Yung-Sen Lin

Electrical Properties of Copper-Filled Electrically Conductive Adhesives and Pressure-Dependent Conduction Behavior of Copper Particles

This study focuses on the effects of particle composition, particle shape, particle size and oxidizing temperature on the electrical properties of copper-filled electrically-conductive adhesives (CFECAs) and the pressure-dependent conduction behavior of compressed copper particles (CCPs). Silver-coated copper particles and un-coated copper particles of both spherical and flake-shaped types were oxidized at 30°C, 175°C and 240°C for two hours. The copper particles were dispersed in an epoxy matrix for CFECAs or compressed in a mold for CCPs. Silver-coated copper particles showed significantly greater oxidation resistance than un-coated copper particles since the silver coating provides good oxidation resistance at temperatures lower than 175°C. Thermogravimetric Analysis (TGA), X-ray diffraction (XRD) and Auger Electron Spectroscopy were used to observe how metal oxides such as AgO and Cu2O affected the electrical properties of CFECAs and the conduction behavior of CCPs. The electrically-conductive adhesives (ECAs) filled with flake-shaped copper particles offer better electrical conduction than the ECAs filled with spherical copper particles.

A surface analysis on oxygen plasma-cleaned gold pattern-plated substrates for wire bondability

Abstract The surface properties of the bond pads of gold pattern-plated (GPP) substrates cleaned by oxygen plasmas dependent on the wire bondability with gold wires are investigated. Optical microscope and scanning electron microscopy are used to interpret the surface morphology of the bond pads. Auger electron spectroscopy and X-ray photoelectron spectroscopy are applied to analyze the surface compositions dependent on the depths and the surface chemical bonds of the bond pads. Oxygen plasmas are found that can reduce the surface impurities such as C, O and Cu for GPP pad and enhance the bonding strength with gold wires. The surface impurities such as Cu, Ni and O are found to cause no gold residue on GPP pad after the wire peel test due to Cu 2 O/CuO and NiO are formed at GPP pad. As the high contents of C and O are observed at the top surface of GPP pad with the contaminants of Cu 2 O/CuO and NiO, the bond pad will be non-bondable with gold wires.

GaN/AlGaN ultraviolet light-emitting diode with an embedded porous-AlGaN distributed Bragg reflector

A GaN/AlGaN-based ultraviolet light-emitting diode (LED) structure with an embedded porous-AlGaN reflector was fabricated by a doping-selective electrochemical (EC) wet-etching process. The n+-AlGaN/undoped-AlGaN (u-AlGaN) stack structures with different Al contents were transformed into porous-AlGaN/u-AlGaN stack structures that acted as the embedded distributed Bragg reflectors (DBRs). The porosity of the EC-treated AlGaN layer was increased by decreasing the Al content in the n+-AlGaN layer. The reflectivity of the porous-AlGaN DBR structure was measured to be 90% at 379.3 nm with a 37.2 nm stopband width. The photoluminescence emission intensity of the DBR-LED was enhanced by forming the embedded porous-AlGaN DBR structure.

Enhanced solder wettability of oxidized‐copper with lead‐free solder via Ar‐H2 plasmas for flip‐chip bumping: the effects of H2 flow rates

Purpose – The purpose of this paper is to investigate the effects of H2 flow rate on improving the solder wettability of oxidized‐copper with liquid lead‐free solder (96.5Sn‐3Ag‐0.5Cu) by Ar‐H2 plasmas. The aim was to improve the solder wettability of oxidized copper from 0 per cent wetting of copper oxidized in air at 260oC for 1 hour to 100 per cent wetting of oxidized‐copper modified by Ar‐H2 plasmas at certain H2 flow rates and to find correlations between the surface characteristics of copper and the solder wettability with liquid lead‐free solder.Design/methodology/approach – To reduce the copper oxides on the surfaces of oxidized‐copper for improving solder wettability with liquid lead‐free solder, this study attempted to apply Ar‐H2 plasmas to ablate the copper oxides from the surfaces of oxidized‐copper by the physical bombardment of the Ar plasmas and to reduce the surfaces of oxidized‐copper by the chemical reaction of H2 plasmas with the surfaces of oxidized‐copper.Findings – The solder wettab...

Ultraviolet GaN Light-Emitting Diodes with Porous-AlGaN Reflectors

A GaN/AlGaN ultraviolet light emitting diode (UV-LED) structure with a porous AlGaN reflector structure has been demonstrated. Inside the UV-LED, the n+-AlGaN/undoped-AlGaN stack structure was transformed into a porous-AlGaN/undoped-AlGaN stack structure through a doping-selective electrochemical etching process. The reflectivity of the porous AlGaN reflector was 93% at 374 nm with a stop-bandwidth of 35 nm. In an angle-dependent reflectance measurement, the central wavelength of the porous AlGaN reflector had blueshift phenomenon by increasing light-incident angle from 10° to 50°. A cut-off wavelength was observed at 349 nm due to the material absorption of the porous-AlGaN/u-AlGaN stack structure. In the treated UV-LED structure, the photoluminescence emission wavelength was measured at 362 nm with a 106° divergent angle covered by the porous-AlGaN reflector. The light output power of the treated UV-LED structure was higher than that of the non-treated UV-LED structure due to the high light reflectance on the embedded porous AlGaN reflector.

Lithium Electrochemical and Electrochromic Properties of Atmospheric Pressure Plasma Jet-Synthesized Tungsten/Molybdenum Mixed Oxide Films for Flexible Electrochromic Devices

Lithium electrochemical and electrochromic (EC) performances of flexible tungsten/molybdenum mixed oxide (WMo_xO_yC_z) films, deposited onto 40-Ω/square flexible polyethylene terephthalate/indium tin oxide substrates at room temperature (~23°C) and at the short exposed durations of 19-26 s using an atmospheric-pressure plasma-enhanced chemical vapor deposition with an atmospheric pressure plasma jet (APPJ) at various precursor injection angles, are investigated. The flexible organo-tungsten-molybdenum oxide (WMo_xO_yC_z) films have been identified for the remarkable EC performance for 200 cycles of reversible Li⁺ ion intercalation and deintercalation in a 1-M LiClO₄-propylene carbonate electrolyte by a potential sweep switching measurement between -1 and 1 V at a scan rate of 50 mV/s, even after being bent 360° around a 2.5-cm diameter rod for 1000 cycles. The optical modulation (AT) is up to of 75.6% at a wavelength of 691.9 nm for WMo_xO_yC_z films cosynthesized with an APPJ.

Low Temperature Plasma Enhanced Chemical Vapor Deposition-Synthesized Electrochromic MoOxCy Thin Films for Flexible Electrochromic Devices

An investigation is conducted into the electrochromic organomolybdenum oxide (MoOxCy) films synthesized onto 60 Ω/ flexible poly(ethylene terephthalate) (PET)/indium tin oxide (ITO) substrates using low temperature (~23 °C) plasma-enhanced chemical vapor deposition (PECVD). The PECVD-synthesized MoOxCy films are proven to offer remarkable electrochromic performance. Cyclic voltammetry switching measurements reveal that only low driving voltages from -1 to 1 V are needed to provide reversible Li+ ion intercalation and de-intercalation in a 1 M LiClO4-propylene carbonate (PC) electrolyte. Light modulation with transmittance variation of up to 65.2%, optical density change of 0.63 and coloration efficiency of 35 cm2/C are achieved at a wavelength of 608 nm for 150 cycles of Li+ intercalation and de-intercalation. PECVD-synthesized MoOxCy thin films show excellent electrochromic properties for applications in flexible electrochromic devices.

Preliminary Study on the Manufacturing Process of a Membrane Filtration for Protein Concentration from the Recycled Materials

Jatropha curcas oil has become an important raw material in manufacturing biodiesel fuel because of its non-edible and rich-oil characteristics. After oil pressing, the recycled press cake of Jatropha curcas seed residue exhibited ample protein, and could be applied in bio-medical, bio-resources, or food industrial products. Protein concentration process using membrane module system combined with the control design has a significant advantage on energy saving compared to the heat drying of protein solution. However, fouling, large membrane area and frequent membrane cleaning will increase the energy consumption and operation cost for the protein concentration process with filter membrane. In this study, the membrane filtration for protein concentration will be conducted. The discussion of control factors, membrane pore size (X1), pH value (X2) and transmembrane pressure (X3), for protein concentration process with response surface methodology (RSM) were discussed. The results showed that R2R2 value for each model was close to one. Future investigation on the mechatronics integration of the membrane separation and purification system will be needed for commercial applications.

Analysis for Thermal Conductance Effect on the Interfacial Thermal Stresses of Anisotropic Composites

The present work applies the regularized boundary integral equations that are newly developed to treat the thermoelastic field in thin anisotropic media. For the anisotropic thermal field, a direct domain mapping technique is applied with a unique interface condition that considers the heat conductance relation. By incorporating the heat conductance effect, the paper investigates how interfacial thermal stresses between generally anisotropic materials vary with the heat conductance coefficient. Accounting for the thermal conductance effect, the paper presents the complete algorithm for computing the thermal as well as the subsequent elastic fields on interfaces between dissimilarly adjoined anisotropic composites.

Fabrication and characterization of ZnS/ZnO core shell nanostructures on silver wires

In this research, ZnS nanoparticles were synthesized on ZnO/silver wires to form ZnS/ZnO core shell structures. Various outward appearance and colors could be observed by different ZnO growth and sulfurization conditions. To evaluate the properties of these nanostructures, optical properties and chemical bindings were analyzed by photoluminescence, Raman analysis, and X-ray photoelectron spectroscopy. Furthermore, material characterizations including transmission electron microscopy and X-ray diffraction confirmed that cubic ZnS (311)/ZnO nanostructures were grown on silver wires for the first time. ZnS/ZnO core shell structures on silver wires are promising for future optoelectronic and biomedical applications.In this research, ZnS nanoparticles were synthesized on ZnO/silver wires to form ZnS/ZnO core shell structures. Various outward appearance and colors could be observed by different ZnO growth and sulfurization conditions. To evaluate the properties of these nanostructures, optical properties and chemical bindings were analyzed by photoluminescence, Raman analysis, and X-ray photoelectron spectroscopy. Furthermore, material characterizations including transmission electron microscopy and X-ray diffraction confirmed that cubic ZnS (311)/ZnO nanostructures were grown on silver wires for the first time. ZnS/ZnO core shell structures on silver wires are promising for future optoelectronic and biomedical applications.