• Progress in Superconductivity
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• 제7권2호
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• pp.179-183
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• 2006

As a material for SFCL(Superconducting Fault Current Limiter), BSCCO tube with metal stabilizer is a promising candidate, assuring the stability and large power capacity, For the application, the proper soldering technique, which overcome the difficulties of the joining between BSCCO and metal stabilizer, is required. In this study, after soldering In-Bi solder and In-Sn solder with BSCCO superconductor, welding properties between BSCCO and solders were investigated. Because ceramic materials is difficult to weld, Ag electro-plating on BSCCO 2212 is used for intermetallic layer. To find out the best welding condition for superconductor, soldering is tested in the maximum temperature from $155^{\circ}C\;to\;165^{\circ}C$ in the reflow oven. By investigating the composition and thickness of IMC (lntermetallic Compound) created in the reaction of Ag with solder, we analyzed the welding properties of High-Tc superconductor from a micro point of view.

• 대한금속재료학회지
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• 제48권11호
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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.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.31-36
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• 2018

전기 소자 중의 하나인 퓨즈는 전기 부품에 비정상적으로 흐르게 되는 과전류로 인한 전로나 기기 보호를 위하여 사용 및 개발되고 있다. 대표적인 형태로는 유리관퓨즈가 많이 사용 되고 있는데, 최근 납이 함유된 솔더의 사용에 대한 국내 및 국제 규제가 강화 되면서 무연 솔더로의 변경으로 인한 문제가 대두 되고 있다. 본 연구에서는 유리관퓨즈의 솔더링 공정에서 솔더를 기존의 납이 함유된 솔더에서 무연 솔더로 변경 한 후, 퓨즈캡을 가용체와 솔더링할 때 용융된 솔더가 퓨즈 바깥으로 넘쳐흐르는 현상을 수치해석으로 모사하였고, 해석 결과를 바탕으로 솔더의 넘침 현상을 막을 수 있는 방안을 찾아 그 효과를 검증하였다. 검증 결과, 솔더링 실시 전에 유리관 내부의 온도를 충분히 증가시키는 것이 솔더의 넘침을 예방하는데 도움이 되며, 중력이 솔더가 흘러나가는 반대방향으로 작용하도록 솔더링을 하게 되면 넘침을 막는 데 효과가 있음을 확인하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.151-155
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• 2003

The requirements for harsh environment electronic controllers in automotive applications have been steadily becoming more and more stringent. Electronic substrate technologists have been responding to this challenge effectively in an effort to meet the performance, reliability and cost requirements. An effect of the plasma cleaning at the alumina substrate and the IMC layer between $Sn-37wt\%Pb$ solder and Ag-Pd thick film conductor after reflow soldering has been studied. Organic residual carbon layer was removed by the substrate plasma cleaning. So the interfacial adhesive strength was enhanced. As a result of AFM measurement, Ag-Pd conductor pad roughness were increased from 304nm to 330nm. $Cu_6Sn_5$ formed during initial ref]ow process at the interface between TiWN/Cu UBM and solder grew by the succeeding reflow process so the grains had a large diameter and dense interval. A cellular-shaped $Ag_3Sn$ was observed at the interface between Ag-Pd conductor pad and solder. The diameters of the $Ag_3Sn$ grains ranged from about $0.1\~0.6{\mu}m$. And a needle-shaped $Ag_3Sn$ was also observed at the inside of the solder.

• Journal of Welding and Joining
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• 제29권5호
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• pp.95-98
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• 2011

Recently, there is a growing tendency that fine-pitch electronic devices are increased due to higher density and very large scale integration. Finer pitch printed circuit board(PCB) is to be decrease insulation resistance between circuit patterns and electrical components, which will induce to electrical short in electronic circuit by electrochemical migration when it exposes to long term in high temperature and high humidity. In this research, the effect of soldering flux acting as an electrical carrier between conductors on electrochemical migration was investigated. The PCB pad was coated with OSP finish. Sn3.0Ag0.5Cu solder paste was printed on the PCB circuit and then the coupon was treated by reflow process. Thereby, specimen for ion migration test was fabricated. Electrochemical migration test was conducted under the condition of DC 48 V, $85^{\circ}C$, and 85 % relative humidity. Their life time could be increased about 22% by means of removal of flux. The fundamentals and mechanism of electrochemical migration was discussed depending on the existence of flux residues after reflow process.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1347-1355
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• 1996

The purpose of this paper is to evaluate the delamination and fracture integrity of the IC plastic package under hygrothermal loading by stress analysis and fracture mechanics approaches. The plastic SOJ package with a dimpled diepad under the reflow slodering process of IR heating type is considered. On the package without a crack, the stress variation according to the change of the design variables such as the material and shape of the package is calculated and the possibility of delamination is considered. For the model fully delaminated between the chip and diepad, J-integrals are calculated for the various design variables and the fracture integrity is discussed. From the results, optimal design values of variables to prevent the delamination and fracture of IC package are obtained. In this study, FDM program to obtain the vapor pressure from the content of moisture absorbed into the package is developed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.450-455
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• 2002

Cu-cored Sn-Ag solder balls were fabricated by coating pure Sn and Ag on Cu balls. The melting behavior and the solderability of the BGA joint with the Ni/Au coated Cu pad were investigated and were compared with those of the commercial Sn-Ag and Sn-Ag-Cu balls. DSC analyses clarified the melting of Cu-cored solders to start at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. It was ascribed to the diffusion of Cu and Ag into Sn plating during the heating process. After reflow soldering the microstructures of the solder and of the interfacial layer between the solder and the Cu pad were analyzed with SEM and EPMA. By EDX analysis, formation of a eutectic microstructure composing of $\beta$-Sn, Ag$_3$Sn, ad Cu$_{6}$Sn$_{5}$ phases was confirmed in the solder, and the η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer was found to form at the interface between the solder and the Cu pad. By conducting shear tests, it was found that the BGA joint using Cu-cored solder ball could prevent the degradation of joint strength during aging at 423K because of the slower growth me of η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer formed at the solder, pad interface. Furthermore, Cu-cored multi-component Sn-Ag-Bi balls were fabricated by sequentially coating the binary Sn-Ag and Sn-Bi solders on Cu balls. The reflow property of these solder balls was investigated. Melting of these solder balls was clarified to start at the almost same temperature as that of Sn-2Ag-0.75Cu-3Bi solder. A microstructure composing of (Sn), Ag$_3$Sn, Bi and Cu$_{6}$Sn$_{5}$ phases was found to form in the solder ball, and a reaction layer containing primarily η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ was found at the interface with Ni/Au coated Cu pad after reflow soldering. By conducting shear test, it was found that the BGA joints using this Cu-core solder balls hardly degraded their joint shear strength during aging at 423K due to the slower growth rate of the η'-(Au, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer at the solder/pad interface.he solder/pad interface.

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.1-6
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• 2004

자동차 전장품의 시험환경 조건이 엄격해짐에 따라, 전장품 개발 기술자들은 이에 부합하는 성능, 신뢰성, 비용 등을 고려한 보다 효과적인 제품 설계를 위해 노력하고 있다. 본 논문에서는 ECM 알루미나 기판의 플라즈마 세척 영향과 리플로우 후 Sn-37wt%Pb 솔더와 패드 접합부 계면에서 형성되는 금속간 화합물을 관찰하였다. 기판의 플라즈마 세척은 계면 접착력을 저해하였던 C에 의한 유기 잔류물 층이 제거되어 계면 접착력을 향상시키는 효과가 있다. 또한 AFM 분석 결과 도체 패드의 표면 거칠기는 304 nm에서 330 m로 증가하였다. 리플로우 과정에서 솔더와 TiWN/Cu 패드 계면에서 형성된 $Cu_6/Sn_5$는 리플로우 횟수가 증가할 수록 결정립의 크기도 조대화되었다. 솔더와 Ag-Pd 도체패드 계면에서는 세포질 형태의 $Ag_3Sn$화합물이 관찰되었다. $Ag_3Sn$은 지름이 약 0.1∼0.6 $\mu\textrm{m}$이며, 솔더 내부에서는 침상 모양도 관찰되었다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 The IMAPS-Korea Workshop 2001 Emerging Technology on packaging
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• pp.119-126
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• 2001

Chip-on-glass(COG) mounting of area array electronic packages was attempted by heating the rear surface of a contact pad film deposited on a glass substrate. The pads consisted of an adhesion(i.e. Cr or Ti) and a top coating layer(i.e. Ni or Cu) was heated by an UV laser beam transmitted through the glass substrate. The laser energy absorbed on the pad raised the temperature of a solder ball which is in physical contact with the pad, forming a reflowed solder bump. The effects of the adhesion and top coating layer on the laser reflow soldering were studied by measuring temperature profile of the ball during the laser heating process. The results were discussed based on the measurement of reflectivity of the adhesion layer. In addition, the microstructures of solder bumps and their mechanical properties were examined.

• Journal of Welding and Joining
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• 제25권2호
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• pp.76-81
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• 2007

Solder bumps have been used to interconnect the chip and substrate, and the size of the solder bump decreases below $100{\mu}m$ to accommodate higher packaging density. In order to fabricate solder bumps, a mold to chip transfer process is suggested in this work. Since the thin stainless steel mold is not wet by the solder, the molten solder is forced to fill the mold cavities with ultrasonic vibration. The solders within the mold cavities are transferred to the Cu pads on the polyimide film through reflow soldering.