Method and apparatus for mold cleaning by reverse sputtering

摘要

A method and apparatus for cleaning at least selected surfaces of a mold apparatus to remove plastic residue and surface contaminates and impurities to enable the molds to be used in a continuous in-line type process for encapsulating lead frame assemblies or similar semi-conductor circuits. After the molds are separated and the large pieces of excess plastic are broken away, they are transported to a vacuum chamber and electrically coupled as, or at least proximate, the cathode. The vacuum chamber is evacuated and an inert ionizable gas such as argon is admitted. An electrical field is established between the anode and cathode to create a plasma or glow discharge causing the gas to ionize. The positive ions are accelerated by the electrical field toward the cathode and bombard at least selected areas of the mold portion to be cleaned for removing surface contaminates and producing an extremely clean surface to enable the mold portion to be used again and again in a continuous cyclical or in-line process. Portions of the mold surface which are not to be bomdarded by ions, may be masked or shielded during the reverse sputtering operation.