• 한국자동차공학회논문집
• /
• 제21권1호
• /
• pp.145-153
• /
• 2013

In this study, shear punch-creep (SP-Creep) at Sn-4Ag/Cu pad the joint was tested by using environment-friendly Pb-free solder alloy Sn-4Ag of electronic components. Pb eutectic alloy (Sn-37Pb) joints limited to environmental issues with reflow time (10sec, 30sec, 100sec, 300sec) according to two types of solder alloy joints are compared and evaluated by creep strain rate, rupture time and IMC (Intermetallic Compound) behavior. As the results, reflow time increases with increasing thickness of IMC can be seen at overall 100sec later in case of two solder joints on the IMC thickness of Sn-4Ag solder joints thicker than Sn-37Pb solder joints. In addition, when considering creep evaluation factors, lead-free solder alloy Sn-4Ag has excellent creep resistance more than Pb eutectic alloy. For this reason, the two solder joints, such as in the IMC (Cu6Sn5) was formed. However, the creep resistance of Sn-4Ag solder joints was largely increased in the precipitation strengthening effect of dispersed Ag3Sn with interface more than Sn-37Pb solder joints.

• 청정기술
• /
• 제11권4호
• /
• pp.205-211
• /
• 2005

마이크로렌즈 어레이의 제작은 매우 다양한 재료와 방법이 제안되어 지고 있으나, 폴리머를 이용한 사출법은 광학적 특성, 내충격성, 가공성, 경량화 및 환경친화성 등의 장점으로 주목 받고 있다. 사출법 템플레이트를 제작하기 위한 PR(Photo-Resist) reflow법은 형상제어가 용이하고 대량생산과 정밀가공의 측면에서 효율적이어서, 집적화가 용이하고 공정을 줄일 수 있는 장점을 갖게 되어 매우 환경친화적이다. 그러나 마이크로렌즈 어레이의 사출성형은 사용되는 폴리머재료의 성질에 따라 성형에 어려움이 있는 것으로 알려져 있다. 본 연구에서는 이와 같은 성형의 어려움을 극복하기 위한 방법으로 급가열/급냉각 사출을 통하여 마이크로렌즈 어레이를 제작하고 특성을 이해하였다. 템플레이트의 급격한 온도상승과 고온에서의 모양이 냉각으로 인한 변형이 없도록 급속히 냉각시켜 줌으로서 마이크로렌즈 어레이의 사출성형을 구현 하였다. PC(Poly-Cabon ate)와 PMMA(Poly-Methyl-Meth-Acrylate)를 비교하여, PMMA가 낮은 용융점에 의해 성형성이 우수함을 확인하였다. 사출시 압력과 속도를 변수로 마이크로렌즈 어레이의 제작을 위한 사출조건을 도출하였다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.280-283
• /
• 2004

Micro-lens patterned micro-mold fabrication method for Light Guiding Plate(LGP), kernel part of LCD-BLU(Back Light Unit), was presented. Instead of erosion dot pattern for LGP optical design, micro-lens pattern, fabricated by LIGA-reflow process, was applied. Optical pattern design method was also developed not only for negative pattern LGP, but also positive pattern LGP. During injection molding process, experimental study was conducted to improve replication quality and brightness of ${\sim}50um$ micro-lens pattern mold. The effect of mold temperature for the replication quality of micro-lens array was studied.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
• /
• pp.219-220
• /
• 2000

We propose a new method for the formation of an aluminum parting layer in the fabrication of field emitter arrays, in which we used a reflow property of aluminum at a lower temperature than the deformation point of glass. After the sputtered aluminum layer on the gate metal was etched for the formation of gate holes, we carried out a rapid thermal annealing process, by which the aluminum slightly diffused into the gate hole. This reflowed aluminum could be used as a parting layer and emitter arrays were easily fabricated using this method.

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

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
• /
• pp.85-91
• /
• 2002

Even though electroless Hi and Sn-Ag-Cu solder are widely used materials in electronic packaging applications, interfacial reactions of the ternary Ni-Cu~Sn system have not been known well because of their complexity. Because the growth of intermetallics at the interface affects reliability of solder joint, the intermetallics in Ni-Cu-Sn system should be identified, and their growth should be investigated. Therefore, in present study, interfacial reactions between electroless Ni UB7f and 95.5Sn-4.0Ag-0.5Cu alloy were investigated focusing on morphology of the IMCs, thermodynamics, and growth kinetics. The IMCs that appear during a reflow and an aging are different each other. In early stage of a reflow, ternary IMC whose composition is Ni$_{22}$Cu$_{29}$Sn$_{49}$ forms firstly. Due to the lack of Cu diffusion, Ni$_{34}$Cu$_{6}$Sn$_{60}$ phase begins growing in a further reflow. Finally, the Ni$_{22}$Cu$_{29}$Sn$_{49}$ IMC grows abnormally and spalls into the molten solder. The transition of the IMCs from Ni$_{22}$Cu$_{29}$Sn$_{49}$ to Ni$_{34}$Cu$_{6}$Sn$_{60}$ was observed at a specific temperature. From the measurement of activation energy of each IMC, growth kinetics was discussed. In contrast to the reflow, three kinds of IMCs (Ni$_{22}$Cu$_{29}$Sn$_{49}$, Ni$_{20}$Cu$_{28}$Au$_{5}$, and Ni$_{34}$Cu$_{6}$Sn$_{60}$) were observed in order during an aging. All of the IMCs were well attached on UBM. Au in the quaternary IMC, which originates from immersion Au plating, prevents abnormal growth and separation of the IMC. Growth of each IMC is very dependent to the aging temperature because of its high activation energy. Besides the IMCs at the interface, plate-like Ag3Sn IMC grows as solder bump size inside solder bump. The abnormally grown Ni$_{22}$Cu$_{29}$Sn$_{49}$ and Ag$_3$Sn IMCs can be origins of brittle failure.failure.

• 마이크로전자및패키징학회지
• /
• 제17권1호
• /
• pp.1-7
• /
• 2010

본 연구에서는 $430^{\circ}C$에서 Bi-10Cu-20Sb-0.3Ni 조성의 솔더 합금과 Cu간의 리플로루 솔더링 시 생성되는 계면 반응층을 분석하였고, 솔더링 시간에 따른 계면 반응층의 성장 속도를 측정하였다. 리플로우 솔더링 후 Bi-10Cu-20Sb-0.3Ni/Cu의 계면 반응층을 분석한 결과, $(Cu,Ni)_2Sb$ 및 $Cu_4Sb$ 금속간 화합물층, 그리고 Bi 조성과 $Cu_4Sb$ 상이 주기적으로 존재하는 아지랑이 형상층이 연속적으로 생성되었다. 또한 120 s까지의 솔더링 시간 영역에서는 계면 반응층의 총 두께가 솔더링 시간에 대해 직선적으로 증가하는 경향이 관찰되었다. 합금원소로 첨가된 Ni은 가장 두꺼운 $Cu_4Sb$ 반응층의 형성에 참여하지 않아 계면 금속간 화합물의 성장 속도를 억제시키는 작용을 나타내지 못했다.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.450-455
• /
• 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
• /
• 제25권3호
• /
• pp.13-19
• /
• 2018

본 연구에서는 태양광 접속함 모듈 적용을 위한 유연 솔더(Sn-Pb) 및 무연 솔더(Sn-3.0Ag-0.5Cu 및 Sn-1.0Ag-0.7Cu-1.6Bi-0.2In)의 특성을 비교 평가하였다. 접속함 내에는 전압 및 전류 검출용 모듈, 고내압용 다이오드가 실장된 정류모듈 등 다양한 모듈이 내장되어있다. 본 연구에서는 솔더링특성, 인쇄성, 솔더형상 검사, X-ray를 이용한 솔더 내 void 검사 및 접합강도를 측정하였고, 무연 솔더 합금의 공정최적화는 step 1과 step 2로 구분하여 검토를 실시하였다. Step 1은 유연 솔더와 무연 솔더 페이스트 인쇄 검사 시험을 1차와 2차로 나누어 실험을 진행하였고 printability는 void 함량 및 접합강도의 상관관계로 검토하였다. 전체적으로 유연 솔더의 특성은 무연 솔더에 비하여 상대적으로 우수하였다. Step 2는 리플로우 공정의 최고점 온도 변화에 따른 접합부 특성 변화를 관찰하였다. 리플로우 최고 온도가 증가할수록 접합부 내의 void 함량이 2~4% 정도 감소하였고, 접합강도는 약 0.5 kgf 범위내에서 큰 차이 없이 나타났다. 기판 표면처리종류에 있어서는 ENIG 표면처리가 OSP 및 Pb-free 솔더 표면처리보다 우수한 접합강도를 나타내었다. 1종류의 무연솔더와 OSP 표면처리로 접합된 태양광 접속함 모듈의 500 싸이클 열충격 신뢰성시험 전후에 전기적 특성변화는 0.3% 내의 범위에서 안정적으로 작동함을 확인하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2007년도 SMT/PCB 기술세미나
• /
• pp.37-47
• /
• 2007

Factor : Structure Metal pad & SMO size Board level TC test : - Large SMO size better Board level Drop test : - Large SMO size better Factor : Structure Substrate thickness Board level TC test : - Thick substrate better Board level Drop test : - Substrate thickness is not a significant factor for drop test Factor : Material Solder alloy Board level TC test : - Not so big differences over Pb-free solder and NiAu, OSP finish Board level Drop test : - Ni/Au+SAC105, CuOSP+LF35 are better Factor : Material Pad finish Board level TC test : - NiAu/NiAu is best Board livel Drop test : - CuOSP is best Factor : Material Underfill Board level TC test - Several underfills (reworkable) are passed TCG x500 cycles Board level Drop test : - Underfill lots have better performance than non-underfill lots Factor : Process Multiple reflow Board level TC test : - Multiple reflow is not a significant actor for TC test Board level Drop test : N/A Factor : Process Peak temp Board level TC test : - Higher peak temperature is worse than STD Board level Drop test : N/A Factor : Process Stack method Board level TC test : - No big difference between pre-stack and SMT stack Board level Drop test : - Flux dipping is better than paste dipping but failure rate is more faster