JP-7857471-B1 - β-type silicon nitride powder, resin composition, thermally conductive paste, and method for producing β-type silicon nitride powder

JP7857471B1JP 7857471 B1JP7857471 B1JP 7857471B1JP-7857471-B1

Abstract

[Problem] To provide a β-type silicon nitride powder having a particle shape in which the particle diameter in the ab-plane direction is larger than that in the c-axis direction. [Solution] The β-type silicon nitride powder is a β-type silicon nitride powder having a β fraction of 80% or more, and is characterized in that the ratio Iβ(101)/Iβ( 210 ), which is the ratio of the X-ray diffraction peak intensity Iβ(101) of the ( 101 ) plane of β- Si3N4 obtained from the X-ray diffraction pattern of the β-type silicon nitride powder to the X-ray diffraction peak intensity Iβ(210) of the (210) plane of β-Si3N4, is 1.1 or more. [Selection Diagram] Figure 2

Inventors

松本理
高橋光隆

Assignees

株式会社MARUWA

Dates

Publication Date: 20260512
Application Date: 20250411

Claims (9)

A β-type silicon nitride powder having a β fraction of 80% or more and containing Sr element , A β-type silicon nitride powder characterized in that the ratio Iβ(101)/ Iβ (210), which is the ratio of the X-ray diffraction peak intensity Iβ(101) of the (101) plane of β- Si3N4 obtained from the X-ray diffraction pattern of the β-type silicon nitride powder to the X-ray diffraction peak intensity Iβ(210) of the (210) plane of β-Si3N4, is 1.1 or higher.
The β-type silicon nitride powder according to claim 1, characterized in that the average aspect ratio W/L, where L is the length in the c-axis direction of the primary particle and W is the length in the ab-plane direction, is 2.5 or greater.
A β-type silicon nitride powder having a β fraction of 80% or more and containing Sr element , A β-type silicon nitride powder characterized in that the average aspect ratio W/L of the primary particle, where L is the length in the c-axis direction and W is the length in the ab-plane direction, is 2.5 or greater.
A β-type silicon nitride powder according to any one of claims 1 to 3, characterized in that its thermal conductivity is 0.12 W/mK or higher.
A resin composition characterized by containing the β-type silicon nitride powder described in any one of claims 1 to 3.
The resin composition according to claim 5 , characterized in that it is a thermoplastic resin or a thermosetting resin.
A thermally conductive paste characterized by containing the β-type silicon nitride powder described in any one of claims 1 to 3.
A method for producing β-type silicon nitride powder having a β fraction of 80% or more, A step to produce a mixed powder comprising a raw material containing SiO2 powder and an Sr compound powder in which the amount of Sr compound added is 5 to 10 mol% when the SiO2 powder is considered as 100 mol%, and carbon powder in which the mol ratio (C/SiO2 ) is 2 to 3 times that of the SiO2 powder, A step of nitriding the mixed powder by a reduction-nitridation reaction in a nitrogen atmosphere, A method characterized by including the following.
The method according to 8 , characterized in that the Sr compound is a halogen compound.

Description

This invention relates to β-type silicon nitride powder, a resin composition, a thermally conductive paste, and a method for producing β-type silicon nitride powder. In recent years, with the increasing density and power output of electronic devices and semiconductor devices, the heat generation density of power modules has also increased. This temperature rise in power modules can cause malfunctions in the components and damage to the circuit board. By incorporating β-type silicon nitride powder, an excellent thermally conductive material, as a filler into resin compositions (e.g., substrates, sheets, spacers, etc.) and paste-like electronic materials (thermally conductive pastes) such as greases, adhesives, and paints used in such electronic devices and semiconductor devices, heat dissipation performance can be improved. Here, silicon nitride exists in two forms with different crystalline phases: α-type silicon nitride (α- Si₃N₄ ) and β-type silicon nitride (β- Si₃N₄ ). α -type silicon nitride has the property of irreversibly transforming into β-type silicon nitride at high temperatures (around the sintering temperature of 1500-1700°C). β-type silicon nitride crystal grains are columnar crystal grains elongated in the c-axis direction and are known to have higher thermal conductivity than α-type silicon nitride crystal grains. The plane perpendicular to the c-axis in the elongation direction is defined as the ab plane. Generally, a hexagonal crystal structure has six faces: hexagonal upper and lower faces and rectangular faces perpendicular to the opposing upper and lower faces. The hexagonal upper and lower faces are called the base planes, and the six rectangular faces perpendicular to the base planes are also called prism planes. Therefore, when silicon nitride powder is used as a filler for heat dissipation applications, a higher proportion of β-type silicon nitride crystal grains is considered preferable. Furthermore, larger β-type silicon nitride crystal grains result in longer heat conduction paths, which is advantageous for the heat dissipation properties of the filler. On the other hand, the required material properties for fillers include packing ability and fluidity (or mixability). The higher the packing ability of the filler, the higher the concentration of powder that can be mixed into materials such as resins. Also, the higher the fluidity of the filler, the easier it is to mix the filler into the material at a higher concentration. For example, Patent Document 1 discloses a silicon nitride filler added to resins and the like that constituting insulating members for the purpose of improving heat dissipation performance. According to Patent Document 1, when the silicon nitride filler contains 50% or more by volume of condensed particles with a particle diameter of 5 μm or more and 200 μm or less, the proportion of particles with a particle diameter of less than 5 μm and particles with a particle diameter of more than 200 μm decreases, thereby improving dispersibility. Furthermore, it is possible to prevent surface roughness and a decrease in mechanical strength of the resin composite obtained by mixing with resins and the like, and to improve thermal conductivity. This silicon nitride filler can preferably be manufactured by a manufacturing method having the following steps. The manufacturing method includes (a) a step of filling a heat-resistant container with silicon, or a mixture of silicon and silicon nitride, (b) a step of producing condensed silicon nitride lumps by a self-combustion reaction in a non-oxidizing atmosphere containing nitrogen at 1 atmosphere or more, and (c) a step of crushing the condensed silicon nitride lumps. The self-combustion reaction of silicon (nitriding combustion reaction) proceeds at high temperatures of 1900°C or higher. During this reaction, silicon nitride particles grow sufficiently, resulting in a condensed mass with a structure of intertwined β-phase silicon nitride particles having well-developed crystalline surfaces. Alternatively, instead of using the self-combustion method to produce silicon nitride filler, a direct nitriding method can be used. This involves nitriding silicon powder granules or molded bodies in nitrogen at around 1400°C, followed by further heat treatment at high temperatures to develop β-phase columnar particles, and then crushing the resulting condensed mass. The silicon nitride filler thus obtained can be used to form a resin composite containing the silicon nitride filler and a resin composition. Japanese Patent Publication No. 2015-81205 The X-ray diffraction patterns of silicon nitride powders from Examples 1-4 and Comparative Examples 1-3 are shown.SEM image of silicon nitride powder from Example 1.SEM image of silicon nitride powder from Example 2.SEM image of silicon nitride powder from Example 3.SEM image of silicon nitride powder from Example 4.SEM image of silicon nitride powder of Comparative Example 1.SEM image of si