Alteration of Cu3Sn growth and retention of multi-orientation Cu6Sn5 during thermal aging in Cu-xNi-yZn/Sn3.5Ag/Cu transient liquid-phase bonding

Abstract

With the development of the artificial intelligence (AI) industries, electronic packaging is developing in the direction of high-density, high efficiency and multi-functionality. To realize the high density and tiny scale interconnection, application of microbumps is inevitable. Thus, the mechanical and thermal properties of intermetallic compounds (IMCs) become quite important as the proportion of IMC in the bump is greatly increased. In this study, three types of full IMCs bump, Cu/Sn-3.5Ag(SA)/Cu, Cu18Ni/SA/Cu and Cu18Ni18Zn/SA/Cu, were fabricated through transient liquid phase (TLP) bonding. The evolution of orientation and the sizes of the Cu6Sn5 grain before and after long-term thermal aging were analyzed and compared. After long-term thermal aging, the full IMCs bump with Ni and Zn added into Cu substrate simultaneously maintained consistent structure. In addition, the unusual growth of network-like Cu3Sn was observed in Cu18Ni/SA/Cu. Furthermore, the mechanical test and fracture cross-section analysis were conducted to discuss the crack paths. The study focused on establish the correlation between microstructure and mechanical performance. Network-like Cu3Sn was considered to enhance the strength of interfaces. Finally, the full IMCs bump which demonstrated the extraordinary thermal stability provided a reliable microstructure for application.