Physical Design Automation of MCMs

Abstract

MultiChip Modules (MCMs) have been introduced as an alternative packag-ing approach to complement the advances taking place in the IC technology. Even though the steps in the physical design cycle of MCMs are similar to those in PCB and IC design cycle, the design tools for PCB and IC cannot be used for MCM directly. This is mainly due to the fact that MCM layout problems are different from both IC layout and PCB layout problems. The existing PCB design tools cannot handle the dense and complex wiring structure of MCMs. On the other hand, IC layout tools are inadequate to decipher the complex electrical, thermal and geometrical constraints of the MCM problems. As a re-sult, the lack of CAD tools for MCMs is impeding further development in this area. Most of the commercial CAD tools available are the adapted versions of existing PCB tools and do not address the real problems associated with the MCM designs. Let us just consider the problem of routing in MCM. The signal effects of long lines in terms of crosstalk, noise, and reflections must be taken into account during routing. In addition, as high speeds are explored, the transmission line behavior of the interconnect must be modeled accurately to optimize the layout. All of these conditions have to be met, subject to the main goal of the interconnect, which is to route the signals between the chips. In designing CAD tools for MCM, many effects have to be taken into consideration such as clock skew, power noise disturbance, assembly effects of thermal mechanical nature that are caused by close positioning of chips, and limitations of assembly equipment. As a result, the design of multichip modules involves several disciplines such as electrical, chemical, material and mechanical engineering.