High performance thin film single chip module

This paper describes development of high density single chip modules for flip chip (C4) area array interconnect such that the electrical, thermal, and reliability needs are met through an optimal tradeoff between system performance and module cost. Prototype test vehicles were designed and built using co-fired alumina as the base carrier for two levels of copper-polyimide thin films containing the bulk of signal wiring and a power/ground plane. Flip-chip die with high melt bumps were joined directly to copper pads on the thin film substrate. Reliability aspects of this interconnect product, such as, wettability and joinability characteristics of thin Cu films and integrity of thin film via interconnections as a function of pre- and post-thermal cycling have been studied. Also, module encapsulation aspects are briefly discussed. The results of electrical characterization of the thin film substrate prior to die attach, as well as simultaneous switching noise measurements with a functional test die are presented.