Low-temperature flexible composite preform based on silver nanowires aerogel and SnBi58 solder

Complex structures have recently found extensive application in flexible electronics systems, including wearable electronics, electronic textiles, and structural health monitoring. Owing to the diverse manufacturing conditions of flexible structures, the operability of microelectronic packaging encounters great difficulties. This work proposes a low-temperature flexible preform composed of silver nanowires (AgNW) aerogel and SnBi58 solder. The AgNW aerogel, formed by the self-assembly and cross-linking of silver nanowires, exhibits excellent deformation capabilities to act as a solder carrier. Therefore, the preform can adaptively deform to match curved, V-shaped, and stepped surfaces during alignment. The results show that the preform can effectively control the wetting area, preventing solder overflow and excessive spreading during reflow. The joints exhibit a unique near-continuous horizontal distribution of Ag 3 Sn near the pads and a gradient Ag 3 Sn in the joints, observed for the first time in SnBi58 joint. The preform joint achieved a shear strength of 78.9 MPa through mechanisms such as grain refinement, precipitation hardening, and back stress hardening. Furthermore, this work provides new insights and possibilities for the design and application of low-temperature solder in the future flexible electronics.