Fast pad redistribution from periphery-IO to area-IO

The problem of redistributing IO from bondpads on the periphery of an IC to an array of solder bumps occurs frequently in MCM layout. We show that the commonly held belief that providing enough escapes at the perimeter of the array is not sufficient to guarantee routability of the design. We analyze the even wiring distribution (EWD) routing heuristic and show that it produces designs whose critical wire density is no greater that √2 times the best possible design. Then, we employ the bound on EWD to establish a surprisingly non-monotonic relationship between bump pitch and design routability, and present our implementation of a design system that employs these principles