• 한국포장학회지
• /
• 제12권1호
• /
• pp.45-53
• /
• 2006

Thermal insulation is used in a variety of applications to protect temperature sensitive products from thermal damage. Several factors affect the performance of insulation packages. Among these factors, the thermal resistance of the insulating wall is the most important factor to determine the performance of the insulating package. In many cases, insulating wall consists of multi-layered structure and the heat transfer through this structure is a very complex process. In this study, an one-dimensional mathematical model, which includes all of the heat transfer principles covering conduction, convection and radiation in multi-layered structure, were developed. Based on this model, several heat transfer phenomena occurred in the air space between the layer of the insulating wall were investigated. From the simulation results, it was observed that the heat transfer through the air space between the layer were dominated by conduction and radiation and the low emissivity of the surface of each solid layer of the wall can dramatically increase the thermal resistance of the wall. For practical use, an equation was derived for the calculation of the thermal resistance of a multi-layered wall.

• 마이크로전자및패키징학회지
• /
• 제13권4호
• /
• pp.1-7
• /
• 2006

WLCSP(wafer level chip size package)는 웨이퍼 레벨에서 패키지 공정이 이루어지는 차세대 패키지 중 하나이다. WLCSP는 웨이퍼 레벨에서 패키지 공정이 이루어진다는 특징으로 인하여 웨이퍼당 생산되는 반도체 칩의 수에 따라 그 패키징 비용을 크게 줄일 수 있다는 장점이 있다. 그러나 응력 버퍼 역할을 하는 기판을 없애는 혁신적인 구조로 인하여 솔더 조인트의 신뢰성이 기존의 BGA 패키지에 비하여 취약하게 되는데, 이러한 솔더 조인트 신뢰성에 대하여 반도체 칩과 솔더볼을 연결하는 폴리머 절연층은 열팽창계수 차이에 의해 발생하는 응력을 흡수하는 중요한 역할을 하게 된다. 본 연구에서는 하이닉스에서 개발한 Omega-CSP를 사용하여 솔더볼 배열 변화와 제 1 절연층의 특성에 따른 솔더 조인트의 열피로 특성을 평가하였다. 그 결과 절연층의 특성 변화가 솔더 조인트의 열피로 특성에 주는 영향은 솔더볼 배열 구조에 따라 변화되는 것을 확인하였다.

• International Journal of Safety
• /
• 제1권1호
• /
• pp.36-42
• /
• 2002

This paper is aimed at predicting the life of rubber insulating gloves under normal operating stresses from relatively rapid test performed at higher stresses. Specimens of rubber insulating gloves are subject to multiple stress conditions, i.e. combined electrical and thermal stresses. Two modes of electrical stress, step voltage stress and constant voltage stress are used in specimen aging. There are two types of test for electrical stress in this experiment: the one is Breakdown Voltage (BDV) test under step voltage stress and thermal stress and the other is lifetime test under constant voltage stress and temperature stress. The ac breakdown voltage defined as the break-down point of insulation that leakage current excesses a limit value, l0mA in this experiment, is determined. Because the very high variability of aging data requires the application of statistical model, Weibull distribution is used to represent the failure times as the straight line on Weibull probability paper. Weibull parameters are deter-mined by three statistical methods i.e. maximum likelihood method, graphical method and least squares method, which employ SAS package, Weibull probability paper and FORTRAN, respectively. Two chosen models for predicting the life under simultaneous electrical and thermal stresses are inverse power model and exponential model. And the constants of life equation for multistress aging are calculated using numerical method, such as Gauss Jordan method etc.. The completion of life equation enables to estimate the life at normal stress based on the data collected from accelerated aging test. Also the comparison of the calculated lifetimes between the inverse power model and the exponential model is carried out. And the lifetimes calculated by three statistical methods with lower voltage than test voltage are compared. The results obtained from the suggested experimental method are presented and discussed.

• 한국주조공학회지
• /
• 제31권4호
• /
• pp.205-211
• /
• 2011

Al-Si alloys have been steadily used as a potential material for the achievement of an efficient weight reduction in the automobile and aerospace industries due to its excellent castability and high strength-to-weight ratio. In this study, riser effect and mechanical properties were investigated according to the size of the sleeve. In addition, the effects of riser size on mechanical properties of castings were investigated. On the other hand flow and solidification process were simulated with a hybrid FDM/FEM package named ZCast. As a result, results of simulation and experiments were comparable regarding to the yield strength, tensile strength, elongation and hardness of casting. It proves the reliability of the simulation. It is expected that the proper size of riser can improve the recycling rate of metallic materials and reduce the cost of casting.

• Journal of Magnetics
• /
• 제20권3호
• /
• pp.201-206
• /
• 2015

Using the Vienna ab initio simulation package (VASP) incorporating both semiempirical and nonlocal van der Waals interaction, the structural, adsorption, and magnetic properties of Ni/BN/Co systems were investigated. We proposed that the relative spin direction of Ni and Co magnets can be easily tuned, because the total energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) states is small. Despite this feature, very interestingly, both Ni and Co layers manifest half-metallic state, whereas the spacer BN layer becomes weak metal for one monolayer (ML) thickness and an insulating barrier for two ML thicknesses. The half-metallic behavior of the magnetic layers seems very robust, because it is independent of the magnetic coupling between Ni and Co. This finding indicates that the Ni/BN/Co system can be used as a potential candidate for tunneling magnetoresistance system.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2013년도 자성 및 자성재료 국제학술대회
• /
• pp.32-32
• /
• 2013

Using the Vienna ab initio simulation package (VASP) incorporating van der Waals interaction, we have explored structural, adsorption, and magnetic properties of Ni(111)/BN/Co(111) systems. We have found that both Ni(111) and Co(111) layers shows half metallic state, while the spacer BN layer becomes weak metal for one monolayer (ML) thickness and an insulating barrier for two ML thickness. The half metallic states in both Ni(111) and Co(111) layers are robust because it is unchanged independently on the magnetic coupling of Ni(111) and Co(111). This finding suggests that the Ni(111)/BN/Co(111) systems can be utilized for perfect tunneling magnetoresistance system. Moreover, it can be applied for potential spin injecting into semiconductor in FM/semiconductor system due to the fact that the half metallic state in FM layers at the interface will be unchanged.

• 마이크로전자및패키징학회지
• /
• 제30권1호
• /
• pp.63-70
• /
• 2023

오늘날 심각한 환경 오염과 에너지의 중요성으로 전력 반도체의 중요도가 지속적으로 높아지고 있다. 특히 wide band gap(WBG)소자 중 하나인 SiC-MOSFET은 우수한 고전압 특성을 가지고 있어 그 중요도가 매우 높다. 하지만 SiC-MOSFET의 전기적 특성이 열에 민감하기 때문에 패키지를 통한 열 관리가 필요하다. 본 논문에서는 기존 전력 반도체에서 사용하는 direct bonded copper(DBC) 기판 방식이 아닌 insulated metal substrate(IMS) 방식을 제안한다. IMS는 DBC에 비해 공정이 쉬우며 coefficient of thermal expansion (CTE)가 높아서 비용과 신뢰성 측면에서 우수하다. IMS의 절연층인 dielectric film의 열전도도가 낮은 문제가 있지만 매우 얇은 두께로 공정이 가능하기 때문에 낮은 열 전도도를 충분히 극복할 수 있다. 이를 확인하기 위해서 이번 연구에서는 electric-thermal co-simulation을 수행하였으며 검증을 위해 DBC 기판과 IMS를 제작하여 실험하였다.