• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.21-29
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• 2021

Recently, semiconductor chips and electronic components are increasingly being used in IT devices such as wearable watches, autonomous vehicles, and smart phones. As a result, there is a growing concern about device malfunctions that may occur due to electromagnetic interference being entangled with each other. In particular, electromagnetic wave emissions from wearable or flexible smart devices have detrimental effects on human health. Therefore, flexible and transparent electromagnetic interference (EMI) shielding materials and films with high optical transmittance and outstanding shielding effectiveness have been gaining more attention. The EMI shielding films for flexible and transparent electronic devices must exhibit high shielding effectiveness, high optical transmittance, high flexibility, ultrathin and excellent durability. Meanwhile, in order to prepare this EMI shielding films, many materials have been developed, and results regarding excellent EMI shielding performance of a new materials such as carbon nano tube (CNT), graphene, Ag nano wire and MXene have recently been reported. Thus, in this paper, we review the latest research results to EMI shielding films for flexible and transparent device using the new materials.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.47-50
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• 2021

Nanoimprint lithography (NIL) has revolutionized the fabrications of electronics, photonics, optical and biological devices. Among all the NIL processes, roll-to-roll nanoimprinting is regarded best for having the attributes of low cost, continuous, simple, and energy-efficient process for nanoscale device fabrication. However, large-area printing is limited by the master mold deformation. In this study, a finite element model (FEM) has been constructed to assess the deformation of the roll mold adhesively wrapped on the carbon fiber reinforced material (CFRP) base roll. This study also optimizes the deformations in the metallic roll mold with respect to nip-forces applied in the printing process of nano-fabrication on large scale. The numerical simulations were also conducted to evaluate the deflection in roll mold assembly due to gravity. The results have shown decreasing trend of the deformation with decreasing nip-force. Also, pressure uniformity of about 40% has been optimized by using the current numerical model along with an acceptable deflection value in the vertical axis due to gravity.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.67-71
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• 2014

An attempt to grow high quality GaN on silicon substrate using metal organic chemical vapor deposition (MOCVD), herein GaN epitaxial layers were grown on various Si(111) substrates. Thin Platinum layer was deposited on Si(111) substrate using sputtering, followed by thermal annealing to form Pt nano-clusters which act as masking layer during dry-etched with inductively coupled plasma-reactive ion etching to generate nano-patterned Si(111) substrate. In addition, micro-patterned Si(111) substrate with circle shape was also fabricated by using conventional photo-lithography technique. GaN epitaxial layers were subsequently grown on micro-, nano-patterned and conventional Si (111) substrate under identical growth conditions for comparison. The GaN layer grown on nano-patterned Si (111) substrate shows the lowest crack density with mirror-like surface morphology. The FWHM values of XRD rocking curve measured from symmetry (002) and asymmetry (102) planes are 576 arcsec and 828 arcsec, respectively. To corroborate an enhancement of the growth quality, the FWHM value achieved from the photoluminescence spectra also shows the lowest value (46.5 meV) as compare to other grown samples.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.4
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• pp.65-69
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• 2012

Composite coating can be manufactured during the electroplating with the bath containing a suspension of particles: ceramic, polymer, nanopowders. Improvement of hardness, wear resistance, corrosion resistance and lubrication properties are well-known advantage of composite coating. In this study, nano $TiO_2$ powder dispersed Ni composite plating was investigated. The improvement of surface hardness and photo decomposition effects can be expected in this coating. Zeta potential was measured with pH. The effect of ultrasonication time and types of ultrasonicator were studied to minimize the agglomeration of $TiO_2$ nanopowders in the electrolyte. Optimum conditions for nano $TiO_2$ dispersed Ni composite coating were $40mA/cm^2$ of current density, pH 3.5, and $50^{\circ}C$. At these conditions, $TiO_2$ nanoparticles contents in the Ni deposit was 15-20 at.%.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.61-65
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• 2009

We produced noble surface structure of crystalline Si for solar cells by using preferential aqueous etching on crystallographic defects which were induced by grinding process. We analyzed the reflectance of textured surface according to surface topography resulting from various etchant concentrations and duration of etching process. The crystallographic defects and textured surface topography were investigated by using transmission electron microscopy and secondary electron microscopy, respectively. Also, the measurement of reflectance of textured surface utilizes spectrophotometer. The optimized texture surface exhibits improved result indicating reflectance of below ave. 1%. And it is cost-effective as well as taking short time within a few minutes.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.51-57
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• 2021

This paper analyzed the effects of the concentration of nano-silica particles contained in epoxy resin on the thermomechanical properties of the composite materials. The 12nm sized nanoparticles were mixed with epoxy polymer by 5 different weight ratios for the test samples. The glass transition temperature, stress relaxation, and thermal expansion behaviors were measured using dymanic mechanical analyzer (DMA) and thermomechanical analyzer (TMA). It was shown that the nano particle mixing ratios had significant influences on the viscoelastic behaviors of the materials. As the content of the silica particles was increased, the elastic modulus was also increased, while the glass transition temperatures were decreased. Fourier Transform Infrared Spectroscopy (FTIR) results played an important role in determining the causes of the property changes by the filler contents in terms of the molecular structures, enabling the interpretations on the material behaviors based on the chemical structure changes.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.55-59
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• 2022

In this paper, we compared the electric field and absorptance of nano particles in nanostructures by amplifying the electric field around the nanoparticles through plasmon resonance and comparing the structure that can increase the absorptance with the nanostructure by using the Finite Different Time Domain (FDTD) simulation. In addition, the width of the nanostructure was adjusted to 240 nm ~ 300 nm, and the light absorptance rate was higher as the gap between the particles was short. In addition, a study was conducted on the formation of nanoparticles and nanostructures on the surface through UV imprint. In order to form particles in the structure, the nano particles were first arranged in the mold used for the fabrication of the structure using spray coating, and then fabricated through UV imprinting. The nanostructure and particles were formed together by scanning electron microscopy.

• Polymer(Korea)
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• v.32 no.1
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• pp.38-42
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• 2008

Ultrathin films were coated on low density Polyethylene (LDPE) food packaging films by plasma polymerization of methane, acetylene, hexamethyldisiloxane (HMDSO), and HMDSO+oxygen to improve the barrier property of the LDPE films. The film coated in HMDSO +oxygen (flow rate: 0.6+ 9.0 SCCM) plasma at 40 W for 10 min showed the highest improvement in the barrier property against oxygen, reducing the permeability of oxygen as much as 18.6 times. The film coated in acetylene (flow rate 0.75 SCCM) plasma at 10 W for 10 min showed the highest improvement in the barrier property against carbon dioxide and moisture, reducing the permeability of carbon dioxide and moisture as much as 12.0 and 3.0 times, respectively. In addition, cherry tomato, cucumber, and mushroom (Flammulina velutipes) wrapped with the coated films were kept fresh $1.5{\sim}3.0$ times longer than those wrapped with an LDPE film.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.95-100
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• 2019

Nanoindentation has been widely used for evaluating mechanical properties of nano-devices, from MEMS to packaging modules. Residual stress is also estimated from indentation tests, especially the Knoop indenter which is used for the determination of residual stress directionality. According to previous researches, the ratio of the two stress conversion factors of Knoop indentation is a constant at approximately 0.34. However, the ratio is supported by insufficient quantitative analyses, and only a few experimental results with indentation depth variation. Hence, a barrier for in-field application exists. In this research, the ratio of two conversion factors with variation in indentation depth using finite elements method has been attempted at. The magnitudes of each conversion factors were computed at uniaxial stress state from the modelled theoretical Knoop indenter and specimen. A model to estimate two stress conversion factor of the long and short axis of Knoop indenter at various indentation depths is proposed and analyzed.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.1-6
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• 2016

The Internet of Things (IoT) is a new technology paradigm demanding one packaged system of various semiconductor and MEMS devices. Therefore, the development of electronic packaging technology with very high connectivity is essential for successful IoT applications. This paper discusses both fan-out wafer level packaging (FOWLP) and 3D stacking technologies to achieve the integrattion of heterogeneous devices for IoT. FOWLP has great advantages of high I/O density, high integration, and design flexibility, but ultra-fine pitch redistribution layer (RDL) and molding processes still remain as main challenges to resolve. 3D stacking is an emerging technology solving conventional packaging limits such as size, performance, cost, and scalability. Among various 3D stacking sequences wafer level via after bonding method will provide the highest connectivity with low cost. In addition substrates with ultra-thin thickness, ultra-fine pitch line/space, and low cost are required to improve system performance. The key substrate technologies are embedded trace, passive, and active substrates or ultra-thin coreless substrates.