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Reactions in Ag-In System for Bonding Optoelectronic Devices at 180°C
Keywords: Ag-In TLP bonding, High melting temperature, Optoelectronic packaging
There are many optoelectronic devices that are temperature sensitive and require bonding to perform at low temperature. Traditionally, the most common low temperature solder is pure indium with a melting temperature of 156°C. Indium is ductile but weak. The most commonly used solder, Sn-based Pb-free solder, melts at 220°C and has reflow temperature of 260°C. We study the Ag-In binary system and identify the reactions that can be utilized to develop bonding processes performed at 180°C. With right layer Ag-In design, the melting temperature of the resulting joints can increase to 660°C and beyond. In a Ag/In two layer structure, as temperature increases towards 166C, In and Ag react to form AgIn2 compound. When it goes beyond 166℃, AgIn2 decomposes and converts to (L) phase immersed with Ag2In grains, where (L) is the molten phase. The (L) phase can react with Ag layer on the second object to be bonded and grow more Ag2In grains. When (L) is consumed completely, the joint solidifies as Ag2In even at the bonding temperature. The bonding temperature can range from 166 to 205°C. In our bonding process development, 180°C is used with successful results. The understanding of reactions in Ag-In system enables us to develop several bonding processes at 180°C, which should be valuable in optoelectronic packaging that needs low process temperature but high re-melting temperature.
Wen P. Lin, Student
University of California, Irvine
Irvine, CA

  • Amkor
  • ASE
  • Canon
  • Corning
  • EMD Performance Materials
  • Honeywell
  • Indium
  • Kester
  • Kyocera America
  • Master Bond
  • Micro Systems Technologies
  • MRSI
  • Palomar
  • Promex
  • Qualcomm
  • Quik-Pak
  • Raytheon
  • Specialty Coating Systems
  • Technic