Ultrasonic bonding between Si-wafer and FR-4 at room temperature using Sn-3.5Ag solder

Sn-3.5Ag 무연 솔더를 이용한 Si-wafer와 FR-4기판의 상온접합

  • 김정모 (서울 시립대학교 신소재공학과) ;
  • 조선연 (서울 시립대학교 신소재공학과) ;
  • 김규석 (서울 시립대학교 신소재공학과) ;
  • 이영우 (서울 시립대학교 신소재공학과) ;
  • 정재필 (서울 시립대학교 신소재공학과)
  • Published : 2005.06.23

Abstract

Ultrasonic soldering using of Si-wafer to FR-4 PCB atroom temperature was investigated. Sn3.5Ag foil rolled $100{\mu}m$ was used for solder. The UBM of Si-die was Cu/ Ni/ Al from top to bottom and its thickness was $0.4{\mu}m$, $0.4{\mu}m$, $0.3{\mu}m$ respectively. Pad on FR-4 PCB comprised of Au/ Ni/ Cu from top to bottom and its thickness was $0.05{\mu}m$, $5{\mu}m$, $18{\mu}m$ respectively. The ultrasonic soldering time was changed from 0.5sec to 3.0sec and its power 1400W. As experimental result, reliable bond joint by ultrasonic at room temperature was obtained. The shear strength increased with soldering time up to 2.5 sec. That means at 2.5sec, the shear strength showed maximum rate of 65.23N. The strength decreased to 33.90N at 3.0 sec because the cracks generated along the intermetallic compound between Si-wafer and Sn-3.5mass%Ag solder. intermetallic compound produced by ultrasonic between the solder and the Si-die was $(Cu, Ni)_{6}Sn_{5}$ and the intermetallic compound between solder and pad on FR-4 was $(Ni, Cu)_{3}Sn_{4}$.

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