Low-temperature Sintering of Cu/functionalized Multi-walled Carbon Nanotubes Composite Paste for Power Electronic Packaging

Sintered Cu is considered as the most promising strategy in die-attachment, since its capacities of low-temperature bonding and high-temperature working. Many studies have reported the excellent properties of sintered Cu, but there is still some room for improvement. Here, strong Cu–Cu joints and insulated-gate bipolar transistor (IGBT) devices are achieved by sintering Cu paste and three composite pastes, and the mechanical, electrical, and microstructure properties of joints are investigated. The shear strength of pure Cu bonded joint is 23.4 MPa, which is improved to 26.64 MPa by introducing 0.6 wt% N-doped multi-walled carbon nanotubes (N-doped MWCNTs) into Cu paste. Excellent electrical properties are achieved as the resistivities of sintered Cu/N-doped MWCNTs layer and Cu/carboxylated WMCNTs are 2.252 and 2.551 μ Ω·cm, respectively, which are lower than the sintered pure Cu layer (3.473 μ Ω·cm). In addition, the functionalized MWCNTs are found exerted positive effects on the joint reliability. The enhancements on the joint qualities are attributed to that the functionalized MWCNTs improve the affinity of the Cu and CNTs and increase the density of bonding layer. This article provides an effective way to improve the sintered Cu joints sintering qualities, which is suitable for the attachment of next-generation devices and substrates.