Micro bumps by gravure offset printing method

We examined to utilize the gravure offset printing method to print high-precision micro bumps.
Currently, the minimum diameter that can be printed with SAC (Sn, Ag, Cu) solder paste is 6 μm and the distance between the centers of the bumps is 30 μm.
For the reflow method, the formic acid reduction method is used for bumps with a diameter of 15 μm or more.
The film thickness can be increased by printing several times.
The smaller the bump diameter, the higher the aspect ratio.