Low energy O2 and N2O ion beam modification of polyimide for improving adhesive strength of Cu/PI in roll-to-roll process |
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Authors: | Dong-Hee Park |
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Affiliation: | Materials Science and Technology Research Division, Korea Institute of Science and Technology (KIST), P.O. Box 131, Cheongryang, Seoul 130-650, Republic of Korea |
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Abstract: | To enhance the weak mechanical durability of directly deposited copper layers on polyimide (PI) film due to their poor adhesive strength, a continuous roll-to-roll process involving surface modification using a reactive ion beam irradiation and in-situ deposition process is studied. The polyimide film is modified by an ion source with a linear stationary plasma thruster (LSPT) in the vacuum roll-to-roll process. An O2 ion beam, with beam energy of 214 eV and beam current density of 0.78 mA/cm2, and N2O ion beam, with 220 eV and 0.69 mA/cm2, irradiate PI film in winding speed of 0.5 m/min. The surface energy increases from 38 mN/m for the pristine PI film to 80 mN/m after beam irradiation at an ion fluence of 3.5 × 1016 ions/s. After beam irradiation, a 10 nm thick tie layer and 200 nm thick copper layer are successively deposited by in-situ DC magnetron web coating. The peel strength of the copper layer on the PI film is enhanced from 0.4 kgf/cm without ion beam treatment to 0.71 kgf/cm after O2 beam treatment and to 0.75 kgf/cm after N2O beam treatment. This enhancement is closely related to the increase in the polar force originating from the formation of hydrophilic C O (carbonyl) groups on the modified PI surface. |
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Keywords: | Copper on polyimide Linear stationary plasma thruster Ion beam Peel strength |
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