Shyh-Biau Jiang

Surface and transverse morphology of micrometer nickel columns fabricated by localized electrochemical deposition

Micrometer nickel columns were fabricated locally on a copper substrate in a Watts bath by microanode guided electroplating which is commonly known as localized electrochemical deposition (LECD). A microanode of platinum (125 ?m in diameter) served to move up intermittently, thus guiding the growth of Ni deposit from the substrate. The separation between the microanode and top of the microcolumn was initially set at 10 ?m before setting out the electroplating. The electroplating current and local potential near the local region after the LECD were monitored and examined in this work. Surface and transverse morphology of the microcolumns were examined through a scanning electron microscope. LECD performed at biases less than 3.56 ? 0.01 V led to columns with smooth surfaces and circular internal transverse fully compacted, whereas when performed at biases higher than 3.56 ? 0.01 V it led to columns with a rough surface and distorted circular internal transverse with porosity in the center. The higher the bias, the worse the surface smoothness. The less circular the transverse, the less compactness in the transverse center. A compromise between the estimated supplying rate and the consumption rate of the nickel ions in the local region after the LECD is discussed to understand the dependence of the morphologies on the biases.

Fabrication of a micrometer Ni–Cu alloy column coupled with a Cu micro-column for thermal measurement

Micrometer Ni–Cu alloy columns have been fabricated by the micro-anode-guided electroplating (MAGE) process in the citrate bath. The surface morphology and chemical composition of the micro-columns were determined by copper concentration in the bath and by the electrical bias of MAGE. When fabricated in a bath of dilute copper (i.e. 4 mM) at lower voltages (e.g. 3.8 and 4.0 V), the alloy micro-columns revealed uniform diameter and smooth appearance. The alloy composition demonstrated an increase in the wt% ratio of Ni/Cu from 75/25, 80/20, 83/17 to 87/13 with increasing electrical bias from 3.8, 4.0, 4.2 to 4.4 V. However, it decreases from 75/25, 57/43 to 47/53 with increasing copper concentration from 4, 8 to 12 mM in the bath. Citrate plays a role in forming complexes with nickel and copper at similar reduction potentials, thus reducing simultaneously to Ni–Cu alloy. The mechanism for fabricating alloy micro-columns could be delineated on the basis of cathodic polarization of the complexes. A couple of micro-columns were fabricated using MAGE in constructing a pure copper micro-column on the top of a Ni/Cu (at 47/53) alloy micro-column. This micro-thermocouple provides a satisfactory measurement with good sensitivity and precision.

An Innovative Ultrasonic Time-of-Flight Measurement Method Using Peak Time Sequences of Different Frequencies: Part I

This paper proposes an innovative ultrasonic time of flight (TOF) measurement method with narrow-band transducers. By introducing the received ultrasonic wave peak time sequences (PTSs) of two slightly different frequencies, the relative TOF can be accurately identified with a much better resolution than a wave period. The new PTS TOF measurement is achieved in two steps. First, a PTS is built for receiving the ultrasound signal of each frequency according to the arrival time of the wave peaks by calculating the mean value of the adjacent crossover time. Second, the arrival time of the wave front is rebuilt by estimating the common initiation time of the PTSs for the received waves of slightly different frequencies. A mathematical model is derived to describe the signal reception, from which the TOF estimation algorithm was derived. A simulation model describing the characteristics of the ultrasonic transducer and the ultrasonic wave propagation physics was developed to verify the feasibility of the new algorithm. Finally, an experimental system for measuring the relative TOF over the known distance of 550-1450 mm was implemented to confirm feasibility and to demonstrate that a subwavelength resolution of 0.015 times of the wavelength was indeed achievable in measuring distances over meters.

Localized Ni deposition improved by saccharin sodium in the intermittent MAGE process

Localized Ni deposition improved by saccharin sodium (SS) in the intermittent microanode guided electroplating (intermittent MAGE) process has been investigated. This effect is more complicated than conventional planar electroplating. If there was an insignificant amount of SS in the bath (i.e. less than 1.0 mM), then the radius of the fabricated nodular columns would range from 37.5 to 42.5 ?m cyclically along the axis and the surface would be covered with a homogeneous layer of 3?8 ?m Ni particles. In the presence of an optimal amount of SS (i.e. around 1.0?3.0 mM), columns with uniform radius (around 42.5 ?m) were fabricated and the surface was covered by a homogeneous layer of fine Ni particles (i.e. diameter 1 ?m). With higher SS (4.0?6.0 mM in the bath), columns were constructed with uniform radius but the surface was covered by alternating zones of coarse and fine Ni particles. For SS beyond critical concentrations (8.0 mM at 4.0 V and 10.0 mM at 4.5 and 5.0 V), no microcolumn could be constructed and a universal planar Ni deposition on the substrate was formed instead. SS is an absorbent and it leads to cathodic polarization in the electroplating process. The influence of SS on the asymmetrical electric field distributed in the local area and formed by localized electrochemical deposition (LECD) has been studied by the use of the proposed model in this work and commercial finite element software.

Assessing the degree of localization in localized electrochemical deposition of copper

The localization of localized electrochemical deposition (LECD) was investigated using the microanode-guided electroplating (MAGE) technique. Two modes (i.e., one-step and intermittent-step) of the MAGE process were employed to explore the circular area around the bottom of the copper microcolumns deposited on a substrate. The diameter was utilized to estimate the localization occupied by the column instead of using the bottom area. For the hillocks deposited by one-step MAGE, the localization diameter increases with increasing the electric biases between the microanode and the substrate. For the copper microcolumns fabricated by intermittent-step MAGE, the localization diameter increases to a critical magnitude and levels off upon increasing the height of the columns. The critical localization diameter was found to be dependent on the electric biases and the initial gap between the microanode and the top of the microcolumn deposited earlier. The less the electric biases and the initial gap in intermittent MAGE, the smaller the localization diameter of the microcolumn. A model is proposed to illustrate the localization defined by one-step MAGE and the critical localization diameter (Dc) obtained from intermittent-step MAGE. A relationship between the ratio of the conical core strength to the conical periphery strength (i.e., Ecore/Ep) and the electric bias has been established for the critical localization diameter of the microcolumns. The strength ratio can be used as a criterion to predict whether a localization diameter increases or not.

Topside ionospheric electron temperature and density along the Weddell Sea latitude

It has been well known that the ionospheric electron density Ne is greater in the summer nighttime than daytime around the Weddell Sea region, which is named Weddell Sea Anomaly (WSA). This paper for the first time reports unusual increases (decreases) of the daytime (nighttime) electron temperature Te at about 830 km altitude over the WSA latitudes probed by Tatiana-2 during December 2009 to January 2010. Concurrent measurements at 660–830 km altitude observed by Tatiana-2, Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER), and Formosa Satellite 3/Constellation Observing System for Meteorology, Ionosphere and Climate (F3/C) reveal the anticorrelation between Te and Ne along the WSA latitudes in the daytime and nighttime. Based on F3/C Ne along the WSA latitudes observed at various local times, the associated Te values are computed. The Tatiana-2 and DEMETER observations as well as the computed results show that Te yield the maximum values over the WSA region during daytime and over the Indian and Atlantic Ocean area during nighttime. The maxima or minima in F3/C Ne and the computed Te reveal eastward phase shifts.

An Innovative Ultrasonic Time-of-Flight Measurement Method Using Peak Time Sequences of Different Frequencies—Part II: Implementation

This paper researches on the implementation of an ultrasonic time-of-flight (TOF) measuring system by the difference of the peak time sequences (PTSs) of dual frequencies. The process to develop appropriate implementation parameters was demonstrated. Critical characteristics of the transient behavior of the PTS were studied, and their counteracting data processing measures were devised in the process. Obtaining the PTS by averaging repeated test data and the linear regression on the PTS was found to be effective in uncovering the actual TOF of the first wavefront with high precision. A PC-based test bench was built to test the characteristics and to verify the performance of the new TOF measurement system. In our TOF measurement over the distance of 145 cm, a standard deviation (STD) of 0.0113 of a period was achieved by a nominal driving wave period of 25.6 μs (39 kHz) and a frequency difference factor of 0.0048. When applied to a distance measurement, the worst STD of 0.097 mm was achieved with a relative distance ranging up to 1450 mm, given the nominal driving wavelength of 8.6 mm. This new dual-frequency PTS-based TOF measurement system can be economically embedded in a microcontroller, together with a field-programmable gate array, and some simple transistors that are suitable for positioning mobile units indoors or in small open-field environments.

Micro-Anode Guided Electroplating (MAGE) Control System with Digital Imaging Enhancement

This article releases the details of the digital imaging enhancement for the micro-anode guided electroplating MAGE fabrication equipment. The control system architecture, the micro stepping architecture, the electroplating power source, the measurement system, the man machine interface, the control procedure and the digital imaging subsystem are described. The profile of the electroplating deposit during the initiation phase as monitored in real-time by the new imaging subsystem could verify the simulation prediction.

Micro-Anode Guided Electroplating (MAGE) Control System

This article releases the details of the equipment development for the micro-anode guided electroplating MAGE fabrication. The microstepping architecture, electroplating power source, control system architecture, measurement system, man machine interface and the control prodedure will be described. Metallic columns around 100 micrometers in diameter were fabricated up to 2cm long with this equipment to demonstrate its performance. An innovative intermittent MAGE mode is supported by this equipment so that it can produce micro columns of finer surface morphology and better circumferential uniformity than the conventional continuous electroplating.