A method for manufacturing a bump structure includes depositing a layer of photosensitive material on a substrate. Next, multiple strip-shaped shielding sections are arranged on an optical mask at intervals and multiple irregularly arranged circular holes are distributed in the respective strip-shaped shielding sections. Multiple irregularly arranged circular shielding sections are distributed in spacing sections between the adjacent strip-shaped shielding sections and multiple irregularly arranged arch notches and arch shielding sections are distributed on the edges of the strip-shaped shielding sections. The photosensitive material layer is then exposed and developed to form bumps thereon and the heat is applied to solidify the surface of the bumps. Then a reflective film is laid on the substrate and the bumps to form a reflective board.