Wetting confined conformal soldering for large-scale interconnection through AgNW aerogel composite preform

With the development of highly integrated and multifunctional communication, mechanical and aerospace systems, it is increasingly necessary to complete high precision and large-scale conformal packaging on complex structure. Normally, the thermocompression soldering is needed to overcome the thermal deformation caused by bulk heating. However, this process is susceptible to solder overflow for the synergistic effect of gravity and applied pressure. Thus, a composite solder preform of Ag nanowire aerogel and In40Pb60 solder is proposed to enable the confined conformal soldering, and the interfacial reaction and confined wetting mechanism were investigated. The AgNW aerogel features a highly cross-linked nanowire network, which can provide structural flexibility and liquid solder absorption capacity without affecting the metallurgical reactions. Using this composite preform, the liquid solder could be confined, as such 0 % overflow were achieved even under 10 MPa pressure. Meanwhile, compared with pure solder joints, the shear strength was also improved by 125 % for the second-phase strengthening effect. Thus, this AgNW aerogel-solder composite preform can effectively address the uncontrolled solder overflow issue to enable the design and precise integration of large-scale components or circuits on planar and even curved structures.