• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.469-474
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• 2002

Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bumps reflowed by laser was superior than the solder bumps reflowed by hot air, and the microstructure inside the solder bumps reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn$_4$ layer and remnant Au element. Needle-like AuSn$_4$ grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni$_3$Sn$_4$ intermetallic compound was found at the interface of solder bump reflowed by hot air, AuSn$_4$ particles distributed inside the whole solder bump randomly. It is the combination effect of the continuous AuSn$_4$ layer and finer eutectic microstructure inside the solder bump reflowed by laser that resulted in higher shear strength.

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

• 마이크로전자및패키징학회지
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• 제8권1호
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• pp.45-51
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• 2001

UBM층과의 젖음 특성 및 표면 산화정도가 미세 피치를 갖는 저 융점 솔더 범프의 볼 형성에 미치는 영향을 연구하였다. Au/Cu/Cr 과 Au/Ni/Ti UBM 위에 공정 조성에 가까운 In-Ag와 공정 조성의 Bi-Sn 솔더를 솔더 층의 증착 순서를 달리하여 증발 증착한 후 lift-off 공정과 열처리 공정을 사용하여 솔더 범프를 형성하였다. In-Ag솔더의 경우 In이 UBM 층과 접한 범프가, 또한 Bi-Sn 솔더의 경우 Sn을 먼저 UBM층위에 먼저 증착시켜 리플로 한 범프가 솔더 볼 형성 경향이 다른 범프에 비해 높았다. 구형의 솔더 범프 형성 정도는 UBM 층과의 젖음 특성에 따라 크게 달라졌다.

• Journal of Welding and Joining
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• 제18권3호
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• pp.89-96
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• 2000

As solder becomes small and fine, the reliability and solderability of solder joint are the critical issue in present electronic packaging industry. Besides the use of lead(Pb) containing solders for the interconnections of microelectronic subsystem assembly and packaging has enviromental problem. In this study, using Sn/Pb and Sn/Ag eutectic solder paste, in order to obtain decrease of solder joint strength with increasing aging time, initial solder joint strength and aging strength after 1000 hour aging at $100^{\circ}C$ were measured by peel test. And in order to obtain the growth of intermetallic compound(IMC) layer thickness, IMC layer thickness was measured by scanning electron microscope(SEM). As a result, solder joint strength was decreased with increasing aging time. The mean IMC layer thickness was increased linearly with the square root of aging time. The diffusion coefficient(D) of IMC layer was found to $1.29{\times}10^{-13}{\;}cm^2/s$ at using Sn/Pb solder paste, 7.56{\times}10^{-14}{\textrm}{cm}^2/s$ at using Sn/Ag solder paste.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.345-350
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• 2014

The surface oxidation mechanism of lead-free solder alloys has been investigated with multiple reflow using X-ray photoelectron spectroscopy. It was found that the solder surface of Sn-Ag-Cu-In solder alloy is surrounded by a thin $InO_x$ layer after reflow process; this coating protects the metallic surface from thermal oxidation. Based on this result, we have performed a wetting balance test at various temperatures. The Sn-Ag-Cu-In solder alloy shows characteristics of both thermal oxidation and wetting balance better than those of Sn-Ag-Cu solder alloy. Therefore, Sn-Ag-Cu-In solder alloy is a good candidate to solve the two problems of easy oxidation and low wettability, which are the most critical problems of Pb-free solders.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 추계학술발표 개요집
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• pp.110-112
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• 1995

Initial solder joint strengths of various solder pastes, such as Sn-Pb(63-37wt%), Sn-In(52-48wt%), Sn-In-Ag(77.5-20-2.5wt%), and Sn-Ag(96.5-3.5wt%) has been studied. A system that can control the solder joint interface temperature during bonding process was also desined and implemented to improve solder joint integrity.

• 마이크로전자및패키징학회지
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• 제9권1호
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• pp.21-28
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• 2002

Sn-Cu-Ni계 솔더 합금에 소량의 Bi와 In을 첨가하여 새로운 무연솔더 합금 개발을 진행하였다. Sn-0.7%(Cu+Ni)에 2~5% Bi. 2~10% In을 첨가하여 각각의 열적, 전기적, 기계적 특성을 평가하였다. 솔더합금의 융점은 200~$222^{\circ}C$, 응고온도범위는 20~$37^{\circ}C$로 중.고온계 솔더로서 적용이 가능하다. 실험 조성별 솔더 합금중 실용적, 경제적인 면을 고려하여 Sn-0.7%(Cu+Ni)-3.5%Bi-2%In이 최적의 합금 조성으로 판단된다. 이 합금은 융점이 $220^{\circ}C$정도이며 응고범위는 $25^{\circ}C$, 강도 면에서는 타 합금에 비해 상당히 우수한 값을 나타내었으며 연신율은 비교적 낮은 값을 나타내었다. 다른 기계적, 전기적 특성은 타 솔더 합금과 유사하거나 우수한 편이었으며 젖음특성도 양호하였다.

• Journal of Welding and Joining
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• 제33권3호
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• pp.19-24
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• 2015

Joint properties of electric control unit (ECU) module using Sn-Cu-(X)Al(Si) lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-0.01Al(Si) and Sn-0.5Cu-0.03Al(Si) (wt.%) lead-free alloys were fabricated as bar type by doped various weight percentages (0.01 and 0.03 wt.%) of Al(Si) alloy to Sn-0.5Cu. After fabrications of lead-free alloys, the ball-type solder alloys with a diameter of 450 um were made by rolling and punching. The melting temperatures of 0.01Al(Si) and 0.03Al(Si) were 230.2 and $230.8^{\circ}C$, respectively. To evaluation of properties of solder joint, test printed circuit board (PCB) finished with organic solderability perseveration (OSP) on Cu pad. The ball-type solders were attached to test PCB with flux and reflowed for formation of solder joint. The maximum temperature of reflow was $260^{\circ}C$ for 50s above melting temperature. And then, we measured spreadability and shear strength of two Al(Si) solder materials compared to Sn-0.7Cu solder material used in industry. And also, microstructures in solder and intermetallic compounds (IMCs) were observed. Moreover, thickness and grain size of $Cu_6Sn_5$ IMC were measured and then compared with Sn-0.7Cu. With increasing the amounts of Al(Si), the $Cu_6Sn_5$ thickness was decreased. These results show the addition of Al(Si) could suppress IMC growth and improve the reliability of solder joint.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.89-98
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• 2001

Pb-free wave soldering process of AC Adapter was implemented by six sigma method using Sn-Cu-Ni type solder. The solder joint appearance, microstructural change, a lift-off phenomenon and reliability were evaluated through thermal shock teal. $(Cu,Ni)_6Sn_5$-type intermetallic compound of which thickness is about 5 micron was found at solder joint between Sn-Cu-Ni solder and copper land. After applying the thermal shock test of as-soldered product up to 750 cycles, no crack was found at the solder joint and the newly developed product was superior to conventions; one in terms of productivity and reliability.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.155-158
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• 2014

The phase transformation of Sn-Pb-Bi solder for photovoltaic ribbon during soldering was studied using real-time synchrotron x-ray scattering. At room temperature, Sn and Pb crystal phases in the solder existed separately. By heating to $92^{\circ}C$, a new PbBi alloy crystal phase was formed, which grew further up to $160^{\circ}C$. The Sn crystal phase first started to melt at $160^{\circ}C$, and was mostly melted at $165^{\circ}C$. In contrast, the Pb and PbBi crystal phases started to melt at $165^{\circ}C$, and were mostly melted at $170^{\circ}C$. The useful result was obtained, that the solder's melting temperature decreased from $183^{\circ}C$ to $170^{\circ}C$ by addition of a small amount of Bi atoms to the eutectic Sn62-Pb38 (wt%) solder. Our study first revealed the detailed in-situ phase transformation of Sn-Pb-Bi solder during heating to the eutectic temperature. Considering the results of peel strength and hardness, adding 1 wt% of Bi atoms to the Sn62-Pb38 (wt%) solder produced an appropriate composition.