• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.29-34
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• 2020

본 연구에서는 무전해 니켈 도금액 pH 변화에 따른 electroless nickel immersion gold (ENIG)/Sn-3.0wt.%Ag-0.5wt.%Cu(SAC305) 솔더 접합부 취성 파괴 거동에 대하여 평가하였다. ENIG 표면처리를 위한 무전해 니켈 도금액의 pH는 4.0에서 5.5로 변화 시켰다. 무전해 니켈 도금 후 Ni-P 표면 관찰 결과, 도금액의 pH가 낮아질수록 Ni-P 층 nodule 표면에 핀홀이 증가하였다. 솔더링 후 접합부 계면에서는 (Cu,Ni)6Sn5 금속간화합물이 형성되었으며, 무전해 니켈 도금액의 pH가 증가할수록 솔더접합부의 계면 금속간화합물의 두께는 증가하였다. 고속전단 시험을 통하여 ENIG/SAC305 솔더 접합부의 취성파괴 거동을 확인하였으며, 무전해 니켈 도금액의 pH가 증가할수록 솔더접합부의 전단강도는 감소하는 경향을 보였다. 또한, 솔더 접합부의 취성 파괴율은 pH가 5일 때 가장 높은 값을 보였다.

• International Journal of Quality Innovation
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• 제10권1호
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• pp.1-23
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• 2009

Face the process yield rate improvements of motherboard, although general enterprises finish deployment goal of each functions by overall quality managements, through quality improvement methods, industry engineering methods, plan-do-check-act (PDCA) methods and other improvement solutions, but it is only can be improved partially and unable to enhance the yield rate of product to the target. It only can takes one step ahead to enhance the process yield rate of motherboard with six sigma ($6{\sigma}$) overall DMAIC process and tactics. This research aimed to use six sigma quality improvement tactics by DMAIC systematic procedure and tactics, and find the key factors that effect to the process yield rate of surface mount technology. It also identified the keys input and process and output index to satisfy customer requirements and internal process index. The results showed that the major effective factors by fishbone and process failure modes and effects analysis (PFMEA). If the index of input and output that can be quantified, the optimum parameter can be found through design of experiment to ensure that the process is stable. If the factor of input and output that cannot be quantified, we found out the effective countermeasure by Mind_Mapping, make sure whole processes can be controlled stably, to reach the high product quality and enhance the customer satisfaction.

• 마이크로전자및패키징학회지
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• 제29권3호
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• pp.63-71
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• 2022

본 연구에서는 Sn-Ag-Cu (SAC)솔더와 electroless nickel autocatalytic gold (ENAG) 표면처리 간 계면반응 및 낙하충격 신뢰성을 연구하였다. ENAG 솔더 접합부의 특성은 다른 Ni계 표면처리인 electroless nickel immersion gold(ENIG)와 electroless nickel electroless palladium immersion gold (ENEPIG)와 비교 평가 하였다. SAC솔더와 Ni계 표면처리 계면에서는 (Cu, Ni)6Sn5 intermetallic compound (IMC)가 형성되었다. IMC 두께는 SAC/ENAG와 SAC/ENEPIG는 1.15 ㎛, 1.12 ㎛로 비슷하였고, SAC/ENIG는 IMC 두께가 2.99 ㎛로 SAC/ENAG보다 2배 정도 높았다. 또한 솔더 접합부의 IMC두께는 무전해 Ni(P) 도금액의 metal turnover (MTO)조건에 영향을 받는 다는 것을 알 수 있었고, MTO가 0에서 3으로 증가하면 IMC두께가 증가함을 알 수 있었다. 전단강도는 SAC/ENEPIG의 접합강도가 가장 높았고, SAC/ENAG, SAC/ENIG 순이었다. 또한, MTO가 증가하면, 전단강도가 낮아짐을 알 수 있었다. 취성파괴도 SAC/ENEPIG가 세가지 접합부 중 가장 낮았으며, SAC/ENAG, SAC/ENIG 순이였고, 마찬가지로 MTO가 증가하면 취성파괴가 높아짐을 알 수 있었다. 낙하충격 시험에서도 0 MTO조건이 3 MTO조건보다 높은 평균파괴횟수를 갖는 것을 확인하였고, 평균파괴횟수도 SAC/ENEPIG, SAC/ENAG, SAC/ENIG순으로 높았다. 낙하 충격 후 파단면을 관찰한 결과 크랙은 IMC와 Ni(P)층 사이에서 진행되었다.

• Corrosion Science and Technology
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• 제4권6호
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• pp.217-221
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• 2005

In the present investigation, holographic interferometry was utilized for the first time to monitor in situ the thickness of the oxide film of aluminium samples during anodization processes in boric acid solutions. The anodization process (oxidation) of the aluminium samples was carried out by the technique of the electrochemical impedance spectroscopy(EIS), in different concentrations of boric acid (0.5-5.0% $H_3BO_3$) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in solutions. Consequently, holographic interferometry is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film of the aluminium samples can be determined without any physical contact. In addition, measurements of electrochemical values such as the alternating current (A.C) impedance(Z), the double layer capacitance($C_{dl}$), and the polarization resistance(Rp) of anodized films of aluminium samples in boric acid solutions were made by the electrochemical impedance spectroscopy(EIS). Attempts to measure electrochemical values of Z, Cdl, and Rp were not possible by holographic interferometry in boric acid especially in low concentrations of the acid. This is because of the high rate of evolutions of interferometric fringes during the anodization process of the aluminium samples in boric acid, which made measurements of Z, Cdl, and Rp are difficult.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.404-409
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• 2004

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool life. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. Also, co-cure bonding method for functional part mounting was exhibited experimentally, by which manufacturing time and cost for polymer concrete bed will be remarkably reduced.

• 한국CDE학회논문집
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• 제11권3호
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• pp.223-233
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• 2006

Layered manufacturing(LM) is emerging as a new technology that enables the fabrication of three dimensional heterogeneous objects such as Multi-materials and Functionally Gradient Materials (FGMs). Among various types of heterogeneous objects, more attention has recently paid on the fabrication of FGMs because of their potentials in engineering applications. The necessary steps for LM fabrication of FGMs include representation and process planning of material information inside an FGM. This paper introduces a new process planning algorithm that takes into account the processing of material information. The detailed tasks are discretization (i.e., decomposition-based approximation of volume fraction), orientation (build direction selection), and adaptive slicing of heterogeneous objects. In particular, this paper focuses on the discretization process that converts all of the material information inside an FGM into material features like geometric features. It is thus possible to choose an optimal build direction among various pre-selected ones by approximately estimating build time. This is because total build time depends on the complexity of features. This discretization process also allows adaptive slicing of heterogeneous objects to minimize surface finish and material composition error. In addition, tool path planning can be simplified into fill pattern generation. Specific examples are shown to illustrate the overall procedure.

• 마이크로전자및패키징학회지
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• 제17권2호
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• pp.11-20
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• 2010

The effects of heat treatment on matte pure tin-plated Cu leadframes at high temperature and humidity conditions were investigated. After 1800 hrs of storage at $55^{\circ}C/85%$ RH, approximately 14.5 ${\mu}m$ long striation-shaped whiskers were observed on the surface of the without postbake treatment (WOPB) samples, while no whiskers were found in with postbake treatment (WPB) samples. The preferred orientations of Sn grains in WOPB and WPB sample did not change after the postbake treatment at $125^{\circ}C$ for 1 hr. However, both changed from (112) to (321) and (101), respectively, after 1800 hrs of storage at $55^{\circ}C/85%$ RH. The tensile stress of 8 MPa generated in as-plated sample was changed to a compression stress of 17 MPa after 2 days in room temperature storage. Due to the grain growth during postbake treatment, the WPB samples have more regular grains than the WOPB samples. In the as-plated sample, 0.32 ${\mu}m$ thickness of planar intermetallic compound (IMC) was observed. The IMCs in the WOPB and WPB samples had two distinct layers with large grains of $Cu_6Sn_5$ and with small grains of ${\eta}-Cu_{6.26}Sn_5$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.158-158
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• 2008

모바일 정보통신기기를 중심으로 실장모듈의 초소형화, 고집적화로 인해 접속단자의 피치가 점점 미세화 됨에 따라 플립칩 본딩용 접착제에 함유되는 무기충전제인 실리카 필러의 크기도 미세화되고 있다. 본 연구에서는 NCP (non-conductive paste)의 실리카 필러의 크기가 COB(chip-on-board) 플립칩 패키지의 신뢰성에 미치는 영향을 조사하였다. 실험에 사용된 실리카 필러는 Fused silica 3 종과 Fumed silica 3종이며 response surface 실험계획법에 따라 혼합하여 최적의 혼합비를 정하였다. 테스트베드로 사용된 실리콘 다이는 투께 $700{\mu}m$, 면적 5.2$\times$7.2mm로 $50\times50{\mu}m$ 크기의 Au 도금범프를 $100{\mu}m$ 피치, peripheral 방식으로 형성시켰으며, 기판은 패드를 Sn으로 finish 하였다. 기판을 플라즈마 전처리 후 Panasonic FCB-3 플립칩 본더를 이용하여 플립칩 본딩을 수행하였다. 패키지의 신뢰성 평가를 위해 $-40^{\circ}C{\sim}80^{\circ}C$의 열충격시험과 $85^{\circ}C$/85%R.H.의 고온고습시험을 수행하였으며 Die shear를 통한 접합 강도와 4-point probe를 통한 접속저항을 측정하였다.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1958-1967
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• 2004

This paper describes the method to rapidly fabricate the large-sized physical model with the envelope model size of more than 600 mm${\times}$ 600 mm${\times}$ 600 mm using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology. The fabrication procedure of the large-sized solid shape is as follows: (1) Generation of STL data from 3D scan data using 3D scanner, (2) generation of shell-type STL data by Boolean operation, (3) division of shell-type STL data into several pieces by solid splitting, (4) generation of USL data for each piece with VLM-Slicer, (5) fabrication of each piece by cutting and stacking according to USL data using VLM-ST apparatus, (6) completion of a shell-type prototype by zigzag stacking and assembly for each piece, (7) completion of a 3D solid shape by foam backing, (8) surface finish of a completed 3D solid shape by coating and sanding. In order to examine the applicability of the proposed method, the miniature of the Mount Rushmore Memorial has been fabricated. The envelope model size of the miniature of the Mount Rushmore Memorial is 1,453 mm${\times}$ 760 mm${\times}$ 853 mm in size. From the result of the fabricated miniature of the Mount Rushmore Memorial, it has been shown that the method to fabricate the large object using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology are very fast and efficient.

• 한국정밀공학회지
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• 제27권3호
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• pp.135-141
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• 2010

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats positioned on a rotating vat carousel that contain different photo-curable materials. To change the material during the process, the build platform is raised out of the current vat, a new vat with a different material is rotated under the platform, and the platform is submerged into the new vat so that the new material can be used. This paper introduces a new vat exchange mechanism, cleaning process, recoating process, resin leveling mechanism and process planning technologies for the implementation of multiple material SL. An overview of the system framework is provided and the system integration and control software is described. In addition, several multiple material test parts are designed, fabricated, and described.