• 한국초전도ㆍ저온공학회논문지
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• 제6권3호
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• pp.6-11
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• 2004

YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) films were deposited on MgO(100) and SrTiO$_3$(100) single crystal substrates by cold-wall type MOCVD method using continuous source supplying system. Under the deposition temperature of 740∼76$0^{\circ}C$, c-axis oriented YBCO films were obtained. In case of the YBCO films deposited on MgO (100) single crystal substrate, the critical temperature (T$_{c}$) was under 81 K regardless of the deposition conditions, whereas T$_{c}$ of the YBCO films deposited on SrTiO$_3$(100) single crystal substrate was 83∼84 K. The critical current (I$_{c}$) of the YBCO film deposited on SrTiO$_3$(100) single crystal substrate for 30 min was 49 A/cm-width and the critical current density (J$_{c}$) was 0.82 MA/$\textrm{cm}^2$ to film thickness of 0.6 ${\mu}{\textrm}{m}$. I$_{c}$ increased to 84.4 A/cm-width as the deposition time increased to 50 min, but J$_{c}$ decreased to 0.53 MA/$\textrm{cm}^2$ to film thickness of 1.8 ${\mu}{\textrm}{m}$.rm}{m}$.

• 한국재료학회지
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• 제15권5호
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• pp.285-292
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• 2005

Anti-reflection film was coated by using spherical silica nano colloids. Silica colloid sol was reserved between two inclined slide glasses by capillary force, and particles were convectively stacked to form a film onto the substrate as the water evaporates. As the sliding speed increased, the thickness of the film decreased and the wavelength at the maximum transmittance decreased. The microstructure observed by SEM showed that silica particles were nearly close packed, which enabled the calculation of the effective refractive index of the film. The film thickness was measured by proffer and calculated from the wavelength of maximum transmittance and the effective refractive index. The effective refractive index of the film could be controlled by a subtle controlling of the coating speed and by mixing two different sized silica particles. When the 100 nm and 50 m particles were mixed at 4:1-5:1 volume ratio, the maximum transmittance of $95.2\%$ for one-sided coating was obtained. This is the one that has increased by $3.8\%$ compared to bare glass substrate, and shows that $99.0\%$ of transmittance or $1.0\%$ of reflectance can be achieved by the simple process if both sides of the substrate are coated.

• 센서학회지
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• 제28권6호
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• pp.390-394
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• 2019

This paper presents an inkjet-printed plastic force sensor using PEDOT:PSS. Using a piezoelectric-type inkjet printer, the force sensor was manufactured by printing PEDOT:PSS ink onto a polyimide (PI) substrate film. Applying a vertical force of 0 to 100 N to the force sensor on the PI substrate with a thickness of 64 mm, the resistance of the force sensor increased in proportion to the input force by the length deformation of the PI substrates and the sensor pattern. As a result, the fabricated sensor has a characteristic of 0.001% /N with a linearity of 99.38%. In addition, as the thickness of the PI substrate film increased, the sensitivity of the sensor increased linearly. The fabricated force sensor is expected to be applied to industrial sites and healthcare fields.

• Journal of Welding and Joining
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• 제20권2호
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• pp.90-94
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• 2002

FC-BGA has advantages over other interconnection methods including high I/O counts, better electrical performance, high throughput, and low profile. But, FC-BGA has a lot of reliability issues. The 2nd level solder joint reliability of the FC-BGA with large chip on laminate substrate was studied in this paper. The purpose of this study is to discuss solder joint failures of 2nd level thermal cycling test. This work has been done to understand the influence of the structure of package, the properties of underfill, the properties and thickness of bismaleimide tiazine substrate and the temperature range of thermal cycling on 2nd level solder joint reliability. The increase of bismaleimide tiazine substrate thickness applied to low modulus underfill was improve of solder joint reliability. The resistance of solder ball fatigue was increased solder ball size in the solder joints of FC-BGA.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2007년도 SMT/PCB 기술세미나
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• pp.37-47
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• 2007

Factor : Structure Metal pad & SMO size Board level TC test : - Large SMO size better Board level Drop test : - Large SMO size better Factor : Structure Substrate thickness Board level TC test : - Thick substrate better Board level Drop test : - Substrate thickness is not a significant factor for drop test Factor : Material Solder alloy Board level TC test : - Not so big differences over Pb-free solder and NiAu, OSP finish Board level Drop test : - Ni/Au+SAC105, CuOSP+LF35 are better Factor : Material Pad finish Board level TC test : - NiAu/NiAu is best Board livel Drop test : - CuOSP is best Factor : Material Underfill Board level TC test - Several underfills (reworkable) are passed TCG x500 cycles Board level Drop test : - Underfill lots have better performance than non-underfill lots Factor : Process Multiple reflow Board level TC test : - Multiple reflow is not a significant actor for TC test Board level Drop test : N/A Factor : Process Peak temp Board level TC test : - Higher peak temperature is worse than STD Board level Drop test : N/A Factor : Process Stack method Board level TC test : - No big difference between pre-stack and SMT stack Board level Drop test : - Flux dipping is better than paste dipping but failure rate is more faster

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.91-94
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• 2006

In this paper, in order to get micro or nano size optical patterns, an analytical and experimental investigation on a LGP (light guide plate) injection molding process has performed. The LGP, which diffusing and emitting the light from the CCFL or the LEDs to the panel front direction uniformly, typically has an under 1mm thick base substrate and numerous 60 to $170{\mu}m$ width and 6 to $10{\mu}m$ thick dot patterns on it. Generally, the small size LGPs, for mobile devices, have been and are being made of PMMA through the injection molding process. However, the substrate thickness and the dot pattern size are decreasing, it becomes hard to fill the micro to sub-micro cavities completely. To investigate the flow behavior of resin in micro/nano cavities and identify the characteristics of the LGP injection molding process, we carried out the flow analyses with respect to the variations of the substrate thickness, the dot pattern size and the pitch of a cavity.

• 한국표면공학회지
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• 제32권4호
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• pp.496-502
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• 1999

Electroplating of Ag and Au on the functional area of lead frames are required for good bonding ability in IC packaging. As the patterns of the lead frame become finer, development of new deposition technology has been required for solving problems associated with process control for uniform thickness on selected area. Sputtering was employed to investigate the adhesion between substrate Alloy42 and Ag film as a new candidate process alternative to conventional electroplating. Coating thickness of Ag film was controlled to 3.5$\mu\textrm{m}$ at room temperature as a reference. The deposition of film was optimized to ensure the adhesion by process parameters of substrate heating temperature at $100~300^{\circ}C$, sputter etching time at -300V for 10~30min, bias voltage of -100~-500V, and existence of Cr interlayer film of $500\AA$. The critical $load L_{c}$ /, defined as the minimum load at which initial damage occurs, was the highest up to 29N at bias voltage of -500V by scratch test. AFM surface image and AES depth profile were investigated to analyze the interface. The effect of bias voltage in sputtering was to improve the surface roughness and remove the oxide on Alloy42.

• 접착 및 계면
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• 제5권2호
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• pp.31-42
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• 2004

Many animals possess on their legs adhesive pads, which have undergone evolutionary optimization to be able to attach to variable substrates and to control adhesive forces during locomotion. Insect adhesive pads are either relatively smooth or densely covered with specialized adhesive hairs. Theoretical models predict that adhesion can be increased by splitting the contact zone into many microscopic, elastic subunits, which provides a functional explanation for the widespread 'hairy' design. In many hairy and all smooth attachment systems, the adhesive contact is mediated by a thin film of liquid secretion between the cuticle and the substrate. By using interference reflection microscopy (IRM), the thickness and viscosity of the secretion film was estimated in Weaver ants (Oecophylla smaragdina). 'Footprint' droplets deposited on glass are hydrophobic and form low contact angles. IRM of insect pads in contact showed that the adhesive liquid is an emulsion consisting of hydrophilic, volatile droplets dispersed in a persistent, hydrophobic phase. I tested predictions derived from film thickness and viscosity by measuring friction forces of Weaver ants on a smooth substrate. The measured friction forces were much greater than expected assuming a homogenous film between the pad and the surface. The findings indicate that the rubbery pad cuticle directly interacts with the substrate. To achieve intimate contact between the cuticle and the surface, secretion must drain away, which may be facilitated by microfolds on the surface of smooth insect pads. I propose a combined wet adhesion/rubber friction model of insect surface attachment that explains both the presence of a significant static friction component and the velocity-dependence of sliding friction.

• 마이크로전자및패키징학회지
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• 제9권3호
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• pp.31-36
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• 2002

PBGA에 비해 상대적으로 큰 칩을 실장하는 고속 SRAM용 153 FC-BGA을 대상으로 2차 솔더접합부의 신뢰성을 평가하였다. 실험은 열사이클 시험에서 발생하는 단면과 양면 실장, 패키지 구조, 언더 필 재료, 기판의 종류와 두께, 솔더 볼의 크기에 따른 영향을 분석하였다. BT기판의 두께가 0.95mm에서 1.20mm로 증가하고, 낮은 영률 의 언더 필 재료에서 솔더접합부의 피로 수명이 30% 향상됨을 확인하였다. 또한 솔더 볼의 크기가 0.76 mm에서 0.89mm로 증가하면, 솔더접합부에서 균열에 대한 저항성은 2배 정도 증가하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.355-358
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• 2000

Magnetoresistance changes of NiFe thin films were investigated as a function of deposition temperature. DC magnetron sputtering was employed to fabricate Ta/NiFe(t)/Ta thin films on Si(001) substrates with in-situ field or with no-field. The thickness(t) of NiFe films was a range of 4 to 15nm. Substrate temperature was a range of 30 to 400$^{\circ}C$. MR measurement was carried out as a function of angle $\theta$, between external field and current direction. MR ratio increased with increasing substrate temperature, also, max. MR ratio was observed in samples deposited at 300$^{\circ}C$. With increasing upto 400$^{\circ}C$, MR ratio was rapidly decreased in the case of thinner NiFe films. In non-field deposited NiFe films, both angle $\theta$=0, 90。, there was no significant change in MR curves. However, MR curves of in-situ field deposited NiFe films were different in both angles $\theta$=0 and 90。