• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.13-19
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• 2000

Shear strengths of BGA solder joints on Cu pads were studied for Cu-containing Sn (0, 1.5, and 2.5 wt.% Cu) and Sn-40Pb (0 and 0.5wt.% Cu) solders, with emphasis on the roles of the Cu-Sn intermetallic layer thickness and the roughness of the interface between the intermetalic layer and solder. The shear strength test was performed for as-soldered solder joints with various soldering reaction times up to 4 min. The addition of Cu to the pure Sn solder results in an enhanced growth of the intermetallic layer whereas the effect of Cu addition to the Sn-40Pb solder is primarily on the reduction of the roughness of the intermetallic/solder interface. The critical thickness of the intermetallic layer for a maximum shear strength depends on the solder materials, which was measured to be ~ 2.3 $\mu\textrm{m}$ for Sn-Cu solders and ~ 1.2 $\mu\textrm{m}$ for Sn-Pb-Cu solders. The shear strength at the critical intermetallic layer thickness seems to increase as the intermetallic/solder interface becomes rougher. This is in accordance with the observation that the sheared fracture occurred initially within the solder tends to shift towards the intermetallic/solder interface as the intermetallic layer grows above the critical thickness.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.230-234
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• 2011

High density plasma etching of ZnO film was performed in $CF_4$/Ar and $SF_6$/Ar inductively coupled plasmas. Maximum etch rates of ~1950 ${\AA}$/min and ~1400 ${\AA}$/min were obtained for $10CF_4$/5Ar and $10SF_6$/5Ar ICP discharges, respectively. The etched ZnO surfaces showed better RMS roughness values than the unetched control sample under most of the conditions examined. In the $10CF_4$/5Ar ICP discharges, very high etch selectivities were obtained for ZnO over Ni (max. 11) while Al showed etch selectivities in the range of 1.6~4.7 to ZnO.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.213-217
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• 2005

The polymer light emitting diodes (PLED) with ITO/PEDOT:PSS/MEH-PPV/Al structure were prepared on ITO(indium tin oxide)/Glass substrates using PEDOT:PSS[poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as the hole transport material and MEH-PPV[poly(2-methoxy-5-(2-ethyhexoxy)-1,4phenylenvinylene)] as emission material layer. The dependences on the surface roughnees and friction coefficient between film layers were investigated as a function of the MEH-PPV concentrations$(0.1\;wt\%\~0.9\;wt\%)$. The RMS values decreased from 1.72 nm to 1.00 nm as the concentration of MEH-PPV increased from $0.1\;wt\%\;to\;0.9\;wt\%$, indicating improvement of surface roughness. In addition, friction coefficients decreased from 0.048 to 0.035, which means the deteriorating of the adhesion condition. The PLED sample with $0.5\;wt\%$ of MEH-PPV showed the maximum luminance of $409\;cd/m^2$.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.91-96
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• 2003

Cross-geometrical Cr/Co/Al-Ox/Co/Ni-Fe tunnel junctions were fabricated by magnetron sputtering. To form an insulating layer, The Al layer was oxidized in an atmosphere of oxygen-argon mixture at low power after deposition. To enhance the coercivity of the bottom Co layer, The Cr seed layer was deposited on the glass and it led to increase in coercivity. The coercivity increase is due to the increase of roughness through the Cr thickness. In over oxidation time, the oxidation of Co bottom layer and flat interface of insulator can increase the bottom Co coercivity. But TMR ratio gradually decrease. TMR ratio is relevant with Cr thickness, insulator thickness, and oxidation time. The maximum TMR ratio was 14% at room temperature and the TMR ratio was decreased to half at 0.51 V.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.73-73
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• 2000

Shear strength of BGA solder joints on Cu pad was studied for Cu-contained Sn n.5 a and 2.5wt.% Cu) and Sn-Pb (o.5wt.% Cu) solders, with emphasis on the roles of the C Cu-Sn intermetallic layer thickness and the roughness of the interface between the i intermetallic layer and solder. The shear strength test was performed both for a as-soldered s이der joints with soldering reaction times of 1, 2, 4 min and for aged s이der j joints at 170 C up to 16 days. The Cu addition to both pure Sn and eutectic Sn-Pb s solders increased the intermetallic layer thickness at both soldering and aging t temperatures. The Cu addition also resulted in changes in the roughness of the interface b between the intermetallic layer and solder at as-soldered states. With increasing Cu c content. the interface roughened for Sn-Cu solders whereas it flattened for Sn-Pb-Cu s solders. The shear fractures in all solder joints investigated were confined in the bulk s solder rather than through the intermetallic layer. Therefore, the effect of Cu content in s solders on the shear strength of the solder joints was primarily attributed to its i influence on the micros$\sigma$ucture of bulk solder, such as the size and spatial distributions of CU6Sn5 precipitates. In addition, the critical intermetallic layer thickness for a m maximum shear strength seemed to depend on the Cu content in bulk solder.older.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.732-736
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• 2013

AlN epilayers were grown on a c-plane sapphire substrate using hydride vapor phase epitaxy (HVPE). A series of AlN epilayers were grown at $1120^{\circ}C$ with V/III ratios 1.5, 2.5 and 3.5, and the influence of V/III ratio on their properties was investigated. As the V/III ratio was increased, the surface roughness (RMS roughness), Raman shift of $E_2$ high peaks and full-width at half-maximum (FWHM) of symmetrical (002) & asymmetrical (102) of the AlN epilayers increased. However, the intensities of the Raman $E_2$ high peaks were reduced. This indicates that the crystal quality of the grown AlN epilayers was degraded by activation of the parasitic reaction as the V/III ratio was increased. Smooth surface, stress free and high crystal quality AlN epilayers were obtained at the V/III ratio of 1.5. The crystal quality of AlNepilayers is worsened by the promotion of three-dimensional (3D) growth mode when the flow of $NH_3$ is high.

• Membrane and Water Treatment
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• v.12 no.1
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• pp.43-49
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• 2021

The Commercial polymeric membranes like Polysulfone (PSF), Polyvinylidene difluoride (PVDF) and Polyacrylonitrile (PAN) which are an integral part of water purification investigation were chosen for the shockwave (SW) exposure experiment. These membranes were prepared by blending polymer (wt. %) / DMF (solvent) followed by phase-inversion casting technique. Shockwaves are generated by using Reddy Tube lab module (Table-top Shocktube) with range of pressure (1.5, 2.5 and 5 bar). Understanding the changes in membrane before and after shock wave treatment by parameters, i.e., pure water flux (PWF), rejection (%), porosity, surface roughness (AFM), morphology (SEM) and contact angle which can significantly affect the membrane's performance. Flux values PSf membranes shows increase, 465 (pristine) to 524 (1.5wt%) LMH at 50 Psi pressure and similar enhancement was observed at 100Psi (625 to 696 LMH). Porosity also shows improvement from 73.6% to 76.84% for 15wt% PSf membranes. It was observed that membranes made of polymers such as PAN and PSF (of high w/w %) exhibits some resistance against shockwaves impact and are stable compared to other membranes. Shockwave pressure of up to 1.5 bar was sufficient enough to change properties which are crucial for performance. Membranes exposed to a maximum pressure of 5 bar completely scratched the surface and with minimum pressure of 1.5bar is optimum enough to improve the water flux and other parameters. Initial results proved that SW may be suitable alternative route to minimize/control membrane fouling and improve efficiency.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.61-69
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• 2022

In this study, a large-scale direct shear test was performed to evaluate the shear characteristics of the pile-soil interface according to the fines content and confining pressure conditions as a reasonable evaluation method of the pullout resistance performance of pile considering the soil conditions. It was found that the shear stress was greatly generated under the conditions of high normal stress and low fines content. In addition, the maximum shear stress was found to be rather large under the conditions of the same normal stress and fines content, when pile surface had high roughness. The internal friction angle decreased at the pile-soil interface, when the fines content in the ground increased. On the other hand, the cohesion decreased under the condition of high fines content. And the internal friction angle and cohesion were large regardless of the fines content in the model ground, when the roughness of the pile surface was high.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.5
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• pp.298-302
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• 2023

Transparent and conducting tungsten (W) doped indium oxide (IWO) thin films were deposited on the glass substrate by using RF magnetron sputtering and then electron irradiation was conducted to investigate the effect of electron irradiation on the optical and electrical properties of the films. The electron irradiated films showed three x-ray diffraction peaks of the In₂O₃ (222), (431) and (046) planes and the full width at half maximum values are decreased as increased electron irradiation energy. In the atomic force microscope analysis, the surface roughness of as deposited films was 1.70 nm, while the films electron irradiated at 700 eV, show a lower roughness of 1.28 nm. In this study, the figure of merit (FOM) of as deposited films is 2.07 × 10^-3 Ω^-1, while the films electron irradiated at 700 eV show the higher FOM value of 5.53 × 10^-3 Ω^-1. Thus, it is concluded that the post-deposition electron beam irradiation is the one of effective methods to enhance optical and electrical performance of IWO thin films.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1D
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• pp.35-43
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• 2008

This paper mainly deals with the performance evaluation of 33 asphalt sections of Korea Expressway Corporation Test Road (KECTR) during the past four years. Since the construction of the KECTR in December 2002, key performance indicators of asphalt pavements have been collected five times with an Automatic Road Analyzer (ARAN), and have been analyzed for permanent deformation, surface distress, and road roughness. Linear viscoelastic characteristics of four dense graded HMAs used in KECTR were investigated with a series of complex modulus test. The effect of air void in HMAs on dynamic modulus was investigate at two air void contents for a surface course HMA (19 mm Nominal Maximum Size of Aggregate). Layer densification due to traffic was estimated from air void contents of field cored samples, and was correlated with pavement distresses and performances. One of findings of this study was that both permanent deformation and cracking were suspectible to pavement temperatures, rather than traffic. However, it was found that road roughness was mostly affected by traffic loading.