New technologies to improve density on multichip modules

It is pointed out that the multichip module on cofired ceramic substrate is a promising technology for high-performance systems. The reduction of feature size and the possibility of obtaining vias and conductors at the same pitch allow increased density and wiring flexibility. However, vias crossing through several levels at fixed positions reduce connectivity to such an extent that they occupy two places on each metal level with conventional technology. Design considerations for improving the density and processing in order to obtain stacked vias are discussed. It is shown that a judicious distribution of fixed trough vias allows a reduction of the pitch of the chips. In addition, when stacked vias are possible, the space, needed for vias is reduced by almost 30%, leaving better availability for wiring.<
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