Synthesis of Hierarchical Structured Cu-Sn Alloy Mesoparticles and Its Application of Cu-Cu Joint Materials

In the synthesis of Cu-Sn alloy nanoparticles, we found that the addition of Tin-Ethylhexanoate provided Cu-Sn alloy mesoparticles, which are aggregates of nanoparticles with a diameter of less than 100 nm. HRTEM observation revealed that Cu-Sn alloy constituent nanoparticles contain plane defects and domains with various crystal orientations. Also, mesoparticles have a Cu2O layer with approximately 4nm thickness on their surface, in which the Cu2O (111) plane is parallel to the Cu (111) plane of the lower layer or is inclined slightly. When Cu-Sn alloy mesoparticles with a composition of Sn: 0.42 at% were used as joint materials of the Cu-Cu joint, the maximum shear stress of the joint interface was measured to be more than 11 MPa. In the case of Cu-Sn alloy mesoparticles with 1.5 at% Sn, the maximum shear stress decreased significantly, which is considered to be attributed to the formation of the Cu-Sn intermetallic compound phase. Therefore, mesoparticles with 0.42 at% Sn may be a strong candidate for a low-cost Cu-Cu joint material, which could be used as joint materials for electronic devices under high temperatures than conventional ones.