Next generation integral passives: materials, processes, and integration of resistors and capacitors on PWB substrates

Integral passives are becoming increasingly important in realizing next generation electronics industry needs through gradual replacement of discretes. The need for integral passives emerges from the increasing consumer demand for product miniaturization thus requiring components to be smaller and packaging to be space efficient. In this paper, the feasibility of integration of polymer/ceramic thin film (5 m thick) capacitors (C) with other passive components such as resistors (R) and inductors (L) has been discussed. An integrated RC network requiring relatively large capacitance and resistance is selected as a model for co-integration of R and C components using low temperature PWB compatible fabrication processes. This test vehicle is a subset of a large electrical circuit of a functional medical device. In order to produce higher capacitance density and reduce in-plane device area, multi-layer (currently two-layer) capacitors are stacked in the thickness direction. A commercially available Ohmega-Ply resistor/conductor material is selected for integral resistors. Resistors were fabricated using a multi-step lithography process with the utilization of two separate masks. Bottom copper electrodes for capacitors were also defined during the resistor fabrication process. Photodefinable epoxies filled with a high permittivity ceramic powder were used for fabrication of thin film capacitors. Epoxy and ceramic powders were mixed in the required proportion and blended using a high shear apparatus. The coating solution was homogenized in a roll miller for 3 to 5 days prior to casting in order to prevent settling of the higher density ceramic particles. Capacitors were fabricated by spin-coating on the sub-etched copper electrodes. The deposited dielectric layers were dried, exposed with UV radiation, patterned, and thermally cured. Top capacitor electrodes (copper) were deposited using a metal or an e-beam evaporator. The electrodes were patterned using the standard photolithography processes. Selected good samples were used for depositing the second capacitor layer. The RC network is extended to incorporate electroplated polymer/ferrite core micro-inductors through the fabrication of an industry prototype low pass RLC filter. Meniscus coating was evaluated for large area manufacturing with high process yield. A capacitance density of 3 nF cm^–2 was obtained on a single layer capacitor with 6 m thick films. The capacitance density was increased to 6 nF cm^–2 with the two-layer deposition process. The capacitors were relatively stable up to a frequency range of 120 Hz to 100 KHz. Meniscus coating was qualified to be a viable manufacturable method for depositing polymer/ceramic capacitors on large area (300mm x 300mm) PWB substrates. Dielectric constant values in the range of 3.5 to 35 with increase in filler loading up to 45 vol% were achieved in the epoxy nanocomposite system where the dielectric constant of the host polymer was limited to 3.5. Higher dielectric constant polymers are required to meet the increasingly higher capacitance needs for the next generation electronics packaging. Possible avenues for achieving higher capacitance density in polymer/ceramic nanocomposite system have been discussed.     

Determining the value of reference air capacitors at high frequencies

Conclusions Reference three-terminal capacitors are affected by frequencies to a greater extent than the two-terminal capacitors and, therefore, the range of their application is limited to several megahertz.The effect of distributed parameters appears in air capacitors with a rising frequency, thus raising their inductance measured at a high frequency as compared with its low-frequency value. The extent of this difference depends on the capacitor's design features and nominal value. The maximum difference amounts to about 20%.The applicability limit of (1), which corresponds to the simple equivalent circuit of the capacitor (Fig. 1) and is used for calculating its effective value, depends on the tolerated error in determining that value and on the capacitor's parameters. For an error of 1% the value of the frequency correction ²LC_o must not exceed 10%, and this approximately corresponds to the upper frequency boundary of 1/3 of the capacitor's natural resonant frequency.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 46–48, July, 1972.     

Optical properties of high density InGaN QDs grown by MOCVD

In this article, we investigate the relaxation time constant and optical properties of InGaN QDs following different durations of SiN_x treatment. We find that the smaller size QDs have smaller red shift as temperature increasing, only about 10 meV. Time-resolved PL at various emitting wavelength of the three samples is also investigated. Decreasing time constant as increasing QDs size is observed. Besides, we also find the decreasing time constant with shorter wavelength. Meanwhile, decreasing time constant as increasing emitting wavelength is characterized and attributed as an increasing confinement of excitons in QDs with higher localization energy and thus with a higher electron-hole overlap.     

Simple integral high vacuum valve

A simple mechanical system is described which enables a vessel to be roughly evacuated by a rotary pump, then by turning a handle through a third of a revolution, the vessel can be evacuated by combined rotary and diffusion pumps. A further turn will allow air into the vessel, and completing one revolution brings the system back to the initial state of being roughed. This is effected by coupling a baffle valve and specially designed rotating plate valve.     

High-growth rate YSZ thermal barrier coatings deposited by MOCVD demonstrate high thermal cycling lifetime

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) were prepared by metalorganic chemical vapor deposition (MOCVD) using Y(OButⁿ)₃, Zr(OButⁿ)₄ precursors and O₂ carrier gas. A thermodynamic analysis guided experiments by optimizing elemental molar (n) stoichiometric ratios for the (Zr-Y-O-C-H system). This analysis showed single-phase YSZ was favored at 950 °C, 1 kPa, n_O/(n_Y + n_Zr) > 30, n_Y/(n_Y + n_Zr) = 0.06-0.10 (fixed n_C, n_H). Experimental YSZ growth had multiple phases (fcc, monoclinic), had a relatively high growth rate (43 μm/h, 1005 °C), had an Arrhenius dependence (845-950 °C, E_a = 53.8 ± 7.9 kJ/mol), had columnar grains (SEM analysis), and had a coating through-thickness n_Y/(n_Y + n_Zr) = 0.04 (EPMA analysis). Doubling the inlet yttrium precursor mole fraction resulted in fcc YSZ growth with a coating through-thickness n_Y/(n_Y + n_Zr) = 0.07. Hot-insertion thermal cycling of YSZ coatings on FeCrAlY bond coats showed >1000 h lifetime, matching current standards for EB-PVD YSZ coatings.     

Solution of plane anisotropic elastostatical boundary value problems by singular integral equations

Summary Basis for the presented method is the knowledge of certain fundamental solutions for theinfinite anisotropic medium. By superimposing these singular solutions in a suitable fashion, the given boundary value problem can be formulated as a tensorial integral equation (singularity method).We start from two basic singularities in the anisotropicplane, viz. the single force and the edge dislocation, and then consider the corresponding integral equations and a method for approximating their solution.With 2 Figures     

Alumina composite membranes prepared by MOCVD

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

An initial value method for dual integral equations

An initial value method is derived for a set of dual integral equations encountered in solving mixed boundary value problems in mathematical physics with a circular line of separation of boundary conditions. It is shown that the solution itself, not just a transform of the solution, of the dual integral equations satisfies a Fredholm integral equation. The initial value problem is derived from this Fredholm equation.     

Potentiodynamical deposition of nanosized manganese oxides as high capacitance electrochemical capacitors

Nanosized manganese oxides powders were potentiodynamically deposition onto the Pb substrates by anodic oxidation in 0.5 mol L⁻¹ MnSO₄ and 0.5 mol L⁻¹ H₂SO₄ mixed solution at 40 °C. The chemical composition of the sample was determined by complex titration with ethylene diamine tetraacetic acid and redox titration. X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and chronopotentiometry were employed to characterize the materials. The highest specific capacitance of the MnO_x composite electrode was up to 420 F g⁻¹ in 1.0 mol L⁻¹ Na₂SO₄ electrolyte at the scan rate 5 mV s⁻¹. The synthesized nanosized manganese oxide exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

A method for the numerical solution of singular integral equations with a principal value integral

A method for the numerical solution of singular integral equations with kernels having a singularity of the Cauchy type is presented. The singular behavior of the unknown function is explicitly built into the solution using the index theorem. The integral equation is replaced by integral relations at a discrete set of points. The integrand is then approximated by piecewise linear functions involving the value of the unknown function at a finite set of points. This permits integration in a closed form analytically. Thus the problem is reduced to a system of linear algebraic equations. The results obtained in this way are compared with the more sophisticated procedures based on Gauss-Chebyshev and Lobatto-Chebyshev quadrature formulae. An integral equation arising in a crack problem of the classical theory of elasticity is used for this purpose.     

Viewing angle enhanced integral imaging display by using a high refractive index medium

In the integral imaging system, the viewing angle is limited by the size and focal length of the elemental lens. In this regard, we propose a new method for the viewing angle enhancement in the InIm. The proposed method employs a refractive index medium between the elemental image plane and the lens array. The viewing angle enhanced InIm display is analyzed based on the imaging terms. The experimental result shows that the viewing angle is doubled.     

Potentiodynamical co-deposited manganese oxide/carbon composite for high capacitance electrochemical capacitors

Manganese oxide/carbon composite materials were prepared by introducing the carbon powders into the potentiodynamical anodic co-deposited manganese oxide in 0.5 mol L^− 1 MnSO₄ and 0.5 mol L^− 1 H₂SO₄ mixed solution at 40 °C. The surface morphology and structure of the composite material were examined by scanning electron microscope and X-ray diffraction. Cyclic voltammetry tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of manganese oxide and carbon. These composite materials with rough surface, which consisted of approximately amorphous manganese oxide, were confirmed to possess the ideal capacitive property. The highest specific capacitance of manganese oxide/carbon composite electrode was up to 410 F g^− 1 in 1.0 mol L^− 1 Na₂SO₄ electrolyte at the scan rate 10 mV s^− 1. The synthesized composite materials exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

Mechanical vs. electrical failure mechanisms in high voltage,high energy density multilayer ceramic capacitors

Causes of breakdown, both mechanical and electrical, in high voltage, high energy density, BaTiO₃ capacitors were studied. The flexural strength of the capacitors was 96 MPa. Failure was due to surface defects or pores close to the surfaces of the samples. The dielectric breakdown strength of the samples was 181 kV/cm. The causes of breakdown were either electrode end effects or pores between the dielectric and electrode layers. Weibull statistics were used to determine if there was a correlation between mechanical failure and dielectric breakdown. A strong correlation between the two types of failure was not found in the study, in contrast to earlier studies of single dielectric layer capacitor materials.     

片式化高压电容器的内电极结构及优化

耐高压片式化多层陶瓷电容器(MLCC)要求其内电极具有特殊的结构以保证产品的可靠性。本文对比了普通MLCC和高压MLCC的内电极结构，用有限元方法对两种ML—CC中若干典型位置的电场分布进行了分析，从电学角度对高压MLCC中内电极结构尺寸进行了优化，建立了高压MLCC内电极结构尺寸和所选用陶瓷介质材料的电学性能、MLCC的额定工作电压等参数之间的关系，这对中、高压MLCC的设计和制造具有指导意义。     

The solution of a new mixed boundary value problem by use of an integral transformation

The solution of the two-dimensional potential problem for a finite plate charged to arbitrary potential in the presence of two-parallel earthed planes is solved by successive integral transformations in which a four-part boundary value problem is reduced to a two-part problem which in turn can be solved by standard methods.     

Indium rich InGaN solar cells grown by MOCVD

This study focuses on both epitaxial growths of In_xGa_1?xN epilayers with graded In content, and the performance of solar cells structures grown on sapphire substrate by using metal organic chemical vapor deposition. The high resolution X-ray and Hall Effect characterization were carried out after epitaxial InGaN solar cell structures growth. The In content of the graded InGaN layer was calculated from the X-ray reciprocal space mapping measurements. Indium contents of the graded InGaN epilayers change from 8.8 to 7.1 % in Sample A, 15.7–7.1 % in Sample B, and 26.6–15.1 % in Sample C. The current voltage measurements of the solar cell devices were carried out after a standard micro fabrication procedure. Sample B exhibits better performance with a short-circuit current density of 6 mA/cm², open-circuit voltage of 0.25 V, fill factor of 39.13 %, and the best efficiency measured under a standard solar simulator with one-sun air mass 1.5 global light sources (100 mW/cm²) at room temperature for finished devices was 0.66 %.     

MOCVD制备定向生长ZnO压电薄膜

采用大气开放式金属有机化合物化学气相沉积(A-MOCVD)的方法,在普通多晶黄铜基片上制备ZnO薄膜.薄膜的SEM、XRD结果表明ZnO沿C轴取向垂直生长在基片上.综合分析ZnO自身晶体生长习性,提出了ZnO薄膜在普通多晶铜表面的生长模型.并将ZnO薄膜制备成压电双晶片元件,在光学显微镜下能观察到元件尖端产生了很大的位移量,结果表明高定向性ZnO薄膜具有优异的压电特性.该压电器件使得传统的小变形双晶片元件的数学模型失效,有必要建立新型大变形双晶片物理、数学模型.