National Cheng Kung University

About: National Cheng Kung University is a education organization based out in Tainan City, Taiwan. It is known for research contribution in the topics: Population & Thin film. The organization has 49723 authors who have published 69799 publications receiving 1437420 citations. The organization is also known as: NCKU.

Influence of interfacial intermetallic compound on fracture behavior of solder joints

Abstract: This paper studies the solder joints of an Sn–Ag lead-free solder system with pure copper wires. The study focuses upon the interrelationships, which exist between the adhesive strength of the joint, its shear strength, the formation of interfacial intermetallic compounds (IMC) and the fractographic morphology. Additionally, the paper determines how these characteristics, and the relationships between them, are influenced by the storage duration and the storage temperature. Experimental results show that both the adhesive strength and the shear strength of the solder joints decrease significantly following short-term thermal storage. As the storage time is increased, it is noted that both the thickness and the roughness of the interfacial IMC layers increase. Regarding the fracture of the solder joints, fractographic observation reveals that fracture morphology under adhesive loading are similar to those observed under shear loading conditions. In the as-soldered condition, the fracture surface appears to be flat, and some broken Cu6Sn5 and residual solder pieces are evident. When the total thickness of the IMC layer lies within the range 1–10 μm, it is observed that the fracture morphology gradually becomes a dimple-like structure. This phenomenon may be attributed to the residual stresses caused by phase transformation, and by the increasing roughness of the IMC layers which causes an increase in the stress concentration within the Cu6Sn5 layer, and which ultimately results in fracturing of this layer. When the total thickness of the interfacial IMC layers exceeds 10 μm, the roughness of the IMC layers and the residual stress between them and the solder both continue to increase. Eventually this results in a fracture being initiated and propagated within the Cu6Sn5 layer. Fractographic observation shows the fracture to have a cleavage-like morphology.

Arsenic methylation and skin cancer risk in southwestern Taiwan.

Abstract: Arsenic is a known carcinogen, but data are especially lacking on the health effects of low-level exposure, and on the health significance of methylation ability. We conducted a case-control study (76 cases and 224 controls from 1996 to 1999) in southwestern Taiwan to explore the association among primary and secondary arsenic methylation index (PMI and SMI, respectively), cumulative arsenic exposure (CAE), and the risk of skin cancer. As compared with the controls, the skin cancer group reported more sun exposure (P 0.02) and had a lower BMI (P 0.03), as well as lower education level (P 0.01). Skin cancer patients and controls were similar with regard to age, gender, smoking and alcohol consumption. Given a low SMI (5), CAE 15 mg/L-year was associated with an increased risk of skin cancer (OR, 7.48; 95% CI, 1.65-33.99) compared to a CAE2 mg/L-year. Given the same level of PMI, SMI, and CAE, men had a higher risk of skin cancer (OR, 4.04; 95% CI, 1.46 -11.22) when compared to women. Subjects with low SMI and high CAE have a substantially increased risk of skin cancer. Males in all strata of arsenic exposure and methylation ability had a higher risk of skin cancer than women. ( J Occup Environ Med. 2003;45: 241-248)

Classifying different emotional states by means of EEG-based functional connectivity patterns.

Abstract: This study aimed to classify different emotional states by means of EEG-based functional connectivity patterns. Forty young participants viewed film clips that evoked the following emotional states: neutral, positive, or negative. Three connectivity indices, including correlation, coherence, and phase synchronization, were used to estimate brain functional connectivity in EEG signals. Following each film clip, participants were asked to report on their subjective affect. The results indicated that the EEG-based functional connectivity change was significantly different among emotional states. Furthermore, the connectivity pattern was detected by pattern classification analysis using Quadratic Discriminant Analysis. The results indicated that the classification rate was better than chance. We conclude that estimating EEG-based functional connectivity provides a useful tool for studying the relationship between brain activity and emotional states.