Manabu Bonkohara

Ultra-high-density interconnection technology of three-dimensional packaging

Abstract The study of 20-μm-pitch interconnection technology of three-dimensional (3D) packaging focused on reliability, ultrasonic flip–chip bonding and Cu bump bonding is described. The interconnection life under a temperature cycling test (TCT) was at an acceptable level for semiconductor packages. Failure analysis and finite element analysis revealed the effect of material properties. Basic studies on ultrasonic flip–chip bonding and very small Cu bump formation were investigated for low-stress bonding methods. The accuracy of ultrasonic flip–chip bonding was almost the same level as that of thermocompression bonding and the electrical connection was also confirmed. Atomic-level bonding was established at the interface of Au bumps. For Cu bump bonding, a dry process was applied for under bump metallurgy (UBM) removal. Electroless Sn diffusion in Cu was investigated and the results clarified that the intermetallic layer was formed just after plating. Finally, we succeeded in building a stacked chip sample with 20-μm-pitch interconnections.

An approach to the low cost flip-chip technology development with punched-out solder disks by micro-press punching method

A new low cost bare-chip LSI inter-connection lead-less-chip technology was installed by Au ball-bump (1976) and Ag-Sn solder on the printed wiring board under none flux condition. Au ball-bumps were made on the LSI Al pads directly by conventional wire bonding method and Ag-Sn bumps on the leads of the build-up processed PWB by the solder micro-press punching technology less than 120 microns pads-pitch. This micro-press punching technology has reached the higher stability of 500,000 times continuously at nearly 0.1 sec/piece speed with 50 /spl mu/m thickness soft solder tape. And the diameter of punched-out solder disk was realized at 50 /spl mu/m level on the tips of the PWB pads directly. This lead-less-chip technology of the flip-chip assembly on MCM-L, has the high reliability and the low cost possibility.

Mcm Development Using Fine Pitch Ball Bump

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.