molded body cannot have a sufficient thermal conductivity. Accordingly, an object of the present invention is to provide a spherical aluminum nitride filler with improved resin filling properties.

Thus, as a result of intensive studies to achieve the above object, the present inventors have found that the filling properties can be improved by adding an appropriate amount of boron nitride to the spherical aluminum nitride granules.

That is, a raw material step of preparing spherical aluminum nitride granules, and a mixing step of preparing a raw material mixture by mixing 0.2 parts by weight or more and less than 1 part by weight of boron nitride powder with respect to 100 parts by weight of the spherical aluminum nitride granules,
A firing step of sintering the raw material mixture in a temperature range of 1700 to 1900 ° C;
By adopting a method for producing a flowable spherical aluminum nitride filler characterized in that it contains, the filling property into the resin is improved.

Furthermore, in the mixing step, the filling property can be further improved by mixing only the spherical aluminum nitride granules and the boron nitride powder in a container rotary mixer.

According to the present invention, it is possible to obtain a spherical aluminum nitride filler having high filling properties, and therefore it is possible to provide an aluminum nitride filler capable of imparting excellent thermal conductivity.

The production method of the present invention will be described in detail below. First, the raw material process will be described. As the aluminum nitride powder as the main component of the spherical aluminum nitride granules according to the present invention, commercially available conventionally known aluminum nitride powders such as direct nitriding method and reduction nitriding method can be used. To this, a rare earth oxide such as yttrium oxide is added as a sintering aid, an organic solvent and a binder are added, and the slurry is sprayed with a spray dryer to obtain spherical aluminum nitride granules. .

Next, the mixing process will be described. A commercially available boron nitride powder can also be used. When producing a spherical aluminum nitride filler, boron nitride powder is added to prevent the aluminum nitride fillers from being seized together. The added amount is 0.2 parts by weight or more and less than 1 part by weight of boron nitride powder with respect to 100 parts by weight of the aluminum nitride granules obtained in the above raw material process. When the addition amount is less than 0.2 parts by weight, seizure between the aluminum nitride fillers cannot be sufficiently prevented in the firing step described later. When the addition amount is 1 part by weight or more, the viscosity increases during kneading with the resin, and the aluminum nitride filler cannot be sufficiently filled.

In the mixing step, it is possible to manufacture a spherical aluminum nitride filler with further improved filling properties by mixing only the spherical aluminum nitride granules and the boron nitride powder in a container rotary mixer. A container rotation type mixer uses a motor or the like to rotate the container body containing the powder particles to be mixed, and the powder particles are dispersed and mixed by repeating rising and falling along the rotation of the container. A homogeneous raw material mixture can be obtained without destroying. In addition, in a mixing method such as a ball mill generally used as a conventional technique, in addition to spherical aluminum nitride granules and boron nitride powder, for example, zirconia balls are also mixed and mixed so that spherical aluminum nitride granules in contact with zirconia balls are mixed. Will be destroyed and the spherical shape cannot be maintained.

As the container rotating type mixer, it is particularly desirable to use a V-type blender. The V-type blender combines two cylindrical containers into a V-shape. By rotating the container, the contained granular material is gathered from two places to one place by gravity and centrifugal force, and is divided into two places. Among them, the assembly and separation are repeated, and the dispersion mixing is performed by the three-dimensional collision alternating current and the convolution action, so that a uniform raw material mixture can be obtained in a short time without destroying the spherical shape. Therefore, a spherical aluminum nitride filler with further improved fillability can be obtained.

Next, the firing process will be described. The raw material mixture obtained in the mixing step is filled into a boron nitride crucible, and degreased at 400 to 600 ° C. in the atmosphere. Next, baking is performed at 1700 to 1900 ° C. in a nitrogen atmosphere. At this time, when the boron nitride powder is not added or when the addition amount of the boron nitride powder is not sufficient, the liquid phase component deposited on the surface of the spherical aluminum nitride granules is solidified in the cooling process, so that the aluminum nitride granules are melted together. I wear it. In this sintering process, aluminum nitride and boron nitride do not react with each other, and since boron nitride is stable at the sintering temperature of aluminum nitride, it is preferable to use boron nitride powder as a release agent.

The aluminum nitride filler of the present invention obtained through the above steps maintains a spherical shape without being destroyed by employing a specific mixing method. Furthermore, since boron nitride added in an appropriate amount as a mold release agent suppresses fusion of the aluminum nitride filler, it is possible to prevent the aluminum nitride filler from being broken and damaging the spherical shape. Therefore, when the resin is filled with the aluminum nitride filler obtained in the present invention, it becomes a state close to closest packing, so that the filling rate can be increased, and the mixed molded body has high thermal conductivity.

Although the present invention has been described in detail above, what has been described here is an example of a specific embodiment of the present invention. It should be understood that some of the embodiments can be modified and practiced.

The product of the present invention can be widely used in fields such as electronic parts and the automobile industry as a filler for filling a heat-dissipating sheet, grease, or insulating resin.

Claims (2)

A raw material process for preparing spherical aluminum nitride granules;
A mixing step of preparing a raw material mixture by mixing 0.2 parts by weight or more and less than 1 part by weight of boron nitride powder with respect to 100 parts by weight of the spherical aluminum nitride granules;
A firing step of sintering the raw material mixture in a temperature range of 1700 to 1900 ° C;
A method for producing a highly filled spherical aluminum nitride filler, comprising: 2. The method for producing a highly-filled spherical aluminum nitride filler according to claim 1, wherein in the mixing step, only the spherical aluminum nitride granules and the boron nitride powder are mixed in a container rotary mixer.