Low-temperature Cu-to-Cu bonding using silver nanoparticles stabilised by saturated dodecanoic acid

We developed a new method to prepare silver NP paste that can be used as a Cu-to-Cu bonding material under an additional pressure of 10MPa. This new paste consists of a high concentration of uniform silver NPs with a thin layer of dodecanoate coated on the surface. Shear strengths indicate that the silver NP paste prepared with our method could serve as a bonding material in electronic packaging and interconnections. The microstructure of the interface between the silver and the copper substrate was examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Based on this analysis, a metallic bond is formed at the interface between the sintered Ag layer and both sides of the joint when bonding Cu pads above 250°C.