The electroplating and screen printing are widely used in the micro-electric industry but they have disadvantages of a complicated series of bumping process, equipments and materials. Furthermore, they are not suitable for the fine pitch bumping technology. To overcome these weak points, a maskless bumping technology using SBM has been developed. Solder Bump Masker (SBM) technology does not need any special equipment and mask tools. It is composed of solder powder and a resin. The solder is Sn58Bi and the resin is designed to have low viscosity for theological characteristics of the solder droplets. In this paper, we optimized the bumping condition with controlling the process time. After bumping, the coining process, which the various loads were applied, has been investigated to get the bump with the extremely uniform heights. Finally, low-volume bumps with the excellent uniformity were successfully achieved.
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