• Journal of Welding and Joining
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• v.10 no.3
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• pp.63-72
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• 1992

The joining methods of ceramics to metals which can be expected to obtain high temperature strength are mainly classified into the solid-state diffusion bonding method and the active brazing method. Between these two, the solid-state diffusion bonding method is given attentions as substituting method for active brazing method due to being capable of obtaining higher bonding strength at high temperature and accurate bonding. In this paper, the solid-state diffusion bonding of $Al_{2}$O$_{3}$ ceramics to Ni-Cr-Mo alloy steel (SNCM21) using insert metal was carried out. The insert metal employed in this study was experimentally home-made, Ag-Cu-Ti alloy. Influence of several bonding parameters of $Al_{2}$O$_{3}$SNCM21 joint was quantitatively evaluated by bonding strength test, and microstructural analyses at the interlayer were performed by SEM/EDX. From above experiments, the optimum bonding condition of the solid-state diffusion bonding of $Al_{2}$O$_{3}$/SNCM21 using Ag-Cu-Ti insert metal was determined. Futhermore, high temperature strength and thermal-shock properties of $Al_{2}$O$_{3}$/SNCM21 joint were also examined. The results obtained are as follows. 1. The maximum bonding strength was obtained at the temperature of 95% melting point of insert metal. 2. The high temperature strength of $Al_{2}$O$_{3}$/SNCM21 joint appeared to bemaximum value at test temperature 500.deg.C and the bonding strength with increasingtemperature showed parabolic curve. 3. The strength of thermal-shocked specimens was far deteriorated than those of as-bonded specimens. Especially, water-quenched specimen after heated up to 600.deg. C was directly fractured in quenching.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.431-445
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• 1993

The purpose of this study was to observe corrosion characteristics of six dental amalgams and was to analyse corrosion products electrochemically. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by using mechanical amalgamator, the triturated mass was inserted into the cylinderical metal mold ($12{\times}10mm$) and was condensed with 160kg/$cm^2$ by using the hydrolic press. The specimen was removed from the mold and was stored at room temperature for 1 week, and was polished with amalgam polishing kit. The anodic and cathodic polarization curve was obtained by using cyclic voltammetric method with 3-electrode potentiostat in saline for each amalgam and Ag, Sn, Cu plate specimen at $37{\pm}0.5^{\circ}C$. The potential sweep range was -1.7V~0. 4V(vs SCE) in working electrode and scan rate was 50mV/s and the exposed surface area of each specimen to the electrolytic solution was $0.79cm^2$. The results were as follows. 1. In anodic-cathodic polarization curve of amalgam specimens, two anodic current rising areas and two cathodic current peaks were obtained at the low Cu amalgam(CF, CS) specimen and three anodic current rising areas and three cathodic current peaks were obtained at the high Cu amalgam (TY, DS, HV) specimen. 2. As this compared with the anodic and cathodic current peak potentials of Sn, Cu and Ag specimen, the first cathodic current peak I c was caused by the reduction of divalent tin salt, second cathodic current peak IIIc results from the reduction of quadravalent tin salt, and third cathodic current peak me results from the reduction of copper salt. 3. As reverse potential sweeping was done repeatedly, anodic current was decreased slightly in all amalgam specimens.

• Journal of Technologic Dentistry
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• v.7 no.1
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• pp.13-18
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• 1985

Casting alloys, both precious and non-precious, were by heat in order to observe the change in HB and the results were : 1. The hard treatment showed 1.4 - 1.5 times as high as the soft treatment in HB. 2. The experiment shows that Au-Pt should be contained more than 75% to prevent color change. 3. Cu by hard teatment played the greatect part in creasing the solidity of Ag-Cu alloy. 4. Casting Co-Cr alloys showed little difference of HB in heat treatment.

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.134-141
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• 2013

Reflow soldering process is essential in electronic package. Reflow process for a long time results from the decrease of reliability because IMC is formed excessively. Solder alloys of Sn-37Pb and Sn-Ag with different kinds of Cu contents (0, 0.5 and 1 wt.%) as compared with Ni and Cu plate joints are investigated according to varying reflow time. The interfaces of solder joints are observed to analyze IMC (intermetallic compound) growth rate by scanning electron microscope (SEM). Shear test is also performed by using SP (Share-Punch) tester. The test results are compared with the solder joints of two different plates (Ni and Cu plate). $Cu_6Sn_5$ IMCs are formed on Cu plate interfaces after reflows in all samples. Ni3Sn4 and $(Cu,Ni)_6Sn_5$ IMCs are also formed on Ni plate interfaces. The IMC layer forms are affected by reflow time and contents of solder alloy. These results show that mechanical strength of solder joints strongly depends on thickness and shape of IMC.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.26-34
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• 2016

Automotive today has been transforming to an electronic product by adopting a lot of convenience and safety features, suggesting that joining materials and their mechanical reliabilities are getting more important. In this study, a Sn-Cu-Cr-Ca solder composition having a high melting temperature ($>230^{\circ}C$) was fabricated and its joint properties and reliability was investigated with an aim to evaluate the suitability as a joining material for electronics of engine room. Furthermore, mechanical properties change under complex environment were compared with several existing solder compositions. As a result of contact angle measurement, favorable spreadability of 84% was shown and the average shear strength manufactured with corresponding composition solder paste was $1.9kg/mm^2$. Also, thermo-mechanical reliability by thermal shock and vibration test was compared with that of the representative high temperature solder materials such as Sn-3.5Ag, Sn-0.7Cu, and Sn-5.0Sb. In order to fabricate the test module, solder balls were made in joints with ENIG-finished BGA and then the BGA chip was reflowed on the OPS-finished PCB pattern. During the environmental tests, resistance change was continuously monitored and the joint strength was examined after tests. Sn-3.5Ag alloy exhibited the biggest degradation rate in resistance and shear stress and Sn-0.7Cu resulted in a relatively stable reliability against thermo-mechanical stress coming from thermal shock and vibration.

• Restorative Dentistry and Endodontics
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• v.9 no.1
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• pp.81-87
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• 1983

The purpose of this study was to observe and identify the phases of amalgam and to know the transformation of microstructure in the set amalgam by lapse of time. In this study, shofu spherical-D alloy was used. After trituration of amalgam alloy and mercury (Wig-L-Bug), it was filled in the stone dies. This specimens being polished and etched by usual method was observed under optical microscope using metallurgical microscope. And then X-ray diffractometer was used to analyze the phases contents and transformation of microstructure at $2{\frac{1}{2}}$ hours, 15 hours, 28 hours and 2 years after being amalgamated. The following results were obtained: 1. Shofu spherical-D alloy powder was composed of ${\gamma}$ phase, ${\epsilon}$phase and Ag-Cu eutectic phases. 2. ${\gamma}_2$ phases were appeared at $2{\theta}$ values ($32.0^{\circ}$ and $43.8^{\circ}$) in the amalgam which was analyzed at $2{\frac{1}{2}}$ hours and 15 hours after trituration with mercury. 3. In the amalgam at 28 hours, ${\gamma}_2$ phase was found at $2{\theta}$ value ($43.8^{\circ}$) at 35 hour, $r_2$ phase was appeared at $2{\theta}$ value $32.0^{\circ}$. 4. No ${\gamma}_2$ phases were observed in the 2 years old amalgam. But ${\eta}$ ($Cu_6Sn_5$) phases were found at $2{\eta}$ values $29.4^{\circ}$ and $42.4^{\circ}$.

• The Journal of Korean Academy of Prosthodontics
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• v.19 no.1
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• pp.17-27
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• 1981

This study was conducted to determine the chemical composition and the mechanical properties of four commercially available low gold-based crown and bridge alloy produced in Korea. Four dental casting gold-silver-palladium alloys, i.e., A, B, C and D (code of alloys) were selected for the evaluation of chemical composition, ultimate tensile strength, elongation. values and Vickers hardness. The chemical composition of test specimens was analyzed by both emission spectrography and wet gravitation method with a 1.5gm of low gold ingot. The tensile properties and Vickers hardness was determined with cast specimens treated in following three conditions; as-cast, softening heat treatment and hardening heat treatment. The tensile testing bars were cast in accordance with the model designed by Gettleman and Harrison (1969) which was modified from the A. D. A. Specification No. 14 for dental chromium-cobalt casting alloy. Nine tensile test specimens were made from a split silicone mold for each of the test alloys to the size of 2.5mm in diameter and a gauge length of 10mm. All four alloys were handled in accordance with conventional methods used in Type III gold alloys. Ultimate tensile strength and elongation were measured on an Instron Universal Tensile Testing Machine (Model 1125, Japan) operated at a crosshead rate of 0.1cm/min. Elongation values were measured using Digital Measuring Microscope (MS-152, FUSOH, Japan). Vickers hardness was determined with a Vickers Hardness Tester (Model VKH-l, Japan) at a 1.0kg load on a mounted tensile test specimen. The following results were obtained from this study; 1. All tested alloys were composed of Au, Ag, Pd, Cu, Zn and Fe in common. The composition rate of gold for all four alloys was found in the range of $42{\sim}47$ weight % as shown below. Alloy A; Au 45%, Ag 40.2%, Pd 5.76%, others 9.04%. Alloy B; Au 47.1%, Ag 29.03%, Pd 6.98%, others 16.92%. Alloy C; Au 45%, .Ag 26.9%, Pd 6.83%, others 21.07%. Alloy D; Au 41.8%, Ag 34.4%, Pd 6.95%, others 16.85%. 3. The ultimate tensile strength of the four alloys was in the range of $31{\sim}82kg/mm^2$. The test results were shown in the below order from the highest value; As-cast condition; D, B, C, A. Softening heat treament; B, C, D, A. Hardening heat treatment; D, B, C, A. 4. The test :results of the elongation rate for each alloy were in the range of $0.5{\sim}18%$. The test results were shown in the below order from the highest value; As-cast condition; A, D, B, C. Softening heat treatment; A, C, D, B. Hardening heat treatment; C, D, B, A. 5. Vickers hardness for each of the four alloys was in the range of $120{\sim}230$. The test results were shown in the below order from the highest value; As-cast condition; C, B, D, A Softening heat treatment; D, B, C, A. Hardening heat treatment; D, A, C, B. 6. There were no differences in the physical properties between as-cast condition and softening heat treatment.

• Conservation Science in Museum
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• v.16
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• pp.4-13
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• 2015

In most gold objects crafted using the granulation technique that have been thus far discovered in the Korean Peninsula, granules were joined using a soldering alloy of gold and silver. However, it was recently revealed through SEM-EDS analysis performed on the ornamented dagger sheath from Gyerim-ro Tomb No.14 in Gyeongju that the gold granules were joined to the surface of this sheath using an entirely different technique. The gold granules on the Gyerim-ro dagger sheath are evenly sized and shaped, the surface has a dendritic texture. Dendritic textures are a characteristic feature of metal alloys, not observed in pure metals. As a matter of fact, the gold granules were made of a ternary alloy of 77wt% Au, 18wt% Ag and 4wt% Cu. Due to this component, the alloy has a melting point below 1000℃ (approximately 980℃), which is significantly lower than 1064℃, the melting temperature of pure gold. This makes it possible to join the gold granules directly to the surface of the sheath by briefly heating them to high temperature, without the use of soldering or any other media. When examined through SEM image, the surface of the sheath showed no traces of soldering, it suggests that the granules were joined through unaided fusion.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.31-37
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• 2008

A variety of the porcelain fused to gold(PFG) have been developed to which porcelain can be fused. PFG alloys developed for this purposed have a high melting point and do not discolor when combined with porcelain. The design of the compositions of PFG is very important to esthetic restorative materials applying to porcelain. The purpose of this study is on the change of physical and mechanical characteristics in PFG 18K alloy by the small additional elements. Principal results are as follows. The high Au alloy containing 18Karat gold contents is respectively Au(75%), Pd(10%), Pt(4%), Ag(4%), In(2%), Sn(2%), Cu(2%), Ti(1%). These alloys are composed mainly of gold, platinum, silver and palladium with a few percent of the additional elements. By the addition of small amounts of elements such as In, Sn, Ti, the fine grain castings are produced in gold alloy and the small addition of platinum is very effective in increasing of hardness and strength. These gold alloys are representative of the changes to be expected as a result of heat treatment. These changes in strength and hardness values are sufficient to demonstrate a significant difference in performance between a as-casted and a heat-treated. These alloys have mechanical properties characteristics of Type and Type gold alloys. These alloys are useful to porcelain-metal restorations and dental laboratory. Also the porcelain fused to metal(PFM) alloys containing gold are commonly use for dental purposes in dental laboratory.