Summary form only given. At high frequencies, material properties and properties of signal lines/interconnects are equally important. Thus, the present study deals with material (molding compound) characterization and modeling and characterization of lead frames and bond wires. While the microwave characterization of molding compounds can be utilized in a variety of plastic package structures, the objective of the modeling was to develop an electrical model of the 16 lead SOIC plastic package, which is popular for packaging wireless RFICs. The developed models have been successfully used by ITT GTC in developing a new generation of power amplifier RFICs. Measurement results, error analysis, and time domain package modeling techniques are presented.