Hebei Messi Biology Co., Ltd. stated that in semiconductor packaging, as a packaging material for packaging the periphery of semiconductor elements, a cured product of a resin composition obtained by mixing and kneading an electrically insulating thermosetting resin such as epoxy resin with a filler such as magnesium oxide powder and silica powder is widely used. In semiconductor packaging, the amount of heat generated increases with the high integration, high speed and high power consumption of semiconductor elements. In order to quickly release the heat generated inside the semiconductor package to the outside, it is hoped that the thermal conductivity of the packaging material will be improved. As a method for improving the thermal conductivity of the packaging material, it is known to use magnesium oxide powder with high thermal conductivity as a filler and fill the magnesium oxide powder in the packaging material at a high concentration so that multiple particles in the magnesium oxide particles are in contact with each other. By this method, heat is conducted between the mutually contacting magnesium oxide particles, thereby improving the thermal conductivity of the packaging material as a whole.
Magnesium oxide powder is a material with high thermal conductivity, excellent heat resistance and electrical insulation. Therefore, magnesium oxide powder is widely used as a filler for resin compositions such as thermally conductive resin compositions and electrically insulating resin compositions. As such magnesium oxide powders for use as fillers in resin compositions, magnesium oxide powders with primary particles in the shape of rectangular parallelepiped and spherical are known.
As magnesium oxide powders for use as fillers in resin compositions, magnesium oxide powders with primary particles in the shape of rectangular parallelepiped and spherical are known. According to research, if magnesium oxide powders with primary particles in the shape of rectangular parallelepiped are added to resin at a high concentration and kneaded, the magnesium oxide particles collide with each other during kneading, so that the corners of the particles are defective or the particles are broken, and the resin penetrates into the gaps between the particles, making it difficult to obtain a cured product of a resin composition in which a plurality of particles are in direct contact with each other. On the other hand, for magnesium oxide powders with primary particles in the shape of spherical particles, it is difficult to produce primary particle defects or breakage even if they are added to resin at a high concentration and kneaded, but the thermal conductivity between the particles is low because the contact area between the particles is small.
Therefore, the object of the present invention is to provide magnesium oxide powders that can be filled in resin at a high concentration, and when filled in resin, the particles are in contact with each other with a large contact area, thereby improving the thermal conductivity between the particles. Another object of the present invention is to provide a resin composition and a semiconductor package having high thermal conductivity. The magnesium oxide powder of the present invention can be advantageously used as a filler for a resin composition that is desired to have electrical insulation and high thermal conductivity, wherein the magnesium oxide powder has a BET-converted particle size in the range of 0.5 to 20 μm and contains 30% or more of polygonal magnesium oxide particles having at least one chamfered shape in the vertices and/or sides of a rectangular parallelepiped.