Prof. Hiroaki TatsumiJapan
The University of Osaka
| 2021/11 to present | | Associate Professor, Joining and Welding Research Institute, The University of Osaka |
| 2021/11 - | | Associate Professor, Joining and Welding Research Institute, The University of Osaka |
| 2009/4 - 2021/10 | | Manufacturing process engineer, Mitsubishi Electric Corporation, Japan |
| 2025 | | Best paper award on Japan Institute of Electronics Packaging (JIEP) |
| 2025 | | The University of Osaka Prize |
| 2026 | | Monodzukuri Nippon (Japan’s Manufacturing) Grand Award |
electronics packaging, micro joining, multi scale simulation
Crystallographic orientation control and evolution of β-Sn in lead-free solder joints through processing and thermal fatigue
TBA TBA
Lead-Free Soldering and Interconnect/TBA
The crystallographic anisotropy of β-Sn plays a critical role in the reliability of lead-free solder joints. In this talk, we present our recent research on two complementary aspects of β-Sn grain orientation in lead-free solder joints: a control method during soldering processes utilizing Co-based substrates, and the dynamic evolution of grain structures under thermal fatigue in die-attach solder joints.
For orientation control during processing, we demonstrate that preferentially grown α-CoSn3 intermetallic compounds on polycrystalline Co substrates can guide the nucleation orientation of Sn grains. Ion milling enhances the crystallographic texture of α-CoSn3, and a modified edge-to-edge lattice matching model successfully predicts the favorable orientation pairs. EBSD analysis confirms that Sn grains nucleated on the textured α-CoSn3 surface align their [001] axes predominantly within 30° of the substrate plane, offering a practical and scalable route for Sn orientation control.
For orientation evolution under service conditions, we examine β-Sn grain structures in die-attach solder joints subjected to thermal cycling. Plan-view EBSD observations reveal that the initial solidification texture undergoes dynamic recrystallization during thermal fatigue, leading to progressive grain refinement and orientation redistribution. These results demonstrate that the crystallographic structure of Sn solder joints continuously evolves under thermomechanical loading, highlighting the need for orientation-aware reliability assessment throughout the joint lifecycle.