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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]

A Cu-cored solder ball (CCSB) is often used as the interconnection material for 3D package. The CCSB has a Cu core surrounded by Sn-Ag-Cu alloy. The effect of the Cu core on mechanical reliability of the CCSB was investigated using thermal shock test. Microstructure and thermal shock reliability of the CCSB with organic solderability preservative (OSP) surface finish was compared with that of Sn-3.0wt.%Ag-0.5wt.%Cu (SAC) solder. The thermal shock test was performed in the temperature range of −40 °C to 125 °C in compliance with JESD22-A104. Failure mechanism was analyzed by finite element method analysis. Average number of thermal shock cycles for the CCSB/OSP joints was 1.15 times higher than that for SAC/OSP joints. Maximum value of simulated plastic strain for the SAC/OSP joints was 1.25 times higher than that for the CCSB/OSP joints because the stand-off height of the CCSB/OSP joints could be maintained by the Cu core. • Thermal shock reliability of Cu cored solder joint was investigated. • Simulated stress and strain were reduced because stand-off height of solder ball was maintained by Cu core. • Crack of solder joint was propagated through the solder matrix that was highest simulated plastic strain regions. • Thermal shock reliability of solder joint was improved due to stand-off height. [ABSTRACT FROM AUTHOR]