• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.1041-1046
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• 2010

The reactions between a Sn-3.0Ag-0.5Cu solder alloy and electroless Ni/electroless Pd/immersion Au (ENEPIG) surface finishes with various Pd layer thicknesses (0, 0.05, 0.1, 0.2, $0.4{\mu}m$) were examined for the effect of the Pd layer on the massive spalling of the $(Cu,Ni)_6Sn_5$ layer during reflow at $235^{\circ}C$. The thin layer deposition of an electroless Pd (EP) between the electroless Ni ($7{\mu}m$) and immersion Au ($0.06{\mu}m$) plating on the Cu substrate significantly retarded the massive spalling of the $(Cu,Ni)_6Sn_5$ layer during reflow. Its retarding effect increased with an increasing EP layer thickness. When the EP layer was thin (${\leq}0.1{\mu}m$), the retardation of the massive spalling was attributed to a reduced growth rate of the $(Cu,Ni)_6Sn_5$ layer and thus to a lowered consumption rate of Cu in the bulk solder during reflow. However, when the EP layer was thick (${\geq}0.2{\mu}m$), the initially dissolved Pd atoms in the molten solder resettled as $(Pd,Ni)Sn_4$ precipitates near the solder/$(Cu,Ni)_6Sn_5$ interface with an increasing reflow time. Since the Pd resettlement requires a continuous Ni supply across the $(Cu,Ni)_6Sn_5$ layer from the Ni(P) substrate, it suppressed the formation of $(Ni,Cu)_3Sn_4$ at the $(Cu,Ni)_6Sn_5/Ni(P)$ interface and retarded the massive spalling of the $(Cu,Ni)_6Sn_5$ layer.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.169-175
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• 2012

Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.39-49
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• 1986

The purpose of this study was to observe characteristic properties through the polarization curves and SEM images from 4 different types of amalgam obtained by using the potentiostats (Princeton EG & G) & SEM (Jeol/35), and to investigate the degree of corrosion on the oxidation peak of the each phase of amalgam. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by means of the mechanical amalgamator (Shofu Co.), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10.0mm in height and was condensed by using routine manner. The specimen was removed from the mold and stored at room temperature for about 24 hours. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to confirm the corrosion behaviour of the amalgams in a 0.9% saline solution (P.H: 6.8-7.0) at $37^{\circ}C$. The initial rest potential (corrosion potential) was determined after 30 minutes of immersion of specimen in electrolyte, and the potential scan was begun at the point of 100mV cathodic from the corrosion potential. The scan rate was 0.17mV/sec. in the study to observe the degree of corrosion of each phase. SEI and EPMA images on the determined oxidation peaks of each amalgam were observed. The results were as follows: 1. In the four anodic polarization curves, low copper amalgams have three oxidation peaks and high copper amalgams have two oxidation peaks, -270mV, +26mV and +179mV(SEC) in the low copper lathe cut, and -300mV, +39mV and +163mV(SEC) in the low copper spherical. -4mV and +154mV(SEC) in the Dispersalloy, and +17mV and +180mV(SEC) in the Tytin as high copper amalgams. 2. ${\gamma}_2$ phase in the low copper amalgam and ${\eta}$ phase in the high copper amalgam were the most corrodible phases and Ag-Cu eutectic in high copper amalgam was the most slowly corroded phase. 3. Low copper amalgam was more susceptible in corrosion than high copper amalgam.

• Journal of Conservation Science
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• v.27 no.1
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• pp.41-47
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• 2011

If the nondestructive analysis is carried out by using an X-ray Fluorescence Analyzer(XRF) for ingredient analysis with the target of gold plated silverware that plates gold on a silver basis, a singular point showing big difference at the value of weight percent(wt.%) according to the electron orbit of the principal ingredient can be confirmed. The present research made reproduced samples and carried out comparative analysis in order to suggest a basis that can judge whether the technique of gold plated silverware was used in case of remains uneasy to understand with eyes by using this singular point. As a result, the same result as analysis results of actual remains could be seen in specimens manufactured by a mercury amalgam plating method. However, in case of gold and silver alloy specimens, it could be confirmed that the difference according to the electron orbit of the principal ingredients is slight unlike plated specimens. The reason appearing at plated specimens seems to be generated while absorbing XRF beam at plated layers by double structure due to plating instead of single material. Accordingly, if this result appearing at nondestructive analysis is used, it was confirmed that the application of the technique of gold plated silverware can be judged without observing its section.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.151-156
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• 1995

Low temperature firing $(Ba, Sr)TiO_{3}$ dielectrics were successfully prepared with lead based glass and those electrical properties were investigated. Different amount of PbO content glass materials were added to dielectrics to investigate the sinterability and its dielectric properties. Also, various compositions of ceramic capacitors were prepared to applicate in multilayer ceramic capacitors. A large amount of experiment has been done with various Pb contented glasses and different sintering temperatures. The sintering temperature of $(Ba,Sr)TiO_{3}$can be reduced from $1350^{\circ}C$to as low as $1050^{\circ}C$ with 4wt% addition of $PbO-ZnO-B_{2}O_{2}$ glass materials. Its dielectric constant at room temperature was up to 8100 with low dielectric loss, 0.005. This ceramic capacitor showed fully fired microstructures with its grain size of 1-3$\mu \textrm{m}$. The sintered body which was sintered at $1150^{\circ}C$ for 2hr with 4wt% $PbO-ZnO-B_{2}O_{2}$ glass material addition satisfied the Z5U specification of the EIAS.