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|Universal solders for direct bonding and packaging of opto-electronic devices|
|Keywords: universal solder, low melting point, rare-earth|
|Direct bonding of lead-free solder on opto-electronic materials such as silicon, oxides, nitrides, borides and diamond are highly desired but difficult to achieve at temperatures lower than 300 oC. In this research, the ability of rare-earth-containing lead-free solders to directly wet and bond onto these opto-electronic materials at temperatures between 100 – 300oC was studied. Universal solders that can make direct bonding on opto-electronic materials were made by doping small amounts of rare-earth (RE) metals, such as Lutetium, Cerium, or inexpensive mischmetal rare earth alloy into eutectic Sn-Ag, Sn-Au and Sn-Bi alloys. The bonding strength was in excess of 6.9-13.8 MPa. Melting point of RE-doped universal solder was checked by differential scanning calorimetry (DSC). SEM images showed how RE-metals were dispersed in the solder and cross the interface between solder and the underlying substrates. RE metals were dispersed in the solder matrix and will chemically react with opto-electornic materials to produce strong bonding. The microstructures of the solder bonds were studied. Universal solder can make direct, ohmicl contacts with a variety of opto-electronic materials and produce dimensionally stable and reliable bonding in optical fiber, laser devices, or thermal-management assemblies.|
University of California, San Diego
La Jolla, CA