Effects of impurities on void formation at the interface between Sn-3.0Ag-0.5Cu and Cu electroplated films

Abstract

Void formation is a critical reliability concern for solder joints in electronic packaging. The control of microstructures and impurity quantities in Cu electroplated lms signi cantly affects the void formation at the joint interface, but the studies for their comparison are seldom. In this study, three Cu lms (termed as A, B, and C) are fabricated using an electroplating process. The Cu A lm has a facted grain texture embedded with twins while Cu B and C have a similar columnar texture. After thermal aging at 200°C for 1000 h, the SAC 305 (Sn-3.0Ag-0.5Cu) solder joints with Cu A and B exhibit a robust interfacial structure without voids. However, microstructural collapse is observed in the solder joint of SAC 305/Cu C, where many crevives parallel to the interface are formed. Based on the microanalysis, the concentration of impurity is higher in the Cu C lm than those in Cu A and B. Moreover, discrete voids rather than continuous crevices are presented in the SAC305/Cu C system when the impurity concentration in Cu C is reduced. The ndings demonstrate that the impurity control in the Cu electroplated lm is critical for the control of void/crevice formation in the electronic solder joints.

Significant Hall–Petch effect in micro-nanocrystalline electroplated copper controlled by SPS concentration

“…Moreover, the process occurred at room temperature and did not provide sufficient kinetic energy to migrate the grain boundaries blocked by the impurities. Therefore, if there are numerous impurities in the electroplated Cu, the grain size is typically small 31 . This inference is supported by SIMS analysis of chloride, carbon, sulfur, and oxygen in the electroplated Cu foils of PC, PCS0.2, PCS0.5, PCS1.0, and PCS2.0, as shown in Fig.…”

Void-free interface between in and high-impurity Cu joint

“…These correspond to the microstructural images shown in Figures 5 and 6. In previous studies, impurities of Cu normally induced serious Kirkendall voids formed at the interface of Sn-rich solder joints [7,14,24]. In this study, the findings demonstrate that void formation at the interface did not occur in the In/Cu joints with high impurities.…”

“…In Sn-rich solder/Cu joints, voids are formed in the interfacial layer of the Cu 3 Sn IMC because of the rapid diffusion of Cu into the Sn-rich solder. Additionally, the concentration of impurities in electroplated Cu could affect the degree of void formation [24]. When there is a high concentration of impurities in Cu, these impurities create more incoherent lattice sites in the Cu crystal, resulting in a high concentration of vacancies in the Cu crystal.…”