A transition layer of Ni-P coating will help enhance the hydrogen sensing stability of Pd films supported by silicon wafers. In this work, Pd films were electrodeposited on electroless Ni-P coated silicon wafers. The effect of deposition parameters on the microstructure (especially the morphology) of Ni-P coatings and Pd films were investigated. Experimental results indicated that a lower pH value of electroless plating solution and a longer electroless plating time could increase the size of Ni-P nodular particles. In addition, the morphology of Pd films was shaped by the nanostructures of the Ni-P coating. An optimized Pd/Ni-P structures is expected to present good hydrogen sensing performance.
In the presence of CTMAB and citric acid-sodium hydroxide buffer solution (pH 3 .5) medium,2-(2-quinolinylazo)-4-methyl-1,3-dihydroxidebenzene (QAMDHB) r eacts with vanadium(Ⅴ) and forms a stable 2∶1 color complex with molar absorpt ivity of 8.05×104L·mol -1 ·cm -1 at 552nm.Beer's law is obeyed in the range of 0—0.6μg/mL.This method was applied to the determination of vanadi um in alloy with good results.
In response to lead-free requirements and market forces, pure tin finishes have been widely used as a Pb-free option for semiconductor lead frames and electrical connectors in the microelectronics industry. Pure tin finishes could easy have a discoloration during reflow process since the reflow temperature is as high as 260°C, which could lead to a reliability issue. In this work, matte tin was electroplated onto C194 substrate. The microstructure of the deposit fabricated at different current density and different stannous concentrations was investigated with scanning electron microscope (SEM). It was found that, with increase of the current density and decrease of the stannous concentration, the grain size became smaller and the grain structure became looser, which resulted in the discoloration of pure tin finishes. Moreover, the compactness of the deposit and the current efficiency were also reduced. Copper diffusion was found to occur more easily in the deposit with a lower compactness, which may promote interfacial reaction to form intermetallic compounds (IMC) and further accelerate reflow discoloration of the pure Sn deposits.
Through silicon via (TSV) is a high performance technique to create 3D packages and 3Dintegrated circuits, compared to alternatives such as package-on-package, because the density of the via is substantially higher. The effect of current density and bath's organic additives on internal stress of copper electrodeposited from TSV filling methanesulfonate bath has been studied by Surface Profiler, X-ray diffraction (XRD) and Scanning electron microscope (SEM). We show that addition of the organic additives and current density can affect the internal stress of electrodeposited cupper films. The XRD patterns of copper films reveal the presence of (1 1 1), (2 0 0), (2 2 0), and (3 1 1) peaks, intensity of which is connect with the concentration of the organic additives in the plating bath and the current density of electrodeposition.
The most important factor that causes delamination between copper alloy lead frame and epoxy mold compound is copper oxide. To identify the factors that influence the formation of oxide film on copper substrate, oxidation mechanism of several lead-frame copper alloys was investigated. The oxide film structure of copper alloy was found to be CuO/Cu/sub 2/O/Cu by AES analysis. Various copper alloys had great difference in CuO/Cu/sub 2/O ratio. Oxidation rate of copper alloy was further studied by measuring the oxide thickness as a function of time at 320/spl deg/C. The results showed that C5191 and C7025 had lower oxidation rate than EFTEC64T and C194, which promoted the growth of CuO. The calculation from AES depth profile of copper atom confirmed that grain boundary diffusion coefficients of C5191 and C7025 were nearly two magnitudes smaller than those of EFTEC64T and C194. At a low temperature (usually below half of melting point), the growth of oxide film is mainly dominated by the grain boundary diffusion. It was found by SPM analysis that copper alloys with smaller grain size had more paths for copper atom to diffuse from substrate to the interface of oxide and air, thus leading to higher oxidation rate. The segregation effect of solute elements of copper alloys at the oxide/substrate interface also played an important role in the growth of oxide.
The paper presents a novel on-line transient moving chemical reaction boundary method (tMCRBM) for simply but efficiently stacking ionizable analytes in high-salt matrix in capillary zone electrophoresis (CZE). The powerful function and stability of the tMCRBM are elucidated with the ionizable test analytes of l-phenylalanine (Phe) and l-tryptophan (Trp) in the matrix with 85.6−165.6 mM sodium ion and further compared with the normal CZE of Phe and Trp samples dissolved in running buffer. The results verify that (1) the on-line tMCRBM mode can evidently increase separation efficiency, peak height, and resolution, (2) with the mode, the analytes in a 28-cm high-salt matrix plug can be stacked successfully and further separated well, (3) the values of relative standard deviation of peak height, peak area, and migrating time range from 3.9% to 6.1%; the results indicate the high stability of the technique of tMCRBM-CZE. The techniques implies obvious potential significance for those ionizable analytes, e.g., protein, peptide, and weak alkaline or acidic compound, in such matrixes as serum, urine, seawater, and wastewater, with high salt, which has a deleterious effect on isotachophoresis (ITP) and especially on electrostacking and field-amplified sample injection (FASI). The mechanism of stacking of zwitterionic analytes in a high-salt matrix by the tMCRBM relies on non-steady-state isoelectric focusing (IEF) but not on transient ITP, electrostacking, and FASI.
With the increase of system operating frequency and chip switching speed, electro-magnetic interference (EMI) shielding materials were wildly used in chip packaging technology. Packaging manufacturing process which bring cracks from the outer EMI shielding layer into the inner die has important influence on chip quality. In this paper, the influence on manufacturing parameters, such as film thickness and self-annealing time, on film strength were investigated. The microstructure characteristics and properties of copper films under different film thicknesses and self -annealing time were discussed. Microstructural characteristics were analyzed using field emission scanning electron microscopy (FESEM) and film properties were measured by nano-indentation instrument. Experimental results show that the 4um thickness of sputter copper film can achieve the lowest hardness performance and highest young's modulus of 108.3GPa. After 60 hours of self-annealing at room temperature, the grain was more stable than that of electroplated copper. The film thickness was proved to have significant influence on chips mechanical properties. Microstructure characteristics when stainless steel was sputtered on the top layer is discussed.
Abstract A novel method for intermolecular functionalization of terminal and internal alkenes has been designed. The electrophilic reagent, hypervalent iodine, plays a key role in this process by activating the alkene C=C bond for nucleophilic addition of the palladium catalyst. This process generates an iodonium‐containing palladium species which undergoes CO insertion. The new approach, intermolecular oxycarbonylaton reactions of alkenes, has been achieved and carried out under mild reaction conditions to produce the corresponding β‐oxycarbonylic acids with excellent efficiencies and levels of regio‐ and diastereoselectivity.
A room-temperature NO2 gas sensor of high sensitivity, selectivity and stability based on a low-cost, all-carbon nanoscale heterostructure and eco-friendly 2D rGO–CD hybrids.
Moisture ingression in plastic packages generally occurs through delaminated interfaces between different materials. So the adhesion strength between molding compound and substrate is crucial to the plastic package reliability. In the present work, a sample preparation device was designed for molding compound adhesion test. A series of experiments has been done with this device. The results showed that the data obtained with this device was stable. The data fluctuation was relatively small. The sample preparation device was effective in molding compound adhesion test.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)