Title :
A fine pitch COG technique for a TFT-LCD panel using an indium alloy
Author :
Mori, Miki ; Kizaki, Yukio ; Saito, Masayuki ; Hongu, Akinori
Author_Institution :
Res. & Dev. Center, Toshiba Corp., Yokohama, Japan
fDate :
12/1/1993 12:00:00 AM
Abstract :
A fine-pitch chip-on-glass (COG) bonding technique for liquid-crystal display (LCD) panels is described. An IC chip with gold (Au) bumps was dipped in a stirred indium-tin (InSn) alloy bath in a nitrogen atmosphere without flux. Shallow-bowl-shaped InSn alloy bumps were selectively formed on the Au bumps on the IC electrodes. The minimum examined bump pitch was 50 μm, and the bump size was 31×31 μm. The InSn alloy bumps, which had minimum pitch of 100 μm, were connected to molybdenum (Mo) conductors without flux at low pressure (30 gf/bump or less) and low temperature (110°C or less). The temperature was lower than the alloy melting point. The mean contact resistance was 0.78 Ω. The technique allows easy repair. A thermal shock test, a high-temperature and high-humidity storage test, and a high-temperature storage test showed that the contact resistance changes satisfied the specification, which allows up to 10 Ω. Prototype thin-film-transistor (TFT) LCD panels with 80-μm pitch-driver ICs were developed using the new bonding method
Keywords :
circuit reliability; contact resistance; gold; indium alloys; liquid crystal displays; microassembling; molybdenum; surface mount technology; tin alloys; 0.78 ohm; 110 C; 50 micron; 80 micron; Au bumps; Au-InSn-Mo; IC chip; IC electrodes; Mo conductors; N2; N2 atmosphere; TFT-LCD panel; chip-on-glass bonding; contact resistance; dipping method; driver ICs; fine pitch COG technique; high-humidity storage test; high-temperature storage test; liquid-crystal display; shallow-bowl-shaped alloy bumps; stirred InSn alloy bath; thermal shock test; thin-film-transistor; Atmosphere; Bonding; Contact resistance; Electrodes; Gold alloys; Indium; Liquid crystal displays; Nitrogen; Temperature; Testing;
Journal_Title :
Components, Hybrids, and Manufacturing Technology, IEEE Transactions on
