Solid porous Ag–Ag interface bonding and its application in the die-attached modules
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Solid porous Ag–Ag interface bonding was introduced with the hillocks growth on a solid porous Ag surface. Porous Ag was fabricated on both Cu substrate and Si die by sintering a hybrid Ag paste. The size, density of grown hillocks was investigated at different heating temperature and time to provide an optimized condition in the interface bonding. The growth mechanism of hillocks on the solid porous Ag structure was discussed and analyzed in detail based on stress-induced migration and finite element stress analysis where solid porous Ag was reduced to a polycrystalline structure. The interface between two porous Ag structures bonded together in the die-attached structure with the bonding strength over 30 MPa, considerably stronger than that of traditional Sn–Pb solders. Furthermore, TEM observation revealed that Ag particles with the size of tens nanometers formed between the solid porous Ag–Ag interface, accumulate together and thus bridged the interface. This study provided a new attractive bonding technology based on the solid porous Ag structure in the die-attached module structures for large area bonding and thicker bonding layer design.
This work was supported by the JST Advanced Low Carbon Technology Research and Development Program (ALCA) project “Development of a high frequency GaN power module package technology” (Grant No. JPMJAL1610), the authors also thankful to the Network Joint Research Centre for Materials and Devices, Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials.
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