This paper describes the innovation in single chip package design for mainframe computers coupled with major advances in "Controlled Collapse Chip Connection (C4)" technology, multilayer ceramic technology, and thin-film technology. C4 technology allows the LSI chips to be connected with high integration and high-performance. Applying C4 technology to chip-to-package and package-to-module interconnections provides a higher level of connection pads out from a small package. A new material 96.5 Sn/3.5 Ag for solder joints has been developed to facilitate reliable interconnection where thermal fatigue might have been a problem. The microstructure of a fractured surface and the estimation based on "Finite Element Method (FEM)" are correlated. New material and a process of mullite-glass has been developed to attain a thermal expansion coefficient close to that of silicon. The metallized ceramic technology for the mullite-glass can be applied to the substrate of LSI packages as well as multilayer ceramic multi-chip modules. Thin-film technology has been studied to form high-density wiring on package substrates. Using photolithography technique, it is possible to pattern pads accurately enough for connection to an LSI chip. The polyimide-Al combination can be patterned by subtractive technique using liquid etchants and sputtering. The via formation process is simplified using a photosensitive polyimide so that the fabrication process for multilayer wiring becomes suitable for mass production. Hitachi recently announced the HITAC M-880 Processor Unit which makes extensive use of these technologies. The general features of the LSI package "Micro Carrier for LSI Chip (MCC)" is also outlined.