Micro-ball bump for flip chip interconnections

Kenji Shimokawa, Eiji Hashino, Yoshio Ohzeki, Kohei Tatsumi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

14 Citations (Scopus)


Micro-ball bump technology has been developed for flip (FC) interconnections. This technology is based on (1) a production method of fine metal balls (micro-balls) and (2) a gang-bonding method for forming bumps (micro-ball bumps) on chip electrodes. Solder balls of 60-150 mm and gold balls of 35-100 mm in diameter were prepared with extremely uniform diameters and high sphericity. After holding these micro-balls on through-holes of an arrangement plate by a vacuum suction method, the micro-balls were transferred onto the electrodes of the chips in order to form the micro-ball bumps. An excess ball eliminating system and a ball bouncing system were developed for arranging the ball successfully on the plate. The cycle time of the originally developed mounter was 20 seconds for a chip with 300 bumps. Both bumping on a single chip and on multiple chips in a wafer were possible. The micro-solder bumps were formed onto the electrodes covered with under bump metals (UBMs). The micro-solder-balls of 150 mm in diameter were transferred onto the flux printed electrodes of a chip with 220 mm pitch and 45×45 area array. The micro-solder bumps were uniform in composition, volume, and height because of the use of the micro-solder-balls with precisely controlled diameter and composition. Using the micro-gold-balls of 35 mm in diameter, the bumps with 50 mm pitch were formed on Al pads by means of thermocompression bonding. Proposed micro-ball bump technology could be applied to bumping not only for FC interconnections, but also for TABs.

Original languageEnglish
Title of host publicationProceedings - Electronic Components and Technology Conference
Number of pages5
Publication statusPublished - 1998
Externally publishedYes
EventProceedings of the 1998 48th Electronic Components & Technology Conference - Seattle, WA, USA
Duration: 1998 May 251998 May 28


OtherProceedings of the 1998 48th Electronic Components & Technology Conference
CitySeattle, WA, USA


ASJC Scopus subject areas

  • Electrical and Electronic Engineering

Cite this

Shimokawa, K., Hashino, E., Ohzeki, Y., & Tatsumi, K. (1998). Micro-ball bump for flip chip interconnections. In Proceedings - Electronic Components and Technology Conference (pp. 1472-1476). IEEE.