Abstract: An I.C. die is mounted on a base of an open-tooled package. The open-tooled package comprises a substrate, the substrate having a base, a plurality of sidewalls, and a plurality of leads extending through at least one of the sidewalls. A cavity is formed between the sidewalls of the open-tooled package and the sidewalls of the I.C, die. Electrical connections are made between a plurality of bond pads on said I.C. die and their corresponding leads of said open-tooled package. A first portion of the cavity, enclosing the I.C. die, is filled with a non-conductive material and a second portion of the cavity is filled with a conductive material. In one embodiment, the first portion of the cavity contains leads having electrical connection to the I.C. die and the second portion of the cavity contains leads having electrical connection to ground potential.