Manufacture of thin ball array substrates includes coating copper layer with soldering metal, washing away photosensitive coating layers, and removing surplus copper layer in circuit lines and remaining soldering metal

摘要

Thin ball array substrates are manufactured by coating a copper layer on a recessed circuit track with a soldering metal (29); washing away the photosensitive coating layers with a chemical agent; and removing the surplus copper layer resulting in the circuit lines, and the remaining soldering metal. Manufacture of thin ball array substrates comprises (a) electroplating a thin copper layer (22) on a polyimide film (21); (b) electroplating a thick copper layer (23) on the thin copper layer; (c) applying a first and a second photosensitive coating layer (24, 25) on the top and bottom of the film, respectively; (d) mounting a first and a second mask with optically transmissible circuit tracks on the top and bottom of the film, respectively, and then processing the film with exposure treatment; (e) processing the film with development treatment to remove the photosensitive coating layers aligned with the circuit track and to form a first and a second recessed track (251) on the first and second photosensitive coating layers, respectively; (f) electroplating an additional copper layer (27) on top of the film, with its top slightly lower than that of the first photosensitive coating layer; (g) etching the bottom of the film to remove the second recessed circuit track, i.e. removing the film not covered with the second photosensitive coating layer; (h) coating the additional copper layer on the first recessed circuit track with a soldering metal (29) to make the top of the soldering metal even with that of the photosensitive coating layer; (i) washing away the photosensitive coating layers with a chemical agent; and (j) removing the surplus copper layer resulting in the circuit lines, and the remaining soldering metal.