[Paper] Micro Solder Bumps Forming by Gravure Offset Printing: The design formulas for intaglio cell shape to print your desired bump diameters

Abstract

Gravure offset printing succeeded in forming bumps with a minimum diameter of 6 µm within 5% errors. We attempted to derive the design formulas for the intaglio cell shape in order to accurately print to the specified bump diameter. As a result of experiments, it is found that tapering the cell openings increased the amount of paste released from the intaglio. If the bore diameter of the cell was less than 10 µm, the printed bumps diameter depended on the aperture diameter, about our developed solder paste. We generalized what we reported at IDW ’23 and derived the design formulas that are applied to any paste or printing conditions. We applied the design formulas to a specific example and verified them usefulness.