Size-Controlled Low-Melting-Point-Alloy Particle-Incorporated Transient Liquid-Phase Epoxy Composite Conductive Adhesive with High Performances

With fast developments in the environmental friendly industry, electrically conductive adhesive (ECA) composites with high electrical conductivity, mechanical strength, and electrochemical migration resistance as well as low cost are highly desirable for emerging power electronics applications. In this study, a category of ECAs, namely, size-controllable sonochemical low melting-point-alloy (LMPA) particle-incorporated transient liquid phase ECAs (TLP-ECAs), with excellent electrical conductivity, considerable mechanical strength, and high electrochemical migration resistance has been successfully demonstrated. Experimental results showed that the bulk resistivity of TLP-ECA decreased to a minimum value of 2.37 x 10-4 Cl-cm with the remaining filler content at a low level (the total content of metallic fillers, i.e., 70 wt % in TLP-ECAs), while the mechanical shear strength increased considerably (by 55.4%) compared with pure silver ECA with the same filler content, demonstrating that addition of sonochemical LMPA particles into ECA can simultaneously and considerably improve the electrical and mechanical properties. Moreover, the diffusional reaction mechanism of sonochemical LMPA particle-filled TLP-ECA was systematically investigated via differential scanning calorimetry (DSC), X-ray diffraction (XRD), and high-resolution scanning transmission electron microscopy in high-resolution high-angle annular dark-field mode (STEM-HAADF). The mechanism of the diffusion reaction of TLP-ECA with LMPA particles was rationalized, where Ag9In4 (gamma phase, cP52, and P43m) and Ag3Sn (epsilon phase, oP8, and Pmmm) intermetallic compounds (IMC) and their corresponding nanostructures were responsible for the substantial enhancement in mechanical strength and the antielectrochemical migration property. The sonochemical method is the key to synthesize LMPA particles of desirable compositions and controllable size, thereby enhancing the overall performance of Ag-based TLP-ECAs. Accordingly, the sonochemical LMPA particle-incorporated-TLP-ECAs are the promising interconnection material candidates for power electronics packaging.