Influence of nanoparticles content in silver paste on mechanical and electrical properties of LTJT joints

The need to replace Pb-Sn solder has led to research for new, alternative joining methods maintaining comparable, or even better, properties. One of the methods is known as Low Temperature Joining Technique (LTJT). With the development of nanotechnology, usage of silver nanoparticles has been considered. Silver pastes with nanoparticles exhibit the lowest sintering temperatures due to their high surface energy. They have a high content of organic residues, which prevent agglomeration, but on the other hand -increase the porosity of joints in the case of limited ventilation between joined surfaces. In this paper, the authors prove that mixing silver powders with high and low surface areas helps to improve the mechanical and electrical properties of silver joints sintered at low temperature and low pressure. By mixing micro and silver nanoparticles the organic residues content can be reduced while maintaining sufficient sinterability. The authors also show, that the porosity of joints with pastes made by mixing micro and nanoparticle is much lower. The other main advantages of mixing micro and nanoparticles of silver are the higher shear strength and lower resistivity of the joints. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.