Low Cost Alloy Deposition for High Power Applications
12 Dec 2017-pp 541-545
TL;DR: In this paper, a low cost method for depositing the hard alloy materials for electrical contact as well as MEMS structure application was reported, where the alloy formation was performed using a novel Electroplating method of synthesis.
Abstract: In this paper, we have reported a low cost method for depositing the hard alloy materials for electrical contact as well as MEMS structure application. Conventional methods of deposition like co-sputtering, e-beam PVD, etc. required a high running cost and had a high waste generation due to poor selectivity of deposition. The alloy formation was performed using a novel Electroplating method of synthesis. Au–Co alloy is made using a single bath electrodeposition for Au–Co thin films. XRD peaks analysis was used to confirm the alloy formation. AFM analysis was used to study the grains size, and surface roughness and the hardness measurement was performed using micro-indentation. The less surface roughness and high strength (Hardened) gold alloy formation were observed for a neutral pH (6.6 pH) Au–Co Alloy electroplating conditions. The low pH (4.0 pH) solution results to higher surface roughness while higher pH of the solution was not suitable for Au electroplating.
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24 Feb 2011
TL;DR: Gold has been valuable throughout the ages mainly because of its physical properties of softness, ductility, corrosion resistance, density, and scarcity as discussed by the authors, and it is the most beautiful of all the elements in their pure form.
Abstract: While all that glitters may not be gold, it is the most beautiful of all the elements in their pure form. The name gold comes from the Old English Anglo-Saxon word for geolo meaning “yellow” while the symbol, Au, comes from the Latin word aurum, meaning “glowing dawn.” Historically gold was one of the first metals known. Gold has been valuable throughout the ages chiefly because of its physical properties of softness, ductility, corrosion resistance, density, and scarcity. The first gold coin dates back to about 560 BC. Gold cups and jewelry predating 3500 BC have been found in Iraq. The ancient Egyptians knew how to hammer gold into leaf as thin as 66 nm. The importance of gold as a form of currency was at a high point in the 1900s whenmost countries were on the gold standard. The bullion price of gold over the past 21 years is shown in Figure 4.1. There have been about 160 metric kilotons of gold mined since it was first discovered, and it occupies about 0.005 ppm of the earth’s crust. The world demand for gold in 2007 was approximately 80,000,000 troy ounces. Figure 4.2 shows the breakdown of the gold usage by industry. Jewelry comprises the largest fraction of the usage; however, much of that is not electroplated. For jewelry applications, gold is commonly alloyed with group IB or IIB metals, particularly copper, silver, platinum, and palladium, principally to improve its strength and wear resistance. The electrodeposition of gold is a relatively new process; it has been traced to the early work of Brugnatelli in 1805 [1]. The motives behind the use of electroplated gold changed dramatically in themid-twentieth centurywhen the emerging electronics industry required special-purpose electrical connections. The electronics industry consumed 5,330,000 troy ounces in 1994. Figure 4.3 shows the growth in the use of gold in the electronics industry by year. The use of electroplated gold in a variety of different functions in the electronics industry has led to (1) many advances in our fundamental understanding of the electrodeposition process and (2) new electroplating technologies over the past 25 years. Electrochemically deposited gold has satisfied many of the demands of the electronics industry. Gold has the third best electrical and thermal conductivity of all metals at room temperature. Also it has high ductility and excellent wear resistance, which are important for electrical contacts. The inertness of gold prevents the formation of insulating surface oxides (as compared to metals like aluminum). Group IIB metals (e.g., gold) are not good catalysts for other reactions, thus avoiding certain problems. For example, group IB metals (particularly platinum and palladium) can catalyze the polymerization of organic molecules forming insulating layers. In addition, gold is an excellent metal for wire bonding integrated circuits (ICs). Gold wires can be bonded to pure, soft gold pads by thermocompression bonding (300–400 C at high pressure to form a weld) or thermosonic bonding (150–200 Cwith ultrasonic energy to form a weld). Aluminum wires can be attached by ultrasonic bonding (ambient temperaturewith ultrasonic energy). These benefits have justified the high cost of gold in the packaging and interconnection of ICs. A geographical breakdown of the use of gold in the electronics industry is also shown in Figure 4.3. Japan is the largest consumer of gold for electronic applications, followed by North America, Western Europe, and the Pacific rim (excluding Japan). Although the use of gold for electronic interconnections has maintained steady growth over the past two decades, its use has not kept pace with the more rapid growth in the microelectronics industry, primarily because of gold’s high cost. The microelectronics industry has increased speed, performance, and packing density (number of transistors per unit area) while maintaining
50 citations
TL;DR: In this article, it is suggested that the polymer is not the only source of carbon contamination in electroplated hard gold films, and possible effects of the codeposition of polymer on grain size are also briefly discussed.
Abstract: Transmission electron micrographs of gold films plated in baths containing cobalt or nickel as the hardening agent showed the presence of uniformly distributed nonmetallic objects with diameters ranging from 20 to 70A. These objects are believed to represent single molecules, and their agglomerates, of the so‐called "polymer" which has been isolated by several investigators in the form of a transparent film upon dissolution of gold deposits in aqua regia. Micrographs of gold films plated in room temperature baths containing no hardening agents revealed the presence of much larger nonmetallic objects (up to 150A), which appeared to be gas bubbles, in addition to the features attributable to polymer molecules. Based on a comparison of the polymer content, estimated from the analysis of electron micrographs, with the total carbon content, it is suggested that the polymer is not the only source of carbon contamination in electroplated hard gold films. Possible effects of the codeposition of polymer on grain size are also briefly discussed.
38 citations
TL;DR: In this paper, a low voltage driven RF MEMS capacitive switch with the introduction of perforations and reinforcement is proposed, which reduces the pull-in voltage from 70 V to 16.2 V and the magnitude of deformation from 8 µm to 1 µm.
Abstract: Variation in actuation voltage for RF MEMS switches is observed as a result of stress-generated buckling of MEMS structures. Large voltage driven RF-MEMS switches are a major concern in space bound communication applications. In this paper, we propose a low voltage driven RF MEMS capacitive switch with the introduction of perforations and reinforcement. The performance of the fabricated switch is compared with conventional capacitive RF MEMS switches. The pull-in voltage of the switch is reduced from 70 V to 16.2 V and the magnitude of deformation is reduced from 8 µm to 1 µm. The design of the reinforcement frame enhances the structural stiffness by 46 % without affecting the high frequency response of the switch. The measured isolation and insertion loss of the reinforced switch is more than 20 dB and 0.4 dB over the X band range.
25 citations
TL;DR: In this article, a seed-layer-less gold electroplating method was proposed for growing a gold film on a silicon surface. But due to low adhesion of the gold, it had been considered that it is difficult to obtain the direct electrophoresis of gold on silicon.
Abstract: This paper presents a development and characterization of a novel technology for seedlayer-less gold electroplating This method allows that a gold film grows directly and selectively on a silicon surface In the MEMS field, the gold film is increasingly drawing attention for its low electrical resistivity, high physicochemical stability, high biocompatibility and high reflectivity to the infrared ray Due to low adhesion of the gold, it had been considered that it is difficult to obtain the direct electroplating film on a silicon surface The two-step gold electroplating method presented here, which contains the first thin electroplating of 02 μm with low current density of 075 mA/cm 2 and following annealing process at 250 °C for 30 min, achieves increasing adhesion and realizes practical gold film on a silicon
23 citations