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Abstract We investigated the effect of Ag-coated multi-walled carbon nanotubes (Ag-MWCNT) on the microstructures and electromigration behaviors of a Sn58%Bi solder and organic solderability preservative (OSP) surface finished on the FR-4 printed circuit board (PCB) joint under a current stress of 3000 A/cm2 at 100 °C. Electromigration of Ag-MWCNT Sn58%Bi composite solder was investigated by daisy-chain test-kit. Reaction layers formed at the anode side and cathode side of the Sn58%Bi solder joints consisted of three microstructures; Bi-rich layer, Sn-rich layer, and intermetallic compounds (IMCs, Cu 6 Sn 5 and Cu 3 Sn). The Bi-rich layer was mainly formed at the anode side in the couple of the Sn58%Bi solder joint with various times of applying current stress. The Bi-rich layer of the Ag-MWCNT Sn58%Bi composite solder joint was approximately 2 times thinner than that of the Sn58%Bi solder joint because the Ag-MWCNT acts as a diffusion barrier. Also, the Cu 6 Sn 5 and Cu 3 Sn IMCs that formed at the interface between the Ag-MWCNT Sn58%Bi composite solder joints were thinner than those of the Sn58%Bi solder joints. The time to failure (TTF) was longest at the 0.05% Ag-MWCNT Sn58%Bi composite solder joint. Therefore, Ag MWCNT is expected to improve the reliability of electromigration in the Sn58%Bi composite solder joint. Highlights • The electromigration of the Ag-MWCNT Sn58%Bi composite solders were investigated. • Ag-coated MWCNTs were widely distributed in the Sn58%Bi solder joint. • MWCNT suppressed growths of Cu-Sn IMCs and Bi-rich layer under current stress. • TTF value of the 0.05 wt% Ag-MWCNT Sn58%Bi composite solder joint was the longest. [ABSTRACT FROM AUTHOR]

Nickel-decorated multi-walled carbon nanotubes (Ni-MWCNTs) were synthesized using a colloidal method and an electroless plating method to form Ni nanoparticles on the surface of MWCNTs. The Ni electroless plating process was optimized with solutions at various pH (5, 6, 7, and 8) levels. The Ni-MWCNTs fabricated at pH 7 show the most stable Ni nanoparticles on the surface of the MWNCTs. After optimization of the Ni plating process, the Ni-MWCNTs/Sn-58Bi composite solder were fabricated with varying contents of (0, 0.05, 0.1 and 0.2 wt%) Ni-MWCNTs. The experimental results show that Ni-MWCNTs enhance the mechanical properties of Sn-58Bi solder. The shear strength of Sn-58Bi solder improves by about 14% with 0.1 wt% Ni-MWCNTs. Furthermore, the microstructure evolution after a high temperature storage test shows that Ni-MWCNTs have an effect on grain refining and interrupt growth of the Intermetallic compound layer. The distribution of Ni-MWCNTs could be recognized with the results of EPMA. [ABSTRACT FROM AUTHOR]

A carbon nanotube (CNT) has remarkable properties, but it has disadvantages in application because of its dispersal- and bonding-related issues. Metal–CNT composite materials are necessary in solving these problems. In this study, nickel (Ni)–multi-walled CNTs (Ni–MWCNTs) are synthesized through sequential processing, functionalizing, and electroless plating processes to deposit Ni nanoparticles on MWCNTs. The synthesized Ni–MWCNTs are used to fabricate composite solders with various contents (0, 0.05, 0.1, and 0.2 wt%). The test kit used for the 3-point bending test in this study is designed with a differential package structure to evaluate the bending reliabilities of the Ni–MWCNT composite materials with various contents. The crack initiation and propagation in the microstructure evolution solder joints are also investigated. The bending reliabilities improve with the BGA structure and indicate that the highest bending cycle fails with 0.1 wt% of Ni–MWCNTs. The chemical composition and distribution of the Ni–MWCNTs in the solder joints are investigated with electron probe microanalysis. • Test-kits for 3-point bending test were designed with differential structure. • Bending test was performed to evaluate the mechanical properties of solder joints. • Ni-MWCNTs composite solder could improve the bending reliability of Sn58Bi solder. [ABSTRACT FROM AUTHOR]