Micro-ball wafer bumping for flip chip interconnection

E. Hashino*, K. Shimokawa, Y. Yamamoto, K. Tatsumi

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

12 Citations (Scopus)


A new wafer bumping method using micro-balls was developed that can be used for high-density LSI assembly, specifically for Flip Chip interconnection. Micro solder balls with the diameter ranging from 60 μm to 200 μm were first formed with a high level of accuracy and sphericity. These balls were transferred and bonded to the whole electrode-pads of an 8-inch wafer in one stroke using a fully automated micro ball mounter, which was newly developed. The balls were held on fluxed pads and melted in a reflow furnace. The fluxing was performed using unique stamp system. The productivity and the yield were evaluated under the following conditions. The number of chips on an 8 inch wafer was 616, Pad pitch was 250 μm, Pad number of a chip was 625 (25×25 area array), and the total number of balls on a wafer was 385,000. The yield of forming bumps was confirmed to be higher than 99.995% without repairing and the cycle time of micro ball bumping was ca. 5 min. For an 8 inch wafer. The bump height variation, the bump shear strength and the bond reliability were evaluated in comparison with other methods.

Original languageEnglish
Pages (from-to)957-964
Number of pages8
JournalProceedings - Electronic Components and Technology Conference
Publication statusPublished - 2001 Jan 1
Externally publishedYes
Event51st Electronic Components and Technology Conference - Orlando, FL, United States
Duration: 2001 May 292001 Jun 1

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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