• Journal of Welding and Joining
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• v.25 no.2
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• pp.76-81
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• 2007

Solder bumps have been used to interconnect the chip and substrate, and the size of the solder bump decreases below $100{\mu}m$ to accommodate higher packaging density. In order to fabricate solder bumps, a mold to chip transfer process is suggested in this work. Since the thin stainless steel mold is not wet by the solder, the molten solder is forced to fill the mold cavities with ultrasonic vibration. The solders within the mold cavities are transferred to the Cu pads on the polyimide film through reflow soldering.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.91-99
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• 1995

An effort has been made to more accurately analyze the flow in the chip cavity, particularly to model the flow through the openings in the leadframe and correctly treat the thermal boundary condition at the leadframe. The theoretical analysis of the flow has been done by using the Hele- Shaw approximation in each cavity separated by a leadframe. The cross-flow through the openings in the leadframe has been incorporated into the Hele-Shaw formulation as a mass source term. The temperature of the leadframe has been calculated based on energy balance in the leadframe. The flow behavior in the leadframe has been verified experimentally. In the experiment, a transparent mold and clear fluid have been used for flow visualization. Comparisons were made between the calculation and experimental results which showed a good agreement.