Micro bump height derivation control with dynamic sizing patterning

Ubump is the key element for die-to-die stacking. However, the adoption of ubump will encounter higher cold joint risk than flip chip bump due to less solder volume and symmetry ubump pattern of stacking dies. In this study, the phenomenon of ubump height distribution across the die is analyzed. The mechanism of ubump height variation is discussed, and the approach for cold joint risk mitigation is demonstrated. The experiment result indicated 20% ubump height variation is achieved with dynamic sizing patterning.