A novel Cu@Sn@Ag core-shell particles for die attachment in power device packaging

This paper prepares a novel Cu@Sn@Ag core-shell particles as the die attach material. By the method of Transient Liquid Phase (TLP), the power device can be packaged to realize electrical interconnection and heat conduction. After electroless plating by two-step method, the Cu particles can be coated with Sn layer and Ag layer, successively. The resulting Cu@Sn@Ag particles were compressed into preform. After reflow for 15 min at 250°C, the interconnection can be completed between devices and Substrates. According to the results of SEM, EDS, and XRD, the resulting bondline consists of three phases, namely, Cu3Sn, Ag3Sn and Cu, which indicates that the sample after reflow can withstand high temperature (>475 °C, the melting point of Ag3Sn). Besides, the resulting bondline revealed excellent mechanical properties and thermal properties. After shear testing at high temperature (400°C), the average shear strengths can be maintained at 25.3 MPa. After thermal shocks for 500 cycles, the interface between bondline and substrate was effectively interconnected, rather than occurred the failure. As a novel material for die attachment, the Cu@Sn@Ag core-shell particles reveal great potential of exploration in the field of power device packaging.