• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.9-17
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• 2003

In this paper, thermo-mechanical and rheological properties of NCPs (Non-Conductive Pastes) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermo-mechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature ($T_g$) and storage modulus at room temperature became higher. While, coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermo-mechanical properties such as modulus, CTE, and $T_g$. Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected as adhesives for reliability test of flip chip assemblies. T/C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.13-20
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• 2008

This paper describes the methods of spacer-fabrication for wafer-level CIS(CMOS Image Sensor) assembly. We propose three methods using SU-8, PDMS and Si-interposer for the spacer-fabrication. For SU-8 spacer, novel wafer rotating system is developed and for PDMS(poly-dimethyl siloxane) spacer, new fabrication-method is used to bond with alignment of glass/PDMS/glass structure. And for Si-interposer, DFR(Dry Film Resist) is used as adhesive layer. The spacer using Si-interposer has the strongest bonding strength and the strength is 32.3MPa with shear.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.603-609
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• 2013

In this paper, we describe the analysis of inkjet-printed silver (Ag) patterns on epoxy-coated substrates according to several reliability evaluation test method guidelines for conventional printed circuit boards (PCB). To prepare patterns for the reliability analysis, various regular test patterns were created by Ag inkjet printing on flame retardant 4 (FR4) and polyimide (PI) substrates coated with epoxy for each test method. We coated the substrates with an epoxy primer layer to control the surface energy during printing of the patterns. The contact angle of the ink to the coated epoxy primer was $69^{\circ}$, and its surface energy was 18.6 $mJ/m^2$. Also, the substrate temperature was set at $70^{\circ}C$. We were able to obtain continuous line patterns by inkjet printing with a droplet spacing of $60{\mu}m$. The reliability evaluation tests included the dielectric withstanding voltage, adhesive strength, thermal shock, pressure cooker, bending, uniformity of line-width and spacing, and high-frequency transmission loss tests.

• Journal of the Korean institute of surface engineering
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• v.44 no.6
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• pp.269-276
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• 2011

Phase evolution and tribological behavior of Cr-Mo-N multi compositional films with different interlayer were investigated. The films were deposited by hybrid PVD (Physical Vapor Deposition) system consisted of dc unbalanced magnetron (UBM) sputtering and arc ion plating (AIP) sources. A pure molybdenum (Mo) was used as sputtering target and also a pure Cr was used as AIP target to form the Cr-Mo-N films. Various growth planes were found, no textured surface, in all of the multi composition films. Maximum value of microhardness was measured in Cr-Mo-N film with Mo interlayer as 29 GPa. Composition film was mainly showed the aspect of the adhesive wear than CrN film. The friction coefficient was decreased from 0.6 for pure CrN coating to 0.35 for Cr-Mo-N film with Mo interlayer. This result may come from the formation of metal oxide tribo-layer which is known as solid lubricant during the wear test.

• Tribology and Lubricants
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• v.4 no.1
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• pp.56-68
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• 1988

The wear resistance of P-bronze which is widely used as worm gear material was investigated. In order 1o study the effect of additional elements on the wear resistance of Pbronze, the applied load and sliding time were selected as variables, and SCM4, were used as against metal. The addition of Fe improve wear resistance, for it precipities hard Fe$_3$ P phase and the work hardening coefficients are lowered due to decreasing solubility of P. When Fe is added in conventional P-bronze, the alloy is rather sliding than forming wear debris by frictional force during wear test. Experimental results indicated that the wear mechanisms for P-bronze are mainly consisted of abrasive wear due to Beilby layer forming mechanism and adhesive wear due to thermally activated wear mechanism. Moreover, the weight loss is decreased in accordance with increasing load and time. However the rate of wear loss is decreased as the sliding time is increased.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.481-487
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• 2009

On the paved track, the railway ballast is used as aggregate for the filling layer using the pre-packed concrete method. The condition of ballast as the paved track aggregate ensure that the compressive strength, particle distribution size for the pouring and surface clearance to increase the adhesive strength with mortar. It is profitable to recycle the existing railway ballast as a economical supply. In order to increase recycling characteristic, it is necessary to apply the similar criterion which does not exceed the conventional railway ballast criterion. Consequently, this paper was to investigate physical characteristics of existing ballast, particle size distribution, compressive and flexural strength, bearing capacity and filling capacity to prepare the aggregate's recycling. As a result, optimized aggregate criterion is suggested.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.481-485
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• 2003

Amorphous silicon (a-Si:H) based TFT process has been studied at the maximum temperature of 15$0^{\circ}C$ with 25${\mu}{\textrm}{m}$ thick flexible and adhesive tape type polyimide foil substrate, which has benefit on handling a rugged, flexible plastic substrate trough sticking simply it to glass. This paper summarize the process procedure of the TFT on the plastic substrate and shows its electrical characteristics in comparison with glass substrate using primarily the ON/OFF current ratio and the field effect mobility as the quality criterion. The a-SiN:H coating layer played an important role in decreasing surface roughness of plastic substrate, so leakage current of TFT was decreased and mobility was increased. The results show that high quality a-Si:H TFTs can be fabricated on the plastic substrates through coating a rough plastic surface with a-SiN:H.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.15-20
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• 2017

In this paper, two types of assemblies using CNT-filled SACAs (with 0.03 wt% CNTs and without CNT) were prepared to investigate the influence of carbon nanotubes (CNTs) on the reliability properties of solderable anisotropic conductive adhesives (SACAs) with a low-melting-point alloy (LMPA). Two types of reliability test including thermal shock (TS: -55 to $125^{\circ}C$, 1000 cycles) and high-temperature and high-humidity (HTHH: $85^{\circ}C$, 85% RH, 1000 h) tests were conducted. The SACA assemblies with and without CNTs showed stable electrical reliability properties due to the formation of wide and stable metallurgical interconnection between corresponding metallizations by the molten LMPA fillers. Although the mechanical pull strength of CNT-filled SACA assemblies was decreased after thermal aging (because of the excessive layer growth and planarization of the IMCs), the CNT-filled SACA with 0.03wt% CNTs showed enhanced mechanical reliability properties compared with the SACA assemblies no CNTs. This enhancement in mechanical performance was due to the reinforcement effect of the CNTs. These results demonstrate that CNTs within the CNT-filled SACAs can improve the reliability properties of CNT-filled SACAs joints due to their superior physical properties.

• Fibers and Polymers
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• v.3 no.4
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• pp.153-158
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• 2002

A series of waterborne polyurethanes (WBPU) were prepared from 4,4-dicyclohexylmethane diisocyanate ($H_{12}$MDI),2,2-bis(hydroxylmethyl) propionic acid (DMPA), othylenediarnine (EDA), triethylamine (TEA), and triblock glycol [TBG, ($\varepsilon$-caprolactone)$_{4.5}$-poly(tetramethylene ether) glycol (MW= 2000)-($\varepsilon$-caprolactone)$_{4.5}$: $(CL)_{4.5}$-PTMG-$(CL)_{4.5}$, MW=3000] as a soft segment. Two melting peaks of TBG at about 14$^{\circ}C$ and 38$^{\circ}C$ were observed indicating the presence of two different crystalline domains composed of CL and PTMG dominant component. The effect of soft segment content (60-75 wt%) on the colloidal properties of dispersion, and thermal and mechanical properties of WBPU films, the water vapor permeability (WVP) and water resistance (WR) of WBPU-coated Nylon fabrics, and the adhesive strength of WBPU- coated layer and Nylon fabrics was investigated. As soft segment contents increased, the water vapor permeability of WBPU- coated Nylon fabrics increased from 3615 to 4502 g/$m^2$day, however, the water resistances decreased from 1300 to 500 mm$H_2$O.O.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.475-480
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• 2018

We investigated the tribological properties of amorphous carbon (a-C) films deposited with CrC interlayers of various thicknesses as the adhesive layer. A-C and CrC thin films were deposited using the unbalanced magnetron (UBM) sputtering method with graphite and chromium as the targets. CrC films as the interlayer were fabricated under a-C films, and various structural, surface, and tribological properties of a-C films deposited with various CrC interlayer thicknesses were investigated. With various CrC interlayer thicknesses under a-C films, the tribological properties of CrC/a-C films were improved; the increased film thickness exhibited a maximum high hardness of over 27.5 GPa, high elastic modulus of over 242 GPa, critical load of 31 N, residual stress of 1.85 GPa, and a smooth surface below 0.09 nm at the condition of 30-nm CrC thickness.