Fabrication and interfacial reaction of carbon nanotube-embedded Sn-3.5Ag solder balls for ball grid arrays

Carbon nanotubes (CNTs) that incorporated Sn-3.5Ag solder balls were fabricated by a surface impact mixing (SIM) process. The SIM process consisted of a ball milling process that provided enough impact energy for CNT embedding on the solder surface and at the same time, maintained the size and shape of the solder balls. As the SIM time increased, the density of the embedded CNTs on the solder surface increased and the entire solder surface was covered with CNTs after 24 h of the SIM process. The shear strength of the CNT-embedded Sn-3.5Ag solder balls increased by 10% after the 24 h-SIM process. The thickness of the intermetallic compound (IMC) layer between the solder and Ni decreased when CNTs were included in the Sn-3.5Ag solder. As aging time increased, the IMC thickness difference between CNT-embedded and non-CNT samples remarkably increased as well.