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Flip-Chip Interconnection Technology for Packaging of VLSI Operated in Liquid Nitrogen
Kaoru HASHIMOTO Masayuki OCHIAI Kazuaki KARASAWA Teru NAKANISHI
IEICE TRANSACTIONS on Electronics
Publication Date: 1991/08/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Advanced Packaging Technology for Microelectronics Manufacturing)
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To study a flip-chip connection technology for packaging of VLSIs operated in liquid nitrogen, solder and metallization materials were examined. Flip-chip connection models which consisted of Si and GaAs model chips and alumina substrate were made using four kinds of solders; indium (In), In-48%Sn, In-40%Pb, and Sn-37%Pb (percent symbol stands for mass percent). The fatigue lives of flip-chip solder joints were measured by thermal shock tests between liquid nitrogen and room temperatures. The wettability and dissolution between the In solder and Au, Cu, Pd, Ni, Pt, Au/Cu, Au/Pd, Au/Ni and Au/Pt metallization films were also investigated. The In and In alloy solders exhibit longer fatigue life than Sn-Pb solder, when used with GaAs chips as well as Si chips. In solder shows the longest fatigue life. The Au film has good wettability with In solder, and the Pt film is extremely resistant to dissolution into In solder. Experimental results indicate that In and In alloy solders are suitable for Si and GaAs flip-chip connections in liquid nitrogen, and that Au/Pt/Ti metallization films are suitable for use with In solder for flip-chip connections in liquid nitrogen. A random number generator was assembled with HEMT LSI chips and a multilayer ceramic circuit board, using flip-chip connection with In solder and Au/Pt/Ti metallization film. This equipment generates random numbers with a clock cycle of 1.49 ns in liquid nitrogen, and operates properly after several hundred cycles between liquid nitrogen and room temperatures.