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    Influences of solid-state brazing conditions on microstructure and tensile shear force of Ag-Cu-P brazed copper sheets
    (2018-06-04)
    Jattakul, P.
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    This study aimed to examine the tensile shear force and microstructure of copper sheets when Ag-Cu-P filler metal was applied for the joints involved in the production of laminated micro-channel array (LMA) devices. The properties of the microstructure of the Ag- Cu-P/copper brazed joints were examined following a process which included furnace brazing, with the parameters comprising temperature, holding time, and loading pressure. Analytical tools included an energy dispersive spectrometer (EDS), scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). In addition, tensile tests were performed to measure the tensile shear force. It was difficult to observe the Cu<inf>3</inf>P which forms along with the layer between the Ag-Cu-P filler metal and the copper sheet when the brazing temperature was only 580°C since this allowed gaps to form within the joint, thus producing very low tensile shear force results. When the brazing temperature is increased to 620°C along with longer holding time and increased pressure, this allows a thicker phase of Cu<inf>3</inf>P to form in the brazing joint. With a holding time of 30 minutes and pressure of 12.173 kPa, tensile shear force was maximized since this condition produced thick Cu<inf>3</inf>P phase. It is apparent that it is possible to produce a brazed joint which has an average shear force of 736.27 N under these conditions as described above. Within the joint could be found a Cu<inf>3</inf>P phase with no brittle phase.
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    Effect of Si on Microstructure and Corrosion Behavior of CoCrMo Alloys
    (2018-06-04)
    Peaubuapuan, Chonlawit
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    ; ;
    The aim of this research was to investigate the effect of silicon (Si) on the microstructure and corrosion behavior of CoCrMo alloys. The concentration of Si added in CoCrMo alloys was 0.1, 0.5 and 1 wt %. The corrosion behavior of the present alloys was investigated using potentiodynamic polarization measurements. The normal saline solution with 0.9 wt % was used as an electrolyte. Polarization curves obtained from the polarization test were used to evaluate in terms of corrosion current density (i<inf>corr</inf> ), corrosion potential (E<inf>corr</inf> ) and corrosion parameters that be used to compute corrosion resistant property of CoCrMo alloys. The microstructure of a sample during the polarization test was compared using X-ray diffraction (XRD) and optical microscope (OM). The results indicated that the increase in Si slightly changed the microstructure of CoCrMo alloys and could enhance the resistance to corrosion of CoCrMo alloys in NaCl solution. In addition, the reduction of Cr and Mo concentration in CoCrMo alloys was found to be a significant influence on the decrease in corrosion resistance.
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    The Property Investigation of Solder Mixed with Thermoelectrics Alzno by Using Digital Holography
    (2018-08-10)
    Prakobsang, Tawipon
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    Plaipichit, Suwan
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    In this paper in-line digital holography(DH) technique was used to investigate some properties of solder paste mixed with different percent weight of thermoelectric type AlZnO. By using reconstructed image results different properties of the compound solder pastes i.e. the contact angles, flux thickness were investigated. In addition, their electrical resistance also measured. From our reconstructed image results DH technique plus some computer programming would be one of efficient technique using in electronic industry in the future.
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    Property alterations of Sn-0.6Cu-0.05Ni-Ge lead-free solder by Ag, Bi, In and Sb addition
    (2018-06-01) ;
    KONGCHAYASUKAWAT, Rachata
    The Sn-Cu-Ni-Ge solder is a strong challenger to the Sn-Ag-Cu (SAC) solders as a replacement for the Sn-Pb eutectic solder. This research investigated the effects of addition of Ag, Bi, In, and Sb on the physical properties of the Sn-0.6Cu-0.05Ni-Ge (SCNG) lead-free solder and the interfacial reaction with the Cu substrate. The melting behavior, microstructure, tensile strength, and wettability of the SCNG–x (x=Ag, Bi, In, Sb) solders were examined. The findings revealed that the introduction of Ag, Bi, In, and Sb minimally altered the solidus temperature, liquidus temperature, and tensile strength of the solder. However, the cooling behavior and solidified microstructure of the solder were affected by the concentration of the alloying elements. The wettability of the SCNG solder was improved with the doping of the alloying elements except Sb. The thickness of intermetallic layer was increased by the addition of the alloying elements and was related to the cooling behavior of the solder. The morphology of intermetallic layer between the SCNG–x solders and the Cu substrate was different from that of the typical SAC solders. In conclusion, alloying the SCNG solder with Ag, Bi, In or Sb is able to improve particular properties of the solder.
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    Influences of soldering time on wettability and intermetallic phase between Sn-3.0Cu solder and copper substrate
    (2018-08-14)
    Mookam, Niwat
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    In this paper, the influences of soldering time on the wettability and intermetallic phase between Sn-3.0Cu lead-free solder and copper substrate were investigated. Reflow soldering was performed at 350 ° C under variable soldering times of 10, 20, 40, 60, 120, 240 and 480 s. The results indicated that the wettability and intermetallic growth depend on the soldering time. In addition, the Cu<inf>6</inf>Sn<inf>5</inf> and Cu<inf>3</inf>Sn intermetallic phases with a hexagonal crystal structure were found between the lead-free solder and the copper substrate. The growth of intermetallic phases increased with soldering time, and the growth of intermetallic phases remarkably depended on grain boundary diffusion and was volume diffusion-controlled for Cu<inf>6</inf>Sn<inf>5</inf> and Cu<inf>3</inf>Sn, respectively.
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    Effects of substrate annealing on wettability and intermetallic compound formation in Sn–3.0Cu/Cu systems
    (2019-07-01)
    Mookam, Niwat
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    This paper investigates the effects of Cu substrate annealing on the wettability of Sn–3.0Cu lead-free solder and the subsequent growth of the intermetallic compounds that are formed at the interface between the solder and the substrate. The annealing processes yielded various grain sizes, grain orientations, and residual strains within the substrates. Then, effects of the Cu substrates on the wetting and intermetallic formation were studied via reflow soldering using Sn–3.0Cu lead-free solder. The annealed substrates were compared to an unannealed Cu reference at soldering times of 20, 40, 60 and 120 s. The experimental results demonstrated that the substrate grain orientation, residual strain and grain size exert no influence on the solder wettability. After soldering, only a η-Cu<inf>6</inf>Sn<inf>5</inf> intermetallic compound was observed in the interfacial layer for both the reference and annealed copper substrates. The thickness of the η-Cu<inf>6</inf>Sn<inf>5</inf> layer was found to be independent of the substrate grain size but increased as the misorientation angle and the residual strain in the substrate increased.
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    Effects of indium on the intermetallic layer between low-Ag SAC0307-xIn lead-free solders and Cu substrate
    (2016-05-25) ;
    Sukpimai, Kamtorn
    This research has investigated the effects of indium on the intermetallic layer formation attributable to the reaction between low-Ag SAC0307-xIn lead-free solder and a Cu substrate, where x = 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 wt%. This study has also examined the post-soldering and post-thermal aging interfacial layers. Morphology parameters were utilized to represent the shape of total intermetallic layer at the interface. The findings indicated that indium had no effect on the pre- and post-aging intermetallic layer overall thicknesses but lowered the Cu<inf>3</inf>Sn/Cu<inf>6</inf>Sn<inf>5</inf> thickness ratio; and that the concentrations of indium exhibited no influence over the post-soldering and post-thermal aging morphology parameter values. In the experiments, the morphology parameter value decreased with increase in the aging time. In addition, the suppression effect of indium on the growth of Cu<inf>3</inf>Sn layer was evident in the post-thermal aging stage with the growth inversely correlated to the indium content. Discussion on the suppression mechanism of indium on the Cu<inf>3</inf>Sn formation is also provided herein.
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    Brazing of curved copper sheets using CuNiSnP amorphous filler metal
    (2019-09-30)
    Jattakul, Prajak
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    This research investigates the effect of bending stress using furnace brazing on the interfacial layer between curved copper sheets and CuNiSnP amorphous filler metal. Copper sheet curvatures were varied between 5, 10, 15, 20, and ∞ mm to manipulate the bending stress of the base metal. The thermal behaviors and phase transformations of CuNiSnP amorphous filler metal were also characterized. The results showed that crystallization of the filler metal started at 200 °C, with multiple phases formed over the course of thermal treatment. The curved radius and bending stress were inversely correlated, while the interfacial layer of brazed joints and copper sheet curvatures were positively correlated. The interfacial layer was thin in small curvature specimens and thick in large radius specimens, indicating that the bending stress in the base metal affected the reliability of brazed joints.
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    Simultaneous optimization of dimensional accuracy and surface roughness for finishing cut of wire-EDMed K460 tool steel
    (2013-07-01) ;
    Jattakul, Prajak
    The aim of this research was to determine an optimal cutting condition of dimensional accuracy and surface roughness for finishing cut of wire-EDMed K460 tool steel. The cutting variables investigated in this study encompassed cutting speed, peak current, and offset distance. Box-Behnken design was employed as the experimental strategy, and multiple response optimization on dimensional accuracy and surface roughness was performed using the desirability function. Results showed that both peak current and offset distance have a significant effect on the dimension of the specimen while peak current alone affects the surface roughness. The optimal cutting condition was at 2 A peak current and 772 μm offset distance. Since neither dimension nor surface roughness was affected by cutting speed, the speed was thus set at the highest of 5.5 mm/min to maximize the production rate. Confirmation tests on the optimal cutting condition were executed by which all cut specimens were shown to be within the specifications. © 2013 Elsevier Inc.
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    Optimizing the resistance spot-welding process for dissimilar stainless steels
    (2018-06-04)
    Khuenkaew, T.
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    The objective of this study was to identify the ideal welding circumstances to conduct resistance spot-welding in the case of 316 austenite and 425 ferrite stainless steels, which offer the challenge of being dissimilar. The study examines a number of welding variables, including weld current, weld time, hold time, electrode force, and the upper and lower electrode types. Initially, a 2<sup>6-1</sup> fractional factorial design was used for the screening of variables involved in the process. After this stage, the Box-Behnken design was employed for analysis of those variables and in order to specify the multiple response optimizations applicable to the size of nuggets through examination of the desirability function. The experiment was run using a resistance spot-welding machine at 50 kVA, 50 Hz. The quality of welded specimens was determined by their penetration, nugget diameter and nugget area. The optimal welding conditions were found to be 3.3 kN of electrode force, 25 cycles of weld time, 10,000 amperes of weld current, 50 cycles of hold time, and both R30 types of up-low electrodes. The optimal welding conditions provided nugget sizes of quality which were able to pass the specifications of the customer.