A method for producing a completed base cap for a plastic package sealing a semi-conductor therein includes the steps of forming the initial body of a plastic base cap including a centrally located hollow recess on one side thereof, placing lead frames on said base cap body in such a manner that the terminal end portions of said individual leads rest on the peripheral land of said base cap body surrounding said central recess, and forming outer side sections to the base cap including a step shoulder on the top side thereof by molding the same integrally with said lead frame and said initial body such that an intermediate portion of each of said leads adjacent their inner terminal end portions is embedded within said outer side sections of the base cap. A liquid honing step is provided on the base cap shoulder after the formation thereof, and to the inner terminal end portions of the leads.