Resin composition for printed circuit board, prepreg for printed circuit board, laminate, metal-clad laminate, printed circuit board, and magnesium oxide, and method for manufacturing magnesium oxide

A magnesium oxide comprising particles of which volume average particle size falls within a range from 2 μm to 10 μm, inclusive,

• wherein in a distribution of a particle size, the particle size has maximal frequencies in a first range from 0.3 μm to 1 μm, inclusive, and in a second range from 2 μm to 10 μm, inclusive,
• a maximal volume frequency in the first range is 5% or less, and a maximal volume frequency in the second range is 12% or more,
• a ratio of 50% accumulated particle size D50 with respect to a specific surface area diameter is 4 or less, and
• a ratio of 90% accumulated particle size D90 with respect to 10% accumulated particle size D10 is 10 or less.

A method for manufacturing a magnesium oxide, comprising:

• calcining a magnesium oxide precursor at a temperature from 1500° C. to 2000° C., inclusive, so as to produce calcined material particles;
• crushing the calcined material particles to form a crushed object;
• and
• classifying the crushed object to prepare a magnesium oxide,
• wherein, in the classified magnesium oxide,
• a volume average particle size is in a range from 2 μm to 10 μm, inclusive,
• in a distribution of a particle size, the particle size has a maximal frequencies in a first range from 0.3 μm to 1 μm, inclusive, and in a second range from 2 μm to 10 μm, inclusive,
• a maximal volume frequency in the first range is 5% or less, and a maximal volume frequency in the second range is 12% or more,
• a ratio of 50% accumulated particle size D50 with respect to a specific surface area diameter is 4 or less, and
• a ratio of 90% accumulated particle size D90 with respect to 10% accumulated particle size D10 is 10 or less.