Barbara Dziurdzia

Low cost high performance microwave structures fabricated by advanced thick film techniques

The paper presents the application of two advanced thick‐film techniques: etching of fired thick‐films and photoimaging of photosensitive thick‐films for fabrication bandpass microwave filters operating in the frequency range from 6 to 14 GHz. Modified screen printing through ultra‐thin calendered screens is used for comparative goals. Advanced techniques are combined with novel thick‐film conductors including photosensitive pastes and etchable pastes.

A ceramic mini system for the detection of hydrocarbon radicals

This paper presents two components of a ceramic analytical system—a capillary column and a flame ionization detector designed and produced using photoimageable thick-film dielectric Fodel QM44F combined with a low temperature cofired ceramic tape. The microfluidic components are integrated onto a single piece of alumina substrate, dimensions 65 × 50 mm2, and have incorporated into them thick-film platinum heaters which ensure temperature control. The ceramic analytical minisystem is intended to detect—on the basis of ion current measurements—the presence of hydrocarbons in the analyte being passed through the capillary column and burned in the combustion cavity of the flame ionization detector. Ionic current in the range of nA was detected after introducing the analytes into the separation column.

Stack of Planar Double-Sided Solid Oxide Fuel Cells

A new design of a small power SOFC battery is presented. The battery consists of an array of flat double-sided fuel cells assembled with only two screws. Fuel cells are made with the application of commercially available HTCC green tapes. Eight layers of 180μm thick anode tape (YSZ+NiO) constitute the anode base structure of the double-sided fuel cell. Within the anode base structure, the separate areas serve as: the functional anode, the anode current collector, and the support for the anode functional layer. Also a network of fine micro channels is embedded within the anode base structure. The individual double-sided fuel cell is completed by deposition of the following layers, which constitute the electrolyte, the cathode, and the cathode current collector These layers are deposited on both sides of the anode base structure by means of screen-printing. Each double-sided fuel cell is provided with the own separate fuel distributor and combustion product collector. That beneficial feature enables complet...

FODEL(R) photoimageable technology in microwave applications

New circuit technologies capable of delivering high volume production, low cost microwave hybrids are still being sought. Advanced thick film technology offers new solutions suitable for microwave performance: the etching of fired thick films and the photoimaging of photosensitive thick films. Both techniques, using novel thick film materials and photopatterning gives a performance comparable with thin film techniques at significantly lower cost.

X-ray inspection and Six-Sigma in analysis of LED thermal pad coverage

Purpose The purpose of this paper is to evaluate selected methods of reduction voidings in lead-free solder joints underneath thermal pads of light-emitting diodes (LEDs), using X-ray inspection and Six Sigma methodology. Design/methodology/approach On the basis of cause and effect diagram for solder voiding, the potential causes of voids and influence of process variables on void formation were found. Three process variables were chosen: the type of reflow soldering, vacuum incorporation and the type of solder paste. Samples of LEDs were mounted with convection and vapour phase reflow soldering. Vacuum was incorporated into vapour phase soldering. Two types of solder pastes OM338PT and LFS-216LT were used. Algorithm incorporated into X-ray inspection system enabled to calculate the statistical distribution of LED thermal pad coverage and to find the process capability index (Cpk) of applied soldering techniques. Findings The evaluation of selected soldering processes of LEDs in respect of their thermal pad coverage and statistical Cpk indices is presented. Vapour-phase soldering with vacuum is capable (Cpk > 1) for OM338PT and LFS-216LT paste. Convection reflow without vacuum with LFS-216LT paste is also capable (Cpk = 1.1). Other technological soldering processes require improvements. Vacuum improves radically the capability of a reflow soldering for an LED assembly. When vacuum is not accessible, some improvement of capability to a lower extent is possible by an application of void-free solder pastes. Originality/value Six Sigma statistical methodology combined with X-ray diagnosis was used to check whether applied methods of void reduction underneath LED thermal pads are capable processes.

Stack of solid oxide fuel cells

Purpose – The paper aims to present the innovative design of a planar multilayered high temperature solid oxide fuel cell (SOFC), which is easy to manufacture, and features high resistance to rapid temperature changes. Temperature resistance was accomplished thanks to easy to heat, thin flat ceramic structure of the cell and elimination of metallic interconnections. Design/methodology/approach – The ceramic fuel cell consists of the anode core made of six to eight layers of nickel/yttria-stabilized zirconia tapes (Ni/YSZ) isostatically pressed into a laminate. Two networks of fuel distribution microchannels are engraved on both sides of the anode laminate. The microchannels are subsequently covered with a thin layer of the functional anode tape made of Ni/YSZ and a solid electrolyte tape made of YSZ. Findings – The single planar double-sided ceramic SOFC of dimensions 19 × 60 × 1.2 mm3 provides 3.2 Watts of electric power. The prototype of the battery which consists of four SOFCs provides an output power ...

Photoimageable Thick-Film Components for a Ceramic Analytical Microsystem

This paper presents ceramic microfluidic components—a meander capillary column and a flame ionization detector—which have been designed and fabricated using photoimageable thick-film dielectric Fodel QM44F combined with low-temperature cofired ceramic tape. The components are integrated on a single piece of alumina substrate of dimensions 65 × 50 mm and have incorporated thick-film platinum heaters to ensure their temperature control. Details of the technological process as well as the application set-up for the tested components are presented. The samples of analyte were detected by a flame ionization detector after passage through a capillary column.

The influence of a soldering manner on thermal properties of LED modules

Purpose This paper aims to present the results of the influence of a manner of soldering light emitting diodes (LEDs) to the metal core printed circuit board on thermal parameters of the module LED containing these diodes. Design/methodology/approach Using the authors’ elaborated measuring method and the dedicated measurement set-up, transient thermal impedances of LED modules, mounted using different soldering processes and mounted to the heat-sink with different values of the moment of force, are measured. The obtained results of measurements are discussed. Findings It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. The best thermal properties were obtained for soldering using vapour phase technology with vacuum and paste LFS-216LT. It was also proved that the moment of force used while mounting the considered modules on the heat-sink can result in a change of the value of thermal resistance of this module exceeding even 12 per cent. Research limitations/implications The investigations were performed for five LED modules operating at one, arbitrarily selected value of power dissipated in these modules mounted on the heat-sink of arbitrarily selected dimensions. Practical implications The obtained results of measurements could be usable for designers of mounting processes of power LED modules. Originality/value This paper presents the results of investigations of thermal properties of LED modules, in which different techniques of soldering are used. It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. It was also proved that the moment of force used while mounting the considered modules on the heat-sink is important.

Convection vs vapour phase reflow in LED and BGA assembly

Purpose The aim of this paper is to evaluate using statistical methods how two soldering techniques – the convection reflow and vapour phase reflow with vacuum – influence reduction of voids in lead-free solder joints under Light Emitted Diodes (LEDs) and Ball Grid Arrays (BGAs). Design/methodology/approach Distribution of voids in solder joints under thermal and electrical pads of LEDs and in solder balls of BGAs assembled with convection reflow and vapour phase reflow with vacuum has been investigated in terms of coverage or void contents, void diameters and number of voids. For each soldering technology, 80 LEDs and 32 solder balls in BGAs were examined. Soldering processes were carried out in the industrial or semi-industrial environment. The OM340 solder paste of Innolot type was used for LED soldering. Voidings in solder joints were inspected with a 2D X-ray transmission system. OriginLab was used for statistical analysis. Findings Investigations supported by statistical analysis showed that the vapour phase reflow with vacuum decreases significantly void contents and number and diameters of voids in solder joints under LED and BGA packages when compared to convection reflow. Originality/value Voiding distribution data were collected on the basis of 2D X-ray images for test samples manufactured during the mass production processes. Statistical analysis enabled to appraise soldering technologies used in these processes in respect of void formation.

New proposal to the electrical representation of a solid oxide fuel cell

Purpose The aim of this paper is to find the electrical representation of a solid oxide fuel cell (SOFC) that enables the application of typical exploitation characteristics of fuel cells for estimation of fuel cell parameters (for example, exchange current) and easy analysis of phenomena occurred during the fuel cell operation. Design/methodology/approach Three-layer structure of an SOFC, where a thin semi-conducting layer of electrolyte separates the anode from the cathode, shows a strong similarity to typical semiconductor devices built on the basis of P-N junctions, like diodes or transistors. Current–voltage (I-V) characteristics of a fuel cell can be described by the same mathematical functions as I-V plots of semiconductor devices. On the basis of this similarity and analysis of impedance spectra of a real fuel cell, two electrical representations of the SOFC have been created. Findings The simplified electrical representation of SOFC consists of a voltage source connected in series with a diode, which symbolizes a voltage drop on a cell cathode, and two resistors. This model is based on the similarity of Butler-Volmer to Shockley equation. The advanced representation comprises a voltage source connected in series with a bipolar transistor in close to saturation mode and two resistors. The base-emitter junction of the transistor represents voltage drop on the cell cathode, and the base-collector junction represents voltage drop on the cell anode. This model is based on the similarity of Butler-Volmer equation to Ebers-Moll equation. Originality/value The proposed approach based on the Shockley and Ebers-Moll formulas enables the more accurate estimation of the ion exchange current and other fuel cell parameters than the approach based on the Butler-Volmer and Tafel formulas. The usability of semiconductor models for analysis of SOFC operation was proved. The models were successively applied in a new design of a planar ceramic fuel cell, which features by reduced thermal capacity, short start-up time and limited number of metal components and which has become the basis for the SOFC stack design.