Heterogeneous Bonding with Nanostructured Silver Langmuir-Blodgett Film

In this paper, an alternative approach of using Langmuir-Blodgett film is proposed to address the issue of heterostructure interconnection between metal substrate and ceramic substrate as dummy wafer. Silver nanoparticles were synthesized in an aqueous reductive bath, modified to be hydrophobic by an alkyl thiol, and dispersed into dichloromethane. Through the liquid-gas interface and solvent polarity interaction, the nanostructured silver Langmuir-Blodgett film is formed on the water, which is then transferred onto the alumina substrate by a lifting machine of materials. Vacuum pumping and nitrogen flooding controlled an oxygen-free sintering and bonding ambience atmosphere at 300°C. A shear test and scanning electron microscope (SEM) were used to detect the heterogeneous bonding layer. The resistivities of the as-coated and sintered silver film are measured by the van der Pauw method, and their difference is as large as seven orders of magnitude. This proposed method represents another solution to realizing heterogeneous interconnection in electronic packaging.