Yap et al. Nanoscale Research Letters 2012, 7:105 http://www.nanoscalereslett.com/content/7/1/105 good electrical connections between the CNT and Au electrodes. The successful growth of CNTs on Au metallization opens up opportunities to evaluate the performance of vertically aligned CNT bundles in very high frequency domain. By increasing the densities of CNT bumps, the first demonstration of CNT-to-CNT joining methodology with bump pitches smaller than 150 μm had been successful. The preferred densities of CNT bumps (area) to the die area must be higher than 1.2% to achieve sufficient mechanical support. Prelimin- ary DC characterization suggests an ohmic contact behavior with a CNT interconnection bundle resistance of 1 kΩ. Most importantly, the CNT bumps were not damaged after repeated bonding, and similar I-V mea- surement had been achieved. Acknowledgements The authors would like to acknowledge the assistance from the Singapore Institute of Manufacturing Technology (SIMTech) to perform the flip chip bonding process in this work. Author details 1CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, Singapore, 637553, Singapore 2School of Electrical and Electronics Engineering, Nanyang Technological University, Block S1, 50 Nanyang Avenue, Singapore, 639798, Singapore 3XLIM UMR 6172, Université de Limoges/CNRS, 123 Avenue Albert Thomas, Limoges Cedex, 87060, France 4Temasek Laboratories@NTU, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 9, Singapore, 637553, Singapore Authors’ contributions CCY and DT carried out the fabrication and the characterization of the structures, as well as drafted the manuscript. CB carried out the simulation and proposed the design. HL and EHTT participated in the analysis and discussion of the results. 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Phys Rev B 2006, 73:235431. doi:10.1186/1556-276X-7-105 Cite this article as: Yap et al.: Carbon nanotube bumps for the flip chip packaging system. Nanoscale Research Letters 2012 7:105.