A method of mounting an electronic device includes: preparing a printed circuit board including a base substrate, connection pads disposed on the base substrate and spaced apart from each other, and a solder resist including contact holes exposing a portion of the connection pads; disposing preliminary bumps on the exposed portion of the connection pads via the contact holes; disposing under-fill patterns in areas between the preliminary bumps on the solder resist; disposing an electronic device on the preliminary bumps and the under-fill patterns; and mounting the electronic device onto the printed circuit board by reflowing the preliminary bumps and the under-fill patterns. The disposing of the under-fill patterns may include: providing an under-fill film including a base film having openings spaced apart from each other, and the under-fill patterns disposed within the openings; applying pressure to the under-fill film; and removing the base film from the under-fill film.