Abstract: A sheet ceramic package includes a plurality of product units, such as ceramic substrates and circuit substrates for semiconductor devices. The individual product units can be separated from the sheet ceramic package by breaking them apart along snap lines. Each product unit has inner layer conductors for providing external connections to a semiconductor to be packaged therein. A dummy part, with conductor patterns for evaluating the electrical characteristics of corresponding units, surrounds at least partially the periphery of each product unit. Exposed conductors of the product units and the dummy parts are plated by means of electroless plating allowing the product units to be electrically independent of each other because of the absence of the need to apply a uniform plating potential. Semiconductors are packaged into the individual product units and are hermetically sealed.