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Ashutosh Sharma,Hansung Lee,Byungmin Ahn 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and sparkplasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFex(x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSnalloy contained FCC with CuxSnywhile AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr andAlCuSiFeMn showed the formation of BCC + FCC with additional σ- and μ-phases in the HEA matrix. The calculated thermodynamicparameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mngive rise to major BCC with brittle σ- and μ-phase, which further improves their mechanical strength.
Effect of Various Factors on the Brazed Joint Properties in Al Brazing Technology
Ashutosh Sharma,Seung Hyun Lee,Hyung Oh Ban,Young Sik Shin,Jae-Pil Jung 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.2
Last few decades have seen a rapid increase in the fabrication and characterization of Al alloys for automobiles, heat exchangers and aerospace industries. Aluminium alloys are popular because of their high specific strength, light weight, excellent wear and high oxidation resistance. The development of aluminium alloys in these applications makes their study and research of utmost importance. Brazing is applied to the aluminium alloys for joining various aluminium parts together in most of the industrial applications. Various parameters affect the joining process of these aluminium alloys. In this article, various types of processing parameters have been discussed, and special attention has been given to the category of aluminium brazing alloys. The article reviews on the various parameters that affect the brazing property in various scientific and technological applications.
Possibility of Al-Si Brazing Alloys for Industrial Microjoining Applications
Sharma, Ashutosh,Jung, Jae Pil The Korean Microelectronics and Packaging Society 2017 마이크로전자 및 패키징학회지 Vol.24 No.3
Aluminium alloys have been used widely since hundreds of years in automotive joining. Silicon is an excellent alloying element that increases the fluidity, depresses the melting temperature and prevents shrinkage defects during solidification, and is cost effective raw material. In recent few decades, research on cast Al-Si alloys has been expanding globally in military, automobile and aerospace industries. These alloys are good wear and corrosion resistant which depends on processing parameters and service conditions. However, the formation of big Si-needles in Al-Si alloys is a serious issue in joining industries. Silicon modification treatments are generally carried out to improve their durability and strength. This paper covers an elaborative study of various Al-Si alloys, the modification strategies to refine the Si-needles, effect of processing parameters and joining characteristics for automotive applications.
Fabrication and Shear Strength Analysis of Sn-3.5Ag/Cu-Filled TSV for 3D Microelectronic Packaging
Ashutosh Sharma,정도현,노명훈,정재필 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.6
In this study, lead free Sn-3.5Ag solder bumps have been depositedon Cu-filled through-silicon via (TSV) by electroplating method. Thesolder bumps are plated using an acidic solution composed of SnSO4,H2SO4, Ag2SO4, thiourea and an additive. The current density isvaried from −30 to −60 mA/cm2 to obtain the eutectic Sn-3.5Agsolder. The copper is electroplated in TSV using an acidic solution ofCuSO4·5H2O, H2SO4, HCl, and an inhibitor. The bottom-up Cufillingin TSV is achieved by a 3-step pulse periodic reverse (PPR)electroplating. It has been observed that the eutectic Sn-3.5Ag solderis achieved at a current density of −55 mA/cm2. The solder bumps arefurther reflowed onto TSV at 260 °C for 20 seconds, and shearstrength of the formed Sn-3.5Ag/Cu-filled TSV joint is investigated. The results indicate the formation of Cu6Sn5 and Ag3Sn intermetalliccompounds (IMCs) at the joint interface. It is found that with anincrease of shear speed from 0.5-10 mm/s, the shear stress initiallyincreases to a maximum, and then decreases beyond shear speed of10 mm/s through 500 mm/s. It is shown that the ductile fracture modegradually decreases beyond shear speed of 10 mm/s and disappearscompletely at 500 mm/s.
Recent advances on H<sub>2</sub> sensor technologies based on MOX and FET devices: A review
Sharma, Bharat,Sharma, Ashutosh,Kim, Jung-Sik Elsevier 2018 Sensors and actuators. B Chemical Vol.262 No.-
<P><B>Abstract</B></P> <P>The importance of metal oxide semiconductor (MOX) and field effect transistor (FET) based sensors has been increasing due to their extended practical applications for gas detection. Various investigations have confirmed that gas sensing characteristics depend on the sensitivity of the metal oxide and catalytic materials. In recent years, hydrogen gas sensor technology has been progressively more capable in practical applications. The propagation velocity of hydrogen flames is high enough to cause severe explosion over an extensive range of 4%–75% H<SUB>2</SUB>. Therefore, the use of hydrogen carries a great risk, and the requirement for its leakage detection is imperative in hydrogen generation, transportation, stockpiling, and its utilization. Usage of MOX and FETs has increased tremendously in designing precise hydrogen sensors. Therefore, in this review, the authors have focused on the recent development in MOX and FET based hydrogen sensors. MOX sensors are most widely available as commercialized ones.Also, FET-type gas sensors have many advantages, compared with traditional ones owing to their reduced shape, size, and lower production cost. Nevertheless, the processing parameters and reproducibility need to be enhanced for expanding their applications. In this review, the role of the important sensing parameters, e.g., measurement range, sensitivity, selectivity, response and recovery time, on the sensing mechanism and operation, and the most recent innovation and improvement in MOX and FET sensing technologies are discussed. Finally, we report the sensing techniques, mechanism and factors affecting the sensitivity for MOX and MOSFET type sensors.</P>
SiC based Technology for High Power Electronics and Packaging Applications
Sharma, Ashutosh,Lee, Soon Jae,Jang, Young Joo,Jung, Jae Pil The Korean Microelectronics and Packaging Society 2014 마이크로전자 및 패키징학회지 Vol.21 No.2
Silicon has been most widely used semiconductor material for power electronic systems. However, Si-based power devices have attained their working limits and there are a lot of efforts for alternative Si-based power devices for better performance. Advances in power electronics have improved the efficiency, size, weight and materials cost. New wide band gap materials such as SiC have now been introduced for high power applications. SiC power devices have been evolved from lab scale to a viable alternative to Si electronics in high-efficiency and high-power density applications. In this article, the potential impact of SiC devices for power applications will be discussed along with their Si counterpart in terms of higher switching performance, higher voltages and higher power density. The recent progress in the development of high voltage power semiconductor devices is reviewed. Future trends in device development and industrialization are also addressed.
Sharma, Swati,Sharma, Ashutosh,Cho, Yoon-Kyoung,Madou, Marc AmericanChemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.1
<P>Single suspended carbon nanowires (CNWs) integrated oncarbon-MEMS(CMEMS) structures are fabricated by electrospinning of SU-8 photoresistfollowed by pyrolysis. These monolithic CNW-CMEMS structures enablefabrication of very high aspect ratio CNWs of predefined length. TheCNWs thus fabricated display core–shell structures having agraphitic shell with a glassy carbon core. The electrical conductivityof these CNWs is increased by about 100% compared to glassy carbonas a result of enhanced graphitization. We suggest some tunable fabricationand pyrolysis parameters that may improve graphitization in the resultingCNWs, making them a good replacement for several carbon nanostructure-baseddevices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-1/am2014376/production/images/medium/am-2011-014376_0002.gif'></P>
Electromigration of Composite Sn-Ag-Cu Solder Bumps
Ashutosh Sharma,Di Erick Xu,Jasper Chow,Michael Mayer,Heung-Rak Sohn,정재필 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.6
This study investigates the electromigration (EM) behavior of lead free Sn- Ag-Cu (SAC) solder alloys that were reinforced with different types of nanoparticles [Copper-coated carbon nanotubes (Cu/CNT), La2O3, Graphene, SiC, and ZrO2]. The composite solders were bumped on a Cu substrate at 220°C, and the resistance of the bumped solders was measured using a four wire setup. Current aging was carried out for 4 hours at a temperature of 160°C, and an increase in resistance was noted during this time. Of all the composite solders that were studied, La2O3 and SiC reinforced SAC solders exhibited the smallest resistances after current aging. However, the rate of change in the resistance at room temperature was lower for the SiC-reinforced SAC solder. The SAC and Graphene reinforced SAC solder bumps completely failed within 15 - 20 min of these tests. The SiC nanoparticles were reported to possibly entrap the SAC atoms better than other nanoparticles with a lower rate of EM.