Investigation of thin film end-termination on multilayer ceramic capacitors with base-metal-electrode

The thin film of copper, chromium and titanium as end-termination studies were performed on multilayer ceramic capacitors (MLCCs) based on BaTiO₃ ceramic with nickel internal electrodes. A green sheet was prepared by tape casting using the X7R/BME powders. Nickel paste was attached to the green sheet as an internal electrode. After lamination, the green chips were sintered at 1300 °C for 2 h, then the external electrodes were sputtered as thin films for end-termination. There is no extra curing process, so that thermal shock of the MLCCs is reduced. To improve the adhesion between thin film end-termination and dielectric body, chromium and titanium were applied as media in this study. The mechanical and electrical properties of the MLCCs were investigated subsequently. The results showed that end-termination with chromium/copper has good performances on electrical and mechanical properties of MLCC, compared to conventional end-termination.     

A study of ceramic addition in end termination of multilayer ceramics capacitors with cofiring process

The silver paste with ceramics addition as end termination was performed on multilayer ceramic capacitors (MLCC) based on ZnO–B₂O₃ + Zn_0.95Mg_0.05TiO₃ + 0.25TiO₂ ceramic (ZnBO-ZMT′) with Ag95–Pd05 internal electrodes. A green sheet was prepared by tape casting using the ZnBO-ZMT′ powders. Ag95–Pd05 was attached on the green sheet as an internal electrode. After lamination, the green chips were pre-sintered at 800 °C for 1 h, then samples were dipped the external electrodes and were cofired together at 900 °C for 2 h. There is no extra curing process, so the production cost may be cut down and thermal shock of the MLCCs may be reduced. To improve the mismatch between end termination and dielectric body during sintering, the silver paste with different amounts of ceramics, e.g., 20, 30 and 40 wt.%, was added in this study. The mechanical and electrical properties of the MLCCs were investigated subsequently. The results showed that end termination with 40 wt.% ceramic addition has good performances on mechanical properties of MLCC, but equivalent series resistance (ESR) is a little bit higher compared to end termination with 20 and 30 wt.% ceramic addition.     

Effect of metal vapor vacuum arc Cr-implanted interlayers on the microstructure of CrN film on silicon

The effect of metal vapor vacuum arc (MEVVA) Cr-implanted interlayers on the microstructure of CrN films on the silicon wafer was investigated. Two types of the CrN-coated specimens (CrN/Si and CrN/Cr/Si) by cathodic arc plasma deposition were prepared with and without a MEVVA Cr-implanted interlayer. The diffraction patterns of the coated specimens revealed the presence of CrN, and the (220) preferred orientation for both CrN/Si and CrN/CrN/Si. The CrN coating thicknesses for CrN/Si and for CrN/Cr/Si were 0.3 μm and 1.3 μm, respectively. Secondary ion mass spectrometry proved the high quality of the films on silicon substrates. Transmission electron microscopy micrographs and selective area diffractions revealed the presence of a large number of nano-scale Cr resulting from the interlayer of MEVVA Cr with a background of single crystal silicon spots. Furthermore, in situ stress measurement demonstrated that the presence of a Cr interlayer between CrN and Si could drastically reduce the residual stress in the CrN/Cr/Si assembly.     

Dewetting Retardation on Ag/Cu Coated Light Emitting Diode Lead Frames During the Solder Immersion Process

The process of SnPb immersion in Ag/Cu coated light emitting diode lead frames (LED LFs) (alloy 42) was investigated. SnPb solder was found to cause dewetting of the LF substrate after 6 s of immersion. We believed that the dewetting of the SnPb solder could be attributed to spalling of the interfacial compound grains. The addition of a small amount of Ni to the molten SnPb solder (0.1 wt.%) retarded that spalling and helped to prevent dewetting. The mechanisms for spalling retardation by the addition of Ni additives are as follows: (1) the Ni additives slow down the reaction rate between the molten SnPb solder and the Ag/Cu plating layer; (2) the Ni additives participate in interfacial reactions to form (Cu,Ni)₆Sn₅ ternary compounds, which are more stable than binary compounds and have a slower ripening process.     

Structure and electrical properties of Mo back contact for Cu(In, Ga)Se2 solar cells

Mo layers were deposited on soda lime glass via DC magnetron sputtering of a Mo target in a pure Ar atmosphere. The structure and electrical resistivity of Mo thin films, which may be varied by controlling the sputtering pressure, were investigated. The films showed (110) preferred orientation regardless of the working pressure. Films sputtered at low working pressure had low resistivity but adhered poorly to glass. A study of the deposition of a Mo bilayer was conducted. Optimum properties of the Mo bilayer were obtained when the bottom layer was deposited at 10 mtorr and the top layer was deposited at 2.5 mtorr. The extremely low resistivity of 6.57 μΩ-cm was obtained, which is better than other literatures. A Cu(In, Ga)Se₂ cell fabricated on a Mo film sputtered under optimized conditions showed 10.40% efficiency.     

Reduced graphene oxide–coated anode gas diffusion layer for performance enhancement of proton‐exchange membrane fuel cell

In this study, we produced reduced graphene oxide (RGO) by reduction of graphene oxide (GO) in Teflon‐lined autoclave, maintained at 100°C for 12 hours, and coated on the anode gas diffusion layer (GDL) of a proton‐exchange membrane fuel cell (PEMFC) to improve the cell performance. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analysis showed the presence of residual oxygen‐containing functional groups in RGO. Field‐emission scanning electron microscopy images revealed the uniform and adequate coating of the GDLs with RGO. The wettability of RGO‐coated GDL was determined by the sessile drop method and has optimum contact angle 117°. The power densities for the membrane electrode assembly (MEA) with RGO coated on the anode GDL were 30.92%, 41%, and 36.20% higher than those for the MEA without the RGO coating at anode gas humidified temperatures of 25°C, 45°C, and 65°C, respectively.     

Study of Interfacial Reactions Between Sn(Cu) Solders and Ni-Co Alloy Layers

The interfacial reactions between electroplated Ni-yCo alloy layers and Sn(Cu) solders at 250°C are studied. For pure Co layers, CoSn₃ is the only interfacial compound phase formed at the Sn(Cu)/Co interfaces regardless of the Cu concentration. Also, the addition of Cu to Sn(Cu) solders has no obvious influence on the CoSn₃ compound growth at the Sn(Cu)/Co interfaces. For Ni-63Co layers, (Co,Ni,Cu)Sn₃ is the only interfacial compound phase formed at the Sn(Cu)/Ni-63Co interfaces. Unlike in the pure Co layer cases, the Cu additives in the Sn(Cu) solders clearly suppress the growth rate of the interfacial (Co,Ni,Cu)Sn₃ compound layer. For Ni-20Co layers, the interfacial compound formation at the Sn(Cu)/Ni-20Co interfaces depends on the Cu content in the Sn(Cu) solders and the reflow time. In the case of high Cu content in the Sn(Cu) solders (Sn-0.7Cu and Sn-1.2Cu), an additional needle-like interfacial (Ni _x ,Co _y ,Cu_1−x−y )₃Sn₄ phase forms above the continuous (Ni _x ,Cu _y ,Co_1−x−y )Sn₂ compound layer. The Ni content in the Ni-yCo layer can indeed reduce the interfacial compound formation at the Sn(Cu)/Ni-yCo interfaces. With pure Sn solders, the thickness of the compound layer monotonically decreases with the Ni content in the Ni-yCo layer. As for reactions with the Sn(Cu) solders, as the compound thickness decreases, the Ni content in the Ni-yCo layers increases.     

Ni Interdiffusion Coefficient and Activation Energy in Cu6Sn5

Ni diffusion in Cu₆Sn₅ intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu₆Sn₅ crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu₆Sn₅ diffusion couples were produced by sputtering from a Ni thin film onto the Cu₆Sn₅ crystal. Ni/Cu₆Sn₅ diffusion couples were annealed at different temperatures of 120°C, 160°C, 200°C, 255°C, 290°C, and 320°C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu₆Sn₅ interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients ([(D)\tilde]_Ni \tilde{D}_{\rm{Ni}} ) in the Cu₆Sn₅ crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu₆Sn₅ crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu_6−x Ni _x Sn₅ compound phase, the activation energy of Ni interdiffusion decreases with the Ni content.     

Effects of manganese oxide addition and reductive atmosphere annealing on the phase stability and microstructure of yttria stabilized zirconia

The effects of Mn₃O₄ addition and reductive atmosphere (N₂:H₂ = 97:3) annealing on the microstructure and phase stability of yttria stabilized zirconia (YSZ) ceramics during sintering at 1500 °C for 3 h in air and subsequent annealing in a reductive atmosphere were investigated. Mn₃O₄ added 6 mol% YSZ (6YSZ) and 10 mol% YSZ (10YSZ) ceramics were prepared via the conventional solid-state reaction processes. The X-ray diffraction results showed that a single cubic phase of ZrO₂ was obtained in 1 mol% Mn₃O₄ added 6YSZ ceramic at a sintering temperature of 1500 °C for 3 h. A trace amount of monoclinic ZrO₂ phases were observed for 1 mol% Mn₃O₄ added 6YSZ ceramics after annealing at 1300 °C for 60 cycles in a reductive atmosphere by transmission electron microscopy. Furthermore, a single cubic ZrO₂ phase existed stably as Mn₃O₄ added 10YSZ ceramics was annealed at 1300 °C for 60 cycles in reductive atmosphere.