Relative figures of merit for chip-to-MCM substrate interconnection methods

Functional performance of an electronic system is proportional to the functional throughput rate, which is defined as the product of the function density (gates/cm²) and the clock rate. Various chip-to-module assembly methods for high-density substrates can provide a functional throughput rate approaching that of the integrated circuit (IC). Results of a comparative study for the performance of simultaneously switching off-chip drivers in various multichip module (MCM) scenarios are reported for CMOS and emitter-coupled-logic (ECL) technologies. Flip-chip technology can provide up to twelvefold improvement in performance over tab automated bonding (TAB) for a CMOS system, and about sevenfold improvement for an ECL system. However, when the delay in the critical path is dominated by on-chip circuits, speed improvement by MCM becomes negligible. Electrical parasitics of the chip-to-substrate interconnections also create undershoot in the switching signal, which reduces the noise margin. It is concluded that the advantages of high-density multichip packaging, in decreasing order of importance, are density of integration, reduction in the switching noise, shorter off-chip delays, and reduction in power dissipation