• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.310-314
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• 2008

Electromigration test of flip chip solder bump is performed at $140^{\circ}C$ C and $4.6{\times}10^4A/cm^2$ conditions in order to compare electromigration with thermomigration behaviors by using electroplated Sn-3.5Ag solder bump with Cu under-bump-metallurgy. As a result of measuring resistance with stressing time, failure mechanism of solder bump was evaluated to have four steps by the fail time. Discrete steps of resistance change during electromigration test are directly compared with microstructural evolution of cross-sectioned solder bump at each step. Thermal gradient in solder bump is very high and the contribution of thermomigration to atomic flux is comparable with pure electromigration effect.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.798-802
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• 2005

The plating shape in the opening of photoresist becomes gradated shape in the fountain plating system, because bubbles from the wafer surface are difficult to escape from the deep openings, vias. In this paper, the bubble flow from the wafer surface during plating process was studied and we designed the tilted electrode ring to get uniform bump height on all over the wafer and evaluated the film uniformity by SEM and $\alpha-step$. In a-step measurement, film uniformities in the fountain plating system and the tilted electrode ring contact system were $\pm16.6\%,\;\pm4\%$ respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.323-327
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• 2004

The bubble flow from the wafer surface during plating process was studied in this paper. The plating shape in the opening of photoresist becomes gradated shape in the fountain plating system, because bubbles from the wafer surface are difficult to escape from the deep openings, vias. So, we designed the tilted electrode ring contact to get uniform bump height on all over the wafer and evaluated the film uniformity by SEM and ${\alpha}-step$. In ${\alpha}-step$ measurement, film uniformities in the fountain plating system and the tilted electrode ring contact system were ${\pm}16.6%,\;{\pm}4%$ respectively.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.146-153
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• 1999

A numerical dynamic simulation is necessary to investigate the capacity of the HDD. The slider surface become more and more complicated to make the magnetized area smaller and readback signal stronger. So a numerical dynamic simulation must be preceded to develop a new slider in HDD. The dynamic simulations of air-lubricated slider bearing have been peformed using FIFD(Factored Implicit Finite Difference) method. The governing equation, Reynolds equation Is modified with Fukui and Kaneko model(FK model) which includes the first and the second-order slip. The equations of motion for the slider bearing are solved simultaneously with the modified Reynolds equation for the case of three degrees of freedom. The slider transient response for disk step bump and slider impulse force is given for various case and for iteration algorithm and new algorithm.

• Tribology and Lubricants
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• v.16 no.4
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• pp.295-301
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• 2000

The dynamic simulation of slider in hard disk drive is performed using Factored Implicit Finite Difference method. The modified Reynolds equation with Fukui and Kaneko model is employed as a governing equation. Equations of motion for the slider of three degrees of freedom are solved simultaneously with the modified Reynolds equation. The transient responses of the slider for disk step bumps and slider impulse forces are shown for various cases and are compared for the iteration algorithm and new algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.366-369
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• 2003

The vertical fountain plating system with the point contact has been used in semiconductor industry. But the plating shape in the opening of photoresist becomes gradated shape, because bubbles from the wafer surface are difficult to escape from the deep openings, vias. So, we designed the tilted electrode ring contact to get uniform bump height on all over the wafer and evaluated the film uniformity by SEM and $\alpha$-step. A photoresist was coated to a thickness of $60{\mu}m$ and vias were patterned by a contact aligner After via opening, solder layer was electroplated using the fountain plating system and the tilted electrode ring contact system. In $\alpha$-step measurement, film uniformities in the fountain plating system and the tilted electrode ring contact system were ${\pm}16%,\;{\pm}3.7%$ respectively. In this study, we could get high uniformity bumps by the tilted electrode ring contact system. So, tilted electrode ring contact system is expected to improve workability and yield in module process.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.65-68
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• 2013

A novel bumping process using solder bump maker (SBM) is developed for fine-pitch flip chip bonding. It features maskless screen printing process. A selective solder bumping mechanism without the mask is based on the material design of SBM. Maskless screen printing process can implement easily a fine-pitch, low-cost, and lead-free solder-on-pad (SoP) technology. Its another advantage is ternary or quaternary lead-free SoP can be formed easily. The process includes two main steps: one is the thermally activated aggregation of solder powder on the metal pads on a substrate and the other is the reflow of the deposited powder on the pads. Only a small quantity of solder powder adjacent to the pads can join the first step, so a quite uniform SoP array on the substrate can be easily obtained regardless of the pad configurations. Through this process, an SoP array on an organic substrate with a pitch of 130 ${\mu}m$ is, successfully, formed.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.225-228
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• 2005

In this work, we studied the optimized copper thickness in Cu ECP (Electrochemical Plating). In order to select an optimized Cu ECP thickness, we examined Cu ECP bulge (bump, hump or over-plating amount), Cu CMP dishing and electrical properties of via hole and line trench over dual damascene patterned wafers split into different ECP Cu thickness. In the aspect of bump and dishing, the bulge increased according as target plating thickness decreased. Dishing of edge was larger than center of wafer. Also in case of electrical property, metal line resistance distribution became broad gradually according as Cu ECP thickness decreased. In conclusion, at least $20\%$ reduced Cu ECP thickness from current baseline; $0.8\;{\mu}m$ and $1.0\;{\mu}m$ are suitable to be adopted as newly optimized Cu ECP thickness for local and intermediate layer.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.13-20
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• 1997

A fundamental study for the numerical scheme to simulate unsteady nonlinear waves by solving Euler equations is presented. First a conservation form and a non-conservation form of the Euler equations with a free surface fitted coordinate system are compared. Next, a time splitting fractional step method and an alternating direction implicit(ADI) method for the time integration are compared. For the comparative study, flow calculations around a bottom bump in a channel and a NACA 0012 hydrofoil in a flume are performed. The results show that the ADI method with a third order upwind differencing scheme is very efficient in reducing the computing time with keeping the accuracy, And, there is no distinct difference between two expression forms except that the non-conservative form shows faster wave propagating velocity than the conservation form. Some results are compared with experiments and show good agreement.

• Transactions of Materials Processing
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• v.24 no.6
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• pp.387-394
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• 2015

Air springs are designed to support loads using the volume elasticity in a cylindrical shaped air bag made of a composite material with a rubber matrix and two plies of reinforced fibers. Recently, applications of these springs have been expanded from railway vehicles to passenger cars. The current study presents a finite element analysis of a manufactured air spring for a passenger car. The analysis was conducted including the mounting steps of the air bag using a static loading condition. A method for controlling the internal pressure and displacements during the mounting step was developed. The characteristic load curve and the shape of the air bag were in good agreement with the experimental data with respect to the design height, the bump height and the rebound height. Results indicate that ply angles of fibers vary from 38 degrees to 56 degrees during static loading.