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Chip on Glass (COG) technology is widely used to mount driver ICs on Liquid Crystal Display (LCD) substrates. This paper reports the development of Resin Core Bump technology as a novel COG technology. Unlike conventional COG bonding with Anisotropic Conductive Film (ACF), Resin Core Bump structures form stable interconnections by direct contact between the bump and the substrate. Moreover, the bump and its bonding structures are optimized to achieve a fine-pitch interconnection. Pitches as fine as 10 μm have been attained with 40 μm-pitch samples. In this study, we evaluated the fine pitch bondability and interconnection reliability of Resin Core Bumps using 20 μm pitch test samples. The ability to compensate for bonding accuracy by shrinking the bump width was also evaluated. Reliability was evaluated by a thermal cycle test. The initial contact resistance was even more stable than with a 40 μm conventional COG structure. The maximum resistance increment was less than 2.0 Ω after 2000 cycles.

Active Si Interposers (ASI), which are device chips with through Si vias (TSVs) and redistribution wirings, are the focus of this study. A feature of the module is that the redistribution layer includes a stress buffer layer so that stress can be alleviated when it is mounted on a motherboard. For the purpose of this study, it was decided to conduct the process from the backside of the wafer for efficiency of production. One feature of this process is that a device wafer was processed with a glass wafer supported throughout the TSVs' process in order to facilitate process of a thin wafer. However, the maximum temperature of each process was limited. We addressed this problem by the optimization of some of the equipment and the modification of the adhesive that attaches the device wafer to a glass wafer. Finally, a module that was a combination with the ASI and a certain device operated normally. In the last part of this study, the results of the evaluation that studied the impact on the devices of the TSVs' process are presented.

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