• Restorative Dentistry and Endodontics
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• 제9권1호
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• pp.101-106
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• 1983

It was the purpose of this study to investigate the fracture mode of dental amalgam by observing the crack propagation, and to relate this to the microstructure of the amalgam. Caulk 20th Century Regular, Caulk Spherical, Dispersalloy, and Tytin amalgam alloys were used for this study. After each amalgam alloy and Hg measured exactly by the balance was triturated by the mechanical amalgamator (Capmaster, S.S. White), the triturated mass was inserted into the cylindrical metal mold which was 4 mm in diameter and 12 mm in height and was pressed by the Instron Universal Testing Machine at the speed of 1mm/min with 120Kg. The specimen removed from the mold was stored in the room temperature for a week. This specimen was polished with the emery papers from #100 to #200 and finally on the polishing cloth with 0.06${\mu}Al_2O_3$ powder suspended in water. The specimen was placed on the Instron testing machine in the method similar to the diametral tensile test and loaded at the crosshead speed of 0.05mm/min. The load was stopped short of fracture. The cracks on the polished surface of specimen was examined with scanning electron microscope (JSM-35) and analyzed by EPMA (Electron probe microanalyzer). The following results were obtained. 1. In low copper lathe-cut amalgam, the crack went through the voids and ${\gamma}_2$ phase, through the ${\gamma}_1$ phase around the ${\gamma}$ particles. 2. In low copper spherical amalgam, it was observed that the crack passed through the ${\gamma}_2$ and ${\gamma}_1$ phase, and through the boundary between the ${\gamma}_1$ and ${\gamma}$ phase. 3. In high copper dispersant (Dispersalloy) amalgam, the crack was found to propagate at the interface between the ${\gamma}_1$ matrix and reaction ring around the dispersant (Ag-Cu) particles, and to pass through the Ag-Sn particles. 4. In high copper single composition (Tytin) amalgam, the crack went through the ${\gamma}_1$ matrix between ${\eta}$ crystals, and through the unreacted alloy particle (core).

• Journal of Welding and Joining
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• 제26권5호
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• pp.43-48
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• 2008

Characteristics of Sn-1.7%Bi-0.7%Cu-0.6%In (hereafter, SBIC) lead-free solder was investigated in this study. The results from SBIC were compared to other lead-free solders such as Sn-3.5%Ag-0.7%Cu (hereafter, SAC), Sn-0.7%Cu (hereafter, SC), and lead-bearing Sn-37%Pb (hereafter, SP) alloy. Tensile properties of bulk solder, wettability, spreading index, bridge and dross were evaluated. As experimental results, tensile strength and elongation of SBIC was 62.5MPa and 21.5%, respectively. The tensile strength was comparable to that of SP solder. The wetting time of SBIC was 1.2 sec at $250^{\circ}C$, and its wetting properties including wetting force were as good as the SAC alloy. However, wettability of the SC was not so good as the SBIC and SAC. The spreading index of SBIC at $250^{\circ}C$ was 71 %, and it was similar level to those of SAC and SC solders. Bridging was not found for all solders of SBIC, SAC and SC in the range from 240 to $260^{\circ}C$. In dross test at $250^{\circ}C$ for an hour, the amount of dross produced from SBIC was about 57% compared to that from SAC.

• 마이크로전자및패키징학회지
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• 제12권1호
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• pp.65-71
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• 2005

At present, Electronic industries push ahead to eliminate the Pb(Lead) -a hazardous material-from all products. Especially, we have performed to select the optimum standard composition of lead free alloy for the application to products for about 3 years from 2000. These days, we have the chance for applying to the mass-production. This project constructed the system for applying the lead free solders on consumer electronic products, which is one of the major products of the LG Electronics. To select the lead free solders with corresponding to the product features, we have passed through the test and applied with Sn-3.0Ag-0.5Cu alloy system to our products, and for the application to the high melting temperature composition, we secured the thermal resistance of the many parts and substrate and optimized the processing conditions. We have operated the temperature cycling test and the high temperature storage test under the standards to confirm the reliability of the products. On these samples, we considered the consequence of our decision by the operating test. For the long life time of the product, we have operated the temperature cycling test at $-45^{\circ}C\;-\;+125^{\circ}C$, 1 cycle/hour, 1000 cycles. Also we have tested the tin whisker growth about lead free plating on lead finish. We have analyzed with the SEM, EDS and any other equipment for confirming the failure mode at the joint and the tin whisker growth on lead free finish.

• Journal of Welding and Joining
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• 제10권3호
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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.

• 마이크로전자및패키징학회지
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• 제12권1호
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• pp.47-52
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• 2005

전세계 전자패키지 산업에서 납(Pb) 사용에 대한 환경규제 움직임이 본격화되고 있어 새로운 무연솔더의 개발이 활발히 이루어지고 있다. 게다가 무연솔더의 신뢰성에 대한정보가 아직까지 많이 부족한 실정이다 무연솔더의 신뢰성에 영향을 줄수 있는 것 중의 하나가 Sn pest라고 알려진 동소체 변태이다. Sn pest가 형성될 때 동반되는 부피의 증가는 솔더 조인트의 신뢰성을 저하시킨다. 이미 보고된 바에 따르면, Sn 고용도가 있는 원소(Pb, Bi, Sb)들을 첨가시킬 경우 Sn pest가 효과적으로 억제된다. 그러나 Sn pest를 억제하는 합금에 대한 기계적인 특성에 연구가 거의 이루어지지 않았다. 본 연구에서는 Sn과 Sn-0.7Cu를 기반으로 하여 Bi, Sb을 첨가한 솔더 합금을 사용하여 lap shear크리프 실험을 하였다. 본 연구에서 사용한 합금들의 변형율은 전체적으로 Sn-3.5Ag를 기반으로 하는 합금들보다 높았다. 파괴까지 이르는 변형량은 Sn-0.5Bi가 가장 크고 Sn-0.7Cu-0.5Sb 합금이 가장 작았는데 이러한 경향은 Sn-0.5Bi 합금의 파단면에 Sn globules이 길게 늘어나 있고 Sn-0.7Cu-0.5Sb 합금에서는 더 짧은 Sn globules 이 관찰되는 결과와 일치하였다.

• 한국세라믹학회지
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• 제39권3호
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• pp.286-293
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• 2002

소성온도에 따른 ZnO계 적층형 세라믹 칩 바리스터(약칭 MLV)의 미세구조와 전기적 특성의 변화를 조사하였다. 소성온도 1100$^{\circ}$C에서 Ag/Pd(7:3) 내부전극층의 두께가 불균일하게 변화하면서 부분적인 공극이 발생하기 시작하고, 1150$^{\circ}$C에서는 상당한 전극 패턴의 소멸과 박리가 관찰되었다. 950$^{\circ}$C로 소성한 MLV의 경우 누설전류의 열화가 특히 컸는데 이는 미반응의 pyrochlore상이 잔류하여 액상과 천이원소의 균일한 분포가 일어나지 않았기 때문이라 사료된다. 1100$^{\circ}$C 이상의 온도로 소성한 경우에는 바리스터 특성 및 그 재현성의 저하가 관찰되었는데, 이는 내부전극의 소멸, 전극물질과 소체의 반응, 그리고 $Bi_2O_3$의 휘발에 기인한 것으로 보인다. 한편, 950∼1100$^{\circ}$C의 전 소성온도 범위에 걸쳐 온도가 증가할수록 정전용량과 누설전류는 증가하고 항복전압과 피크전류는 감소하였으나, 비선형계수와 클램핑 비는 각각 ∼30 및 1.4로 거의 일정한 값을 유지하였다. 특히 1000∼1050$^{\circ}$C 소성체의 경우 칩 바리스터에 적합한 바리스터 특성이 재현성 있게 나타났다. 결과적으로 Ag/Pd(7:3) 합금은 1050$^{\circ}$C의 동시 소성 온도이하에서는 $Bi_2O_3$를 함유한 대부분의 ZnO계 MLV의 내부전극으로 충분히 사용가능한 것으로 판단된다.

• 대한치과기공학회지
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• 제21권1호
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• pp.15-26
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• 1999

This study was carried out by observing to composition of oxide on the surface of dental porcelain low gold alloy with various Indium additions according to the degassing and analysing the change composition of additional elements In on diffusion behaviors of Porcelain-matal surface. The specimens used were Au-Pd-Ag alloys by small indium addition. These specimens were treated for 10min at $1000^{\circ}C$ in vacuum condition. To investigate the microsturcture of oxidized alloy surface, SEM and EDAX were used, and EPMA were used to investigate the diffusion behaviors of porcelain-metal surface. X-ray diffraction were used to observe the morphological changes in the oxidation zone. The results of this study were obtained as follows ; 1) The hardness of alloy increased with increasing amount of In addition. 2) The formation of oxidation increased with increasing In content after heat treatment. 3) Diffusion of indium elements increased with increasing In content in metal-porcelain surface after firing. 4) The oxidations of alloy surface were mainly $In_2O_3$.

• Journal of Welding and Joining
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• 제28권3호
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• pp.49-58
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• 2010

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites (diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature $940^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.66-66
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• 2009

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites(diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature 940 $^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.

• 공업화학
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• 제17권5호
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• pp.458-464
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• 2006

팔라듐 합금 복합막의 제조는 니켈 분말과 무기화합물의 혼합물로 개질된 튜브형 다공성 스테인레스 스틸 지지체 표면 위에 무전해 도금법(elctroless plating technique)에 의해 팔라듐 - 니켈 - 은을 박막으로 도금하는 형태로 이루어졌다. 일반적인 다공성 금속 지지체는 기공이 크기 때문에 그 자체로서 도금에 적합한 지지층이 되기가 어렵고, 결함이 없는 팔라듐 복합막의 제조가 쉽지 않아 본 연구에서는 금속 지지체와 팔라듐 사이에 중간층(intermediate layer)을 형성하여 이와 같은 문제점을 극복하고자 하였다. 중간층의 소재인 실리카 졸, 알루미나 졸, 이산화티타늄 졸 등의 무기화합물과 니켈 분말의 혼합물로 다공성 금속 지지체 위에 코팅하여 박막을 형성하고 제조 조건에 따른 질소 투과도를 측정하고 비교하였다. SEM 분석법에 의해 니켈과 무기화합물 혼합물의 표면층의 형성 모습도 측정하였다. 제조된 중간층 가운데 이산화티타늄 졸과 니켈의 혼합물이 가장 낮은 질소 투과도와 치밀한 표면층을 나타내었다. 최종적으로 니켈과 실리카의 혼합 중간층으로 이루어진 팔라듐-니켈-은 합금 복합막을 제조하고 수소와 질소의 투과도를 측정하였다. 1기압 이하에서 질소에 대한 수소 선택도는 무한대였으며 수소투과 속도는 1 기압, $500^{\circ}C$에서 $1.39{\times}10^{-2}mol/m^2{\cdot}s$의 값을 나타냈다.