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The ball-on-ring test (BoR) is one of the standard tests for biaxial bending, suggested in ASTM F394‐78. This test has been applied to determine the biaxial bending strength of silicon dies to avoid the die edge effect of the three-point bending tests. However, from the literature, when the relatively thin silicon dies are tested, this test suffers from a contact-nonlinearity effect, due to a maximum applied stress moving away from the loading pin center before the specimen failure, and thus results in overestimated maximum stress calculated by the theoretical linear solution. This study aims to investigate this mechanical issue experimentally, theoretically and numerically by taking into account the specimen material anisotropy and thickness effects on the maximum stresses and deflections, and then propose new correction factor equations to the theoretical linear solutions, based on the numerical fitting results of the geometric nonlinear finite element solutions. Those correction factor equations proposed in this study are material-property independent, but specimen thickness dependent, which can be estimated by an interpolation function. It has been proved that the BoR test using the conventional theory associated with the proposed correction factor equations can successfully determine the bending strength of the thin silicon dies on untreated surfaces, which mostly fails in the contact-nonlinear region.

A relatively low-cost and easy-to-use strain gauge measurement is proposed here as an alternative method for simultaneously determining the thermally induced warpages and the coefficients of thermal expansion (CTEs) of the flip-chip packages with a cap (or lid). The feasibility of the strain gauge method is evaluated by the shadow moiré experiment and the finite element analysis. The stiffness effect of the thermal interface materials (TIMs) in the flip-chip packages with a cap is also considered. The result suggests that the general back-to-back gauge measurement method on the top and bottom of the specimen would cause significant errors as the TIM is relatively compliant, but not for stiff TIMs. This study also proposes a modified gauge method with a few related strain equations for those cases with compliant TIMs to effectively determine their thermal warpages and CTEs by the gauge measurement. The finite element method (FEM) simulation, consistent with shadow moiré, has further validated the effectiveness of the modified gauge method. Therefore, the newly developed and modified method of strain gauges is found to be feasible and workable for simultaneously determining both thermal warpages and CTEs of the flip-chip packages with a cap, especially with a compliant TIM.

To meet the requirement of the high I/O and fine-pitch interconnects, the conventional insertion-mount socket for central processing unit (CPU) has been changed to surface-mount one with ball grid array. The solder ball joint reliability of the socket used in the CPU assembly becomes very important. In this study, the socket's solder joint reliability of the backplate-reinforced CPU assembly and its related mechanics under mechanical and thermal loadings are investigated experimentally using strain gauge and shadow moiré, and numerically by a finite element method (FEM). The validated FEM results have suggested that maximum stress of solder balls increases almost linearly with decreasing the backplate thickness under mechanical loading during the CPU assembly, but is insensitive to the backplate thickness under thermal loading during the thermal cycling. It is also found that the residual (bending) strain on the PCB proportional to the maximum von Mises stresses of solder joints (or balls) can be used as a key parameter to correlate with the solder joint failures or cracks during the thermal cycling. Overall, experimental and FEM results in this study reveal that solder joint reliability in the CPU assembly during thermal cycling can be improved by adopting the thicker reinforced backplate.

This paper aims to demonstrate the biaxial bending strength test on thin silicon dies using the classic ball-on-ring (BoR) test and discuss it in detail by comparing those results with the newly-proposed point load on elastic foundation (PoEF) test. The geometric linear and nonlinear solutions to the BoR test are reviewed and also provided with theoretical and numerical formulations, respectively. Three different thicknesses (t = 42 μm, 57 μm, and 82 μm) of the thin silicon dies (with a size of 10 mm × 10 mm) are tested in the BoR test, and their bending strengths, load–displacement curves and failure modes are presented and thoroughly discussed with a comparison of the published data from the PoEF test. It is found that, for the bending strengths of 57 μm and 82 μm-thick dies, the data from both the BoR and PoEF tests are very consistent, but not for 42 μm-thick dies with a relatively lower value in the BoR test. This lower strength value in the BoR test is attributed to the more pronounced local buckling effect than the PoEF test. Based on that, it can concluded that the PoEF test is better and more reliable than the conventional BoR as for testing the ultrathin silicon dies, even though both tests are identical for the regularly thin dies.

Background/Objective:Previous research has focused on associations between dietary fat and body mass index (BMI), but the contributions of different types of fat to BMI remain unclear. The purpose of this study is to estimate whether plasma phospholipid omega-3 (n-3), omega-6 (n-6) or trans fatty acids are associated with BMI at baseline and with subsequent BMI changes over time; and whether total phospholipid n-6 or trans fatty acids modify any association between phospholipid n-3 and BMI.Methods:Cross-sectional and longitudinal linear mixed models include 6243 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. Participants were 45-84 years old, had no history of cardiovascular disease at baseline (2000-2002) and were followed for up to 10 years. Plasma phospholipid fatty acids were measured using fasting plasma samples at baseline. Fully adjusted models include demographics, health behaviors and other fatty acids (n-3, n-6 and trans) as appropriate.Results:In fully adjusted models, phospholipid n-3 fatty acid levels were inversely associated with baseline BMI (Ptrend<0.001). Baseline BMI was 1.14 (95% confidence interval (CI): 0.71, 1.57) kg?m–2lower among participants with total n-3 values in the highest vs the lowest quartiles, but was not associated with changes in BMI. Total phospholipid n-6 was positively associated with baseline BMI in partially adjusted but not fully adjusted models. No overall association was observed between fatty acid levels and changes in BMI. No clear association was observed between trans fatty acids and baseline BMI or BMI change. No effect modification in the association between phospholipid n-3 and baseline BMI or BMI change was observed by either phospholipid n-6 or trans fatty acids.Conclusions:Phospholipid total and specific n-3 fatty acid levels were inversely associated with BMI at baseline, whereas associations tended to be positive for total n-6 fatty acids. Significant associations between fatty acid levels and BMI changes were not observed.

AbstractThe effects of various parameters, such as thermal properties of substrates, thermal interface materials (TIMs) and heat sinks on the thermal performance of the light emitting diode (LED) light bars and backlight module are investigated experimentally and numerically in terms of junction temperature (Tj) and thermal resistances from junction to air (Rj-a). The results show that the measured Rj-aof the light bars by powering-on five LEDs in the test is different from one by powering-on only one LED, resulting from the extra heat coming from the adjacent LED packages affecting the Tjfor the case of powering-on five LEDs. For the modules, Rj-ais significantly reduced by using the heat sinks for all backlight modules, and aluminum and iron heat sinks do not show any obvious difference in heat dissipation along with any substrates and TIMs. Furthermore, both experimental and simulation results show that the thermal conductivity of the substrates are more important and dominant than TIM and heat sink for the Rj-aof the backlight modules concerned, and also demonstrate that the thermal field for the local model can represent the one in full-scale backlight module.

The ball-on-ring (BoR) test, one of the most popular biaxial bending tests, is thoroughly investigated in this study for determining the bending strength of thin silicon dies. The application of this test method with a linear theory to the thin dies is also reevaluated using a nonlinear finite element method (NFEM) by taking into account the geometric nonlinearities, including large-deflection (global) and contact (local) nonlinearities. Mechanics of the BoR test is also discussed in terms of geometric linearity and nonlinearity. It is found that the bending strength calculated by the existing linear theory for the BoR test is still valid for the nonthin die specimens, but not for thin ones. The reason is that the thin-die specimens in the test suffer a contact-nonlinearity effect, due to a maximum applied stress moving away from the loading pin center during the loading process. The global geometric nonlinear (large-deflection) behavior occurring in the three-point bending test is not observed in the test. For applications, the fitting equations of the maximum stress in terms of applied load are proposed based on the NFEM results. Those fitting equations only depend on the specimen thickness, the head radius of the loading pin, and the elastic modulus of the specimen, but not on the specimen radius, a supporting ring radius and the head radius of the ring. The 110 μm and 160 μm-thick silicon dies in the BoR test are also demonstrated with the related fitting equations.

In microelectronic packaging, wire bonding is the preferred method used to form electrical interconnections between integrated circuit chips and a substrate. However, ball lift (i.e., when a ball bond becomes completely detached from the chip) and wire breaking are critical problems that degrade the quality of a wire bond. In this study we considered three parameters of gold-ball bonding—ball bond thickness (7–22μm), gold-wire loop height (180–300μm), and gold-wire loop length (1050–2100μm)—and tried to determine the most suitable bond parameters to realize high-quality gold-ball bonding. For this, we experimented with four different values for each parameter considered. Ball shear and wire pull strength between chip and bond pad were used as parameters to evaluate the quality of the gold-ball bond. Experimental results revealed that the ball shear and wire pull initially increase with an increase in the gold-ball thickness up to 12μm and then starts decreasing gradually with further increases in the gold-ball thickness. Further, ball shear and wire pull between chip and bond pad were found to decrease with increasing gold-wire loop height and loop length. For achieving good-quality gold-ball bonding, a gold-ball thickness of about 12μm, and assuming that the cost of the gold consumed is a major concern, a gold-wire loop height of 180μm and loop length of 1050μm are suggested.

A number of curcumin analogues were prepared and evaluated as potential androgen receptor antagonists against two human prostate cancer cell lines, PC-3 and DU-145, in the presence of androgen receptor (AR) and androgen receptor coactivator, ARA70. Compounds 4 [5-hydroxy-1,7-bis(3,4-dimethoxyphenyl)-1,4,6-heptatrien-3-one], 20 [5-hydroxy-1,7-bis[3-methoxy-4-(methoxycarbonylmethoxy)phenyl]-1,4,6-heptatrien-3-one], 22 [7-(4-hydroxy-3-methoxyphenyl)-4-[3-(4-hydroxy-3-methoxyphenyl)acryloyl]-5-oxohepta-4,6-dienoic acid ethyl ester], 23 [7-(4-hydroxy-3-methoxyphenyl)-4-[3-(4-hydroxy-3-methoxyphenyl)acryloyl]5-oxohepta-4,6-dienoic acid], and 39 [bis(3,4-dimethoxyphenyl)-1,3-propanedione] showed potent antiandrogenic activities and were superior to hydroxyflutamide, which is the currently available antiandrogen for the treatment of prostate cancer. Structure−activity relationship (SAR) studies indicated that the bis(3,4-dimethoxyphenyl) moieties, the conjugated β-diketone moiety, and the intramolecular symmetry of the molecules seem to be important factors related to antiandrogenic activity. The data further suggest that the coplanarity of the β-diketone moiety and the presence of a strong hydrogen bond donor group were also crucial for the antiandrogenic activity, which is consistent with previous SAR results for hydroxyflutamide analogues. When the pharmacophoric elements of dihydrotestosterone (DHT) and compound 4 are superposed, the resulting construct implies that the curcumin analogues may function as a 17α-substituted DHT. Compounds 4, 20, 22, 23, and 39 have been identified as a new class of antiandrogen agents, and these compounds or their new synthetic analogues could be developed into clinical trial candidates to control androgen receptor-mediated prostate cancer growth.

This study was designed to examine the embryotoxic potential of retinoic acid (RA) at the blastocyst stage and during early post-implantation development of mouse embryos in vitro.

The problem of a single-lap bonded joint with laminated polymeric composite adherents and with a spew fillet, subjected to tensile loading, is investigated. Experimental and numerical analyses of this problem are presented to address the mechanics and deformation of such material and bonding configuration. Strain gages are employed to record the geometrically nonlinear deformation of the specimen. Full-field moiré interferometr is used to measure the surface deformation of the adherends and adhesive (including a spew fillet). A geometrically nonlinear, two-dimensional finite element analysis is performed to check the mechanics assumptions by comparing with the experimental measurement. A good correlation between experimental and numerical solutions is obtained. It is observed that the composite single-lap joint deforms nonlinearly when subjected to tensile loading. The resulting displacement and strain fields for the adherend and adhesive layer are also presented. The moire results show that the transverse normal and shear strains, but not the longitudinal stain, for composite adherents on the free surface suffer from the fire edge effect, anticlastic as well as bending-twisting coupling effects. For the adhesive strains, the transverse normal (peel) component on the free surface is compressive throughout all the bond line except for a small region near the tip of the spew fillet, wile this component in the interior becomes tensile near the end of the overlap. The adhesive longitudinal strain in the spew fillet is insensitive to the three-dimensional defamation effect, but not the adhesive shear strain in the spew fillet. The adhesive longitudinal strain is not small enough to be neglected in the stress analysis.

Nineteen early-treated phenylketonuric patients, whose diet was discontinued between 4.5 and 13 years of age, and who have been off the diet for 12–28 years, were reassessed in 1992–93. There was little change in mean IQ between end of diet and follow-up, less than one IQ point on the average, with no change for any individual exceeding 12 IQ points. Both prior and current IQ correlated slightly negatively with mean phenylalanine (Phe) concentration, and positively with parents' education. The phenylalanine level at follow-up was significantly lower on average by about 900 µmol/L. Five of the subjects (26%) have evidence of mental disease. However, the data suggest that the discontinuation of the diet did not cause intellectual deterioration. Nonetheless, the patients' intellect cannot be the only consideration for maintenance of diet. The occurrence of psychopathology among phenylketonuric patients and the possible unknown effects of toxic elevation of phenylalanine during their lifetime suggest the need to maintain the diet. The use of DNA for diagnostic and prognostic purposes might assist in decisions about dietary quality and duration, and in anticipation of psychopathology.

Gallium distribution profiles in Ga+-implanted silicon have been measured by secondary ion mass spectrometry (SIMS) and differential Hall effect methods. The previously reported penetrating tails are not observed for as-implanted samples. The redistribution of Ga during annealing is affected by ion damage and effects due to recrystallization of the amorphous layer. Electrical carrier profiles indicate that carrier concentration higher than the usual Ga solid solubility can be achieved in Ga-implanted Si recrystallized at 600‡C. However, this large acceptor concentration diminishes after higher temperature annealing. For 900‡C anneals, the carrier concentration is limited by the Ga solid solubility and some compensation due to unannealed ion damage.

The three-dimensional nature of the state of deformation in a single-lap test specimen is investigated in a linear elastic finite element analysis in which the boundary conditions account for the geometrically non-linear effects. The validity of the model is demonstrated by comparing the resulting displacement fields with those obtained from a moiré inteferometry experiment. The three-dimensional adherend and adhesive stress distributions are calculated and compared with those from a two-dimensional non-linear numerical analysis, Goland and Reissner's solution, and experimental measurements. The nature of the three-dimensional mechanics is described and discussed in detail. It is shown that three-dimensional regions exists in the specimen, where the adherend and adhesive stress distributions in the overlap near (and especially on) the free surface are quite different from those occurring in the interior. It is also shown that the adhesive peel stress is extremely sensitive to this three-dimensional effect, but the adhesive shear is not. It is also observed that the maximum value of the peel stress occurs at the end of the overlap in the central two-dimensional core region, rather than at the corners where the three-dimensional effects are found. The extent of three-dimensional regions is also quantified.

The window glass substrates are commonly used in optical semiconductor and micro-electrical-mechanical system packages. The determination of bending strength of such glass substrates is important for guaranteeing good yield rate and reliability of those packages. To evaluate the dicing effect on the bending strength of window glass substrate, a three-point bending (3PB) test with a uni-axial loading is adopted in this study. Since the failure initiation of the glass substrate specimen in the most of cases starts at its free edges caused by the dicing, the calculation of the free edge stress of the glass substrate specimen becomes essential and needs to be performed using a finite element analysis during the 3PB test. Furthermore, a point-load on elastic foundation (PoEF) test, which features bi-axial stresses and can avoid the edge chipping effect caused by the dicing, is also applied to evaluate the surface roughness effect on the bending strength of the glass substrate. The test results are presented in terms of both bending strengths for frontside and backside surface control cases, along with the corresponding failure modes. And precise edge-stress calculations for the 3PB test are discussed in detail through the finite element analyses with various models, including noncontact and contact models associated with both displacement and force boundary conditions.