발간논문

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Two types of copper-oxide layers were formed on the surface of a copper-based leadframe sheets by immersing them in two kinds of hot alkaline solutions. The oxide-coated leadframe sheets were molded with EMC (Epoxy Molding Compound), and the molded bodies were machined to form pull-out specimens for the purpose of measuring the adhesion strength between oxide-coated leadframe and EMC. After the pull-out tests, fracture surfaces were analyzed using various techniques to find out the failure loci, and subsequently, finite element modeling was carried out to simulate failure loci forming process. The results revealed that phase angle is a main factor affecting failure locus. Local phase angle changes resulted in locally different failure loci. (Received November 26, 2004)

keyword : Leadframe, Epoxy, Adhesion, Failure Locus, Phase angle

Chip-on-glass bonding using nonconductive adhesive was accomplished with joining of the Sn/Ag bumps, and the average contact resistance of the Sn/Ag bump was measured with variation of the bonding stress. Average contact resistance of the Sn/Ag bump could be obtained from the slope of the curve for daisy chain resistance vs. number of Sn/Ag bumps. With increasing the bonding stress from 31.8 MPa to 69.8 MPa, the average contact resistance decreased from 30 mil/bump to 15.6 mΩ/bump. With further increasing the bonding stress above 69.8 MPa, however, the average contact resistance changed little within the range of 12.9-15.6 mil/bump. Among the factors affecting the contact resistance with variation of the bonding stress, plastic deformation of the Sn/Ag bump had larger effect than the amount of the microvoids remaining at the contact interface between Sn/Ag bumps. (Received November 22, 2004)

keyword : Electronic packaging, Chip on glass, Flip chip, Sn Bump, Contact resistance

The refining efficiency of high-purity Cu was investigated prepared by zone refining, with respect to travel rate, distribution coefficient, number of pass and zone length. Especially, to investigate refining efficiency with respect to zone length, experimental and computer simulation results were compared. The composition of the refined high-purity Cu was analyzed by GDOS (Glow Discharge Optical Spectroscopy) and GDMS (Glow Discharge Mass Spectrometer). The composition profiles of each segment at the given condition were compared with the results of micro hardness profiles. The results showed that the refining efficiency was inversely proportional to the travel rate, while it was proportional to the number of pass. The travel rate was more effective than the number of pass to enhance the refining efficiency in zone refining process. Impurities whose distribution coefficients are below 0.5 were removed efficiently. The effectively refined region increased with decreasing the zone length from 45 mm to 30 mm. Especially, the element S, which is known to be hardly removed by zone refining, could be removed to a level of under 0.1 ppm over the 60% region at 1 mm/min. (Received July 22, 2004)

keyword : High-purity copper, Zone refining, Travel rate, Number of pass, Zone Length, Distribution coefficient