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94 The PCB Magazine • August 2016 References 1. Ciufo, D. In Nano Copper Materials in PCB Manufacturing, IPC Flexible Circuits-HDI Forum, Minneapolis, Minnesota October 28-30, 2015; Minneapolis, Minnesota. 2. Xenon Sinteron 5000 system. 3. Noh, B.-I.; Yoon, J.-W.; Choi, J.-H.; Jung, S.-B. Materials transactions 2010, 51, (1), 85-89. 4. Shih, D. Y.; Klymko, N.; Flitsch, R.; Para - szczak, J.; Nunes, S. Journal of Vacuum Science & Technology A 1991, 9, (6), 2963-2974. 5. Inagaki, N.; Tasaka, S.; Hibi, K. Journal of Adhesion Science and Technology 1994, 8, (4), 395-410. 6. Lee, S.; Park, S. S.; Lee, H. K. Macromo- lecular Symposia 2007, 249-250, (1), 586-590. 7. Wang, Z.; Furuya, A.; Yasuda, K.; Ikeda, H.; Baba, T.; Hagiwara, M.; Toki, S.; Shingubara, S.; Kubota, H.; Ohmi, T. Journal of Adhesion Sci- ence and Technology 2002, 16, (8), 1027-1040. This paper was originally presented at IPC APEX EXPO 2016 and published in the proceedings. David Ciufo is Program Manager PCB Technologies, Hsin-Yi (Sherry) Tsai is Research Scientist and Mi- chael J. Carmody is Chief Scientist, all with Intrinsiq Materials in Rochester, NY. Conclusions The ultra-thin film process is designed to put thinner copper cladding on both flex- ible and rigid printed circuit laminates than is currently available, by coating a 0.5~1 µm nano copper ink layer. There has been dem- onstrated excellent quality of etching on the patterns created by standard masking, plat- ing and etching techniques. The adhesion is significantly affected by sintering condition and ink formulation, while not observed by the surface modification of PI substrate in the system. A few binders/dispersants have been found to give good ink stability and reason- able adhesion. It is concluded that the binder/ dispersant layer between polyimide and nano copper is responsible for the adhesion, and the accessibility of the plating/etching chem- istry toward the interface may determine the adhesion if it has any negative effect on the bonding at the interfaces. Overall, the tech- nique provides the ability of the industry to greatly reduce minimum feature size and to also improve the performance of high speed electronics. Acknowledgements The authors would like to thank Brett Austin and staff at Nationwide Circuits, Inc as well as Professor Mark Poliks and his students at Bing- hamton University. PCB FACTORS AFFECTING THE ADHESION OF THIN FILM COPPER ON POLYIMIDE Figure 9: SEM images of (a) a sintered nano copper coating and (b) the substrate facing side of the same coating after plating to ~5 µm.