• 마이크로전자및패키징학회지
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• 제19권1호
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• pp.17-24
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• 2012

Recently, flip chip interconnection has been increasingly used in microelectronic assemblies. The common Flip chip interconnection is formed by reflow of the solder bumps. Lead-Tin solders and Tin-based solders are most widely used for the solder bump materials. However, the flip chip interconnection using these solder materials cannot be applied to temperature-sensitive components since solder reflow is performed at relatively high temperature. Therefore the development of low temperature bonding technologies is required in these applications. A few bonding techniques at low temperature of $150^{\circ}C$ or below have been reported. They include the reflow soldering using low melting point solder bumps, the transient liquid phase bonding by inter-diffusion between two solders, and the bonding using low temperature curable adhesive. This paper reviews various low temperature bonding methods.

• Applied Microscopy
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• 제45권2호
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• pp.89-94
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• 2015

This article briefly reviews the results of recently reported research on high-temperature Pb-free solder alloys and the research trend for characterization of the interfacial reaction layer. To improve the product reliability of high-temperature Pb-free solder alloys, thorough research is necessary not only to enhance the alloy properties but also to characterize and understand the interfacial reaction occurring during and after the bonding process. Transmission electron microscopy analysis is expected to play an important role in the development of high-temperature solders by providing accurate and reliable data with a high spatial resolution and facilitating understanding of the interfacial reaction at the solder joint.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.1-7
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• 2015

In this study, properties of Pb-free solders for automotive electronics parts were discussed. Lead-free solders for electronics became important after RoHS (Restriction of the use of certain Hazardous Substances) to avoid environmental pollution. Also the growing electronic rate in automotive parts and ELV (End-of Life Vehicles) make Pb-free solder for automotive electronics to be inevitable trend. Definitely, Pb-free solder for automotive electronics should have good wettability, basic strength, but need more reliability than other solders, since it has harsh condition like high temperature, humidity and engine vibration. Thus, shear strength test, thermal shock, drop test and many others are needed to ensure the high reliability. This study describes the properties and requirements of Pb-free solders for automotive electronics.

• Corrosion Science and Technology
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• 제6권2호
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• pp.50-55
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• 2007

The smaller size and higher integration of advanced electronic package systems result in severe electrochemical reliability issues in microelectronic packaging due to higher electric field under high temperature and humidity conditions. Under these harsh conditions, electronic components respond to applied voltages by electrochemical ionization of metal and the formation of a filament, which leads to short-circuit failure of an electronic component, which is termed electrochemical migration. This work aims to evaluate electrochemical migration susceptibility of the pure Sn, Sn-3.5Ag, Sn-3.0Ag-0.5Cu solder alloys in $Na_{2}SO_{4}$. The water drop test was performed to understand the failure mechanism in a pad patterned solder alloy. The polarization test and anodic dissolution test were performed, and ionic species and concentration were analyzed. Ag and Cu additions increased the time to failure of Pb-free solder in 0.001 wt% $Na_{2}SO_{4}$ solution at room temperature and the dendrite was mainly composed of Sn regardless of the solders. In the case of SnAg solders, when Ag and Cu added to the solders, Ag and Cu improved the passivation behavior and pitting corrosion resistance and formed inert intermetallic compounds and thus the dissolution of Ag and Cu was suppressed; only Sn was dissolved. If ionic species is mainly Sn ion, dissolution content than cathodic deposition efficiency will affect the composition of the dendrite. Therefore, Ag and Cu additions improve the electrochemical migration resistance of SnAg and SnAgCu solders.

• Journal of Welding and Joining
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• 제18권6호
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• pp.74-82
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• 2000

The fluxless wetting properties of UBM-coated Si-wafer to the binary lead-free solders(Sn-Ag, Sn-Sb, Sjn-In, Sn0Bi) were estimated by wetting balance method. With the new wettability indices from the wetting curves of one side coated specimen, the wetting property estimation of UBM-coated Si-wafer was possible. For UBM of Si-chip, Au/Cu/Cr UBm was better than au/Ni/TI in the point of wetting time/ At general reflow process temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) was better than that of low melting point one(Sn-Bi, Sn-In). The contact angle of the one side coated Si-plate to the solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2004년도 ISMP Pb-free solders and the PCB technologies related to Pb-free solders
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• pp.93-99
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• 2004

At present, LG Electronics pushes 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.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 International Symposium
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• pp.253-257
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• 2003

The low temperature flip chip technique is applied to the package of the temperature-sensitive devices for LCD systems and image sensors since the high temperature process degrades the polymer materials in their devices. We will introduce the various low temperature flip chip bonding techniques; a conventional flip chip technique using eutectic Bi-Sn (mp: $138^{\circ}C$) or eutectic In-Ag (mp: $141^{\circ}C$) solders, a direct bump-to-bump bonding technique using solder bumps, and a low temperature bonding technique using low temperature solder pads.

• Journal of Welding and Joining
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• 제35권3호
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• pp.7-14
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• 2017

The effect of high temperature-moisture on corrosion and mechanical properties for Sn-0.7Cu, Sn-3.0Ag-0.5Cu (SAC305) solders on flexible substrate was studied using Highly Accelerated Temperature/Humidity Stress Test (HAST) followed by three-point bending test. Both Sn-0.7Cu and SAC305 solders produced the internal $SnO_2$ oxides. Corrosion occurred between the solder and water film near flexible circuit board/copper component. For the SAC305 solder with Ag content, furthermore, octahedral corrosion products were formed near Ag3Sn. For the SAC305 and Sn-0.7Cu solders, the amount of internal oxide increased with the HAST time and the amount of internal oxides was mostly constant regardless of Ag content. The size of the internal oxide was larger for the Sn-0.7Cu solder. Despite of different size of the internal oxide, the fracture time during three-point bending test was not significantly changed. It was because the bending crack was always initiated from the three-point corner of the chip. However, the crack propagation depended on the oxides between the flexible circuit board and the Cu chip. The fracture time of the three-point bending test was dependent more on the crack initiation than on the crack propagation.

• Journal of Welding and Joining
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• 제15권2호
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• pp.36-42
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• 1997

In this paper, stability of initial strength at solder joint with lead free solders, such as Sn-In (52-48%) and Sn-Ag (96.5-3.5wt%) was studied. To obtain at solder joint with high quality, it is very important to control the temperature at the interface of solder joints. It is found that the thermal EMF (electro motive force) occurs betwee lead frame and copper pad on a substrate during reflow soldering process using heated tip. As a result of control the temperature at interface of solder joints, variation of initial strength at solder joint decreases from about $\pm40%$ to $\pm20%$, and it is realized Pb free soldering process using Sn/In and Sn-Ag solder paste.

• 마이크로전자및패키징학회지
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• 제12권2호
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• pp.121-128
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• 2005

전자 기기의 솔더 접합부는 고온에서 작동하고 온도 변화와 부품의 열팽창계수 차에 의해 소성변형을 겪게 된다. 그리고 변형된 솔더는 다시 고온에서 회복과 재결정의 과정을 겪는다. 이와 같은 일련의 열적 기계적 과정은 솔더의 미세구조와 기계적 특성을 변화시킨다. 본 연구에서는 전자 장치가 실제 작동할 때 솔더의 기계적 특성 변화를 예측하기 위해 여러 종류의 무연 솔더와 복합 솔더 (composite solder)의 미소경도 (micohardness)를 다양한 열적 기계적 환경에서 측정하였다. 측정된 무연 솔더에는 Sn, Sn-0.7Cu, Sn-3.5Ag-0.7Cu, Sn-2.8Ag-7.0Cu (복합 솔더), Sn-2.7Ag-4.9Cu-2.9Ni (복합 솔더)가 포함되어 있다. 솔더 시편은 $0.4{\~}7^{\circ}C$/sec의 냉각속도로 주조되었고 $30{\~}50\%$의 압축변형을 가한 후 $150^{\circ}C$에서 48시간 열처리하였다. 미소경도는 $25{\~}130^{\circ}C$에서 측정하였다. 각 시편의 미세구조 역시 관찰하여 미세구조와 비교하였다.