Signal propagation characteristics for thin film, glass-ceramic and alumina based MCM

The authors describe the signal propagation characteristics in three types of package wiring media, namely, thin-film Cu in polyimide (MCM-D), thick-film Cu in glass-ceramic (MCM-C), and thick-film Mo in alumina (MCM-C). The transmission line parameters for the thin-film (MCM-D) and thick-film (MCM-C) package are modeled as a function of frequency using electrostatic and full-wave, electromagnetic programs. The frequency-dependent signal propagation characteristics for the thin and thick film wiring media are compared. Although the TF wiring in the current high density results in lower time-of-flight delay it suffers from higher attenuation, especially for longer nets, leading to risetime degradation and potential circuit delay. Thus, the total net delay including the driver and receiver should be used in choosing a wiring medium for a given system application. The extent of skin effect losses in the signal propagation characteristics were examined for the three types of wiring media. The results of circuit simulations show that the skin effect losses are much more dominant in defining the risetimes for TF wiring as compared to those of the thick-film media