Locus of failure between a nanowire-coated leadframe and an epoxy-based molding compound

CuO nanowires were formed on the surface of copper-based leadframe sheets by oxidation in a hot alkaline solution. The nanowire-coated copper-based leadframe sheets were molded with epoxy molding compound (EMC). The molded bodies of nanowire-coated metal (copper-based leadframe)/polymer (EMC) were machined to form sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of the nanowire-coated leadframe/EMC interfaces. The SBN specimen was designed to measure the fracture toughness of the nanowire-coated leadframe/EMC interfaces under mixed-mode (mode I + mode II) loading condition. Fracture surfaces were analyzed by various equipment to investigate failure path. An attempt to determine the reasons why different types of failure occurred was made by introducing a simple adhesion model. Research results have shown that hackle-type failure occurred in the SBN specimens. Although the failure path in the SBN specimens is not dependent on the phase angle as well as the distance from the tip of the pre-crack, it is found that the failure path of the SBN specimens can be explained well by using the adhesion model.