ABSTRACT The microstructure, mechanical response, and failure behavior of lead free solder joints... more ABSTRACT The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work on aging effects (Ma, et al., ECTC 2006), we demonstrated that the observed material behavior variations of SAC405 and SAC305 lead free solders during room temperature aging (25 °C) were unexpectedly large and universally detrimental to reliability. Such effects for lead free solder materials are much more dramatic at the higher aging temperatures (e.g. 100–150 °C) typical of the harsh environments present in high performance computing and in automotive, aerospace, and defense applications. However, there has been little work in the literature, and the work that has been done has concentrated on the degradation of solder ball shear strength (e.g. Dage Shear Tester). Current finite element models for solder joint reliability during thermal cycling accelerated life testing are based on traditional solder constitutive and failure models that do not evolve with material aging. Thus, there will be significant errors in the calculations with the new lead free SAC alloys that illustrate dramatic aging phenomena. In the current work, we have explored the effects of elevated temperature isothermal aging on the mechanical behavior and reliability of lead free solders. The effects of aging on mechanical behavior have been examined by performing stress-strain and creep tests on SAC405 and SAC305 samples that were aged for various durations (0–6 months) at several elevated temperatures (80, 100, 125, and 150 °C). Analogous tests were performed with 63Sn-37Pb eutectic solder samples for comparison purposes. Variations of the temperature dependent mechanical properties (elastic modulus, yield stress, ultimate strength, creep compliance, etc.) were observed and modeled as a function of aging time and temperature. In this paper, we have concentrated our efforts on presenting the results for samples aged at 125 °C. In addition, the new elevated temperature aging data were correlated with our room temperature results from last year’s investigation. The results obtained in this work have demonstrated the significant effects of elevated temperature exposure on solder joints. As expected, the mechanical properties evolved at a higher rate and experienced larger changes during elevated temperature aging (compared to room temperature aging). After approximately 200 hours of aging, the lead free solder joint material properties were observed to degrade at a nearly constant rate. We have developed a mathematical model to predict the variation of the properties with aging time and aging temperature. Our data for the evolution of the creep response of solders with elevated temperature aging show that the creep behavior of lead free and tin-lead solders experience a “crossover point” where lead free solders begin to creep at higher rates than standard 63Sn-37Pb solder for the same stress level. Such an effect is not observed for solder joints aged at room temperature, where SAC alloys always creep at lower rates than Sn-Pb solder.
The prevalence of type 2 diabetes mellitus (T2DM) is increasing in young Asian adults; however, l... more The prevalence of type 2 diabetes mellitus (T2DM) is increasing in young Asian adults; however, little is known about the associated clinical characteristics and the prevalence of complications. A recent Asia-wide prospective cohort study has revealed poor metabolic control in patients with young-onset T2DM, indicating more efficient health-care strategies are warranted to manage this vulnerable population.
EuroSimE 2008 - International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Micro-Systems, 2008
Solder materials demonstrate evolving microstructure and mechanical behavior that changes signifi... more Solder materials demonstrate evolving microstructure and mechanical behavior that changes significantly with environmental exposures such as isothermal aging and thermal cycling. These physical aging effects are greatly exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In the current study, mechanical measurements of thermal aging effects and material behavior evolution of lead free solders
Chemical communications (Cambridge, England), Jan 25, 2014
We report a simple precipitation method for the construction of spatially co-localized multi-enzy... more We report a simple precipitation method for the construction of spatially co-localized multi-enzyme systems based on inorganic nanocrystal-protein complexes. A spatially controlled multi-enzyme system exhibits enhanced overall catalytic performance, allowing for sensitive detection of glucose in solution.
A comprehensive metabonomic method, in combination with fingerprint analysis and target analysis,... more A comprehensive metabonomic method, in combination with fingerprint analysis and target analysis, was performed to reveal potential mechanisms of berberine action in the treatment of patients with type 2 diabetes and dyslipidemia. Serum samples of 60 patients before and after treatment with either berberine or placebo were collected. Ultra-performance liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (UPLC Q-TOF MS) coupled with pattern recognition analysis were used to identify changes in global serum metabolites. Compared with placebo, patients before and after berberine treatment could be separated into distinct clusters as displayed by the orthogonal signal correction filtered partial least-squares discriminant analysis (OSC-PLS-DA) score plot, which indicated changes in circulating metabolites after berberine treatment. Among them, free fatty acids changed markedly. These were further quantified by UPLC combined with single quadrupole mass spectrometry (UPLC SQ MS). There was a highly significant decrease in the concentrations of 13 fatty acids following berberine administration. 10 fatty acids also differed statistically from placebo. These results suggest that berberine might play a pivotal role in the treatment of type 2 diabetes through down-regulating the high level of free fatty acids and that comprehensive metabonomic measurements are potentially very useful for studying the mechanisms of action of traditional Chinese medicines.
It has long been proposed that elevation of liver enzymes including alanine aminotransferase (ALT... more It has long been proposed that elevation of liver enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ-glutamyltransferase (GGT) may be associated with insulin resistance (IR). In the present study, we aimed to investigate the association of the above mentioned liver enzymes with IR by using hyperinsulinemic euglycemic clamp, as well as their relationship with individual component of metabolic syndrome (MetS) in 95 newly diagnosed type 2 diabetes (T2DM) Chinese patients. All the diagnosed patients did not use drugs for treatment of diabetes or dyslipidemia previously and were divided into IR and non-IR groups. The results showed that IR group had significantly higher ALT, AST, and GGT (P<0.01, P<0.01, and P<0.05, respectively) compared with non-IR group. According to the individual MetS component, ALT and AST were significantly increased in patients with high blood pressure compared with those without (both P<0.001); ALT and GGT were increased in patients with high triglyceride (P<0.05 and P<0.01); AST was increased in patients with central obesity (P<0.05). In correlation analysis, a significant association was found between the three liver enzymes and clamp insulin sensitivity index (all P<0.001). In the linear regression analysis, ALT was the determinant of clamp ISI, independent of age, sex, BMI, and fasting and OGTT 2 h plasma glucose (P<0.0001). In conclusion, liver enzymes, especially ALT, were significantly associated with IR according to direct clamp assessment, which were independent of the traditional risk factors in diabetic patients; and individual liver enzymes may have different relationship with individual component of MetS.
Trinucleotide repeats CAG(n) in androgen receptor gene is thought to be a potential site of genet... more Trinucleotide repeats CAG(n) in androgen receptor gene is thought to be a potential site of genetic susceptibility to polycystic ovary syndrome (PCOS). However, previous studies of PCOS have shown variable association of CAG(n )polymorphism with PCOS. In order to evaluate CAG(n )polymorphism in Chinese women with PCOS, we have genotyped CAG(n) repeat numbers in female Chinese subjects (148 PCOS patients and 104 control subjects). The mean CAG(n) repeat lengths of PCOS patients and control subjects were similar (22.88 +/- 1.76 vs. 22.85 +/- 1.60; P = NS). No difference in the mean CAG(n) repeat lengths of hyperandrogenic and nonhyperandrogenic subgroups of PCOS patients was found (22.86 +/- 1.68 vs. 22.91 +/- 1.84; P = NS). Moreover, no difference was found in the term of mean CAG(n) repeat lengths in the nonhyperandrogenic subgroup and the control subjects (22.86 +/- 1.68 vs. 22.85 +/- 1.60; P = NS). However, mean CAG(n) repeat lengths were negatively correlated with serum total cholesterol and low-density lipoprotein-cholesterol concentration in PCOS patients (r = -0.182, P < 0.05 and r = -0.210, P < 0.05, respectively), but not with total testosterone, body mass index, waist and hip circumferences. The CAG(n) repeat length polymorphism may not be a major determinant of PCOS, but it may influence the lipid metabolism of PCOS patients.
SummaryObjective Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain‐of‐fun... more SummaryObjective Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain‐of‐function mutations in the RET proto‐oncogene, which includes multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). In this paper we present the phenotype–genotype correlation of 20 unrelated Chinese families with 15 cases of MEN2A and five cases of MEN2B.Design Cross‐sectional study.Patients A total of 147 members from the 20 families were included. Among them, 119 family members were from MEN2A pedigrees (including 15 MEN2A probands) and 28 members from MEN2B pedigrees (including five MEN2B probands).Measurements Genomic DNA was isolated from peripheral blood leucocytes and was amplified using polymerase chain reaction (PCR). DNA analysis for RET mutations in exons 8, 10, 11, 13, 14, 15 and 16 was performed with specific primers.Results Thirty‐seven MEN2A and five MEN2B patients were identified as having RET mutations. The inci...
ABSTRACT The microstructure, mechanical response, and failure behavior of lead free solder joints... more ABSTRACT The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work on aging effects (Ma, et al., ECTC 2006), we demonstrated that the observed material behavior variations of SAC405 and SAC305 lead free solders during room temperature aging (25 °C) were unexpectedly large and universally detrimental to reliability. Such effects for lead free solder materials are much more dramatic at the higher aging temperatures (e.g. 100–150 °C) typical of the harsh environments present in high performance computing and in automotive, aerospace, and defense applications. However, there has been little work in the literature, and the work that has been done has concentrated on the degradation of solder ball shear strength (e.g. Dage Shear Tester). Current finite element models for solder joint reliability during thermal cycling accelerated life testing are based on traditional solder constitutive and failure models that do not evolve with material aging. Thus, there will be significant errors in the calculations with the new lead free SAC alloys that illustrate dramatic aging phenomena. In the current work, we have explored the effects of elevated temperature isothermal aging on the mechanical behavior and reliability of lead free solders. The effects of aging on mechanical behavior have been examined by performing stress-strain and creep tests on SAC405 and SAC305 samples that were aged for various durations (0–6 months) at several elevated temperatures (80, 100, 125, and 150 °C). Analogous tests were performed with 63Sn-37Pb eutectic solder samples for comparison purposes. Variations of the temperature dependent mechanical properties (elastic modulus, yield stress, ultimate strength, creep compliance, etc.) were observed and modeled as a function of aging time and temperature. In this paper, we have concentrated our efforts on presenting the results for samples aged at 125 °C. In addition, the new elevated temperature aging data were correlated with our room temperature results from last year’s investigation. The results obtained in this work have demonstrated the significant effects of elevated temperature exposure on solder joints. As expected, the mechanical properties evolved at a higher rate and experienced larger changes during elevated temperature aging (compared to room temperature aging). After approximately 200 hours of aging, the lead free solder joint material properties were observed to degrade at a nearly constant rate. We have developed a mathematical model to predict the variation of the properties with aging time and aging temperature. Our data for the evolution of the creep response of solders with elevated temperature aging show that the creep behavior of lead free and tin-lead solders experience a “crossover point” where lead free solders begin to creep at higher rates than standard 63Sn-37Pb solder for the same stress level. Such an effect is not observed for solder joints aged at room temperature, where SAC alloys always creep at lower rates than Sn-Pb solder.
The prevalence of type 2 diabetes mellitus (T2DM) is increasing in young Asian adults; however, l... more The prevalence of type 2 diabetes mellitus (T2DM) is increasing in young Asian adults; however, little is known about the associated clinical characteristics and the prevalence of complications. A recent Asia-wide prospective cohort study has revealed poor metabolic control in patients with young-onset T2DM, indicating more efficient health-care strategies are warranted to manage this vulnerable population.
EuroSimE 2008 - International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Micro-Systems, 2008
Solder materials demonstrate evolving microstructure and mechanical behavior that changes signifi... more Solder materials demonstrate evolving microstructure and mechanical behavior that changes significantly with environmental exposures such as isothermal aging and thermal cycling. These physical aging effects are greatly exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In the current study, mechanical measurements of thermal aging effects and material behavior evolution of lead free solders
Chemical communications (Cambridge, England), Jan 25, 2014
We report a simple precipitation method for the construction of spatially co-localized multi-enzy... more We report a simple precipitation method for the construction of spatially co-localized multi-enzyme systems based on inorganic nanocrystal-protein complexes. A spatially controlled multi-enzyme system exhibits enhanced overall catalytic performance, allowing for sensitive detection of glucose in solution.
A comprehensive metabonomic method, in combination with fingerprint analysis and target analysis,... more A comprehensive metabonomic method, in combination with fingerprint analysis and target analysis, was performed to reveal potential mechanisms of berberine action in the treatment of patients with type 2 diabetes and dyslipidemia. Serum samples of 60 patients before and after treatment with either berberine or placebo were collected. Ultra-performance liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (UPLC Q-TOF MS) coupled with pattern recognition analysis were used to identify changes in global serum metabolites. Compared with placebo, patients before and after berberine treatment could be separated into distinct clusters as displayed by the orthogonal signal correction filtered partial least-squares discriminant analysis (OSC-PLS-DA) score plot, which indicated changes in circulating metabolites after berberine treatment. Among them, free fatty acids changed markedly. These were further quantified by UPLC combined with single quadrupole mass spectrometry (UPLC SQ MS). There was a highly significant decrease in the concentrations of 13 fatty acids following berberine administration. 10 fatty acids also differed statistically from placebo. These results suggest that berberine might play a pivotal role in the treatment of type 2 diabetes through down-regulating the high level of free fatty acids and that comprehensive metabonomic measurements are potentially very useful for studying the mechanisms of action of traditional Chinese medicines.
It has long been proposed that elevation of liver enzymes including alanine aminotransferase (ALT... more It has long been proposed that elevation of liver enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ-glutamyltransferase (GGT) may be associated with insulin resistance (IR). In the present study, we aimed to investigate the association of the above mentioned liver enzymes with IR by using hyperinsulinemic euglycemic clamp, as well as their relationship with individual component of metabolic syndrome (MetS) in 95 newly diagnosed type 2 diabetes (T2DM) Chinese patients. All the diagnosed patients did not use drugs for treatment of diabetes or dyslipidemia previously and were divided into IR and non-IR groups. The results showed that IR group had significantly higher ALT, AST, and GGT (P<0.01, P<0.01, and P<0.05, respectively) compared with non-IR group. According to the individual MetS component, ALT and AST were significantly increased in patients with high blood pressure compared with those without (both P<0.001); ALT and GGT were increased in patients with high triglyceride (P<0.05 and P<0.01); AST was increased in patients with central obesity (P<0.05). In correlation analysis, a significant association was found between the three liver enzymes and clamp insulin sensitivity index (all P<0.001). In the linear regression analysis, ALT was the determinant of clamp ISI, independent of age, sex, BMI, and fasting and OGTT 2 h plasma glucose (P<0.0001). In conclusion, liver enzymes, especially ALT, were significantly associated with IR according to direct clamp assessment, which were independent of the traditional risk factors in diabetic patients; and individual liver enzymes may have different relationship with individual component of MetS.
Trinucleotide repeats CAG(n) in androgen receptor gene is thought to be a potential site of genet... more Trinucleotide repeats CAG(n) in androgen receptor gene is thought to be a potential site of genetic susceptibility to polycystic ovary syndrome (PCOS). However, previous studies of PCOS have shown variable association of CAG(n )polymorphism with PCOS. In order to evaluate CAG(n )polymorphism in Chinese women with PCOS, we have genotyped CAG(n) repeat numbers in female Chinese subjects (148 PCOS patients and 104 control subjects). The mean CAG(n) repeat lengths of PCOS patients and control subjects were similar (22.88 +/- 1.76 vs. 22.85 +/- 1.60; P = NS). No difference in the mean CAG(n) repeat lengths of hyperandrogenic and nonhyperandrogenic subgroups of PCOS patients was found (22.86 +/- 1.68 vs. 22.91 +/- 1.84; P = NS). Moreover, no difference was found in the term of mean CAG(n) repeat lengths in the nonhyperandrogenic subgroup and the control subjects (22.86 +/- 1.68 vs. 22.85 +/- 1.60; P = NS). However, mean CAG(n) repeat lengths were negatively correlated with serum total cholesterol and low-density lipoprotein-cholesterol concentration in PCOS patients (r = -0.182, P < 0.05 and r = -0.210, P < 0.05, respectively), but not with total testosterone, body mass index, waist and hip circumferences. The CAG(n) repeat length polymorphism may not be a major determinant of PCOS, but it may influence the lipid metabolism of PCOS patients.
SummaryObjective Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain‐of‐fun... more SummaryObjective Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain‐of‐function mutations in the RET proto‐oncogene, which includes multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). In this paper we present the phenotype–genotype correlation of 20 unrelated Chinese families with 15 cases of MEN2A and five cases of MEN2B.Design Cross‐sectional study.Patients A total of 147 members from the 20 families were included. Among them, 119 family members were from MEN2A pedigrees (including 15 MEN2A probands) and 28 members from MEN2B pedigrees (including five MEN2B probands).Measurements Genomic DNA was isolated from peripheral blood leucocytes and was amplified using polymerase chain reaction (PCR). DNA analysis for RET mutations in exons 8, 10, 11, 13, 14, 15 and 16 was performed with specific primers.Results Thirty‐seven MEN2A and five MEN2B patients were identified as having RET mutations. The inci...
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