• Journal of the Korean institute of surface engineering
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• v.36 no.3
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• pp.242-250
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• 2003

Electrodeposition of Ni was carried out on copper substrate from Ni Sulfamate bath by DC and high frequency pulse current. During the electroplating, bath temperature was steady $60^{\circ}C$ , agitation was applied. Morphology and surface roughness of electrodeposits was investigated with the AFM. Crystalline structure of electrodeposits was investigated with XRD. Also, surface electric resistivity was investigated with 4-point probe. The result of crystalline structure by X-ray diffractometer, in the case of DC, <200> direction was dominant growing direction. But in the case of PC, the ratio of <200> direction vs. other direction decreased. As the pulse frequency increased, the enhanced properties of deposits were shown. With increasing frequency, the degree of surface properties increased DC more than that of PC, eg surface morphology, roughness and the degree of compactness of grains. With increasing duty cycle, the surface properties such as the degree of the morphology, roughness and electroconductivity was deteriorated.

• 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.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.37-43
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• 2006

Surface roughness and hardness of the electroplated Sn were characterized with variations of electroplating current density and current mode. The Sn electroplated at $5{\sim}50mA/cm^{2}$ exhibited the surface roughness of $2.0{\sim}2.4{\mu}m$. The Sn electroplated with pulse current mode exhibited low surface roughness compared one processed with direct current mode. With surface annealing at $300^{\circ}C$ for 3 sec using halogen lamp, surface roughness of the Sn bump was substantially reduced to $1{\mu}m$. The Sn electroplated at $5{\sim}50mA/cm^{2}$ exhibited the hardness of 10 Hv. Low contact resistances of $33{\sim}17m{\Omega}$ were obtained for specimens flip-chip bonded with Sn bumps.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.45-50
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• 2006

Copper via filling is the important factor in 3-D stacking interconnection of SiP (system in package). As the packaging density is getting higher, the size of via is getting smaller. When DC electroplating is applied, a defect-free hole cannot be obtained in a small size via hole. To prevent the defects in holes, pulse and pulse reverse current was applied in copper via filling. The holes, $20\and\;50{\mu}m$ in diameter and $100{\sim}190\;{\mu}m$ in height. The holes were prepared by DRIE method. Ta was sputtered for copper diffusion barrier followed by copper seed layer IMP sputtering. Via specimen were filled by DC, pulse and pulse-reverse current electroplating methods. The effects of additives and current types on copper deposits were investigated. Vertical and horizontal cross section of via were observed by SEM to find the defects in via. When pulse-reverse electroplating method was used, defect free via were successfully obtained.

• Journal of Internet of Things and Convergence
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• v.9 no.3
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• pp.61-67
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• 2023

In order to optimize the pulse electroforming copper process, a double hidden layer BP (Back Propagation) neural network is constructed. Through sample training, the mapping relationship between electroforming copper process conditions and target properties is accurately established, and the prediction of microhardness and tensile strength of the electroforming layer in the pulse electroforming copper process is realized. The predicted results are verified by electrodeposition copper test in copper pyrophosphate solution system with pulse power supply. The results show that the microhardness and tensile strength of copper layer predicted by "3-4-3-2" structure double hidden layer neural network are very close to the experimental values, and the relative error is less than 2.32%. In the parameter range, the microhardness of copper layer is between 100.3~205.6MPa and the tensile strength is between 112~485MPa.When the microhardness and tensile strength are optimal,the corresponding process conditions are as follows: current density is 2A-dm-2, pulse frequency is 2KHz and pulse duty cycle is 10%.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1755-1762
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• 2013

A graphene-Zn/Al layered double hydroxide composite film was simultaneously prepared by electrochemical deposition on the surface of a glassy carbon electrode (G-LDH/GCE) from the mixture solution containing GO and nitrate salts of $Zn^{2+}$ and $Al^{3+}$. The modified electrode showed good electrochemical performances toward the simultaneous electrochemical detection of hydroquinone (HQ), catechol (CA) and resorcinol (RE) due to the unique properties of graphene (G) and LDH such as large active surface area, facile electronic transport and high electrocatalytic activity. The redox characteristics of G-LDH/GCE were investigated with cyclic voltammetry and differential pulse voltammetry. The well-separated oxidation peak potentials, corresponding to the oxidation of HQ, CA and RE, were observed at 0.126 V, 0.228 V and 0.620 V respectively. The amperometric response of the modified electrode exhibited that HQ can be detected without interference of CA and RE. Under the optimized conditions, the oxidation peak current of HQ is linear with the concentration of HQ from 6.0 ${\mu}M$ to 325.0 ${\mu}M$ with the detection limit of 0.077 ${\mu}M$ (S/N=3). The modified electrode was successfully applied to the direct determination of HQ in a local tap water, showing reliable recovery data.

• Journal of the Korean institute of surface engineering
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• v.53 no.4
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• pp.138-143
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• 2020

In this study, we produced a coil of micro-pattern that can be used for electromagnetic wave absorber, heating material, wireless charging, sensor, antenna, etc. by using electrochemical additive manufacturing method. Currently, it contains research contents for manufacturing a micro pattern coil having practicality through control of process control variables such as applied voltage, distance between electrode, and nozzle injection. Circulation of the electrolyte through the nozzle injection control can significantly contribute to improving the surface characteristics of the coil because of minimizing voltage fluctuations that may occur during the additive manufacturing process. In addition, by applying the pulse method in the application of voltage, the lamination characteristics of the plated body were improved, which showed that the formation of a fine line width plays an important role in the production of a micro pattern coil. By applying the pulse signal to the voltage application, the additive manufacturing characteristics of the produced product were improved, and it was shown that the formation of a fine line width plays an important role in the production of a micro pattern coil.

• Nano
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• v.13 no.11
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• pp.1850131.1-1850131.19
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• 2018

In this paper, an electrochemical sensor for epinephrine (EP), a neurotransmitter was developed by anchoring molecularly imprinted polymeric matrix (MIP) on the surface of gold-coated quartz crystal electrode of electrochemical quartz crystal microbalance (EQCM) using starch nanoparticles (Starch NP) - reduced graphene oxide (RGO) nanocomposite as polymeric format for the first time. Use of EP in therapeutic treatment requires proper dose and route of administration. Proper follow-up of neurological disorders and timely diagnosis of them has been found to depend on EP level. The MIP sensor was developed by electrodeposition of starch NP-RGO composite on EQCM electrode in presence of template EP. As the imprinted sites are located on the surface, high specific surface area enables good accessibility and high binding affinity to template molecule. Differential pulse voltammetry (DPV) and piezoelectrogravimmetry were used for monitoring binding/release, rebinding of template to imprinted cavities. MIP-coated EQCM electrode were characterized by contact angle measurements, AFM images, piezoelectric responses including viscoelasticity of imprinted films, and other voltammetric measurements including direct (DPV) and indirect (using a redox probe) measurements. Selectivity was assessed by imprinting factor (IF) as high as 3.26 (DPV) and 3.88 (EQCM). Sensor was rigorously checked for selectivity in presence of other structurally close analogues, real matrix (blood plasma), reproducibility, repeatability, etc. Under optimized conditions, the EQCM-MIP sensor showed linear dynamic ranges ($1-10{\mu}M$). The limit of detection 40 ppb (DPV) and 290 ppb (EQCM) was achieved without any cross reactivity and matrix effect indicating high sensitivity and selectivity for EP. Hence, an eco-friendly MIP-sensor with high sensitivity and good selectivity was fabricated which could be applied in "real" matrices in a facile manner.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.168-172
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• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.108-114
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• 1996

It is one of the most important factors to enhance the efficiency of the solar collectors by in-creasing collecting efficiency and decreasing heat loss. The pulse electrodeposition method has been involved in this study to improve characteristics of the solar selective coating on 230cm${\times}$60cm substrates and electrical efficiency of the process. The composition of the electrolyte was 280 g/$\ell$ chromic acid, 15 g/$\ell$ propionic acid, and 10 g/$\ell$ appropriate additive. 230cm${\times}$60cm copper and aluminium sheets were utilized as the substrates. It has been observed that the black chrome coatings exhibited reasonable optical properties for commercialization when the plating parameters were properly controlled; the absorptance was 0.98 and 0.97 and omittance was 0.17 and 0.23 for copper and aluminium substrate, respectively. This study implies that the pulse current electrolysis method could be applied to the large scale substrates, and the various products can be avilable after the consideration of the thermal conductivity, heat transfer efficiency and cost problems of the substrates.