MCM-D/C packaging solution for IBM latest S/390 servers

The G5, the most recent member of the S390 server family, was announced in May 1998. The multichip module (MCM) at the heart of the G5 system consists of 29 CMOS chips on a 127.5 mm glass ceramic substrate with 6 levels of thin films (TF) including 1 signal plane pair. System performance of the G5 exceeds 1000 MIPS. This breakthrough performance resulted from the synergy created by combining IBM's leadership technologies in CMOS high frequency microprocessor design with advanced packaging and flip chip interconnections. From a substrate perspective. IBM moved from alumina ceramic with molybdenum (Mo) conductor to cordurite/glass ceramic, and copper (Cu) conductor, and from TF redistribution (4 levels) to TF wiring (6 levels). This paper discusses the TF implications from a change of substrate material and increased wiring density, as well as the need to implement a polyimide cushion layer as part of a pin grid array (PGA) fabrication process that supports 4224 I/O's.