Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Novel Low-Volume Solder-on-Pad Process for Fine Pitch Cu Pillar Bump Interconnection

  • Bae, Hyun-Cheol (Energy Harvesting Devices Research Section, Information & Communications Core Technology Research Laboratory) ;
  • Lee, Haksun (Energy Harvesting Devices Research Section, Information & Communications Core Technology Research Laboratory) ;
  • Eom, Yong-Sung (Energy Harvesting Devices Research Section, Information & Communications Core Technology Research Laboratory) ;
  • Choi, Kwang-Seong (Energy Harvesting Devices Research Section, Information & Communications Core Technology Research Laboratory)
  • Received : 2015.06.10
  • Accepted : 2015.06.19
  • Published : 2015.06.30
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Abstract

Novel low-volume solder-on-pad (SoP) process is proposed for a fine pitch Cu pillar bump interconnection. A novel solder bumping material (SBM) has been developed for the $60{\mu}m$ pitch SoP using screen printing process. SBM, which is composed of ternary Sn-3.0Ag-0.5Cu (SAC305) solder powder and a polymer resin, is a paste material to perform a fine-pitch SoP in place of the electroplating process. By optimizing the volumetric ratio of the resin, deoxidizing agent, and SAC305 solder powder; the oxide layers on the solder powder and Cu pads are successfully removed during the bumping process without additional treatment or equipment. The Si chip and substrate with daisy-chain pattern are fabricated to develop the fine pitch SoP process and evaluate the fine-pitch interconnection. The fabricated Si substrate has 6724 under bump metallization (UBM) with a $45{\mu}m$ diameter and $60{\mu}m$ pitch. The Si chip with Cu pillar bump is flip chip bonded with the SoP formed substrate using an underfill material with fluxing features. Using the fluxing underfill material is advantageous since it eliminates the flux cleaning process and capillary flow process of underfill. The optimized interconnection process has been validated by the electrical characterization of the daisy-chain pattern. This work is the first report on a successful operation of a fine-pitch SoP and micro bump interconnection using a screen printing process.

Keywords

References

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