• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.68-68
• /
• 2010

To reduce PV manufacturing costs, the thickness of solar cell is getting thinner. Bow is shown after cooling down the temperature of solder cell. It happens because of different thermal expansion coefficients of different metals. Bowed cell can make micro crack while module processing and it can drop off efficiency of PV module. As thinner solar cell is produced, the thickness of ribbon should be concerned to prevent extra bow. In this paper we investigate the contrast of deflection when we solder different thickness of ribbons on same solar cell. This approach would help to find out the optical thickness of ribbon for particular thickness of solar cell later on.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
• /
• pp.561-564
• /
• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(printed circuit boards), Thermal control of the reflow process is required in oder to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD tool(Fluent) for predicting flow and temperature distributions. There was flow recirculation region that had a weak point in the temperature uniformity. Porous plate was installed to prevent and minimize flow recirculation region for acquiring uniform temperature in oven. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• 마이크로전자및패키징학회지
• /
• 제5권2호
• /
• pp.37-48
• /
• 1998

The popcorn cracking phenomena in plastic IC packages during reflow soldering are investigated by considering the heat transfer and moisture diffusion through the epoxy molding compound(EMC) along with the mechanics of interface delamination. Heat transfer and moisture diffusion through EMC under die pad are analyzed by finite difference method (FDM)during the pre-conditioning and subsequent reflow soldiering pro-cess and the amounts of moisture mass and vapor pressure at delaminated die pad/ EMC interface are calculated as a function of the reflow soldering time. The energy release rate stress intensity factor and phase angle were obtained under various loading conditions which are thermal crack face vapor pressure and mixed loadings. It was shown that thermal loading was the main driving force for the crack propagation for small crack lengths but vapor pressure loading played more significant role as crack grew.

• 마이크로전자및패키징학회지
• /
• 제24권1호
• /
• pp.27-34
• /
• 2017

Recently, a demand in sustainable green technologies is requiring the lead free bonding for high power module packaging due to the environmental pollution. The Transient-liquid phase (TLP) bonding can be a good alternative to a high Pb-bearing soldering. Basically, TLP bonding is known as the combination of soldering and diffusion bonding. Since the low melting temperature material is fully consumed after TLP bonding, the remelting temperature of joint layer becomes higher than the operating temperature of the power module. Also, TLP bonding is cost-effective process than metal nanopaste bonding such as Ag. In this paper, various TLP bonding techniques for power semiconductor were described.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제3권3호
• /
• pp.122-131
• /
• 2003

In this study, some characteristics of conductive and non-conductive adhesive inter-connections are derived, based on data from literature and own projects. Assembly of flip chip on flex is taken as a carrier. Potential failure mechanisms of adhesive interconnections reported in literature are reviewed. Some methods that can be used to evaluate the quality of adhesive interconnections and to evaluate their aging behavior are given. Possible finite element simulation approaches are introduced and the required critical materials properties are summarized. Response to temperature and moisture, resistance to reflow soldering and resistance to rapid change in temperature and humidity are elaborated. The effect of post cure during accelerated testing is discussed. This study shows that only a combined approach using finite element simulations, and use of appropriate experimental evaluation methods can result in revealing, understanding and quantifying the complex degradation mechanisms of adhesive interconnections during aging.

• 전기학회논문지
• /
• 제61권3호
• /
• pp.472-478
• /
• 2012

The inspection machine in PCB (printed circuit board) assembly line checks assembly errors by inspecting the images inside of the component inspection region. The component inspection region consists of region of component package and region of soldering. It is necessary to extract the regions automatically for auto-teaching system of the inspection machine. We propose an image segmentation method to extract the component inspection regions automatically from images of PCB. The acquired image is transformed to HSI color model, and then segmented by several regions by clustering method. We develop a modified K-means algorithm to increase the accuracy of extraction. The heuristics generating the initial clusters and merging the final clusters are newly proposed. The vertical and horizontal projection is also developed to distinguish the region of component package and region of soldering. The experimental results are presented to verify the usefulness of the proposed method.

• Journal of Mechanical Science and Technology
• /
• 제18권3호
• /
• pp.357-369
• /
• 2004

The purposes of the paper are to analyze the fracture phenomenon by delamination and cracking when the encapsulant of plastic IC package with polyimide coating shows viscoelastic behavior under hygrothermal loading in the IR soldering process and to suggest more reliable design conditions by the approaches of stress analysis and fracture mechanics. The model is the plastic SOJ package with the polyimide coating surrounding chip and dimpled diepad. On the package without cracks, the optimum position and thickness of polyimide coating to decrease the maximum differences of strains at the bonding surfaces of parts of the package are studied. For the model delaminated fully between the chip and the dimpled diepad, C(t)-integral values are calculated for the various design variables. Finally, the optimal values of design variables to depress the delamination and crack growth in the plastic IC package are obtained.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.71-74
• /
• 2003

In this paper, electrical properties of photovoltaic module have been observed for 5 years and found to drop around 5 to 25 %. Element technologies which are critical to electrical loss were therefore examined and dark I-V curve were observed with different soldering conditions. From the results, series resistance decreased with the decrease of contact resistance regardless of temperature conditions.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
• /
• pp.224-227
• /
• 2003

The longitudinal thermosonic bonding method is investigated in this work for its application to the soldering process for electronic packaging. The effect of the ultrasonic is analyzed through lumped modeling, and the material properties of a viscoelastic model are measured experimentally. The thermosonic bonding method is verified by inserting the Cu pin and Au bump into solder block. As the solder thickness decreases, temperature of the solder is calculated to increase rapidly because of larger strain. Localized heating due to ultrasonic vibration is observed to melt the solder near the pin, which is adequate to the high density electronic package and Pb-free solder having high melting temperature.

• Journal of Welding and Joining
• /
• 제17권1호
• /
• pp.77-81
• /
• 1999

Through-hole PCB(Printed Circuit Board) was soldered by flow soldering process using cleaning or noncleaning fluxes. Preheating temperature and conveyor speed were changed in the range of 323∼413K and 0.3∼2m/min respectively. The soldered joints were tensile tested in order to evaluated bonding strength. As experimental results, relatively high tensile fracture load, 120∼140N, were obtained in case of preheating temperature of 383K, and conveyor speed was 0.6∼1.0 m/min. Fractured surfaces of higher tensile strength show some dimple area, while those of lower tensile fracture load show brittle fracture.