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A high stability non-cyanide gold-tin alloy electroplating solution was developed to prepare Au-Sn bumps in flip-chip packaging of light-emitting diode. 5, 5- Dimethyl hydantoin (DMH) was used as the main complexing agent for Au(III) and Sn(IV) was used as the main salt of tin. The additions of complexing agents stabilized the Sn(IV) and improved the stability of electroplating solution. To obtain eutectic composition of Au-Sn coating, the ratio of Au (III) to Sn(IV) was determined to be 1:10. The polarization potential of tin ion was positively shifted, which was approaching to the deposition potential of gold ion. The deposition potential of Au-Sn coating was −0.93 V. The stirring rate had an effect on the content of tin atom in Au-Sn coating. Energy dispersive X-ray spectrometer results showed that the tin content decreased with increasing stirring rate. Scanning electron microscope images showed that the Au-Sn coating became denser with increasing stirring rate. The optimal stirring rate was 100 rpm under a current density of 40 mA/cm2. The content of tin atom in the Au-Sn coating increased when the current density was increased in the range of 20~55 mA/cm2. Voids and larger grains of Au-Sn coating formed at high current density.

Since the traditional risk assessment method fails to fully reflect the special operating environment of the electric transmission line and its own characteristics, a multidimensional risk assessment method combining multiple factors is proposed. Firstly, according to the statistical method, the risk assessment model is established based on the historical fault and defect information of the electric transmission line. Secondly, the quantification process of the quantity of state of each component of the electric transmission line is derived, to obtain the risk assessment results with fault probability. Finally, the influence of factors such as the service life of the electric transmission line equipment, time and geographical location information of the electric transmission line and the operating status of the power grid on the risk value of the electric transmission line is studied. Examples show that the proposed method can well predict the risk of the electric transmission line, providing a good reference for the maintenance schedule and equipment replacement of the electric transmission line.

With the development of flip-chip packaging technology in high powered light-emitting diode (LED), the size of bump which plays a vital role to maintain the reliability of interconnects continues to decrease. Au-30at.%Sn eutectic alloy is one of the most promising lead-free solders, which has been widely used in LED packaging, owing to its excellent mechanical property and thermal conductivity. In the present work, a relatively stable non-cyanide electroplating solution was obtained. The co-electrodeposited films with bright silver surface and fine crystal grains were obtained, when the peak current density was between 25 mA/cm2 and 30 mA/cm2. Chronopotentiometry analysis indicated that the irregular and coarsened particles appeared under a relatively low current density. The optimal co-electroplating temperature of Au-Sn alloy was between 30 °C and 40 °C, at which the co- electrodeposited film has a nearly eutectic composition with a bright silver surface and fine crystal grains. The cathodic polarization curve showed the effect of different plating temperature on the co-deposition Au-Sn alloy. When the plating temperature was between 20 °C and 60 °C, the coelectrodeposition of Au-Sn alloy were occurred at -797 mV.

Au-30at.%Sn eutectic alloy is useful in electronics for its superior mechanical and thermal conduction properties. Compared with traditional methods (Au-Sn solder preform and evaporation), the electroplating is an attractive method to obtain Au-Sn solder due to its cost-effective. In this work, Au-Sn films were co-electroplated via a pyrophosphate based bath. Electrochemical studies have been conducted to examine the effects of bath temperature on plating process. It was found that the rate for deposition of Au-Sn alloys was increased with bath temperature increased. Besides, the effects of bath temperature on the morphology and composition of electrodeposits were discussed.

A highly stable non-cyanide electroplating bath which can maintain clear at least one month was developed based on Au(III)-Sn(II) using 5,5-dimetheyl-hydantoin (DMH) and pyrophosphate as complexes. The combination of DMH and pyrophosphate can effectively minimize the difference of the deposition potentials between Au and Sn, making the codeposition of Au-Sn alloys possible. The cyclic voltammetry (CV) curve revealed that the codeposition of Au and Sn occurred at the potential of −790mV with a peak potential of −900mV. Pulsed plating was employed to optimize the morphology and composition of Au-Sn alloy films. The effects of pulse frequency, duty percentsge and peak current density on the morphology and composition of the deposits were investigated. The compact Au-Sn eutectic alloy with Sn content controlled from 10 at.% to 50 at.% can be obtained. The Au-Sn deposits were characterized by the scanning electron microscopic (SEM) and energy-dispersive spectroscopic (EDS) analyses.

Au-30at.%Sn bumps play a very important role in high-power LED chip packaging. The Au-30at.%Sn bumps are usually fabricated by electron-beam evaporation and sputtering. These techniques are either costly or difficult in operation. Moreover, it is difficult to fabricate solder bumps with the continuously downsizing. Co-electroplating is a promising alternative. In the present work, Au-Sn films were co-electroplated using a non-cyanide solution. The effects of stirring speed on composition and morphology of the co-electroplating Au-Sn films and its mechanism were investigated and the mechanism was also discussed. It was found that when the stirring speed was higher than 300 rpm, few pits formed. With increasing stirring speed, in general the Sn content of the Au-Sn film decreased; when the stirring speed was between 300 rpm and 400 rpm, the Sn content of the Au-Sn film was in the range of 29.51at.%∼30.9at.%, which is near the eutectic composition (Au-30at.%Sn). Based on the electrochemical testing and calculation, the diffusion coefficient of Sn was significantly smaller than that of Au, which resulted in the decreasing Sn content in the Au-Sn film with increasing stirring speed.

A novel erbium ions doped fluoro-tellurite glasses were prepared, and intense 2.7 μm emission was observed. The present Er3+-doped fluoro-tellurite glasses with large 2.7 μm emission cross-sections (6.32×10-21 cm2) indicates that it has a very promising application for solid state lasers around 3 μm.

Transparent glass ceramics was obtained by heat-treating in 90TeO2-10Na2O glass. 2.7 μm emission of Er3+ ions in the glass and glass ceramics matrix has been tested and compared, and the results suggest that nucleation is a possible way to enhance 2.7 μm emission. Er3+ ions were embedded into the nano-crystals (Er2Te5O13 and Er6Te5O19.2) evidenced by X-ray powder diffraction (XRD) spectra and the crystal size was calculated by Debye-Scherrer formula.

2.0μm spectroscopy of a new germanate-tellurite glass with Ho3+/Yb3+ codoping is synthesized and analyzed. Efficient 2.0μm emission of Ho3+ ions sensitized by Yb3+ ions from the host glass is observed under 980nm pumping. The maximum emission cross section of Ho3+ ions transition is 4.32×10-21 cm2 around 2.0μm. The good spectroscopic properties and the efficient energy transfer from Yb3+ to Ho3+ suggest that Ho3+/Yb3+ codoped germanate-tellurite glass may become an attractive host for developing solid state lasers operating in the mid-infrared.

In this paper we propose an algorithm to multi-robot cooperative Simultaneous Localization and Mapping (SLAM) with monocular camera mounted on each robot. The map consists of a sparse set of features, and the feature is prominent in the environment that robots explored, we call it salient landmark. The scene of exploration is typical office environment. Vertical lines and doorplates of environment are considered as visual landmarks to implement single-robot localization and multi-robot cooperation. An approach based on duplicate landmarks and rendezvous is also presented to improve the accuracy and reliability of SLAM. Our system was evaluated by an indoor two robot team, the results of this test showed that our approach is valid.

This paper proposed a limit-cycle based algorithm for cooperative hunting task using multiple mobile robots. By integrating the model-based system and the behavior-based system, a hybrid distributed control system is established, which emphasizes on the autonomy and intelligence of each robot. On the one hand, the algorithm uses artificial potential field for multi-robot formation. On the other hand, the limit-cycle based algorithm is introduced to enable the robot team to pursue themoving target and ultimately encircle the target in a symmetrical circle formation. In addition, the paper designs a heading direction control law for obstacle avoidance, and solves the problem of robot freezing caused by counteraction between repulsion and attraction. Simulation results show the effectiveness and reliability of the proposed method in cooperative hunting control.

This paper considers the scenario that a team of autonomous robots pursues a smart evader while concurrently building a global map in an unknown environment. We develop a modular hybrid system architecture to implement the decentralized control and coordination of multiple pursuers. A probabilistic framework is established to integrate the map building process with evader detection. Taking account of the nonholonomic constraints of vehicles, we improve the global-max pursuit policy with a novel underlying navigation method. Experimental results with physical robots demonstrate the effectiveness of our approach.