• Current Photovoltaic Research
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• 제5권3호
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• pp.83-88
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• 2017

The growth of intermetallic compounds is an important factor in the reliability of solar cells. Especially, the temperature change in the soldering process greatly affects the thickness of the intermetallic compound layer. In this study, we investigated the intermetallic compound growth by Sn-diffusion in solder joints of solar cells. The thickness of the intermetallic compound layer was analyzed by IR lamp power and hot plate temperature control, and the correlation between the intermetallic compound layer and the adhesive strength was confirmed by a $90^{\circ}$ peel test. In order to investigate the growth of the intermetallic compound layer during isothermal aging, the growth of the intermetallic compound layer was analyzed at $85^{\circ}C$ and 85% for 500 h. In addition, the activation energy of Sn was calculated. The diffusion coefficient of the intermetallic compound layer was simulated and compared with experimental results to predict the long-term reliability.

• 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.

• 마이크로전자및패키징학회지
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• 제26권3호
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• pp.7-13
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• 2019

In this paper, the principles, types and characteristics of the laser and laser soldering are introduced. Laser soldering methods for electronics, metals, semiconductors are also presented. Laser soldering is a non-contact process that transfers energy to solder joint by a precisely controlled beam. Demands for laser soldering are increasing due to bonding for complex circuits and local heating in micro joint. Laser absorption ratio depends on materials, and each material has different absorption or reflectivity of the laser beam, which requires fine adjustment of the laser beam. Laser types and operating conditions are also important factors for laser soldering performance. In this paper, the performance of Nd:YAG laser soldering is compared to the hot blast reflow. Meanwhile, a diode laser gives different wavelength and smaller parts with high performance, but it has various reliability issues such as heat loss, high power, and cooling technology. These issues need to be improved in the future, and further studies for laser micro-joining and soldering are required.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.29-34
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• 2015

The photovoltaic ribbon attached the flux reduces the solar module manufacturing process and the pollution. This paper presents an analytical method for solving the continuous flux drying system of photovoltaic ribbon. Also, some experiments of the drying of photovoltaic ribbon are carried out in order to design the drying system. Numerical results indicate the air temperature, the air velocity, the air pressure and the timewise temperature variation of ribbon during drying process. In case of the drier process length is short, 400mm, the photovoltaic ribbon is wet. Thus, another study of drying system is necessary to improve the drying ability. As a result, multi-stage drier system is proposed and shown to be good drying ability.

• 마이크로전자및패키징학회지
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• 제28권2호
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• pp.1-12
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• 2021

3차원 인쇄 기술은 제품의 설계를 3차원으로 하여 조립없이 제품의 생산까지의 시간을 획기적으로 줄이고 복잡한 구조도 구현할 수 있어 미래의 기술로 각광받고 있다. 본 논문은 3차원 인쇄기술을 이용한 전자소자에 대한 최근 연구동향을 알아보면서 구성품, 전원공급장치와 회로에서의 연결과 3차원 인쇄기술 PCB의 응용한 연구논문들을 소개하고 있다. 3차원 인쇄기술로 제작한 전자소자는 원스톱으로 전자소자, 솔더링(soldering), 스태킹(stacking), 회로의 봉지막(encapsulation)까지 제작함으로써 생산설비의 단순화와 전자기기를 개인 맞춤형을 할 수 있는 가능성을 보여주었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.87.2-87.2
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• 2012

고출력 반도체 레이저 다이오드는 발진 파장 및 광 출력에 따라 다양한 분야에 응용되고 있으며, 특히 발진파장이 808 nm 및 1470 nm 인 고출력 레이저 다이오드의 경우 재료가공, 펌핑용 광원 (DPSSL, 광섬유 레이저), 의료, 피부미용 (점 제거), 레이저 다이오드 디스플레이 등 가장 다양한 응용분야를 가진 광원 중의 하나라고 할 수 있다. 일례로 재료가공의 경우, 레이저 용접, 레이저 인쇄, 하드디스크의 레이저 텍스쳐링 등 그 응용분야는 무수히 많으며, 최근에는 미래 성장동력 사업의 하나로 중요한 이슈가 되는 태양전지에서 에지 분리 (edge isolation), ID 마킹, 레이저 솔더링 등에서 필수불가결한 광원으로 각광받고 있다. 808 nm 대역 In(Ga)AlAs quantum dots laser diode (QDLD) 성장을 위하여 In(Ga)AlAs QD active 와 In(Ga)AlAs QD LD 성장으로 크게 분류하여 여러 가지 test 실험을 수행하였다. 우선 In(Ga)AlAs QD LD 성장에 앞서 high power LD에 적용 가능한 GaAs/AlGaAs quantum well의 성장 및 전기 측정을 수행하여 그 가능성을 보았다. In(Ga)AlAs QD active layer의 효과적인 실험 조건 조절을 위해 QD layer는 sequential mithod (ex. n x (InGaAlAs t sec + InAs t sec + As 10 sec)를 사용하였다. In(Ga)AlAs QD active layer는 성장 온도, 각 sequence 별 시간, 각 source 양, barrier 두께 조절 및 타입변형, Arsenic flux 등의 조건을 조절하여 실험하였다. 또한 위에서 선택된 몇 가지 active layer 를 이용하여 In(Ga)AlAs QD LD 성장 조건 변화를 시도하였다.

• 마이크로전자및패키징학회지
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• 제7권4호
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• pp.7-15
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• 2000

질소분위기 중에서 솔더 접합부의 특성 및 solderability을 검토하기 위하여 대기분위기와 질소분위기에서의 젖음성을 평가하였다. 또한 솔더접합부의 브리지결함(bridge defect)을 대기와 질소분위기 중에서 비교 검토하였다. 이 결과, 질소분위기 중에서 Cu표면을 사포로 연마한 시편, Cu표면에 Sn-Pb 및 Sn으로 도금한 시편에서 젖음성이 향상되었다. 대기분위기에 비해 젖음시간은 약 0.2~0.45초 정도 시간이 감소하였고, 최대젖음력 ($F_{max}$)도 대기중에 비해 약 1.8~2.8 N 정도가 커졌다. 질소유량에 따른 젖음시간($t_2$)과 젖음력을 측정한 견과 질소유량이 10 1/min에서 30 1/min으로 증가함에 따라 대기중 분위기에 비해 젖음시간($t_2$)는 약 0.25초 정토 감소하였고, 젖음력은 2.3 N 정도 상승하였다. 따라서, 질소분위 기에서 무세정용 플럭스를 사용해도 젖음성이 떨어지는 것을 보완 할 수 있다. 질소분위기에서는 젖음성을 향상시키고 산화물(dross)를 억제시켜주어 대기 중 보다 브리지 (Bridge)발생률이 25~76%정도 떨어졌다. 브리지 발생률은 피치간격이 미세할수록 질소분위기가 대기 중 보다 감소하였다.

• Journal of Welding and Joining
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• 제20권4호
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• pp.505-509
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• 2002

Pb is considered to be eliminated from solder, due to its toxicity. However, melting temperatures of most Pb-free solders are known higher than that of Sn37Pb. Therefore, there is a difficulty to apply Pb-free solders to electronic industry. Since Sn3Ag8Bi5In has relatively lower melting range as $188~200^{\circ}C$, on this study. Wettability and soldering characteristics of Sn3Ag8Bi5In solder in BGA were investigated to solve for what kind of problem. Zero cross time, wetting time, and equilibrium force of Sn3Ag8Bi5In solder for Cu and plated Cu such as Sn, Ni, and Au/Ni-plated on Cu were estimated. Plated Sn on Cu showed best wettability for zero cross time, wetting time and equilibrium farce. Shear strength of the reflowed joint with Sn3Ag8Bi5In ball in BGA was investigated. Diameter of the ball was 0.5mm, UBM(under bump metallurgy) was $Au(0.5\mu\textrm{m})Ni(5\mu\textrm{m})/Cu(18\mu\textrm{m})$ and flux was RMA type. For the reflow soldering, the peak reflow temperature was changed in the range of $220~250^{\circ}C$, and conveyor speed was 0.6m/min.. The shear strength of Sn3Ag8Bi5In ball showed similar level as those of Sn37Pb. The soldered balls are aged at $110^{\circ}C$ for 36days and their shear strengths were evaluated. The shear strength of Sn3Ag8Bi5In ball was increased from 480gf to 580gf by aging for 5 days.

• 한국표면공학회지
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• 제36권5호
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• pp.373-378
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• 2003

With increasing environmental concerns, application of lead-free solder and fluxless soldering process have been taken attention from the electronic packaging industry. Plasma treatment is one of the soldering methods for the fluxless soldering, and it can prevent environmental pollution cased by flux. On this study fluxless soldering process under $Ar-H_2$plasma using lead free solders such as Sn-3.5 wt%Ag, Sn-3.5 wt%Ag-0.7 wt%Cu and Sn-37%Pb for a reference was investigated. As the plasma reflow has higher soldering temperature than normal air reflow, the effects of UBM(Under Bump Metallization) thickness on the interfacial reaction and bonding strength can be critical. Experimental results showed in case of the thin UBM, Au(20 nm)/Cu(0.3 $\mu\textrm{m}$)/Ni(0.4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), shear strength of the soldered joint was relatively low as 19-27㎫, and it's caused by the crack observed along the bonded interface. The crack was believed to be produced by the exhaustion of the thin UBM-layer due to the excessive reaction with solder under plasma. However, in case of thick UBM, Au(20 nm)/Cu(4 $\mu\textrm{m}$)/Ni(4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), the bonded interface was sound without any crack and shear strength gives 32∼42㎫. Thus, by increasing UBM thickness in this study the shear strength can be improved to 50∼70%. Fluxed reflow soldering under hot air was also carried out for a reference, and the shear strength was 48∼52㎫. Consequently the fluxless soldering with plasma showed around 65∼80% as those of fluxed air reflow, and the possibility of the $Ar-H_2$ plasma reflow was evaluated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.252-252
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• 2010

적외선 센서는 빛의 유무에 관계없이 주 야간 전방의 물체에서 발산하는 미약한 적외선(열선)을 감지하여 영상으로 재현하는 열상시스템은 자동차 야간 운전자 보조용 나이트 비젼, 핵심 시설의 감시 관리, 군수 등의 분야에 적용되어지고 있는 최첨단, 고부가가치를 지니고 있는 기술이다. 양자형은 센서 특성은 좋으나 냉각기(작동온도: $-196^{\circ}C$) 및 고진공 패키지인 dewar를 사용하는 반면에, 열형은 대부분 상온에서 동작되는 온도안정화를 위한 전자냉각모듈만을 구비하면 되므로 저가형으로 제작이 가능한 비냉각형 적외선 센서이다. 본 연구에서는 적외선 센서용 진공패키지 조립공정 및 패키지된 센서의 측정기술을 개발하였다. 금속 메탈패키지를 제작하였으며, 금속 진공패키지는 소자냉각용 TE Cooler와 장수명 진공유지를 위한 getter, 그리고 센서칩, 온도센서를. 장착하여 칩을 조립하였다. Cap ass'y와 base envelop의 솔더링 공정을 수행하였으며, 진공패키지의 진공유지를 위해 TMP를 이용하여 진공을 유지하고, 약 5일동안 패키지 bake-out을 수행하였다. 진공압력은 $10^{-7}\;torr$ 이하를 유지하였으며, getter를 활성화시키고, pinch-off 공정으로 조립 ass'y를 완성하였다. 진공 패키지의 기밀성은 He leak tester를 이용하여 측정하였으며, ${\sim}10^{-9}\;std.cm^3/sec$로 기밀성을 유지하였다. TE cooler를 작동한 온도안정성은 0.05 K 이하였다. 볼로미터 센서의 반응도는 $10^2\;V/W$ 이상을 나타내었으며, 탐지도는 $2{\times}10^8cm-Hz^{1/2}/W$를 나타내었다. 본 연구를 통하여 얻어진 결과는 향후 2차원 열영상용 어레이 검출기 및 웨이퍼수준의 패키징 공정에 유용하게 응용될 것으로 판단된다.