Effect of the deposition parameters on the voiding propensity of solder joints with Cu electroplated in a Hull cell

A quantitative study of the impact of key Cu plating parameters on the voiding propensity of solder joints with Cu electroplated in a commercially available plating solution (CAPS) is performed first on 0.3 cm² Cu rotating disk electrode. It is shown that similar to samples plated in a generic plating solution (GPS) containing bis(3-sulfopropyl) disulfide, polyethylene glycol, and Cl⁻ ions, void-prone samples are deposited predominantly at higher overpotentials, in the range from positive to −0.20 V. In the second part, a Hull cell with 46 cm² cathode is used to scale up the voiding study in both, GPS and CAPS. It is demonstrated that plating conditions could be chosen in a way to generate both, void-prone and void-proof Cu on the same cathode panel. Thus, the controlled voiding propensity illustrated for the first time in a prototype of industrial Cu plating helps in realizing the sporadic nature of the voiding phenomenon.     

Counterion Interaction and Association in Metal-Oxide Cluster Macroanionic Solutions and the Consequent Self-Assembly

The interaction between large metal-oxide polyanions and their counterions is unique. Owing to their size disparity, there is a moderate ion-pairing effect and loose distribution of counterions around macroions, which leads to the unique solution behavior and the self-assembly of the macroions in polar solvents, and the counterion exchange capability around macroions. Furthermore, the macroion–counterion interaction also affects the catalytic behavior of the polyoxometalate (POM) clusters. Replacement of functionalized cations helps to modify the POM anions through static charge attraction. At the same time, the strong POM–counterion interaction can also lead to counterion-dependent synthesis. Recent developments on theoretical simulations help to understand this interaction at the molecular scale. This review summarizes the chronological progress of the exploration of macroion–counterion interaction (both theoretically and experimentally) and its impact on related research fields.     

用激光扫描法自动测量齿轮接触斑点

齿轮接触斑点可以作为评价齿轮承载能力的一项重要指标．迄今为上，接触斑点的测量仅限于目视观察，所以精度很低．本文介绍一种全新的、基于激光扫描的接触斑点自动测量装置。并对该装置的测量原理作了简要讨论。     

不锈钢散热器芯体真空钎焊工艺研究

针对散热器芯体产品进行了钎料选择和真空钎焊工艺研究，提出采用粘带钎料的生产方案和真空钎焊工艺参数，经小批量生产，各种试验，试车，证明本项目研究的钎焊工艺是成功的。     

Cathodoluminescence study of crystalline quality of (Al, In, Ga)N heterostructures

Wurtzite InGaN/GaN and AlGaN/GaN heterostructures grown by metal organic vapor phase epitaxy were studied using cathodoluminescence (CL) combined with secondary electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The surface morphology of samples containing InGaN layers is dominated by three types of defects: mesa-like hexagonal structures, hexagonal pyramids and micropipes. At the positions of pyramids the whole epilayer is thicker than at defect free positions, while at the positions of micropipes the whole epilayer is much thinner. The luminescence efficiency as well as the emission wavelength are influenced by these defects. In SL structures an increasing SL period thickness in the growth direction was observed. Panchromatic CL images show intensity inhomogeneity in both InGaN/GaN and AlGaN/GaN heterostructure, which are related to local variations of the interface quality. In AlGaN/GaN SQW structures a broad deep-level luminescence band at around 543 nm was observed, which is generally absent in InGaN/GaN heterostructures. This deep-level emission is strongly enhanced in defect positions.     

Cu(II)-catalyzed THM formation during water chlorination and monochloramination: A comparison study

The catalytic effect of Cu(II) on trihalomethane (THM) formation during chlorination and monochloramination of humic acid (HA) containing water was comparatively investigated under various pH conditions. Results indicate that in the presence of Cu(II), the formation of THMs was significantly promoted as pH decreased in both chlorination and monochloramination. More THMs were formed during Cu(II)-catalyzed monochloramination which was partially due to enhanced hydroxyl radical (OH) generation as demonstrated by electron spin resonance (ESR) analysis. To discriminate the reactive moieties of HA, nine model compounds, which approximately represented the chemical structure of HA, were individually oxidized by chlorine or monochloramine. Results show that Cu(II) could promote THM formation through reacting with citric acid and similar structures in HA. During chlorination and monochloramination of citric acid in the absence of Cu(II), major intermediates including chlorocarboxylic acid, chloroacetone and chloroacetic anhydride were identified. However, the catalysis of Cu(II) did not produce any new intermediate. The complexation of Cu(II) with model compounds was characterized via FTIR analysis. The reaction mechanism for Cu(II)-catalyzed THM formation was proposed to comprise two pathways: (1) indirect catalysis in which OH oxidizes the large molecules of HA into small ones to enhance THM formation; and (2) direct catalysis in which Cu(II) complexes with HA to accelerate the decarboxylation steps for THM formation.     

Modeling and characterization of dynamic failure of borosilicate glass under compression/shear loading

In this paper, we study the impact-induced dynamic failure of a borosilicate glass block using an integrated experimental/analytical approach. Previous experimental studies on dynamic failure of borosilicate glass have been reported by Nie et al. [Nie X, Chen WW, Sun X, Templeton DW. Dynamic failure of borosilicate glass under compression/shear loading – experiments. J Am Ceram Soc, in press.] using the split Hopkinson pressure bar (SHPB) technique. The damage growth patterns and stress histories have been reported for various glass specimen designs. In this study, we propose to use a continuum damage mechanics (CDM)-based constitutive model to describe the initial failure and subsequent stiffness reduction of glass. Explicit finite element analyses are used to simulate the glass specimen impact event. A maximum shear stress-based damage evolution law is used in describing the glass damage process under combined compression/shear loading. The impact test results are used in quantifying the critical shear stress for the borosilicate glass under examination. It is shown that with only two modeling parameters, reasonably good comparisons between the predicted and the experimentally measured failure maps can be obtained for various glass sample geometries. Comparisons between the predicted stress histories for different sample designs are also used as model validations.     

Deterministic global optimization approach to steady-state distribution gas pipeline networks

Natural gas is normally transported through a vast network of pipelines. A pipeline network is generally established either to transmit gas at high pressure from coastal supplies to regional demand points (transmission network) or to distribute gas to consumers at low pressure from the regional demand points (distribution network). In this study, the distribution network is considered. The distribution network differs from the transmission one in a number of ways. Pipes involved in a distribution network are often much smaller and the network is simpler, having no valves, compressors or nozzles. In this paper, we propose the problem of minimizing the cost of pipelines incurred by driving the gas in a distribute non-linear network under steady-state assumptions. In particular, the decision variables include the length of the pipes’ diameter, pressure drops at each node of the network, and mass flow rate at each pipeline leg. We establish a mathematical optimization model of this problem, and then present a global approach, which is based on the GOP primal-relaxed dual decomposition method presented by Visweswaran and Floudas (Global optimization in engineering design. Kluwer book series in nonconvex optimization and its applications. Kluwer, Netherlands, 1996), to the optimization model. Finally, results from application of the approach to data from gas company are presented.