Abstract: Provided is a method for producing surface-treated silica powder that has excellent gap permeability and that allows a resin composition to have low viscosity in a case where the surface-treated silica powder is used as a resin filler, for example, for a semiconductor sealant. A surface treatment agent is brought into contact with silica powder such that: (1) a cumulative 50 mass % diameter D50 of a mass-based particle size distribution obtained by a centrifugal sedimentation method is 300 nm to 500 nm (preferably 330 nm to 400 nm); (2) a loose bulk density is 250 kg/m3 to 400 kg/m3 (preferably 270 kg/m3 to 350 kg/m3); and (3) {(D90?D50)/D50}×100 is 30% to 45% (preferably 33% to 42%), to modify the surface of the silica powder, so that surface-treated silica powder is produced.

Abstract: Provided is silica powder that, when used as a resin filler such as a semiconductor sealant, allows for obtaining a resin composition having excellent gap permeability and low viscosity. The silica powder is such that (1) a cumulative 50% mass diameter D50 of a mass-based particle size distribution obtained by a centrifugal sedimentation method is 300 nm to 500 nm (preferably, 330 nm to 400 nm), (2) a loose bulk density is 250 kg/m3 to 400 kg/m3 (preferably, 270 kg/m3 to 350 kg/m3), and (3) {(D90?D50)/D50}×100 is 30% to 45%. In a silica production method in which a silicon compound is burned, silica powder can be produced by installing a burner having a concentric multiple pipe structure of three or more pipes in a reactor which has a cooling jacket portion provided around the burner, and adjusting flame combustion conditions and cooling conditions.