• 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.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.79-84
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• 2002

The bottom-leaded plastic(BLP) packages have attracted substantial attention since its appearance in the electronic industry. Since the solder materials have relatively low creep resistance and are susceptible to low cycle fatigue, the life of the solder joints under the thermal loading is a critical issue for the reliability The represent study established a finite element model for the analysis of the solder joint reliability under thermal cyclic loading. An elasto-plastic constitutive relation was adopted for solder materials in the modeling and analysis. A 28-pin BLP assembly is modeled to investigate the effects of various epoxy molding compound, leadframe materials on solder joint reliability. The fatigue life of solder joint is estimated by the modified Coffin-Hanson equation. The two coefficients in the equation are also determined. A new design for lead is also evaluated by using finite element analysis. Parametric studies have been conducted to investigate the dependence of solder joint fatigue life on various package materials.

• Journal of Welding and Joining
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• 제20권2호
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• pp.90-94
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• 2002

FC-BGA has advantages over other interconnection methods including high I/O counts, better electrical performance, high throughput, and low profile. But, FC-BGA has a lot of reliability issues. The 2nd level solder joint reliability of the FC-BGA with large chip on laminate substrate was studied in this paper. The purpose of this study is to discuss solder joint failures of 2nd level thermal cycling test. This work has been done to understand the influence of the structure of package, the properties of underfill, the properties and thickness of bismaleimide tiazine substrate and the temperature range of thermal cycling on 2nd level solder joint reliability. The increase of bismaleimide tiazine substrate thickness applied to low modulus underfill was improve of solder joint reliability. The resistance of solder ball fatigue was increased solder ball size in the solder joints of FC-BGA.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.221-226
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• 2004

The thermal stresses induced by difference in Coefficient of Thermal Expansion between FR-4 board and 63Sn-37Pb solder joint directly affect the reliability of 63Sn-37Pb solder joint. This research, thus, focuses to investigate the crack initiation and propagation behavior around solder joint by imposing a designed Acceleration Life Test Procedure on solder joint by using a newly manufactured Thermal Impact Experimental Apparatus. The fracture mechanism of the solder joint was found to be highly influenced by thermal stresses. The reliability of solder joint was evaluated by using a failure probability model in terms of varying parameters such as frequency and temperature. The relationship between failure probability and safety factor was also studied.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2007년도 SMT/PCB 기술세미나
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• pp.67-79
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• 2007

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.117-120
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• 2002

In this paper, several methods to predict the solder joint shape are studied. Although there are various methods to predict the solder joint shape, such as truncated sphere method, force-bal tranced analytical solution, and energy-based methods like surface evolver developed by Ken Brakke, we calculate solder joint shape of $\mu$BGA by two solder joint shape prediction methods(truncated sphere method and surface evolver) and then compare results of each method. The results in dicate that two methods can accurately predict the solder joint shape in an accurate range. After that, we calculate reliability solder joint shape under thermal cycle test by FEA program ANSYS. As a result, it could be found that optimal solder joint shape calculated by solder joint prediction method has best reliability in thermal cycle test.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.630-633
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.365-370
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint' failure. The first order Taylor series expansion of the limit state function incorporating with Tresca failure criterion is used in order to estimate the failure probability of solder joints under heated condition. Using shear stresses and shear strains appeared on the solder joint, we estimate the failure probability of solder joints with the Tresca failure criterion. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically studied by using the failure probability model with first order reliability method(FORM).

• 한국정밀공학회지
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• 제21권2호
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• pp.138-144
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• 2004

The initiation and the propagation of solder joint crack depend on its environmental conditions, such as high temperature creep and thermal fatigue. Creep is known to be the most important factor for the mechanical failure of solder joints in micro-electronic components and micro-systems. This is mainly caused by the different thermal expansion coefficients of the materials used in the micro-electronic packages. To determine the reliability of solder joints and consequently the electronic components, the characterization of the creep behavior of this group of materials is crucial. This paper is to apply the theory of creep into solder joints and to provide related technical information needed for evaluation of reliability of solder joint to failure. 63Sn-37Pb solder was used in this study. This paper experimentally shows a way to enhance the reliability of solder joints.

• 마이크로전자및패키징학회지
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• 제8권4호
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• pp.47-52
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• 2001

Sn-Cu-Ni계 솔더를 이용한 AC Adapter의 Pb-Free Wave 솔더링 공정을 Six Sigma기법으로 개발하였다. 솔더 접합부의 외관, 미세조직, Lift-off현상 및 Crack발생 유.무를 관찰하여 접합기구를 규명하고자 하였으며 열 충격시험을 통하여 신뢰성평가를 수행하였다. 솔더 접합부의 Sn-Cu-Ni계 솔더와 Cu Land 사이에는 약 5 $\mu\textrm{m}$ 두께의 $(Cu,Ni)_6/Sn_5$ 형태의 금속간화합물이 발견되었고 열 충격후 750사이클까지는 Crack이 발견되지 않았다. 본 연구로 개발된 제품은 기존의 Sn-Pb솔더를 사용한 제품에 비해서 양산성 및 신뢰성 측면에서 우수한 특성을 나타내었다.