Isolate micro-bump process development and improvement

Low density micro-bumps were required for assembly of different technologies connection within 3D and 2.5D packaging. 6μm and 8um bump heights after reflow are required for 15μm and 25μm (Cu/SnAg) diameter micro-bump, respectively. At same time, the pattern density of 15um and 25μm diameter micro-bump are 0.045% and 0.127%. This paper reported the process challenges, evaluation and development. The average test yields after process development and optimization for 25μm and 15μm micro-bump are 94.5% and 47.5%, respectively.