Microstructural stability of Ag sinter joining in thermal cycling

Are Sintered Silver Joints Ready for Use as Interconnect Material in Microelectronic Packaging?

“…74 Another explanation for this observation in Table III is that the sintered nano-Ag joints had a higher density than the micron-Ag joints, although this postulate cannot be confirmed because the density for the micron Ag joints was not reported, 63 while the density for the nano-Ag joints was only 80.4 %. 64 In a related study, Suganuma and coworkers 66 researched the influence of Ag-filler shapes on the thermal-fatigue resistance of sintered Ag joints. Nanometer-thick Ag flakes produced sintered Ag joints that continued to densify and achieve higher die shear strengths during thermalcycling tests.…”

“…This mechanism of increasing diffusion and density during thermal cycling was not observed for sintered Ag joints fabricated from Ag nanoparticles and Ag micron flakes. 66 Therefore, it is important to consider the density of a sintered Ag joint instead of the shapes or sizes of the Ag fillers to understand the thermal-fatigue resistance of the joint.…”

“…The inability to accommodate plastic deformation normally results in low fatigue resistance. How is it possible, then, for a sintered Ag joint of high elastic modulus to accommodate less plastic deformation and yet undergo more cycles to failure, as indicated by results presented earlier 66 ? One possible explanation for this anomaly is that the shear strength increases more rapidly than the elastic modulus with increasing density.…”

“…Depending on the plating conditions, a Ag plating of 4 lm in thickness would still be relatively porous, and the oxidation of the underlying copper would increase the CTE mismatch between the copper and the Ag plating, resulting in early thermal-fatigue failure. 66 The formation of Kirkendall voids in the interfacial regions further exacerbate this thermal-fatigue failure. 65,66 Among the various substrates on the market, bare copper has emerged as the most desirable surface for Ag joints.…”

“…66 The formation of Kirkendall voids in the interfacial regions further exacerbate this thermal-fatigue failure. 65,66 Among the various substrates on the market, bare copper has emerged as the most desirable surface for Ag joints. In one thermal-cycling study that used bare copper as a substrate, air-sintered Ag joints exhibited higher thermal and electrical resistance than Ag joints formed in a nitrogen atmosphere.…”