• Proceedings of the KWS Conference
• /
• 2005.11a
• /
• pp.228-230
• /
• 2005

Sn-8wt%Zn-3wt%Bi (이하, Sn-8Zn-3Bi) 솔더의 장기 신뢰성을 평가하기 위하여 고용고습시험을 행하였다. 고온 고습 시험은 $85^{\circ}C$/85RH 조건에서 1000 시간 동안 하였다. 접합 기판으로는 각각 OSP (Organic Solderability Preservative), Sn 그리고 Ni/Au 처리를 한 PCB(Printed Circuit Board) 패드를 사용하였다. 접합에 사용한 부품은 1608Chip 으로 MLCC(Multi Layer Ceramic Capacitor 이하, 1608C) 와 Chip Resister(이하, 1608R)을 사용하였으며, 이 두 부품의 전극부위에 Sn-10wt%Pb(이하 Sn-l0PB), Sn을 각각 도금하였다. 솔더링 후 1608C 와 1608R의 전단 접합 강도와 솔더링부에서 Zn상의 변화를 관찰하였다. 측정결과, Sn-8Zn-3Bi 솔더의 초기 전단 접합 강도는 기판의 표면처리에 상관없이 약 40N 이었다. 그러나 고온 고습 시험 1000 시간 후에는 기판의 표면처리에 상관없이 약 30N 까지 감소하였다. 하지만 이는 reference인 Sn-37Pb 솔더의 강도값과 거의 유사하며, 이는 Sn-8Bi-3Zn 솔더의 고온 고습 시험 후 전단강도 특성은 기존 유연솔더와 비교하여 동등이상이라고 평가할 수 있다.

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.1 s.34
• /
• pp.35-40
• /
• 2005

The oxidation of pure Sn and Sn-0.7Cu, Sn-3.5Ag, Sn-lZn, and Sn-9Zn alloys at $150^{\circ}C$ was investigated. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis by measuring the electrolytic reduction potential and total transferred electrical charges. X-ray photoelectron spectroscopy (XPS) was also conducted to support the results of reduction analysis. The effect of Cu, Ag and Zn addition on surface oxidation of Sn alloys is reported. For Sn, Sn-0.7Cu and Sn-3.5Ag, SnO grew first and then the mixture of SnO and $SnO_2$ was found. $SnO_2$ grew predominantly for a long-time aging. For Zn containing Sn alloys, both ZnO and $SnO_2$ were formed. Zn promotes the formation of $SnO_2$. Sn oxide growth rate of Pb-free solder alloys was also discussed in terms of alloying elements.

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.4 s.37
• /
• pp.307-313
• /
• 2005

Electromigration behavior in the Sn96.5Ag3.0Cu0.5 solder lines was investigated and compared Sn96.5Ag3.0Cu0.5 with eutectic SnPb. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ$\ast$). The threshold current density were measured to be $2.38{\times}10^4A/cm^2$ at $140^{\circ}C$ and the value represented the maximum current density which the SnAgCu solder can carry without electromigration damage at the stressing temperatures. The electromigration energy was measured to 0.56 eV in the temperature range of $110-160^{\circ}C$. The measured products of diffusivity and the effective charge number, DZ$\ast$ were $3.12{\times}10^{-10} cm^2/s$ at $110^{\circ}C$, $4.66{\times}10^{-10} cm^2/s$ at $125^{\circ}C$, $8.76{\times}10^{-10} cm^2/s$ at $140^{\circ}C$, $2.14{\times}10^{-9}cm^2/s$ at $160^{\circ}C$ SnPb solder existed incubation stage, while SnAgCu did not have incubation stage. It was thought that the diffusion mechanism of SnAgCu was different from that of SnPb.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.09a
• /
• pp.93-99
• /
• 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.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2007.04a
• /
• 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

• Journal of the Microelectronics and Packaging Society
• /
• v.14 no.3
• /
• pp.57-64
• /
• 2007

New Chip-on-glass technology to attach an Si chip directly on the glass substrate of LCD panel was studied with local heating method of the Si chip by using thin film heater fabricated on the Si chip. Square-shaped Cu thin film heater with the width of $150\;{\mu}m$, thickness of $0.8\;{\mu}m$, and total length of 12.15 mm was sputter-deposited on the $5\;mm{\times}5\;mm$ Si chip. With applying current of 0.9A for 60 sec to the Cu thin film heater, COG bonding of a Si chip to a glass substrate was successfully accomplished with reflowing the Sn-3.5Ag solder bumps on the Si chip.

• Journal of Welding and Joining
• /
• v.29 no.5
• /
• 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.

• Journal of the Microelectronics and Packaging Society
• /
• v.17 no.4
• /
• pp.11-17
• /
• 2010

The electromigration phenomenon in lead-free flip-chip solder joint has been one of the serious problems. To understand the mechanism of this phenomenon, the crystallographic orientation of Sn grain in the Sn-Ag-Cu solder bump has been analyzed. Different time to failure and different microstructural changes were observed in the all test vehicle and bumps, respectively. Fast failure and serious dissolution of Cu electrode was observed when the c-axis of Sn grain parallel to electron flow. On the contrary of this, slight microstructural changes were observed when the c-axis of Sn perpendicular to electron flow. In addition, underfill could enhance the electromigration reliability to prevent the deformation of solder bump during EM test.

• Korean Journal of Metals and Materials
• /
• v.48 no.11
• /
• pp.1035-1040
• /
• 2010

The research efforts on GaN-based light-emitting diodes (LEDs) keep increasing due to their significant impact on the illumination industry. Surface mount technology (SMT) is widely used to mount the LED packages for practical application. In surface mount soldering both the device body and leads are intentionally heated by a reflow process. We studied on the effects of multiple reflows on microstructural variation and joint strength of the solder joints between the LED package and the substrate. In this study, Pb-free Sn-3.0Ag-0.5Cu solder and a finished pad with organic solderability preservatives (OSP) were employed. A $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed during the multiple reflows, and the thickness of the IMC layerincreased with an increasing number of reflows. The shear force decreased after three reflows. From the observation of the fracture surface after a shear test, partially brittle fractures were observed after five reflows.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.113.2-113.2
• /
• 2011

Sn-Ag계 합금은 대표적인 무연 솔더 조성으로 전자제품의 실장 및 접합에 적용되어 왔으며, 태양전지 분야에서도 모듈의 전극과 bus바로 사용되는 등 다양한 분야에서 사용되고 있다. 그러나 최근 Ag 가격의 급격한 상승과 솔더 접합부의 신뢰성을 보다 향상시키고자 Ag의 함량을 줄이고 다원계 합금 조성의 무연 솔더 연구가 활발히 진행되고 있다. 본 실험에서는 기존의 연구 결과를 바탕으로 Sn-1.0Ag-0.5Cu-0.4In 4원계 무연솔더 조성에 Bi를 첨가하여 최적의 융점과 용융구간을 가지는 5원계 Sn-Ag-Cu-In-Bi 계 솔더 합금을 설계하였다. 이 설계된 합금은 기존의 유연 솔더인 Sn-Pb와 대표적인 무연 솔더인 Sn-3.5Ag와 각각의 특성을 비교 분석하였다. 젖음성을 평가하기 위하여 wetting balance tester를 이용하여 실험을 행하였고 Differential Scanning Calorimetry(DSC)를 분석하여 젖음 정도와 조성 분석 및 고상점과 액상점 등의 녹음 거동을 확인하였다. 또한 각각의 조성별 전단응력에 따른 파괴 거동을 분석하였다.