On the Spreading Resistance of Thin-Film Contacts

The spreading resistance of a microscopic area of contact (the alpha-spot) located in a thin film is studied for both Cartesian and cylindrical geometries. The effect of film thickness h on the spreading resistance is evaluated over a large range of aspect ratios. In the limit h -> 0, the normalized thin-film spreading resistance (R) over bar (s) converges to the finite values, i.e., 2.77 for the Cartesian case and 0.28 for the cylindrical case. An interpretation of these limits is given. Extension to a general a-spot geometry is proposed.