Demand has recently increased for high packaging density and memory capacity of memory modules for electronic equipment. Our new three-dimensional memory (3-DM) module [1] satisfies this demand. This module has almost the same size as single memory packages [thin small outline packages (TSOPs): 17.4 2 9.22 2 1.2 mm] currently being used, and a package density four times as large. Electrical performance is better than that of TSOP's because the length of its wires is about half that of TSOP's wires. Moreover, the cost of fabrication this module is low. This paper reports the module's characteristics and fabrication process. The design concept is that next-generation memory devices will be produced by using current mass-produced memory devices.
A fine-pitch ( less than 100 micro-meter pads pitch ) aluminum pad flip chip assembly technology for use with the built-up Printed Wiring Boards (PWB) has been developed and named “Lead-Less-Chip Assembly (LLC Assembly)” technology. Our newly developed technology consists of three points: Forming gold-ball-bumps on the aluminum pads of the bare LSI chip by a wire ball bonding method. Solder-coating on the copper pads of the built-up PWB using Micro Punching technology or the Super-Juffit technology. Flux-less solder bonding the bare chip onto the PWB with a nitrogen atmosphere.A reliability evaluation performed on a single chip and multi chip modules assembled using this LLC Assembly technology with test chips and real C-MOS devices showed a high level of endurance. We have applied this technology to Multichip modules (MCMs) for Note Personal Computers and portable terminals.
A new low cost Bare-Chip LSI inter-connection Lead-Less-Chip technology wcis installed by Au Ball-B~iiip ' I 1 and Ag-Sn solder on the printed wiring board under none flux condition. Au Ball-Bumps were mcide on the LSI A1 pads directly by conventional wire bonding method and Ag-Sn bumps on the leads of the build-up processed PWB by our newly developed SOLDER-MICRO-PRESS-PUNCHING technology ' at less than 120 microns pads-pitch. This micro-press punching technology has reached the higher stability of 500,000 times continuously at nearly O.Isec/piece speed with 50 micro-meter thickness soft solder tape. And the diameter of punched-out solder dirk wcis renlizecl at 50 micro-meter level on the tips of the PWB pncls directlv. Thir Lead-Less-Chip technology of the flip-chip nssembly on MCM-L, has the high reliability and the low cost possibility.
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