| abstract |
A novel method of filling apertures in substrates, such as through holes, is provided. The method utilizes a phtoimageable film, and comprises the following steps: applying a photoimagable, hole fill film over the apertures, preferably having a solvent content of 7-18%; reflowing the hole fill film to flow into the apertures; exposing the hole fill film to actinic radiation, preferably ultraviolet light, through a phototool, which preferably has openings slightly larger than the diameter of the apertures; then at least partially curing the hole fill film; and developing the hole fill film to remove the unexposed hole fill film. Thus, the apertures may be selectively filled. After the apertures are filled, the hole fill film is cured. Thereafter, the substrate may be subjected to further processing steps, for example, nubs of cured hole fill film can be removed. If desired, the substrate is circuitized and overplated with gold. |