An application of micro-ball wafer bumping to double ball bump for flip chip interconnection

Kohei Tatsumi*, Yukihiro Yamamoto, Keiji Iwata, Eiji Hashino, Shinji Ishikawa, Taro Kohno, Fumio Miyajima, Hideaki Nakazawa

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


Micro-ball wafer bumping method was applied to forming double ball bumps, which increased the bump height to improve the reliability of the flip chip interconnection. The micro solder balls of 100um in diameter were transferred and connected to the whole electrode-pads covered with UBMs(Under Bump Metals) of an 8 inch wafer in one stroke using a fully automated micro ball mounter, which was originally developed. The balls were held on fluxed pads and melted in a reflow furnace. After cleaning the flux residue, the wafer bumped with micro-balls was then encapsulated with epoxy resin containing silica fillers by using Apic Yamada's wafer level molding system. The molding resin was spread to the whole wafer by compressing with a heated flat plate, where the top of the solder bumps were covered with an elastic parting film. The supplied resin volume was previously adjusted to the desired molding thickness. The exposed top of the ball bumps was cleaned and then second micro-ball bumping was processed on the top of the first bumps. The first and second balls were connected by reflowing to form the double ball bumps. The height variation and shear strength of double ball bumps were evaluated. To compare the reliability for the different type of bumps the TCTs and FEM analysis were performed for the chips connected with PCBs.

Original languageEnglish
Pages (from-to)855-860
Number of pages6
JournalProceedings - Electronic Components and Technology Conference
Publication statusPublished - 2005
Externally publishedYes
Event55th Electronic Components and Technology Conference, ECTC - Lake Buena Vista, FL, United States
Duration: 2005 May 312005 Jun 4

ASJC Scopus subject areas

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


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