Effect of Creep Deformation Mechanisms and Power-law Breakdown Stress on Thermal Fatigue Properties of Solder Joints

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15303
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26030:Composite materials and interfaces-related
• Research Institution: Osaka Research Institute of Industrial Science and Technology
• Principal Investigator: Hamada Naoyuki 地方独立行政法人大阪産業技術研究所, 和泉センター, 主任研究員 (90736282)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 鉛フリーはんだ / クリープ / 熱疲労 / 固溶強化 / 累乗則崩壊

Outline of Final Research Achievements

The effects of creep deformation mechanisms and power-law breakdown stress on the thermal fatigue properties of solder joints were investigated. In this study, all Sn-based binary alloys exhibited the same creep deformation mechanism. In contrast, the power-law breakdown stress varied by more than 10 MPa depending on the alloy composition and could influence the thermal fatigue properties. Furthermore, the damage rate owing to the thermal fatigue of solder joints was investigated, and the relationship between the damage rate and power-law breakdown stress was analyzed. The alloys were classified into those with a negative or no correlation between the power-law breakdown stress and damage rate. The electron backscatter diffraction analysis of solder joints indicated that the presence or absence of correlation was attributable to the differences in the recrystallization behavior when the alloy was subjected to thermal fatigue.

Free Research Field

材料工学

Academic Significance and Societal Importance of the Research Achievements

はんだ接合部の熱疲労特性を向上させるために、固溶型の合金元素を添加した固溶強化型のはんだが検討されている。合金元素の中には、累乗則崩壊応力や耐力などの機械的性質が上昇しても熱疲労特性の向上に寄与しない元素が存在することが本研究で明らかになった。熱疲労特性を改善させるためには、再結晶挙動も考慮した元素選定が必要であり、実用はんだ合金の設計において重要な指針を示した。