CN-121986082-A - Silicon nitride sintered substrate and method for manufacturing same

CN121986082ACN 121986082 ACN121986082 ACN 121986082ACN-121986082-A

Abstract

The invention relates to a silicon nitride sintered substrate, which is characterized by comprising a surface layer and an inner layer which are arranged on two surfaces, wherein the surface layer contains silicon nitride particles with an average equivalent round diameter of less than 5 mu m and an average length-diameter ratio of less than 3, and the inner layer contains silicon nitride particles with an average equivalent round diameter of 2.0-10.0 mu m and an average length-diameter ratio of more than 3. According to the present invention, a silicon nitride sintered substrate having high thermal conductivity and excellent adhesion when bonded to a metal plate can be provided.

Inventors

ANDO AKIHIRO
ISHIMOTO RYUJI

Assignees

株式会社德山

Dates

Publication Date: 20260505
Application Date: 20241023
Priority Date: 20231026

Claims (4)

1. A silicon nitride sintered substrate comprising a surface layer and an inner layer, wherein the surface layer comprises silicon nitride particles having an average equivalent round diameter of 5 [ mu ] m or less and an average aspect ratio of less than 3, and the inner layer comprises silicon nitride particles having an average equivalent round diameter of 2.0 [ mu ] m to 10.0 [ mu ] m and an average aspect ratio of 3 or more.
2. The silicon nitride sintered substrate according to claim 1, wherein each surface layer of the silicon nitride sintered substrate has a thickness of 10 μm or more, and a total thickness of both surface layers is 25% or less of the thickness of the silicon nitride sintered substrate.
3. The silicon nitride sintered substrate according to claim 1, wherein the thickness of the silicon nitride sintered substrate is 100 to 1000 μm.
4. A method for producing a silicon nitride sintered substrate, characterized in that a layer containing a silicon nitride green compact composed mainly of a type silicon nitride powder is formed on both surfaces of a layer containing a silicon nitride green compact composed mainly of a type silicon nitride powder, and then the layer is sintered.

Description

Silicon nitride sintered substrate and method for manufacturing same Technical Field The present invention relates to a novel silicon nitride sintered substrate. Background Silicon nitride sintered substrates have been attracting attention as ceramic materials in various industrial fields because of their excellent characteristics such as high thermal conductivity, high insulation, and high strength, and are used as heat dissipation substrates for power modules such as vehicles and semiconductors. When a silicon nitride sintered substrate is used as a heat dissipation substrate, it is required to have high thermal conductivity. In addition, when the heat dissipating substrate is used as the heat dissipating substrate, the heat dissipating substrate is usually bonded to a metal plate, and in order to sufficiently exhibit the heat conductivity, it is necessary to have high adhesion to the metal plate. The high adhesion to the metal plate can be improved by smoothing the surface of the silicon nitride sintered substrate. Therefore, the silicon nitride sintered substrate is required to have high thermal conductivity and a smooth surface. The thermal conductivity is well known to be proportional to the size and length of the grains in the silicon nitride sintered substrate. Accordingly, the larger the crystal grains, the larger the aspect ratio of the crystal grains, and the higher the thermal conductivity of the obtained silicon nitride sintered substrate (see patent document 1). On the other hand, it is known that the surface roughness of a silicon nitride sintered substrate depends on the grain size of the surface layer, and the smaller the grain size of the silicon nitride surface layer, the lower the surface roughness of the manufactured silicon nitride sintered substrate. Further, the adhesion between the silicon nitride sintered substrate having an appropriate surface roughness and the metal plate is high, and the heat cycle resistance of the laminate can be improved (see patent document 2). However, it is difficult to obtain a silicon nitride sintered substrate that satisfies the above characteristics at the same time. That is, if the thermal conductivity of the silicon nitride sintered substrate is increased, the crystal grains are coarsened, the surface roughness is increased, and the adhesion to the metal plate is reduced, whereas if the crystal grain diameter is reduced to increase the adhesion between the silicon nitride sintered body and the metal plate, the thermal conductivity is greatly reduced. Therefore, at present, a silicon nitride sintered substrate satisfying these requirements at the same time is not realized. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 10-194842 Patent document 2 Japanese patent No. 5440947 Disclosure of Invention Problems to be solved by the invention Accordingly, an object of the present invention is to provide a silicon nitride sintered substrate having high thermal conductivity and excellent adhesion when bonded to a metal plate. Means for solving the problems As a result of intensive studies to solve the above problems, the present inventors have found that, as a material constituting a silicon nitride sintered substrate, raw material powders exhibiting different behaviors are molded into a layer and sintered, whereby physical properties of each sintered body can be exhibited without interfering with each other. Based on this finding, as a result of further studies, it was found that a silicon nitride sintered substrate obtained by stacking a green body containing an α -type silicon nitride powder as a main component and a green body containing a β -type silicon nitride powder as a main component and sintering the above-mentioned layers exhibits high thermal conductivity and high adhesion to a metal plate, and the present invention has been completed. Specifically disclosed is a silicon nitride sintered substrate which is characterized by comprising a surface layer and an inner layer that are present on both surfaces, wherein the surface layer contains silicon nitride particles having an average equivalent round diameter of 5 [ mu ] m or less and an average aspect ratio of less than 3, and the inner layer contains silicon nitride particles having an average equivalent round diameter of 2.0-10.0 [ mu ] m and an average aspect ratio of 3 or more. Preferably, each surface layer of the silicon nitride sintered substrate has a thickness of 10 μm or more, and the total thickness of both surface layers is 25% or less of the thickness of the silicon nitride sintered substrate. The thickness of the silicon nitride sintered substrate is preferably 100 to 1000 μm. The invention also provides a manufacturing method of the silicon nitride sintered substrate. That is, according to the present invention, there is provided a method for producing a silicon nitride sintered substrate, characterized by forming a layer containing a silicon nit