Mechanical Properties Measurement of Nanowires Anisotropic Conductive Film by Nanoindentation Technique

As microelectronic packaging industry grows explosively, high I/O density interconnects and reliable packaging design are recognized as the main concern of the IC packaging industry. Hence, in this investigation, a novel type of anisotropic conductive film (ACF) composed of cobalt nanowires and polymer was developed and used in place of conventional solder bumps for ultra-fine pitch interconnect. Unlike some other ACF materials that blend either nanowires, tubes, or powders in polymer, the nanowires entrenched in polymer is well aligned in one direction so as to achieve high anisotropic conductance. Basically, the material properties of the nanowire/polymerbased conductive film would have a great effect on the thermal-mechanical behaviors of the technology, which would generally lead to a reliability issue. Thus, the underlying goal of the study was to characterize the out-ofplane mechanical properties, including reduced modulus and hardness, through a nanoindentation technique. The tip of nanoindentation was 300nm in diameter and measured method was force-control. Results show that the mean value of the reducedmodulus of the film is 14.471GPa at a standard deviation of 2.578GPa. These statistical results were based on 102 data points with high consistency.