• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.57-63
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• 2006

For chip-stack package applications, Cu filling characteristics into trench vias of $75{\sim}10\;{\mu}m$ width and 3 mm length were investigated with variations of electroplating current density and current mode. At $1.25mA/cm^{2}$ of DC mode, Cu filling ratio higher than 95% was obtained for trench vias of $75{\sim}35{\mu}m$ width. When electroplated at DC $2.5mA/cm^{2}$, Cu filling ratios became inferior to those processed at DC $1.25mA/cm^{2}$. Pulse current mode exhibited Cu filling characteristics superior to DC current mode.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.4
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• pp.225-230
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• 2004

An electromagnetic actuator has been designed and fabricated for Probe-based data storage applications. The actuator consists of permanent magnets(SmCo) housing and a media Platform which is connected to the Si frame by four couples of Si leaf springs. In order to generate electromagnetic force, Cu coils were electroplated under the media platform. The magnetic field distribution was calculated with 3D Finite Element Method of Maxwell 3D program. The field strength felt by Cu coils was estimated to be about 0.33T when the distance between the media platform and permanent magnets is $200\mu\textrm{m}$. The static and dynamic motions of the actuator were analyzed by FEM method with ANSYS 5.3. The measured displacements of the actuator were about $\pm$$92\mu\textrm{m}$ for input current of $\pm$40㎃ and the resonance frequency was 100Hz. The proposed electromagnetic actuator can be utilized for media driver of probe-based data storage system.

• Conservation Science in Museum
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• v.9
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• pp.31-49
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• 2008

We have investigated and conserved three small Buddha statues dating from Joseon period that were purchased by the National Museum of Korea. Chemical analysis and investigation of internal structures were enabled us to identify its compositions and hollow spaces which have various materials just like fabrics, silver ornaments, beads and wood fragments. The fabrics date from the early years of the Joseon dynasty to the middle one. The compositions of matrix of the Buddha statues vary 80-90 wt% Ag and 7-15 wt% Cu. And its surface layers were gilt with amalgam. Mechanical and chemical cleaning with EDTA-2Na were applied together during the cleaning process.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.2
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• pp.37-41
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• 2014

One of the important developments in next generation electronic devices is the technology for power delivery and heat dissipation. In this study, the Cu-to-Cu flip chip bonding process was evaluated using the square ABL power bumps and circular I/O bumps. The difference in bump height after Cu electroplating followed by CMP process was about $0.3{\sim}0.5{\mu}m$ and the bump height after Cu electroplating only was about $1.1{\sim}1.4{\mu}m$. Also, the height of ABL bumps was higher than I/O bumps. The degree of Cu bump planarization and Cu bump height uniformity within a die affected significantly on the misalignment and bonding quality of Cu-to-Cu flip chip bonding process. To utilize Cu-to-Cu flip chip bonding with ABL bumps, both bump planarization and within-die bump height control are required.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.554-560
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• 2012

Recently, it has been increasing trend to use conductive materials as electronics and communication technology in electronics industry are developing. The noble metal such as Ag, Pt, Pd etc. are mostly used as conductive materials, To reduce production cost, alternative materials with similar characteristics of noble metals are needed. Copper has advantages, i.e its electronic properties are similar to noble metals and low cost than noble metal, but its use has been restricted because of oxidation in air. In this study, the tin film was coated on copper by electroless plating to protect copper from oxidation and to confirm the effects of temperature, pH, amount of $SnCl_2$, and feeding speed in plating conditions. Additionally, we apply $Cu_{core}Sn_{shell}$ powder as conductive filler with low-temperature densification and analysis by SEM, XRD, FIB and 4-Point Probe techniques. As result of the study, tin film was coated well on copper and was protected from oxidation. After low-temperature densification treatment, the meted tin made chemical interconnections with copper. Accordingly, conductivity was increased than before condition. We hope $Cu_{core}Sn_{shell}$ powder to replace noble metals and use in the electronic field.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.129-134
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• 2005

Electroplating copper is the important role in formation of 3D stacking interconnection in SiP (System in Package). The I-V characteristics curves are investigated at different electrolyte conditions. Inhibitor and accelerator are used simultaneously to investigate the effects of additives. Three different sizes of via are tested. All via were prepared with RIE (reactive ion etching) method. Via's diameter are 50, 75, $100{\mu}m$ and the height is $100{\mu}m$. Inside via, Ta was deposited for diffusion barrier and Cu was deposited fer seed layer using magnetron sputtering method. DC, pulse and pulse revere current are used in this study. With DC, via cannot be filled without defects. Pulse plating can improve the filling patterns however it cannot completely filled copper without defects. Via was filled completely without defects using pulse-reverse electroplating method.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.47-53
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• 2018

Sn-based lithium-ion batteries have low cost and high theoretical specific capacity. However, one of major problem is the capacity fading caused by volume expansion during lithiation/delithiation. In this study, 3-dimensional foam structure of Cu-Sn alloy is prepared by co-electrodeposition including large free space to accommodate the volume expansion of Sn. The Cu-Sn foam structure exhibits highly porous and numerous small grains. The result of EDX mapping and XPS spectrum analysis confirm that Cu-Sn foam consists of $SnO_2$ with a small quantity of CuO. The Cu-Sn foam structure electrode shows high reversible redox peaks in cyclic voltammograms. The galvanostatic cell cycling performances show that Cu-Sn foam electrode has high specific capacity of 687 mAh/g at a current rate of 50 mA/g. Through SEM observation after the charge/discharge processes, the morphology of Cu-Sn foam structure is mostly maintained despite large volume expansion during the repeated lithiation/delithiation reactions.

• Korean Journal of Materials Research
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• v.26 no.12
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• pp.714-720
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• 2016

We performed this study to understand the effect of a single-crystalline anode on the mechanical properties of as-deposited films during electrochemical deposition. We used a (111) single- crystalline Cu plate as an anode, and Si substrates with Cr/Au conductive seed layers were prepared for the cathode. Electrodeposition was performed with a standard 3-electrode system in copper sulfate electrolyte. Interestingly, the grain boundaries of the as-deposited Cu thin films using single-crystalline Cu anode were not distinct; this is in contrast to the easily recognizable grain boundaries of the Cu thin films that were formed using a poly-crystalline Cu anode. Tensile testing was performed to obtain the mechanical properties of the Cu thin films. Ultimate tensile strength and elongation to failure of the Cu thin films fabricated using the (111) single-crystalline Cu anode were found to have increased by approximately 52 % and 37 %, respectively, compared with those values of the Cu thin films fabricated using apoly-crystalline Cu anode. We applied ultrasonic irradiation during electrodeposition to disturb the uniform stream; we then observed no single-crystalline anode effect. Consequently, it is presumed that the single-crystalline Cu anode can induce a directional/uniform stream of ions in the electrolyte that can create films with smeared grain boundaries, which boundaries strongly affect the mechanical properties of the electrodeposited Cu films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.708-711
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• 1999

The Cu/Ni/Au lamellar structure is extensively used as an under bump metallization on silicon file, and on printed circuit board(PCB) pads. Ni is plated Cu by either electroless Ni plating, or electrolytic Ni plating. Unlike the electrolytic Ni plating, the electroless Ni plating does not deposit pure Ni, but a mixture of Ni and phosphorous, because hypophosphite Is used in the chemical reaction for reducing Ni ions. The fracture crack extended at the interface between solder balls of plastic ball grid (PBGA) package and conducting pads of PCB. The fracture is duets to segregation at the interface between Ni$_3$Sn$_4$intermetallic and Ni-P layer. The XPS diffraction results of Cu/Ni/Au results of CU/Ni/AU finishs showed that the Ni was amorphous with supersaturated P. The XPS and EDXA results of the fracture surface indicated that both of the fracture occurred on the transition lesion where Sn, P and Ni concentrations changed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.370-375
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• 2016

In this paper, we investigated the electrical properties of crystalline silicon solar cell fabricated with Ni/Cu/Ag plating. The laser process was used to ablate silicon nitride layer as well as to form the selective emitter. Phosphoric acid layer was spin-coated to prevent damage caused by laser and formed selective emitter during laser process. As a result, the contact resistance was decreased by lower sheet resistance in electrode region. Low sheet resistance was obtained by increasing laser current, but efficiency and open circuit voltage were decreased by damage on the wafer surface. KOH treatment was used to remove the laser damage on the silicon surface prior to metalization of the front electrode by Ni/Cu/Ag plating. Ni and Cu were plated for each 4 minutes and 16 minutes and very thin layer of Ag with $1{\mu}m$ thickness was plated onto Ni/Cu electrode for 30 seconds to prevent oxidation of the electrode. The silicon solar cells with KOH treatment showed the 0.2% improved efficiency compared to those without treatment.