Polyimide (PI) surface modification was carried out by an ion beam treatment to improve the adhesion between the polyimide film and copper. The PI film surface was treated with an ion-beam source at ion doses ranging from 1.96 x 10(13) to 2.38 x 10(13) ions/cm(2) using a mixture of nitrogen (N(2)) and hydrogen (H(2)). Contact angle measurement, atomic force microscopy and X-ray photoelectron spectroscopy, respectively revealed an increase in the surface roughness, a decrease in contact angle, and the formation of oxygen complexes and functional groups on the treated PI surfaces. Adhesion between the copper and PI film treated with the beam was superior to that of the untreated PI film. The 90 degrees peel test revealed the highest peel strength of 7.8 N/cm. (C) Koninklijke Brill NV, Leiden, 2011