To provide a process for producing a package for mounting a semiconductor element by using a mold, said a package for mounting a semiconductor element comprising a substrate having a mounting surface for mounting a semiconductor element and a packaging body formed from a cured product of a curable resin and having a frame-shaped portion surrounding the mounting surface, and the package has a concave portion formed by the mounting surface and the packaging body, which allows it to prevent resin burrs without occurrence of dents or damage of a substrate and failure in releasing from a mold, and to provide a mold release film to be suitably used for the production process.
A mold release film having a substantially constant thickness over the film, is disposed on the upper mold having a convex portion of which shape corresponds to the concave portion, the substrate is disposed on the lower portion, the upper mold and the lower mold are closed so as to be in close contact with the convex portion to the mounting portion of the substrate via the mold release film, a space formed between the upper mold and the lower mold is filled with a curable resin, followed by curing the curable resin, and the cured product is released together with the substrate, from the mold.