scholarly journals Study on the Reliability of Sn50Pb49Sb1/Cu Solder Joints Subjected to γ-ray Irradiation

2018 ◽  
Vol 8 (10) ◽  
pp. 1706 ◽  
Author(s):  
Jianhao Wang ◽  
Songbai Xue ◽  
Zhaoping Lv ◽  
Li Wen ◽  
Siyi Liu
Keyword(s):  
Solder Joints ◽  
Space Exploration ◽  
Energetic Electron ◽  
Compound Layer ◽  
Intermetallic Compound Layer ◽  
Deep Space Exploration ◽  
Long Duration ◽  
Micro Cracks ◽  
Γ Ray ◽  
Main Factor

Cosmic radiation has always been the most obvious barrier to planetary travels, especially in long-duration deep space exploration missions. Therefore, the reliability of satellite materials and the requirements of satellite miniaturization have received considerable attention. In this paper, the effect of γ-ray irradiation on the reliability of Sn50Pb49Sb1/Cu solder joints was investigated. It was found that the influence of γ-ray irradiation on the thickness and morphology of the intermetallic compound layer in Sn50Pb49Sb1/Cu was not obvious. However, the formation and growth of micro-voids and micro-cracks was observed in Pb-based solid solutions. Due to the Compton effect, the γ-ray photon could knock the electron out of its orbit, which created the energetic electron. The accumulation of dislocated atoms and lattice vacancies generated by energetic electrons could be the main factor that caused the formation of micro-voids and micro-cracks. The pull force of Sn50Pb49Sb1/Cu solder joints was reduced by 22% after being irradiated at the dose rate of 0.25 Gy(Si)/s for 960 h. Fractographic analysis showed that after irradiation, the fracture type of solder joints was still ductile but the ductility of the solder joints decreased with slightly inconspicuous dimples.

Cracking of the Intermetallic Compound Layer in Solder Joints Under Drop Impact Loading

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Tong An ◽  
Fei Qin
Keyword(s):  
Intermetallic Compound ◽  
Solder Joint ◽  
Impact Loading ◽  
Driving Force ◽  
Solder Joints ◽  
Compound Layer ◽  
Drop Impact ◽  
Lead Free ◽  
Intermetallic Compound Layer ◽  
Crack Driving Force

The significant difference between failure modes of lead-containing and lead-free solder joints under drop impact loading remains to be not well understood. In this paper, we propose a feasible finite element approach to model the cracking behavior of solder joints under drop impact loading. In the approach, the intermetallic compound layer/solder bulk interface is modeled by the cohesive zone model, and the crack driving force in the intermetallic compound layer is evaluated by computing the energy release rate. The numerical simulation of a board level package under drop impact loading shows that, for the lead-containing Sn37Pb solder joint, the damage in the vicinity of the intermetallic compound layer initiates earlier and is much greater than that in the lead-free Sn3.5Ag solder joint. This damage relieves the stress in the intermetallic compound layer and reduces the crack driving force in it and consequently alleviates the risk of the intermetallic compound layer fracturing.

scholarly journals Materials for Shielding Astronauts from the Hazards of Space Radiations

1998 ◽  
Vol 551 ◽  
Author(s):  
J. W. Wilson ◽  
F. A. Cucinotta ◽  
J. Miller ◽  
J. L. Shinn ◽  
S. A. Thibeault ◽  
...  
Keyword(s):  
Space Exploration ◽  
Solar Energetic Particle ◽  
Heavy Ion ◽  
Galactic Cosmic Rays ◽  
Biological Data ◽  
Space Environment ◽  
High Hydrogen ◽  
Deep Space Exploration ◽  
Long Duration ◽  
Human Space Exploration

AbstractOne major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thickness of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two reasons: the hydrogen is efficient in breaking up the heavy GCR ions into smaller less damaging fragments and the light constituents produce few secondary radiations (especially few biologically damaging neutrons). An overview of the materials related issues and their impact on human space exploration will be given.

scholarly journals Off-world mental health: considerations for the design of wellbeing supportive technologies for deep space exploration

2021 ◽  
Author(s):  
Nathan Smith ◽  
Dorian Peters ◽  
Caroline Jay ◽  
Gro Mjeldheim Sandal ◽  
Emma Barrett ◽  
...  
Keyword(s):  
Digital Health ◽  
Space Exploration ◽  
Digital Technologies ◽  
Deep Space ◽  
Health Technologies ◽  
Health And Wellbeing ◽  
Deep Space Exploration ◽  
Long Duration ◽  
Determining Factors ◽  
Research Programmes

During future long duration space exploration missions, humans will be exposed to combinations of extreme physical, psychological and interpersonal demands. These demands create risks for safety, performance, health, and wellbeing of both individuals and crew. The communication latency in deep space means that explorers will increasingly have to operate independently and take responsibility for their own self-care and self-management. At present, several research programmes are focused on developing and testing digital technologies and countermeasures that support the effective functioning of deep space crews. Although promising, these initiatives have been stimulated mostly by technological opportunity rather than cogent theory. In this perspective, we argue that digital technologies developed for spaceflight should be informed by wellbeing supportive design principles and be cognisant of broader conversations around the development and use of digital health applications, especially pertaining to issues of autonomy, privacy and trust. These issues are important for designing potentially mission critical health technologies and may be determining factors in the safe and successful completion of future off-world endeavours.

Fatigue Strength Evaluation for Sn-Zn-Bi Lead-Free Solder Joints

2002 ◽  
Author(s):  
Qiang Yu ◽  
Doseop Kim ◽  
Jaechul Jin ◽  
Yasuhiro Takahashi ◽  
Masaki Shiratori
Keyword(s):  
Fatigue Strength ◽  
Solder Joint ◽  
Solder Joints ◽  
Layer Structure ◽  
Solder Matrix ◽  
High Stress ◽  
Compound Layer ◽  
Intermetallic Compound Layer ◽  
Mechanical Fatigue ◽  
Free Solder

In this paper, the authors have investigated mechanical fatigue strength of Sn-Zn-Bi lead-free solder joints. The use of Sn-Zn-Bi solder is increasing for the advantage of low cost and low melting point. Therefore, it becomes important to ensure the fatigue strength of Sn-Zn-Bi solder joint. However, when the Sn-Zn-Bi solder was used as a solder material, there is serious problem that the fatigue crack is easy to generate at the interface between intermetallic compound layer and the solder matrix, and it makes the fatigue life of solder joint lower. Because the yield strength of Sn-Zn-Bi solder is high, and the difficulty of deformation causes high stress level concentrating at the corner of the interface between solder joint and substrate/package. It seems that the crack become easy to generate at the interface between intermetallic compound layer and solder matrix by this high stress concentration. The authors have found if Sn-Zn-Bi is used with another Pb-free solder material, a kind of composite structure can be built during the reflowing processes. In this study, the mechanical fatigue strength of this kind of Sn-Zn-Bi solder joint was studied. Based upon the results of mechanical shear fatigue test and FEM (Finite Element Method) analysis, it was found that if SnZn-Bi was used as reflow solder with Sn-Ag-Cu ball, the CSP solder joints are as reliable as thc pure Sn-Ag-Cu CSP. This is because Sn-Zn-Bi solder paste and Sn-Ag-Cu solder ball did not melt together completely and formed two-layer structure, and this two-layer structure reduces the stress concentration at the joint corners, and prevents successfully the occurrence of the interface cracks. As a result the fatigue life of Sn-Zn-Bi/Sn-Ag-Cu CSP is equivalent to that of Sn-Ag-Cu joints.

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