• Korean Journal of Materials Research
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• 제21권5호
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• pp.283-287
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• 2011

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

• Design & Manufacturing
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• 제7권1호
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• pp.55-59
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• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.

• Journal of Adhesion and Interface
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• 제17권1호
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• pp.21-28
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• 2016

Foam-type biodegradable polyurethane adhesives were developed as a non-lethal weapon against illegal fishing boats. The adhesives were prepared from a hardener of polymeric methylene diphenyl diisocyanate (MDI) and a base composed of polyester and/or polyether polyols. In order to accelerate biodegradability, starch, dextrin, and amylase were added into the base, and which present about 34% degradability within 4 weeks confirmed by OECD 301C method. For proper mixing and corresponding prompt foam reaction, viscosities of hardener and base compositions were investigated in the temperature ranges from 0 to $50^{\circ}C$. For fast completion of the foam forming and corresponding adhesion, rising time was recorded in the same temperature range, and the rising time of the adhesive was varied within around 1 minute. T-peel adhesion tests with cotton fabrics were performed which showed 20.78 N/cm and 11.95 N/cm as the maximum and the average values, respectively.

• Journal of Technologic Dentistry
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• 제34권3호
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• pp.227-235
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• 2012

Purpose: This study compared the surface hardness (Vickers) and microstructural characteristics between a type IV stone with and without die hardening treatment, a polyurethane die material. Methods: Materials used were a type IV stone(MG Crystal Rock), two die hardeners (Hardening bath, Epox-it), and a polyurethane resin material(Polyluck). Six specimens per group were prepared according to manufacturer's directions. The prepared specimens were tested by means of hardness test, one-way ANOVA analysis, scanning electron microscopic(SEM) observations and energy dispersive spectroscopic(EDS) analysis. Results: In the hardness test and its statistical analysis, there was no significant difference in the surface hardness between a type IV stone and type IV stone with die hardener coating, type IV stone mixed with an epoxy like material instead of water. In contrast, polyurethane resin material exhibited significantly greater surface hardness than other specimen groups (p<0.05). Conclusion: By considering the results of the hardness test, SEM observations and EDS analysis, although the die hardeners on type IV stone did not show remarkable improvement in surface hardness, the die hardener coating on the surface of type IV stone material did show decrease of microporous and improvement of surface defects.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제7권2호
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• pp.87-92
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• 2009

Remote detecting system for a radiation contamination using a plastic scintillator and an optical fiber was developed. Using a commercially available silica optical fiber and a plastic scintillator, we tested then for a real possibility as a remote monitoring detector. Also, a plastic scintillator was developed by itself, and evaluated as a radiation sensor. The plastic scintillator was made of epoxy resin, a hardener and an organic scintillation material. The mixture rate of the epoxy resin, hardener and organic scintillator was fixed by using their emission spectrum, transmittance, intensity etc. In this study, in order to decrease the light loss of an incomplete connection between an optical fiber and a scintillator, the optical fiber was inserted into the scintillator during the fabrication process. The senor used a plastic optical fiber and was estimated for its detection efficiency by an optic fiber's geometric factor.

• Journal of The Korean Society of Clinical Toxicology
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• 제16권2호
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• pp.157-160
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• 2018

Chronic silica nephropathy has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease, and end-stage renal disease. On the other hand, acute intentional exposure is extremely rare. The authors' experienced a 44-year-old man who took rapid cement hardener (sodium silicate) in a suicide attempt whilst in a drunken state. He visited the emergency department approximately 1 hour after ingestion. Information on the material was obtained after 3 L gastric lavage. The patient complained of a sore throat, epigastric pain, and swollen to blood tinged vomitus. Proton pump inhibitors, hemostats, steroid, and fluids were administered. Nine hours after ingestion, he was administered 200 mL hematochezia. Immediately after, a gas-troenterologist performed an endoscopic procedure that revealed diffuse hyperemic mucosa with a color change and variable sized ulceration in the esophagus, whole stomach, and duodenal $2^{nd}$ portion. Approximately 35 hours later, persistent oligouria and progressive worsening of the renal function parameters (BUN/Cr from 12.2/1.2 to 67.5/6.6 mg/dL) occurred requiring hemodialysis. The patient underwent 8 sessions of hemodialysis for 1 month and the BUN/Cr level increased to 143.2/11.2 mg/dL and decreased to 7.6/1.5 mg/dL. He was discharged safely from the hospital. Follow up endoscopy revealed a severe esophageal stricture and he underwent endoscopic bougie dilatation. Acute cement hardener (sodium silicate) intoxication can cause renal failure and strong caustic mucosal injury. Therefore, it is important to consider early hemodialysis and treatment to prevent gastrointestinal injury and remote esophageal stricture.

• Journal of the Semiconductor & Display Technology
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• 제21권2호
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• pp.57-67
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• 2022

The curing characteristics of naphthalene type epoxy resin systems according to the change of curing agent were investigated to develop a new next-generation EMC(Epoxy Molding Compound) with excellent warpage characteristics, low thermal expansion, and excellent fluidity for WLP(Wafer Level Package). As epoxy resins, DGEBA, which are representative bisphenol type epoxy resins, NE-16, which are the base resins of naphthalene type epoxy resins, and NET-OH, NET-MA, and NET-Epoxy resins newly synthesized based on NE-16 were used. As a curing agent, DDM (Diamino Diphenyl Methane) and CBN resin with naphthalene moiety were used. The curing reaction characteristics of these epoxy resin systems with curing agents were analyzed through thermal analysis experiments. In terms of curing reaction mechanism, DGEBA and NET-OH resin systems follow the nth curing reaction mechanism, and NE-16, NET-MA and NET-Epoxy resin systems follow the autocatalytic curing reaction mechanism in the case of epoxy resin systems using DDM as curing agent. On the other hand, it was found that all of them showed the nth curing reaction mechanism in the case of epoxy resin systems using CBN as the curing agent. Comparing the curing reaction rate, the epoxy resin systems using CBN as the curing agent showed a faster curing reaction rate than them with DDM as a hardener in the case of DGEBA and NET-OH epoxy resin systems following the same nth curing reaction mechanism, and the epoxy resin systems with a different curing mechanism using CBN as a curing agent showed a faster curing reaction rate than DDM hardener systems except for the NE-16 epoxy resin system. These reasons were comparatively explained using the reaction rate parameters obtained through thermal analysis experiments. Based on these results, low thermal expansion, warpage reduction, and curing reaction rate in the epoxy resin systems can be improved by using CBN curing agent with a naphthalene moiety.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.120-123
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• 2000

The geopolymer technique may be a future-oriented technology for saving energies and resources. This technique requires 3 fundamental elements so-called filler, hardener and geopolymer liquor being generally an alkaline silicate solution. Quartz powder, water quenched granulated blast furnace slag and sodium silicate solution prepared from $Na_2O\cdot2SiO_2$were chosen for these three elements. After mixing these starting materials in appropriate proportions, monoliths were prepared by casting at room temperature. Strength tests showed the following results for 28d age speciment: 7.9-12.7 MPa in flexural strength and 20.2-32.8 MPa in compressive strength, depending on geopolymer liquor/solid ratio, P/S and fineness of the quartz powders used.

• Polymer(Korea)
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• 제27권4호
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• pp.392-395
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• 2003

Phosrhonium salt exchanged montmorillonites were prepared from a reaction between alkyl triphenyl phosponium bromide and Na$^{＋}$-montmorillonite. Epoxy-clay nanocomposites were also prepared by using cycloaliphtic epoxy, methyl tetrahydrophthalic anhydride as a hardener, and triphenyl butyl phosphonium bromide as an accelerator. TEM and XRD results suggested that clay minerals in the epoxy-montmorillonites composite were intercalated. Mechanical properties such as tensile modulus and strength were measured and the effect of nanocomposite formation was also discussed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.110-113
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• 2001

Dielectrometry has been used to monitor the cure of epoxy resin using composite matrix. In this investigation, physical properties of the mixture of epoxy resin(LY564), bisphenol A type, and cycloaliphatic hardener(HY 2954) were observed. Activation energy at maximum tan $\delta$ and gelation point was determined during isothermal scanning. From IonViscosity data, it was found that vitrification peak after gelation was appeared on slow heating rate. It was also measured that the duration time for full cure was necessary and it was about 24 hr at $145^{\circ}C$. Therefore, epoxy resin used in this research is required the extended time for full cure.