Flux-free Flexible Bonding Based on Silver Aerogel Reinforced by Ag-Cu Solid Solution Nanoparticles

Integrating functional devices on 3D surfaces expands the capabilities of the original matrix in terms of sensors, display and detection. However, the size and structural characteristics of different systems vary greatly, which brings great difficulties to alignment and mounting. In this paper, a novel flexible composite preform, composed of silver nanowire aerogel and Ag-Cu solid solution nanoparticles, is proposed to enable the flexible packaging on complex structures. The three-dimensional porous silver nanowires network inside the aerogel can provide a dispersion space for Ag-Cu solid solution nanoparticles and adaptively fill various surface structures with its unique characteristics of free deformation, stress absorption and gap filling of silver nanowires aerogel. Meanwhile, alloy nanoparticles of 50 nm-200 nm can be successfully incorporated into the aerogel with an average pore diameter of 5 μm-15 μm. From the results, the proportion of the alloy nanoparticles can reach more than 50 wt.%, as the massive silver nanowires can provide a large number of sites for adsorption. With the appropriate time and pressure applied, the bonding strength can reach over 50.6 MPa at room condition and 20.4 MPa at 350 °C high temperature, because the additional alloy nanoparticles can promote the sintering reaction and inhibit the generation of voids during the sintering process. Similar strength properties can also be obtained at large sizes, indicating that the composite preform has good dimensional compatibility. Therefore, these unique properties make the proposed composite silver nanowires aerogel preform suitable for the packaging and manufacturing of flexible electronic devices without organic. And it also provides a new way for the adaptive bonding process of non-planar structure with the requirements of low temperature mounting but high temperature service.